#. Named values are represented as a string of characters with their
prefix. For example, ``%foo``, ``@DivisionByZero``,
``%a.really.long.identifier``. The actual regular expression used is
- '``[%@][a-zA-Z$._][a-zA-Z$._0-9]*``'. Identifiers that require other
+ '``[%@][-a-zA-Z$._][-a-zA-Z$._0-9]*``'. Identifiers that require other
characters in their names can be surrounded with quotes. Special
characters may be escaped using ``"\xx"`` where ``xx`` is the ASCII
code for the character in hexadecimal. In this way, any character can
can be used on global variables to suppress mangling.
#. Unnamed values are represented as an unsigned numeric value with
their prefix. For example, ``%12``, ``@2``, ``%44``.
-#. Constants, which are described in the section Constants_ below.
+#. Constants, which are described in the section Constants_ below.
LLVM requires that values start with a prefix for two reasons: Compilers
don't need to worry about name clashes with reserved words, and the set
; Definition of main function
define i32 @main() { ; i32()*
; Convert [13 x i8]* to i8 *...
- %cast210 = getelementptr [13 x i8]* @.str, i64 0, i64 0
+ %cast210 = getelementptr [13 x i8], [13 x i8]* @.str, i64 0, i64 0
; Call puts function to write out the string to stdout.
call i32 @puts(i8* %cast210)
}
; Named metadata
- !0 = metadata !{i32 42, null, metadata !"string"}
+ !0 = !{i32 42, null, !"string"}
!foo = !{!0}
This example is made up of a :ref:`global variable <globalvars>` named
Some languages allow differing globals to be merged, such as two
functions with different semantics. Other languages, such as
``C++``, ensure that only equivalent globals are ever merged (the
- "one definition rule" --- "ODR"). Such languages can use the
+ "one definition rule" --- "ODR"). Such languages can use the
``linkonce_odr`` and ``weak_odr`` linkage types to indicate that the
global will only be merged with equivalent globals. These linkage
types are otherwise the same as their non-``odr`` versions.
"``anyregcc``" - Dynamic calling convention for code patching
This is a special convention that supports patching an arbitrary code
sequence in place of a call site. This convention forces the call
- arguments into registers but allows them to be dynamcially
+ arguments into registers but allows them to be dynamically
allocated. This can currently only be used with calls to
llvm.experimental.patchpoint because only this intrinsic records
the location of its arguments in a side table. See :doc:`StackMaps`.
"``preserve_mostcc``" - The `PreserveMost` calling convention
- This calling convention attempts to make the code in the caller as little
- intrusive as possible. This calling convention behaves identical to the `C`
+ This calling convention attempts to make the code in the caller as
+ unintrusive as possible. This convention behaves identically to the `C`
calling convention on how arguments and return values are passed, but it
uses a different set of caller/callee-saved registers. This alleviates the
burden of saving and recovering a large register set before and after the
The idea behind this convention is to support calls to runtime functions
that have a hot path and a cold path. The hot path is usually a small piece
- of code that doesn't many registers. The cold path might need to call out to
+ of code that doesn't use many registers. The cold path might need to call out to
another function and therefore only needs to preserve the caller-saved
registers, which haven't already been saved by the caller. The
`PreserveMost` calling convention is very similar to the `cold` calling
be used. The target may choose a different TLS model if the specified
model is not supported, or if a better choice of model can be made.
-A model can also be specified in a alias, but then it only governs how
+A model can also be specified in an alias, but then it only governs how
the alias is accessed. It will not have any effect in the aliasee.
+For platforms without linker support of ELF TLS model, the -femulated-tls
+flag can be used to generate GCC compatible emulated TLS code.
+
.. _namedtypes:
Structure Types
---------------
LLVM IR allows you to specify both "identified" and "literal" :ref:`structure
-types <t_struct>`. Literal types are uniqued structurally, but identified types
-are never uniqued. An :ref:`opaque structural type <t_opaque>` can also be used
+types <t_struct>`. Literal types are uniqued structurally, but identified types
+are never uniqued. An :ref:`opaque structural type <t_opaque>` can also be used
to forward declare a type that is not yet available.
-An example of a identified structure specification is:
+An example of an identified structure specification is:
.. code-block:: llvm
%mytype = type { %mytype*, i32 }
-Prior to the LLVM 3.0 release, identified types were structurally uniqued. Only
+Prior to the LLVM 3.0 release, identified types were structurally uniqued. Only
literal types are uniqued in recent versions of LLVM.
.. _globalvars:
Global variables define regions of memory allocated at compilation time
instead of run-time.
-Global variables definitions must be initialized.
+Global variable definitions must be initialized.
Global variables in other translation units can also be declared, in which
case they don't have an initializer.
By default, global initializers are optimized by assuming that global
variables defined within the module are not modified from their
-initial values before the start of the global initializer. This is
+initial values before the start of the global initializer. This is
true even for variables potentially accessible from outside the
module, including those with external linkage or appearing in
``@llvm.used`` or dllexported variables. This assumption may be suppressed
Globals can also have a :ref:`DLL storage class <dllstorageclass>`.
-Variables and aliasaes can have a
+Variables and aliases can have a
:ref:`Thread Local Storage Model <tls_model>`.
Syntax::
[@<GlobalVarName> =] [Linkage] [Visibility] [DLLStorageClass] [ThreadLocal]
[unnamed_addr] [AddrSpace] [ExternallyInitialized]
<global | constant> <Type> [<InitializerConstant>]
- [, section "name"] [, align <Alignment>]
+ [, section "name"] [, comdat [($name)]]
+ [, align <Alignment>]
For example, the following defines a global in a numbered address space
with an initializer, section, and alignment:
attributes <paramattrs>`), optional :ref:`function attributes <fnattrs>`,
an optional section, an optional alignment,
an optional :ref:`comdat <langref_comdats>`,
-an optional :ref:`garbage collector name <gc>`, an optional :ref:`prefix <prefixdata>`, an opening
-curly brace, a list of basic blocks, and a closing curly brace.
+an optional :ref:`garbage collector name <gc>`, an optional :ref:`prefix <prefixdata>`,
+an optional :ref:`prologue <prologuedata>`,
+an optional :ref:`personality <personalityfn>`,
+an opening curly brace, a list of basic blocks, and a closing curly brace.
LLVM function declarations consist of the "``declare``" keyword, an
optional :ref:`linkage type <linkage>`, an optional :ref:`visibility
an optional ``unnamed_addr`` attribute, a return type, an optional
:ref:`parameter attribute <paramattrs>` for the return type, a function
name, a possibly empty list of arguments, an optional alignment, an optional
-:ref:`garbage collector name <gc>` and an optional :ref:`prefix <prefixdata>`.
+:ref:`garbage collector name <gc>`, an optional :ref:`prefix <prefixdata>`,
+and an optional :ref:`prologue <prologuedata>`.
A function definition contains a list of basic blocks, forming the CFG (Control
Flow Graph) for the function. Each basic block may optionally start with a label
LLVM allows an explicit section to be specified for functions. If the
target supports it, it will emit functions to the section specified.
-Additionally, the function can placed in a COMDAT.
+Additionally, the function can be placed in a COMDAT.
An explicit alignment may be specified for a function. If not present,
or if the alignment is set to zero, the alignment of the function is set
is specified, the function is forced to have at least that much
alignment. All alignments must be a power of 2.
-If the ``unnamed_addr`` attribute is given, the address is know to not
+If the ``unnamed_addr`` attribute is given, the address is known to not
be significant and two identical functions can be merged.
Syntax::
define [linkage] [visibility] [DLLStorageClass]
[cconv] [ret attrs]
<ResultType> @<FunctionName> ([argument list])
- [unnamed_addr] [fn Attrs] [section "name"] [comdat $<ComdatName>]
- [align N] [gc] [prefix Constant] { ... }
+ [unnamed_addr] [fn Attrs] [section "name"] [comdat [($name)]]
+ [align N] [gc] [prefix Constant] [prologue Constant]
+ [personality Constant] { ... }
-The argument list is a comma seperated sequence of arguments where each
-argument is of the following form
+The argument list is a comma separated sequence of arguments where each
+argument is of the following form:
Syntax::
``linkonce_odr``, ``weak_odr``, ``external``. Note that some system linkers
might not correctly handle dropping a weak symbol that is aliased.
-Alias that are not ``unnamed_addr`` are guaranteed to have the same address as
+Aliases that are not ``unnamed_addr`` are guaranteed to have the same address as
the aliasee expression. ``unnamed_addr`` ones are only guaranteed to point
to the same content.
Comdat IR provides access to COFF and ELF object file COMDAT functionality.
-Comdats have a name which represents the COMDAT key. All global objects that
+Comdats have a name which represents the COMDAT key. All global objects that
specify this key will only end up in the final object file if the linker chooses
-that key over some other key. Aliases are placed in the same COMDAT that their
+that key over some other key. Aliases are placed in the same COMDAT that their
aliasee computes to, if any.
Comdats have a selection kind to provide input on how the linker should
.. code-block:: llvm
$foo = comdat largest
- @foo = global i32 2, comdat $foo
+ @foo = global i32 2, comdat($foo)
- define void @bar() comdat $foo {
+ define void @bar() comdat($foo) {
ret void
}
+As a syntactic sugar the ``$name`` can be omitted if the name is the same as
+the global name:
+
+.. code-block:: llvm
+
+ $foo = comdat any
+ @foo = global i32 2, comdat
+
+
In a COFF object file, this will create a COMDAT section with selection kind
``IMAGE_COMDAT_SELECT_LARGEST`` containing the contents of the ``@foo`` symbol
and another COMDAT section with selection kind
$foo = comdat any
$bar = comdat any
- @g1 = global i32 42, section "sec", comdat $foo
- @g2 = global i32 42, section "sec", comdat $bar
+ @g1 = global i32 42, section "sec", comdat($foo)
+ @g2 = global i32 42, section "sec", comdat($bar)
From the object file perspective, this requires the creation of two sections
-with the same name. This is necessary because both globals belong to different
+with the same name. This is necessary because both globals belong to different
COMDAT groups and COMDATs, at the object file level, are represented by
sections.
-Note that certain IR constructs like global variables and functions may create
-COMDATs in the object file in addition to any which are specified using COMDAT
-IR. This arises, for example, when a global variable has linkonce_odr linkage.
+Note that certain IR constructs like global variables and functions may
+create COMDATs in the object file in addition to any which are specified using
+COMDAT IR. This arises when the code generator is configured to emit globals
+in individual sections (e.g. when `-data-sections` or `-function-sections`
+is supplied to `llc`).
.. _namedmetadatastructure:
nodes <metadata>` (but not metadata strings) are the only valid
operands for a named metadata.
+#. Named metadata are represented as a string of characters with the
+ metadata prefix. The rules for metadata names are the same as for
+ identifiers, but quoted names are not allowed. ``"\xx"`` type escapes
+ are still valid, which allows any character to be part of a name.
+
Syntax::
; Some unnamed metadata nodes, which are referenced by the named metadata.
- !0 = metadata !{metadata !"zero"}
- !1 = metadata !{metadata !"one"}
- !2 = metadata !{metadata !"two"}
+ !0 = !{!"zero"}
+ !1 = !{!"one"}
+ !2 = !{!"two"}
; A named metadata.
!name = !{!0, !1, !2}
the callee (for a return value).
``inreg``
This indicates that this parameter or return value should be treated
- in a special target-dependent fashion during while emitting code for
+ in a special target-dependent fashion while emitting code for
a function call or return (usually, by putting it in a register as
opposed to memory, though some targets use it to distinguish between
two different kinds of registers). Use of this attribute is
``inalloca``
The ``inalloca`` argument attribute allows the caller to take the
- address of outgoing stack arguments. An ``inalloca`` argument must
+ address of outgoing stack arguments. An ``inalloca`` argument must
be a pointer to stack memory produced by an ``alloca`` instruction.
The alloca, or argument allocation, must also be tagged with the
- inalloca keyword. Only the last argument may have the ``inalloca``
+ inalloca keyword. Only the last argument may have the ``inalloca``
attribute, and that argument is guaranteed to be passed in memory.
An argument allocation may be used by a call at most once because
- the call may deallocate it. The ``inalloca`` attribute cannot be
+ the call may deallocate it. The ``inalloca`` attribute cannot be
used in conjunction with other attributes that affect argument
- storage, like ``inreg``, ``nest``, ``sret``, or ``byval``. The
+ storage, like ``inreg``, ``nest``, ``sret``, or ``byval``. The
``inalloca`` attribute also disables LLVM's implicit lowering of
large aggregate return values, which means that frontend authors
must lower them with ``sret`` pointers.
When the call site is reached, the argument allocation must have
been the most recent stack allocation that is still live, or the
- results are undefined. It is possible to allocate additional stack
+ results are undefined. It is possible to allocate additional stack
space after an argument allocation and before its call site, but it
must be cleared off with :ref:`llvm.stackrestore
<int_stackrestore>`.
.. _noalias:
``noalias``
- This indicates that pointer values :ref:`based <pointeraliasing>` on
- the argument or return value do not alias pointer values that are
- not *based* on it, ignoring certain "irrelevant" dependencies. For a
- call to the parent function, dependencies between memory references
- from before or after the call and from those during the call are
- "irrelevant" to the ``noalias`` keyword for the arguments and return
- value used in that call. The caller shares the responsibility with
- the callee for ensuring that these requirements are met. For further
- details, please see the discussion of the NoAlias response in :ref:`alias
- analysis <Must, May, or No>`.
+ This indicates that objects accessed via pointer values
+ :ref:`based <pointeraliasing>` on the argument or return value are not also
+ accessed, during the execution of the function, via pointer values not
+ *based* on the argument or return value. The attribute on a return value
+ also has additional semantics described below. The caller shares the
+ responsibility with the callee for ensuring that these requirements are met.
+ For further details, please see the discussion of the NoAlias response in
+ :ref:`alias analysis <Must, May, or No>`.
Note that this definition of ``noalias`` is intentionally similar
- to the definition of ``restrict`` in C99 for function arguments,
- though it is slightly weaker.
+ to the definition of ``restrict`` in C99 for function arguments.
For function return values, C99's ``restrict`` is not meaningful,
- while LLVM's ``noalias`` is.
+ while LLVM's ``noalias`` is. Furthermore, the semantics of the ``noalias``
+ attribute on return values are stronger than the semantics of the attribute
+ when used on function arguments. On function return values, the ``noalias``
+ attribute indicates that the function acts like a system memory allocation
+ function, returning a pointer to allocated storage disjoint from the
+ storage for any other object accessible to the caller.
+
``nocapture``
This indicates that the callee does not make any copies of the
pointer that outlive the callee itself. This is not a valid
This indicates that the parameter or return pointer is not null. This
attribute may only be applied to pointer typed parameters. This is not
checked or enforced by LLVM, the caller must ensure that the pointer
- passed in is non-null, or the callee must ensure that the returned pointer
+ passed in is non-null, or the callee must ensure that the returned pointer
is non-null.
``dereferenceable(<n>)``
array), however ``dereferenceable(<n>)`` does imply ``nonnull`` in
``addrspace(0)`` (which is the default address space).
+``dereferenceable_or_null(<n>)``
+ This indicates that the parameter or return value isn't both
+ non-null and non-dereferenceable (up to ``<n>`` bytes) at the same
+ time. All non-null pointers tagged with
+ ``dereferenceable_or_null(<n>)`` are ``dereferenceable(<n>)``.
+ For address space 0 ``dereferenceable_or_null(<n>)`` implies that
+ a pointer is exactly one of ``dereferenceable(<n>)`` or ``null``,
+ and in other address spaces ``dereferenceable_or_null(<n>)``
+ implies that a pointer is at least one of ``dereferenceable(<n>)``
+ or ``null`` (i.e. it may be both ``null`` and
+ ``dereferenceable(<n>)``). This attribute may only be applied to
+ pointer typed parameters.
+
.. _gc:
-Garbage Collector Names
------------------------
+Garbage Collector Strategy Names
+--------------------------------
-Each function may specify a garbage collector name, which is simply a
+Each function may specify a garbage collector strategy name, which is simply a
string:
.. code-block:: llvm
define void @f() gc "name" { ... }
-The compiler declares the supported values of *name*. Specifying a
-collector will cause the compiler to alter its output in order to
-support the named garbage collection algorithm.
+The supported values of *name* includes those :ref:`built in to LLVM
+<builtin-gc-strategies>` and any provided by loaded plugins. Specifying a GC
+strategy will cause the compiler to alter its output in order to support the
+named garbage collection algorithm. Note that LLVM itself does not contain a
+garbage collector, this functionality is restricted to generating machine code
+which can interoperate with a collector provided externally.
.. _prefixdata:
Prefix Data
-----------
-Prefix data is data associated with a function which the code generator
-will emit immediately before the function body. The purpose of this feature
-is to allow frontends to associate language-specific runtime metadata with
-specific functions and make it available through the function pointer while
-still allowing the function pointer to be called. To access the data for a
-given function, a program may bitcast the function pointer to a pointer to
-the constant's type. This implies that the IR symbol points to the start
-of the prefix data.
-
-To maintain the semantics of ordinary function calls, the prefix data must
-have a particular format. Specifically, it must begin with a sequence of
+Prefix data is data associated with a function which the code
+generator will emit immediately before the function's entrypoint.
+The purpose of this feature is to allow frontends to associate
+language-specific runtime metadata with specific functions and make it
+available through the function pointer while still allowing the
+function pointer to be called.
+
+To access the data for a given function, a program may bitcast the
+function pointer to a pointer to the constant's type and dereference
+index -1. This implies that the IR symbol points just past the end of
+the prefix data. For instance, take the example of a function annotated
+with a single ``i32``,
+
+.. code-block:: llvm
+
+ define void @f() prefix i32 123 { ... }
+
+The prefix data can be referenced as,
+
+.. code-block:: llvm
+
+ %0 = bitcast void* () @f to i32*
+ %a = getelementptr inbounds i32, i32* %0, i32 -1
+ %b = load i32, i32* %a
+
+Prefix data is laid out as if it were an initializer for a global variable
+of the prefix data's type. The function will be placed such that the
+beginning of the prefix data is aligned. This means that if the size
+of the prefix data is not a multiple of the alignment size, the
+function's entrypoint will not be aligned. If alignment of the
+function's entrypoint is desired, padding must be added to the prefix
+data.
+
+A function may have prefix data but no body. This has similar semantics
+to the ``available_externally`` linkage in that the data may be used by the
+optimizers but will not be emitted in the object file.
+
+.. _prologuedata:
+
+Prologue Data
+-------------
+
+The ``prologue`` attribute allows arbitrary code (encoded as bytes) to
+be inserted prior to the function body. This can be used for enabling
+function hot-patching and instrumentation.
+
+To maintain the semantics of ordinary function calls, the prologue data must
+have a particular format. Specifically, it must begin with a sequence of
bytes which decode to a sequence of machine instructions, valid for the
module's target, which transfer control to the point immediately succeeding
-the prefix data, without performing any other visible action. This allows
+the prologue data, without performing any other visible action. This allows
the inliner and other passes to reason about the semantics of the function
-definition without needing to reason about the prefix data. Obviously this
-makes the format of the prefix data highly target dependent.
-
-Prefix data is laid out as if it were an initializer for a global variable
-of the prefix data's type. No padding is automatically placed between the
-prefix data and the function body. If padding is required, it must be part
-of the prefix data.
+definition without needing to reason about the prologue data. Obviously this
+makes the format of the prologue data highly target dependent.
-A trivial example of valid prefix data for the x86 architecture is ``i8 144``,
+A trivial example of valid prologue data for the x86 architecture is ``i8 144``,
which encodes the ``nop`` instruction:
.. code-block:: llvm
- define void @f() prefix i8 144 { ... }
+ define void @f() prologue i8 144 { ... }
-Generally prefix data can be formed by encoding a relative branch instruction
-which skips the metadata, as in this example of valid prefix data for the
+Generally prologue data can be formed by encoding a relative branch instruction
+which skips the metadata, as in this example of valid prologue data for the
x86_64 architecture, where the first two bytes encode ``jmp .+10``:
.. code-block:: llvm
%0 = type <{ i8, i8, i8* }>
- define void @f() prefix %0 <{ i8 235, i8 8, i8* @md}> { ... }
+ define void @f() prologue %0 <{ i8 235, i8 8, i8* @md}> { ... }
-A function may have prefix data but no body. This has similar semantics
+A function may have prologue data but no body. This has similar semantics
to the ``available_externally`` linkage in that the data may be used by the
optimizers but will not be emitted in the object file.
+.. _personalityfn:
+
+Personality Function
+--------------------
+
+The ``personality`` attribute permits functions to specify what function
+to use for exception handling.
+
.. _attrgrp:
Attribute Groups
computing edge weights, basic blocks post-dominated by a cold
function call are also considered to be cold; and, thus, given low
weight.
+``convergent``
+ This attribute indicates that the callee is dependent on a convergent
+ thread execution pattern under certain parallel execution models.
+ Transformations that are execution model agnostic may only move or
+ tranform this call if the final location is control equivalent to its
+ original position in the program, where control equivalence is defined as
+ A dominates B and B post-dominates A, or vice versa.
``inlinehint``
This attribute indicates that the source code contained a hint that
inlining this function is desirable (such as the "inline" keyword in
normally. This produces undefined behavior at runtime if the
function ever does dynamically return.
``nounwind``
- This function attribute indicates that the function never returns
- with an unwind or exceptional control flow. If the function does
- unwind, its runtime behavior is undefined.
+ This function attribute indicates that the function never raises an
+ exception. If the function does raise an exception, its runtime
+ behavior is undefined. However, functions marked nounwind may still
+ trap or generate asynchronous exceptions. Exception handling schemes
+ that are recognized by LLVM to handle asynchronous exceptions, such
+ as SEH, will still provide their implementation defined semantics.
``optnone``
This function attribute indicates that the function is not optimized
by any optimization or code generator passes with the
On an argument, this attribute indicates that the function does not write
through this pointer argument, even though it may write to the memory that
the pointer points to.
+``argmemonly``
+ This attribute indicates that the only memory accesses inside function are
+ loads and stores from objects pointed to by its pointer-typed arguments,
+ with arbitrary offsets. Or in other words, all memory operations in the
+ function can refer to memory only using pointers based on its function
+ arguments.
+ Note that ``argmemonly`` can be used together with ``readonly`` attribute
+ in order to specify that function reads only from its arguments.
``returns_twice``
This attribute indicates that this function can return twice. The C
``setjmp`` is an example of such a function. The compiler disables
some optimizations (like tail calls) in the caller of these
functions.
+``safestack``
+ This attribute indicates that
+ `SafeStack <http://clang.llvm.org/docs/SafeStack.html>`_
+ protection is enabled for this function.
+
+ If a function that has a ``safestack`` attribute is inlined into a
+ function that doesn't have a ``safestack`` attribute or which has an
+ ``ssp``, ``sspstrong`` or ``sspreq`` attribute, then the resulting
+ function will have a ``safestack`` attribute.
``sanitize_address``
This attribute indicates that AddressSanitizer checks
(dynamic address safety analysis) are enabled for this function.
``sspstrong``
This attribute indicates that the function should emit a stack smashing
protector. This attribute causes a strong heuristic to be used when
- determining if a function needs stack protectors. The strong heuristic
+ determining if a function needs stack protectors. The strong heuristic
will enable protectors for functions with:
- Arrays of any size and type
If a function that has an ``sspstrong`` attribute is inlined into a
function that doesn't have an ``sspstrong`` attribute, then the
resulting function will have an ``sspstrong`` attribute.
+``"thunk"``
+ This attribute indicates that the function will delegate to some other
+ function with a tail call. The prototype of a thunk should not be used for
+ optimization purposes. The caller is expected to cast the thunk prototype to
+ match the thunk target prototype.
``uwtable``
This attribute indicates that the ABI being targeted requires that
- an unwind table entry be produce for this function even if we can
+ an unwind table entry be produced for this function even if we can
show that no exceptions passes by it. This is normally the case for
the ELF x86-64 abi, but it can be disabled for some compilation
units.
characters. The escape sequence used is simply "\\xx" where "xx" is the
two digit hex code for the number.
-The inline asm code is simply printed to the machine code .s file when
-assembly code is generated.
+Note that the assembly string *must* be parseable by LLVM's integrated assembler
+(unless it is disabled), even when emitting a ``.s`` file.
.. _langref_datalayout:
``p[n]:<size>:<abi>:<pref>``
This specifies the *size* of a pointer and its ``<abi>`` and
``<pref>``\erred alignments for address space ``n``. All sizes are in
- bits. The address space, ``n`` is optional, and if not specified,
- denotes the default address space 0. The value of ``n`` must be
+ bits. The address space, ``n``, is optional, and if not specified,
+ denotes the default address space 0. The value of ``n`` must be
in the range [1,2^23).
``i<size>:<abi>:<pref>``
This specifies the alignment for an integer type of a given bit
Instead, if specified, the target data layout is required to match what
the ultimate *code generator* expects. This string is used by the
mid-level optimizers to improve code, and this only works if it matches
-what the ultimate code generator uses. If you would like to generate IR
-that does not embed this target-specific detail into the IR, then you
-don't have to specify the string. This will disable some optimizations
-that require precise layout information, but this also prevents those
-optimizations from introducing target specificity into the IR.
+what the ultimate code generator uses. There is no way to generate IR
+that does not embed this target-specific detail into the IR. If you
+don't specify the string, the default specifications will be used to
+generate a Data Layout and the optimization phases will operate
+accordingly and introduce target specificity into the IR with respect to
+these default specifications.
.. _langref_triple:
following rules:
- A pointer value formed from a ``getelementptr`` operation is *based*
- on the first operand of the ``getelementptr``.
+ on the first value operand of the ``getelementptr``.
- The result value of a ``bitcast`` is *based* on the operand of the
``bitcast``.
- A pointer value formed by an ``inttoptr`` is *based* on all pointer
this holds for an l-value of volatile primitive type with native
hardware support, but not necessarily for aggregate types. The
frontend upholds these expectations, which are intentionally
- unspecified in the IR. The rules above ensure that IR transformation
+ unspecified in the IR. The rules above ensure that IR transformations
do not violate the frontend's contract with the language.
.. _memmodel:
LLVM IR floating-point binary ops (:ref:`fadd <i_fadd>`,
:ref:`fsub <i_fsub>`, :ref:`fmul <i_fmul>`, :ref:`fdiv <i_fdiv>`,
-:ref:`frem <i_frem>`) have the following flags that can set to enable
-otherwise unsafe floating point operations
+:ref:`frem <i_frem>`, :ref:`fcmp <i_fcmp>`) have the following flags that can
+be set to enable otherwise unsafe floating point operations
``nnan``
No NaNs - Allow optimizations to assume the arguments and result are not
-------------------------
Use-list directives encode the in-memory order of each use-list, allowing the
-order to be recreated. ``<order-indexes>`` is a comma-separated list of
-indexes that are assigned to the referenced value's uses. The referenced
+order to be recreated. ``<order-indexes>`` is a comma-separated list of
+indexes that are assigned to the referenced value's uses. The referenced
value's use-list is immediately sorted by these indexes.
-Use-list directives may appear at function scope or global scope. They are not
-instructions, and have no effect on the semantics of the IR. When they're at
+Use-list directives may appear at function scope or global scope. They are not
+instructions, and have no effect on the semantics of the IR. When they're at
function scope, they must appear after the terminator of the final basic block.
If basic blocks have their address taken via ``blockaddress()`` expressions,
...where '``<parameter list>``' is a comma-separated list of type
specifiers. Optionally, the parameter list may include a type ``...``, which
-indicates that the function takes a variable number of arguments. Variable
+indicates that the function takes a variable number of arguments. Variable
argument functions can access their arguments with the :ref:`variable argument
-handling intrinsic <int_varargs>` functions. '``<returntype>``' is any type
+handling intrinsic <int_varargs>` functions. '``<returntype>``' is any type
except :ref:`label <t_label>` and :ref:`metadata <t_metadata>`.
:Examples:
label
+.. _t_token:
+
+Token Type
+^^^^^^^^^^
+
+:Overview:
+
+The token type is used when a value is associated with an instruction
+but all uses of the value must not attempt to introspect or obscure it.
+As such, it is not appropriate to have a :ref:`phi <i_phi>` or
+:ref:`select <i_select>` of type token.
+
+:Syntax:
+
+::
+
+ token
+
+
+
.. _t_metadata:
Metadata Type
having to print large zero initializers (e.g. for large arrays) and
is always exactly equivalent to using explicit zero initializers.
**Metadata node**
- A metadata node is a structure-like constant with :ref:`metadata
- type <t_metadata>`. For example:
- "``metadata !{ i32 0, metadata !"test" }``". Unlike other
- constants that are meant to be interpreted as part of the
- instruction stream, metadata is a place to attach additional
+ A metadata node is a constant tuple without types. For example:
+ "``!{!0, !{!2, !0}, !"test"}``". Metadata can reference constant values,
+ for example: "``!{!0, i32 0, i8* @global, i64 (i64)* @function, !"str"}``".
+ Unlike other typed constants that are meant to be interpreted as part of
+ the instruction stream, metadata is a place to attach additional
information such as debug info.
Global Variable and Function Addresses
entry:
%poison = sub nuw i32 0, 1 ; Results in a poison value.
%still_poison = and i32 %poison, 0 ; 0, but also poison.
- %poison_yet_again = getelementptr i32* @h, i32 %still_poison
+ %poison_yet_again = getelementptr i32, i32* @h, i32 %still_poison
store i32 0, i32* %poison_yet_again ; memory at @h[0] is poisoned
store i32 %poison, i32* @g ; Poison value stored to memory.
- %poison2 = load i32* @g ; Poison value loaded back from memory.
+ %poison2 = load i32, i32* @g ; Poison value loaded back from memory.
store volatile i32 %poison, i32* @g ; External observation; undefined behavior.
%narrowaddr = bitcast i32* @g to i16*
%wideaddr = bitcast i32* @g to i64*
- %poison3 = load i16* %narrowaddr ; Returns a poison value.
- %poison4 = load i64* %wideaddr ; Returns a poison value.
+ %poison3 = load i16, i16* %narrowaddr ; Returns a poison value.
+ %poison4 = load i64, i64* %wideaddr ; Returns a poison value.
%cmp = icmp slt i32 %poison, 0 ; Returns a poison value.
br i1 %cmp, label %true, label %end ; Branch to either destination.
Convert a constant pointer or constant vector of pointer, CST, to another
TYPE in a different address space. The constraints of the operands are the
same as those for the :ref:`addrspacecast instruction <i_addrspacecast>`.
-``getelementptr (CSTPTR, IDX0, IDX1, ...)``, ``getelementptr inbounds (CSTPTR, IDX0, IDX1, ...)``
+``getelementptr (TY, CSTPTR, IDX0, IDX1, ...)``, ``getelementptr inbounds (TY, CSTPTR, IDX0, IDX1, ...)``
Perform the :ref:`getelementptr operation <i_getelementptr>` on
constants. As with the :ref:`getelementptr <i_getelementptr>`
instruction, the index list may have zero or more indexes, which are
- required to make sense for the type of "CSTPTR".
+ required to make sense for the type of "pointer to TY".
``select (COND, VAL1, VAL2)``
Perform the :ref:`select operation <i_select>` on constants.
``icmp COND (VAL1, VAL2)``
----------------------------
LLVM supports inline assembler expressions (as opposed to :ref:`Module-Level
-Inline Assembly <moduleasm>`) through the use of a special value. This
-value represents the inline assembler as a string (containing the
-instructions to emit), a list of operand constraints (stored as a
-string), a flag that indicates whether or not the inline asm expression
-has side effects, and a flag indicating whether the function containing
-the asm needs to align its stack conservatively. An example inline
-assembler expression is:
+Inline Assembly <moduleasm>`) through the use of a special value. This value
+represents the inline assembler as a template string (containing the
+instructions to emit), a list of operand constraints (stored as a string), a
+flag that indicates whether or not the inline asm expression has side effects,
+and a flag indicating whether the function containing the asm needs to align its
+stack conservatively.
+
+The template string supports argument substitution of the operands using "``$``"
+followed by a number, to indicate substitution of the given register/memory
+location, as specified by the constraint string. "``${NUM:MODIFIER}``" may also
+be used, where ``MODIFIER`` is a target-specific annotation for how to print the
+operand (See :ref:`inline-asm-modifiers`).
+
+A literal "``$``" may be included by using "``$$``" in the template. To include
+other special characters into the output, the usual "``\XX``" escapes may be
+used, just as in other strings. Note that after template substitution, the
+resulting assembly string is parsed by LLVM's integrated assembler unless it is
+disabled -- even when emitting a ``.s`` file -- and thus must contain assembly
+syntax known to LLVM.
+
+LLVM's support for inline asm is modeled closely on the requirements of Clang's
+GCC-compatible inline-asm support. Thus, the feature-set and the constraint and
+modifier codes listed here are similar or identical to those in GCC's inline asm
+support. However, to be clear, the syntax of the template and constraint strings
+described here is *not* the same as the syntax accepted by GCC and Clang, and,
+while most constraint letters are passed through as-is by Clang, some get
+translated to other codes when converting from the C source to the LLVM
+assembly.
+
+An example inline assembler expression is:
.. code-block:: llvm
first, the '``alignstack``' keyword second and the '``inteldialect``'
keyword last.
+Inline Asm Constraint String
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+The constraint list is a comma-separated string, each element containing one or
+more constraint codes.
+
+For each element in the constraint list an appropriate register or memory
+operand will be chosen, and it will be made available to assembly template
+string expansion as ``$0`` for the first constraint in the list, ``$1`` for the
+second, etc.
+
+There are three different types of constraints, which are distinguished by a
+prefix symbol in front of the constraint code: Output, Input, and Clobber. The
+constraints must always be given in that order: outputs first, then inputs, then
+clobbers. They cannot be intermingled.
+
+There are also three different categories of constraint codes:
+
+- Register constraint. This is either a register class, or a fixed physical
+ register. This kind of constraint will allocate a register, and if necessary,
+ bitcast the argument or result to the appropriate type.
+- Memory constraint. This kind of constraint is for use with an instruction
+ taking a memory operand. Different constraints allow for different addressing
+ modes used by the target.
+- Immediate value constraint. This kind of constraint is for an integer or other
+ immediate value which can be rendered directly into an instruction. The
+ various target-specific constraints allow the selection of a value in the
+ proper range for the instruction you wish to use it with.
+
+Output constraints
+""""""""""""""""""
+
+Output constraints are specified by an "``=``" prefix (e.g. "``=r``"). This
+indicates that the assembly will write to this operand, and the operand will
+then be made available as a return value of the ``asm`` expression. Output
+constraints do not consume an argument from the call instruction. (Except, see
+below about indirect outputs).
+
+Normally, it is expected that no output locations are written to by the assembly
+expression until *all* of the inputs have been read. As such, LLVM may assign
+the same register to an output and an input. If this is not safe (e.g. if the
+assembly contains two instructions, where the first writes to one output, and
+the second reads an input and writes to a second output), then the "``&``"
+modifier must be used (e.g. "``=&r``") to specify that the output is an
+"early-clobber" output. Marking an ouput as "early-clobber" ensures that LLVM
+will not use the same register for any inputs (other than an input tied to this
+output).
+
+Input constraints
+"""""""""""""""""
+
+Input constraints do not have a prefix -- just the constraint codes. Each input
+constraint will consume one argument from the call instruction. It is not
+permitted for the asm to write to any input register or memory location (unless
+that input is tied to an output). Note also that multiple inputs may all be
+assigned to the same register, if LLVM can determine that they necessarily all
+contain the same value.
+
+Instead of providing a Constraint Code, input constraints may also "tie"
+themselves to an output constraint, by providing an integer as the constraint
+string. Tied inputs still consume an argument from the call instruction, and
+take up a position in the asm template numbering as is usual -- they will simply
+be constrained to always use the same register as the output they've been tied
+to. For example, a constraint string of "``=r,0``" says to assign a register for
+output, and use that register as an input as well (it being the 0'th
+constraint).
+
+It is permitted to tie an input to an "early-clobber" output. In that case, no
+*other* input may share the same register as the input tied to the early-clobber
+(even when the other input has the same value).
+
+You may only tie an input to an output which has a register constraint, not a
+memory constraint. Only a single input may be tied to an output.
+
+There is also an "interesting" feature which deserves a bit of explanation: if a
+register class constraint allocates a register which is too small for the value
+type operand provided as input, the input value will be split into multiple
+registers, and all of them passed to the inline asm.
+
+However, this feature is often not as useful as you might think.
+
+Firstly, the registers are *not* guaranteed to be consecutive. So, on those
+architectures that have instructions which operate on multiple consecutive
+instructions, this is not an appropriate way to support them. (e.g. the 32-bit
+SparcV8 has a 64-bit load, which instruction takes a single 32-bit register. The
+hardware then loads into both the named register, and the next register. This
+feature of inline asm would not be useful to support that.)
+
+A few of the targets provide a template string modifier allowing explicit access
+to the second register of a two-register operand (e.g. MIPS ``L``, ``M``, and
+``D``). On such an architecture, you can actually access the second allocated
+register (yet, still, not any subsequent ones). But, in that case, you're still
+probably better off simply splitting the value into two separate operands, for
+clarity. (e.g. see the description of the ``A`` constraint on X86, which,
+despite existing only for use with this feature, is not really a good idea to
+use)
+
+Indirect inputs and outputs
+"""""""""""""""""""""""""""
+
+Indirect output or input constraints can be specified by the "``*``" modifier
+(which goes after the "``=``" in case of an output). This indicates that the asm
+will write to or read from the contents of an *address* provided as an input
+argument. (Note that in this way, indirect outputs act more like an *input* than
+an output: just like an input, they consume an argument of the call expression,
+rather than producing a return value. An indirect output constraint is an
+"output" only in that the asm is expected to write to the contents of the input
+memory location, instead of just read from it).
+
+This is most typically used for memory constraint, e.g. "``=*m``", to pass the
+address of a variable as a value.
+
+It is also possible to use an indirect *register* constraint, but only on output
+(e.g. "``=*r``"). This will cause LLVM to allocate a register for an output
+value normally, and then, separately emit a store to the address provided as
+input, after the provided inline asm. (It's not clear what value this
+functionality provides, compared to writing the store explicitly after the asm
+statement, and it can only produce worse code, since it bypasses many
+optimization passes. I would recommend not using it.)
+
+
+Clobber constraints
+"""""""""""""""""""
+
+A clobber constraint is indicated by a "``~``" prefix. A clobber does not
+consume an input operand, nor generate an output. Clobbers cannot use any of the
+general constraint code letters -- they may use only explicit register
+constraints, e.g. "``~{eax}``". The one exception is that a clobber string of
+"``~{memory}``" indicates that the assembly writes to arbitrary undeclared
+memory locations -- not only the memory pointed to by a declared indirect
+output.
+
+
+Constraint Codes
+""""""""""""""""
+After a potential prefix comes constraint code, or codes.
+
+A Constraint Code is either a single letter (e.g. "``r``"), a "``^``" character
+followed by two letters (e.g. "``^wc``"), or "``{``" register-name "``}``"
+(e.g. "``{eax}``").
+
+The one and two letter constraint codes are typically chosen to be the same as
+GCC's constraint codes.
+
+A single constraint may include one or more than constraint code in it, leaving
+it up to LLVM to choose which one to use. This is included mainly for
+compatibility with the translation of GCC inline asm coming from clang.
+
+There are two ways to specify alternatives, and either or both may be used in an
+inline asm constraint list:
+
+1) Append the codes to each other, making a constraint code set. E.g. "``im``"
+ or "``{eax}m``". This means "choose any of the options in the set". The
+ choice of constraint is made independently for each constraint in the
+ constraint list.
+
+2) Use "``|``" between constraint code sets, creating alternatives. Every
+ constraint in the constraint list must have the same number of alternative
+ sets. With this syntax, the same alternative in *all* of the items in the
+ constraint list will be chosen together.
+
+Putting those together, you might have a two operand constraint string like
+``"rm|r,ri|rm"``. This indicates that if operand 0 is ``r`` or ``m``, then
+operand 1 may be one of ``r`` or ``i``. If operand 0 is ``r``, then operand 1
+may be one of ``r`` or ``m``. But, operand 0 and 1 cannot both be of type m.
+
+However, the use of either of the alternatives features is *NOT* recommended, as
+LLVM is not able to make an intelligent choice about which one to use. (At the
+point it currently needs to choose, not enough information is available to do so
+in a smart way.) Thus, it simply tries to make a choice that's most likely to
+compile, not one that will be optimal performance. (e.g., given "``rm``", it'll
+always choose to use memory, not registers). And, if given multiple registers,
+or multiple register classes, it will simply choose the first one. (In fact, it
+doesn't currently even ensure explicitly specified physical registers are
+unique, so specifying multiple physical registers as alternatives, like
+``{r11}{r12},{r11}{r12}``, will assign r11 to both operands, not at all what was
+intended.)
+
+Supported Constraint Code List
+""""""""""""""""""""""""""""""
+
+The constraint codes are, in general, expected to behave the same way they do in
+GCC. LLVM's support is often implemented on an 'as-needed' basis, to support C
+inline asm code which was supported by GCC. A mismatch in behavior between LLVM
+and GCC likely indicates a bug in LLVM.
+
+Some constraint codes are typically supported by all targets:
+
+- ``r``: A register in the target's general purpose register class.
+- ``m``: A memory address operand. It is target-specific what addressing modes
+ are supported, typical examples are register, or register + register offset,
+ or register + immediate offset (of some target-specific size).
+- ``i``: An integer constant (of target-specific width). Allows either a simple
+ immediate, or a relocatable value.
+- ``n``: An integer constant -- *not* including relocatable values.
+- ``s``: An integer constant, but allowing *only* relocatable values.
+- ``X``: Allows an operand of any kind, no constraint whatsoever. Typically
+ useful to pass a label for an asm branch or call.
+
+ .. FIXME: but that surely isn't actually okay to jump out of an asm
+ block without telling llvm about the control transfer???)
+
+- ``{register-name}``: Requires exactly the named physical register.
+
+Other constraints are target-specific:
+
+AArch64:
+
+- ``z``: An immediate integer 0. Outputs ``WZR`` or ``XZR``, as appropriate.
+- ``I``: An immediate integer valid for an ``ADD`` or ``SUB`` instruction,
+ i.e. 0 to 4095 with optional shift by 12.
+- ``J``: An immediate integer that, when negated, is valid for an ``ADD`` or
+ ``SUB`` instruction, i.e. -1 to -4095 with optional left shift by 12.
+- ``K``: An immediate integer that is valid for the 'bitmask immediate 32' of a
+ logical instruction like ``AND``, ``EOR``, or ``ORR`` with a 32-bit register.
+- ``L``: An immediate integer that is valid for the 'bitmask immediate 64' of a
+ logical instruction like ``AND``, ``EOR``, or ``ORR`` with a 64-bit register.
+- ``M``: An immediate integer for use with the ``MOV`` assembly alias on a
+ 32-bit register. This is a superset of ``K``: in addition to the bitmask
+ immediate, also allows immediate integers which can be loaded with a single
+ ``MOVZ`` or ``MOVL`` instruction.
+- ``N``: An immediate integer for use with the ``MOV`` assembly alias on a
+ 64-bit register. This is a superset of ``L``.
+- ``Q``: Memory address operand must be in a single register (no
+ offsets). (However, LLVM currently does this for the ``m`` constraint as
+ well.)
+- ``r``: A 32 or 64-bit integer register (W* or X*).
+- ``w``: A 32, 64, or 128-bit floating-point/SIMD register.
+- ``x``: A lower 128-bit floating-point/SIMD register (``V0`` to ``V15``).
+
+AMDGPU:
+
+- ``r``: A 32 or 64-bit integer register.
+- ``[0-9]v``: The 32-bit VGPR register, number 0-9.
+- ``[0-9]s``: The 32-bit SGPR register, number 0-9.
+
+
+All ARM modes:
+
+- ``Q``, ``Um``, ``Un``, ``Uq``, ``Us``, ``Ut``, ``Uv``, ``Uy``: Memory address
+ operand. Treated the same as operand ``m``, at the moment.
+
+ARM and ARM's Thumb2 mode:
+
+- ``j``: An immediate integer between 0 and 65535 (valid for ``MOVW``)
+- ``I``: An immediate integer valid for a data-processing instruction.
+- ``J``: An immediate integer between -4095 and 4095.
+- ``K``: An immediate integer whose bitwise inverse is valid for a
+ data-processing instruction. (Can be used with template modifier "``B``" to
+ print the inverted value).
+- ``L``: An immediate integer whose negation is valid for a data-processing
+ instruction. (Can be used with template modifier "``n``" to print the negated
+ value).
+- ``M``: A power of two or a integer between 0 and 32.
+- ``N``: Invalid immediate constraint.
+- ``O``: Invalid immediate constraint.
+- ``r``: A general-purpose 32-bit integer register (``r0-r15``).
+- ``l``: In Thumb2 mode, low 32-bit GPR registers (``r0-r7``). In ARM mode, same
+ as ``r``.
+- ``h``: In Thumb2 mode, a high 32-bit GPR register (``r8-r15``). In ARM mode,
+ invalid.
+- ``w``: A 32, 64, or 128-bit floating-point/SIMD register: ``s0-s31``,
+ ``d0-d31``, or ``q0-q15``.
+- ``x``: A 32, 64, or 128-bit floating-point/SIMD register: ``s0-s15``,
+ ``d0-d7``, or ``q0-q3``.
+- ``t``: A floating-point/SIMD register, only supports 32-bit values:
+ ``s0-s31``.
+
+ARM's Thumb1 mode:
+
+- ``I``: An immediate integer between 0 and 255.
+- ``J``: An immediate integer between -255 and -1.
+- ``K``: An immediate integer between 0 and 255, with optional left-shift by
+ some amount.
+- ``L``: An immediate integer between -7 and 7.
+- ``M``: An immediate integer which is a multiple of 4 between 0 and 1020.
+- ``N``: An immediate integer between 0 and 31.
+- ``O``: An immediate integer which is a multiple of 4 between -508 and 508.
+- ``r``: A low 32-bit GPR register (``r0-r7``).
+- ``l``: A low 32-bit GPR register (``r0-r7``).
+- ``h``: A high GPR register (``r0-r7``).
+- ``w``: A 32, 64, or 128-bit floating-point/SIMD register: ``s0-s31``,
+ ``d0-d31``, or ``q0-q15``.
+- ``x``: A 32, 64, or 128-bit floating-point/SIMD register: ``s0-s15``,
+ ``d0-d7``, or ``q0-q3``.
+- ``t``: A floating-point/SIMD register, only supports 32-bit values:
+ ``s0-s31``.
+
+
+Hexagon:
+
+- ``o``, ``v``: A memory address operand, treated the same as constraint ``m``,
+ at the moment.
+- ``r``: A 32 or 64-bit register.
+
+MSP430:
+
+- ``r``: An 8 or 16-bit register.
+
+MIPS:
+
+- ``I``: An immediate signed 16-bit integer.
+- ``J``: An immediate integer zero.
+- ``K``: An immediate unsigned 16-bit integer.
+- ``L``: An immediate 32-bit integer, where the lower 16 bits are 0.
+- ``N``: An immediate integer between -65535 and -1.
+- ``O``: An immediate signed 15-bit integer.
+- ``P``: An immediate integer between 1 and 65535.
+- ``m``: A memory address operand. In MIPS-SE mode, allows a base address
+ register plus 16-bit immediate offset. In MIPS mode, just a base register.
+- ``R``: A memory address operand. In MIPS-SE mode, allows a base address
+ register plus a 9-bit signed offset. In MIPS mode, the same as constraint
+ ``m``.
+- ``ZC``: A memory address operand, suitable for use in a ``pref``, ``ll``, or
+ ``sc`` instruction on the given subtarget (details vary).
+- ``r``, ``d``, ``y``: A 32 or 64-bit GPR register.
+- ``f``: A 32 or 64-bit FPU register (``F0-F31``), or a 128-bit MSA register
+ (``W0-W31``). In the case of MSA registers, it is recommended to use the ``w``
+ argument modifier for compatibility with GCC.
+- ``c``: A 32-bit or 64-bit GPR register suitable for indirect jump (always
+ ``25``).
+- ``l``: The ``lo`` register, 32 or 64-bit.
+- ``x``: Invalid.
+
+NVPTX:
+
+- ``b``: A 1-bit integer register.
+- ``c`` or ``h``: A 16-bit integer register.
+- ``r``: A 32-bit integer register.
+- ``l`` or ``N``: A 64-bit integer register.
+- ``f``: A 32-bit float register.
+- ``d``: A 64-bit float register.
+
+
+PowerPC:
+
+- ``I``: An immediate signed 16-bit integer.
+- ``J``: An immediate unsigned 16-bit integer, shifted left 16 bits.
+- ``K``: An immediate unsigned 16-bit integer.
+- ``L``: An immediate signed 16-bit integer, shifted left 16 bits.
+- ``M``: An immediate integer greater than 31.
+- ``N``: An immediate integer that is an exact power of 2.
+- ``O``: The immediate integer constant 0.
+- ``P``: An immediate integer constant whose negation is a signed 16-bit
+ constant.
+- ``es``, ``o``, ``Q``, ``Z``, ``Zy``: A memory address operand, currently
+ treated the same as ``m``.
+- ``r``: A 32 or 64-bit integer register.
+- ``b``: A 32 or 64-bit integer register, excluding ``R0`` (that is:
+ ``R1-R31``).
+- ``f``: A 32 or 64-bit float register (``F0-F31``), or when QPX is enabled, a
+ 128 or 256-bit QPX register (``Q0-Q31``; aliases the ``F`` registers).
+- ``v``: For ``4 x f32`` or ``4 x f64`` types, when QPX is enabled, a
+ 128 or 256-bit QPX register (``Q0-Q31``), otherwise a 128-bit
+ altivec vector register (``V0-V31``).
+
+ .. FIXME: is this a bug that v accepts QPX registers? I think this
+ is supposed to only use the altivec vector registers?
+
+- ``y``: Condition register (``CR0-CR7``).
+- ``wc``: An individual CR bit in a CR register.
+- ``wa``, ``wd``, ``wf``: Any 128-bit VSX vector register, from the full VSX
+ register set (overlapping both the floating-point and vector register files).
+- ``ws``: A 32 or 64-bit floating point register, from the full VSX register
+ set.
+
+Sparc:
+
+- ``I``: An immediate 13-bit signed integer.
+- ``r``: A 32-bit integer register.
+
+SystemZ:
+
+- ``I``: An immediate unsigned 8-bit integer.
+- ``J``: An immediate unsigned 12-bit integer.
+- ``K``: An immediate signed 16-bit integer.
+- ``L``: An immediate signed 20-bit integer.
+- ``M``: An immediate integer 0x7fffffff.
+- ``Q``, ``R``, ``S``, ``T``: A memory address operand, treated the same as
+ ``m``, at the moment.
+- ``r`` or ``d``: A 32, 64, or 128-bit integer register.
+- ``a``: A 32, 64, or 128-bit integer address register (excludes R0, which in an
+ address context evaluates as zero).
+- ``h``: A 32-bit value in the high part of a 64bit data register
+ (LLVM-specific)
+- ``f``: A 32, 64, or 128-bit floating point register.
+
+X86:
+
+- ``I``: An immediate integer between 0 and 31.
+- ``J``: An immediate integer between 0 and 64.
+- ``K``: An immediate signed 8-bit integer.
+- ``L``: An immediate integer, 0xff or 0xffff or (in 64-bit mode only)
+ 0xffffffff.
+- ``M``: An immediate integer between 0 and 3.
+- ``N``: An immediate unsigned 8-bit integer.
+- ``O``: An immediate integer between 0 and 127.
+- ``e``: An immediate 32-bit signed integer.
+- ``Z``: An immediate 32-bit unsigned integer.
+- ``o``, ``v``: Treated the same as ``m``, at the moment.
+- ``q``: An 8, 16, 32, or 64-bit register which can be accessed as an 8-bit
+ ``l`` integer register. On X86-32, this is the ``a``, ``b``, ``c``, and ``d``
+ registers, and on X86-64, it is all of the integer registers.
+- ``Q``: An 8, 16, 32, or 64-bit register which can be accessed as an 8-bit
+ ``h`` integer register. This is the ``a``, ``b``, ``c``, and ``d`` registers.
+- ``r`` or ``l``: An 8, 16, 32, or 64-bit integer register.
+- ``R``: An 8, 16, 32, or 64-bit "legacy" integer register -- one which has
+ existed since i386, and can be accessed without the REX prefix.
+- ``f``: A 32, 64, or 80-bit '387 FPU stack pseudo-register.
+- ``y``: A 64-bit MMX register, if MMX is enabled.
+- ``x``: If SSE is enabled: a 32 or 64-bit scalar operand, or 128-bit vector
+ operand in a SSE register. If AVX is also enabled, can also be a 256-bit
+ vector operand in an AVX register. If AVX-512 is also enabled, can also be a
+ 512-bit vector operand in an AVX512 register, Otherwise, an error.
+- ``Y``: The same as ``x``, if *SSE2* is enabled, otherwise an error.
+- ``A``: Special case: allocates EAX first, then EDX, for a single operand (in
+ 32-bit mode, a 64-bit integer operand will get split into two registers). It
+ is not recommended to use this constraint, as in 64-bit mode, the 64-bit
+ operand will get allocated only to RAX -- if two 32-bit operands are needed,
+ you're better off splitting it yourself, before passing it to the asm
+ statement.
+
+XCore:
+
+- ``r``: A 32-bit integer register.
+
+
+.. _inline-asm-modifiers:
+
+Asm template argument modifiers
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+In the asm template string, modifiers can be used on the operand reference, like
+"``${0:n}``".
+
+The modifiers are, in general, expected to behave the same way they do in
+GCC. LLVM's support is often implemented on an 'as-needed' basis, to support C
+inline asm code which was supported by GCC. A mismatch in behavior between LLVM
+and GCC likely indicates a bug in LLVM.
+
+Target-independent:
+
+- ``c``: Print an immediate integer constant unadorned, without
+ the target-specific immediate punctuation (e.g. no ``$`` prefix).
+- ``n``: Negate and print immediate integer constant unadorned, without the
+ target-specific immediate punctuation (e.g. no ``$`` prefix).
+- ``l``: Print as an unadorned label, without the target-specific label
+ punctuation (e.g. no ``$`` prefix).
+
+AArch64:
+
+- ``w``: Print a GPR register with a ``w*`` name instead of ``x*`` name. E.g.,
+ instead of ``x30``, print ``w30``.
+- ``x``: Print a GPR register with a ``x*`` name. (this is the default, anyhow).
+- ``b``, ``h``, ``s``, ``d``, ``q``: Print a floating-point/SIMD register with a
+ ``b*``, ``h*``, ``s*``, ``d*``, or ``q*`` name, rather than the default of
+ ``v*``.
+
+AMDGPU:
+
+- ``r``: No effect.
+
+ARM:
+
+- ``a``: Print an operand as an address (with ``[`` and ``]`` surrounding a
+ register).
+- ``P``: No effect.
+- ``q``: No effect.
+- ``y``: Print a VFP single-precision register as an indexed double (e.g. print
+ as ``d4[1]`` instead of ``s9``)
+- ``B``: Bitwise invert and print an immediate integer constant without ``#``
+ prefix.
+- ``L``: Print the low 16-bits of an immediate integer constant.
+- ``M``: Print as a register set suitable for ldm/stm. Also prints *all*
+ register operands subsequent to the specified one (!), so use carefully.
+- ``Q``: Print the low-order register of a register-pair, or the low-order
+ register of a two-register operand.
+- ``R``: Print the high-order register of a register-pair, or the high-order
+ register of a two-register operand.
+- ``H``: Print the second register of a register-pair. (On a big-endian system,
+ ``H`` is equivalent to ``Q``, and on little-endian system, ``H`` is equivalent
+ to ``R``.)
+
+ .. FIXME: H doesn't currently support printing the second register
+ of a two-register operand.
+
+- ``e``: Print the low doubleword register of a NEON quad register.
+- ``f``: Print the high doubleword register of a NEON quad register.
+- ``m``: Print the base register of a memory operand without the ``[`` and ``]``
+ adornment.
+
+Hexagon:
+
+- ``L``: Print the second register of a two-register operand. Requires that it
+ has been allocated consecutively to the first.
+
+ .. FIXME: why is it restricted to consecutive ones? And there's
+ nothing that ensures that happens, is there?
+
+- ``I``: Print the letter 'i' if the operand is an integer constant, otherwise
+ nothing. Used to print 'addi' vs 'add' instructions.
+
+MSP430:
+
+No additional modifiers.
+
+MIPS:
+
+- ``X``: Print an immediate integer as hexadecimal
+- ``x``: Print the low 16 bits of an immediate integer as hexadecimal.
+- ``d``: Print an immediate integer as decimal.
+- ``m``: Subtract one and print an immediate integer as decimal.
+- ``z``: Print $0 if an immediate zero, otherwise print normally.
+- ``L``: Print the low-order register of a two-register operand, or prints the
+ address of the low-order word of a double-word memory operand.
+
+ .. FIXME: L seems to be missing memory operand support.
+
+- ``M``: Print the high-order register of a two-register operand, or prints the
+ address of the high-order word of a double-word memory operand.
+
+ .. FIXME: M seems to be missing memory operand support.
+
+- ``D``: Print the second register of a two-register operand, or prints the
+ second word of a double-word memory operand. (On a big-endian system, ``D`` is
+ equivalent to ``L``, and on little-endian system, ``D`` is equivalent to
+ ``M``.)
+- ``w``: No effect. Provided for compatibility with GCC which requires this
+ modifier in order to print MSA registers (``W0-W31``) with the ``f``
+ constraint.
+
+NVPTX:
+
+- ``r``: No effect.
+
+PowerPC:
+
+- ``L``: Print the second register of a two-register operand. Requires that it
+ has been allocated consecutively to the first.
+
+ .. FIXME: why is it restricted to consecutive ones? And there's
+ nothing that ensures that happens, is there?
+
+- ``I``: Print the letter 'i' if the operand is an integer constant, otherwise
+ nothing. Used to print 'addi' vs 'add' instructions.
+- ``y``: For a memory operand, prints formatter for a two-register X-form
+ instruction. (Currently always prints ``r0,OPERAND``).
+- ``U``: Prints 'u' if the memory operand is an update form, and nothing
+ otherwise. (NOTE: LLVM does not support update form, so this will currently
+ always print nothing)
+- ``X``: Prints 'x' if the memory operand is an indexed form. (NOTE: LLVM does
+ not support indexed form, so this will currently always print nothing)
+
+Sparc:
+
+- ``r``: No effect.
+
+SystemZ:
+
+SystemZ implements only ``n``, and does *not* support any of the other
+target-independent modifiers.
+
+X86:
+
+- ``c``: Print an unadorned integer or symbol name. (The latter is
+ target-specific behavior for this typically target-independent modifier).
+- ``A``: Print a register name with a '``*``' before it.
+- ``b``: Print an 8-bit register name (e.g. ``al``); do nothing on a memory
+ operand.
+- ``h``: Print the upper 8-bit register name (e.g. ``ah``); do nothing on a
+ memory operand.
+- ``w``: Print the 16-bit register name (e.g. ``ax``); do nothing on a memory
+ operand.
+- ``k``: Print the 32-bit register name (e.g. ``eax``); do nothing on a memory
+ operand.
+- ``q``: Print the 64-bit register name (e.g. ``rax``), if 64-bit registers are
+ available, otherwise the 32-bit register name; do nothing on a memory operand.
+- ``n``: Negate and print an unadorned integer, or, for operands other than an
+ immediate integer (e.g. a relocatable symbol expression), print a '-' before
+ the operand. (The behavior for relocatable symbol expressions is a
+ target-specific behavior for this typically target-independent modifier)
+- ``H``: Print a memory reference with additional offset +8.
+- ``P``: Print a memory reference or operand for use as the argument of a call
+ instruction. (E.g. omit ``(rip)``, even though it's PC-relative.)
+
+XCore:
+
+No additional modifiers.
+
+
Inline Asm Metadata
^^^^^^^^^^^^^^^^^^^
.. _metadata:
-Metadata Nodes and Metadata Strings
------------------------------------
+Metadata
+========
LLVM IR allows metadata to be attached to instructions in the program
that can convey extra information about the code to the optimizers and
code generator. One example application of metadata is source-level
debug information. There are two metadata primitives: strings and nodes.
-All metadata has the ``metadata`` type and is identified in syntax by a
-preceding exclamation point ('``!``').
+
+Metadata does not have a type, and is not a value. If referenced from a
+``call`` instruction, it uses the ``metadata`` type.
+
+All metadata are identified in syntax by a exclamation point ('``!``').
+
+.. _metadata-string:
+
+Metadata Nodes and Metadata Strings
+-----------------------------------
A metadata string is a string surrounded by double quotes. It can
contain any character by escaping non-printable characters with
.. code-block:: llvm
- !{ metadata !"test\00", i32 10}
+ !{ !"test\00", i32 10}
+
+Metadata nodes that aren't uniqued use the ``distinct`` keyword. For example:
+
+.. code-block:: llvm
+
+ !0 = distinct !{!"test\00", i32 10}
+
+``distinct`` nodes are useful when nodes shouldn't be merged based on their
+content. They can also occur when transformations cause uniquing collisions
+when metadata operands change.
A :ref:`named metadata <namedmetadatastructure>` is a collection of
metadata nodes, which can be looked up in the module symbol table. For
.. code-block:: llvm
- !foo = metadata !{!4, !3}
+ !foo = !{!4, !3}
Metadata can be used as function arguments. Here ``llvm.dbg.value``
function is using two metadata arguments:
More information about specific metadata nodes recognized by the
optimizers and code generator is found below.
-'``tbaa``' Metadata
-^^^^^^^^^^^^^^^^^^^
+.. _specialized-metadata:
-In LLVM IR, memory does not have types, so LLVM's own type system is not
-suitable for doing TBAA. Instead, metadata is added to the IR to
-describe a type system of a higher level language. This can be used to
-implement typical C/C++ TBAA, but it can also be used to implement
-custom alias analysis behavior for other languages.
+Specialized Metadata Nodes
+^^^^^^^^^^^^^^^^^^^^^^^^^^
-The current metadata format is very simple. TBAA metadata nodes have up
-to three fields, e.g.:
+Specialized metadata nodes are custom data structures in metadata (as opposed
+to generic tuples). Their fields are labelled, and can be specified in any
+order.
-.. code-block:: llvm
+These aren't inherently debug info centric, but currently all the specialized
+metadata nodes are related to debug info.
- !0 = metadata !{ metadata !"an example type tree" }
- !1 = metadata !{ metadata !"int", metadata !0 }
- !2 = metadata !{ metadata !"float", metadata !0 }
- !3 = metadata !{ metadata !"const float", metadata !2, i64 1 }
+.. _DICompileUnit:
-The first field is an identity field. It can be any value, usually a
-metadata string, which uniquely identifies the type. The most important
-name in the tree is the name of the root node. Two trees with different
-root node names are entirely disjoint, even if they have leaves with
-common names.
+DICompileUnit
+"""""""""""""
-The second field identifies the type's parent node in the tree, or is
-null or omitted for a root node. A type is considered to alias all of
-its descendants and all of its ancestors in the tree. Also, a type is
-considered to alias all types in other trees, so that bitcode produced
-from multiple front-ends is handled conservatively.
+``DICompileUnit`` nodes represent a compile unit. The ``enums:``,
+``retainedTypes:``, ``subprograms:``, ``globals:`` and ``imports:`` fields are
+tuples containing the debug info to be emitted along with the compile unit,
+regardless of code optimizations (some nodes are only emitted if there are
+references to them from instructions).
-If the third field is present, it's an integer which if equal to 1
-indicates that the type is "constant" (meaning
-``pointsToConstantMemory`` should return true; see `other useful
-AliasAnalysis methods <AliasAnalysis.html#OtherItfs>`_).
+.. code-block:: llvm
-'``tbaa.struct``' Metadata
-^^^^^^^^^^^^^^^^^^^^^^^^^^
+ !0 = !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang",
+ isOptimized: true, flags: "-O2", runtimeVersion: 2,
+ splitDebugFilename: "abc.debug", emissionKind: 1,
+ enums: !2, retainedTypes: !3, subprograms: !4,
+ globals: !5, imports: !6)
-The :ref:`llvm.memcpy <int_memcpy>` is often used to implement
-aggregate assignment operations in C and similar languages, however it
-is defined to copy a contiguous region of memory, which is more than
-strictly necessary for aggregate types which contain holes due to
-padding. Also, it doesn't contain any TBAA information about the fields
-of the aggregate.
+Compile unit descriptors provide the root scope for objects declared in a
+specific compilation unit. File descriptors are defined using this scope.
+These descriptors are collected by a named metadata ``!llvm.dbg.cu``. They
+keep track of subprograms, global variables, type information, and imported
+entities (declarations and namespaces).
-``!tbaa.struct`` metadata can describe which memory subregions in a
-memcpy are padding and what the TBAA tags of the struct are.
+.. _DIFile:
-The current metadata format is very simple. ``!tbaa.struct`` metadata
-nodes are a list of operands which are in conceptual groups of three.
-For each group of three, the first operand gives the byte offset of a
-field in bytes, the second gives its size in bytes, and the third gives
-its tbaa tag. e.g.:
+DIFile
+""""""
+
+``DIFile`` nodes represent files. The ``filename:`` can include slashes.
.. code-block:: llvm
- !4 = metadata !{ i64 0, i64 4, metadata !1, i64 8, i64 4, metadata !2 }
+ !0 = !DIFile(filename: "path/to/file", directory: "/path/to/dir")
-This describes a struct with two fields. The first is at offset 0 bytes
-with size 4 bytes, and has tbaa tag !1. The second is at offset 8 bytes
-and has size 4 bytes and has tbaa tag !2.
+Files are sometimes used in ``scope:`` fields, and are the only valid target
+for ``file:`` fields.
-Note that the fields need not be contiguous. In this example, there is a
-4 byte gap between the two fields. This gap represents padding which
-does not carry useful data and need not be preserved.
+.. _DIBasicType:
-'``noalias``' and '``alias.scope``' Metadata
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+DIBasicType
+"""""""""""
-``noalias`` and ``alias.scope`` metadata provide the ability to specify generic
-noalias memory-access sets. This means that some collection of memory access
-instructions (loads, stores, memory-accessing calls, etc.) that carry
-``noalias`` metadata can specifically be specified not to alias with some other
-collection of memory access instructions that carry ``alias.scope`` metadata.
-Each type of metadata specifies a list of scopes where each scope has an id and
-a domain. When evaluating an aliasing query, if for some some domain, the set
-of scopes with that domain in one instruction's ``alias.scope`` list is a
-subset of (or qual to) the set of scopes for that domain in another
-instruction's ``noalias`` list, then the two memory accesses are assumed not to
-alias.
+``DIBasicType`` nodes represent primitive types, such as ``int``, ``bool`` and
+``float``. ``tag:`` defaults to ``DW_TAG_base_type``.
-The metadata identifying each domain is itself a list containing one or two
-entries. The first entry is the name of the domain. Note that if the name is a
-string then it can be combined accross functions and translation units. A
-self-reference can be used to create globally unique domain names. A
-descriptive string may optionally be provided as a second list entry.
+.. code-block:: llvm
-The metadata identifying each scope is also itself a list containing two or
-three entries. The first entry is the name of the scope. Note that if the name
-is a string then it can be combined accross functions and translation units. A
-self-reference can be used to create globally unique scope names. A metadata
-reference to the scope's domain is the second entry. A descriptive string may
-optionally be provided as a third list entry.
+ !0 = !DIBasicType(name: "unsigned char", size: 8, align: 8,
+ encoding: DW_ATE_unsigned_char)
+ !1 = !DIBasicType(tag: DW_TAG_unspecified_type, name: "decltype(nullptr)")
-For example,
+The ``encoding:`` describes the details of the type. Usually it's one of the
+following:
.. code-block:: llvm
- ; Two scope domains:
- !0 = metadata !{metadata !0}
- !1 = metadata !{metadata !1}
-
- ; Some scopes in these domains:
- !2 = metadata !{metadata !2, metadata !0}
- !3 = metadata !{metadata !3, metadata !0}
- !4 = metadata !{metadata !4, metadata !1}
+ DW_ATE_address = 1
+ DW_ATE_boolean = 2
+ DW_ATE_float = 4
+ DW_ATE_signed = 5
+ DW_ATE_signed_char = 6
+ DW_ATE_unsigned = 7
+ DW_ATE_unsigned_char = 8
- ; Some scope lists:
- !5 = metadata !{metadata !4} ; A list containing only scope !4
- !6 = metadata !{metadata !4, metadata !3, metadata !2}
- !7 = metadata !{metadata !3}
+.. _DISubroutineType:
- ; These two instructions don't alias:
- %0 = load float* %c, align 4, !alias.scope !5
- store float %0, float* %arrayidx.i, align 4, !noalias !5
+DISubroutineType
+""""""""""""""""
- ; These two instructions also don't alias (for domain !1, the set of scopes
- ; in the !alias.scope equals that in the !noalias list):
- %2 = load float* %c, align 4, !alias.scope !5
- store float %2, float* %arrayidx.i2, align 4, !noalias !6
+``DISubroutineType`` nodes represent subroutine types. Their ``types:`` field
+refers to a tuple; the first operand is the return type, while the rest are the
+types of the formal arguments in order. If the first operand is ``null``, that
+represents a function with no return value (such as ``void foo() {}`` in C++).
- ; These two instructions don't alias (for domain !0, the set of scopes in
- ; the !noalias list is not a superset of, or equal to, the scopes in the
- ; !alias.scope list):
- %2 = load float* %c, align 4, !alias.scope !6
- store float %0, float* %arrayidx.i, align 4, !noalias !7
+.. code-block:: llvm
-'``fpmath``' Metadata
-^^^^^^^^^^^^^^^^^^^^^
+ !0 = !BasicType(name: "int", size: 32, align: 32, DW_ATE_signed)
+ !1 = !BasicType(name: "char", size: 8, align: 8, DW_ATE_signed_char)
+ !2 = !DISubroutineType(types: !{null, !0, !1}) ; void (int, char)
-``fpmath`` metadata may be attached to any instruction of floating point
-type. It can be used to express the maximum acceptable error in the
-result of that instruction, in ULPs, thus potentially allowing the
-compiler to use a more efficient but less accurate method of computing
-it. ULP is defined as follows:
+.. _DIDerivedType:
- If ``x`` is a real number that lies between two finite consecutive
- floating-point numbers ``a`` and ``b``, without being equal to one
- of them, then ``ulp(x) = |b - a|``, otherwise ``ulp(x)`` is the
- distance between the two non-equal finite floating-point numbers
- nearest ``x``. Moreover, ``ulp(NaN)`` is ``NaN``.
+DIDerivedType
+"""""""""""""
-The metadata node shall consist of a single positive floating point
-number representing the maximum relative error, for example:
+``DIDerivedType`` nodes represent types derived from other types, such as
+qualified types.
.. code-block:: llvm
- !0 = metadata !{ float 2.5 } ; maximum acceptable inaccuracy is 2.5 ULPs
+ !0 = !DIBasicType(name: "unsigned char", size: 8, align: 8,
+ encoding: DW_ATE_unsigned_char)
+ !1 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !0, size: 32,
+ align: 32)
-'``range``' Metadata
-^^^^^^^^^^^^^^^^^^^^
+The following ``tag:`` values are valid:
-``range`` metadata may be attached only to ``load``, ``call`` and ``invoke`` of
-integer types. It expresses the possible ranges the loaded value or the value
-returned by the called function at this call site is in. The ranges are
-represented with a flattened list of integers. The loaded value or the value
-returned is known to be in the union of the ranges defined by each consecutive
-pair. Each pair has the following properties:
+.. code-block:: llvm
-- The type must match the type loaded by the instruction.
-- The pair ``a,b`` represents the range ``[a,b)``.
-- Both ``a`` and ``b`` are constants.
-- The range is allowed to wrap.
-- The range should not represent the full or empty set. That is,
- ``a!=b``.
+ DW_TAG_formal_parameter = 5
+ DW_TAG_member = 13
+ DW_TAG_pointer_type = 15
+ DW_TAG_reference_type = 16
+ DW_TAG_typedef = 22
+ DW_TAG_ptr_to_member_type = 31
+ DW_TAG_const_type = 38
+ DW_TAG_volatile_type = 53
+ DW_TAG_restrict_type = 55
-In addition, the pairs must be in signed order of the lower bound and
-they must be non-contiguous.
+``DW_TAG_member`` is used to define a member of a :ref:`composite type
+<DICompositeType>` or :ref:`subprogram <DISubprogram>`. The type of the member
+is the ``baseType:``. The ``offset:`` is the member's bit offset.
+``DW_TAG_formal_parameter`` is used to define a member which is a formal
+argument of a subprogram.
-Examples:
+``DW_TAG_typedef`` is used to provide a name for the ``baseType:``.
-.. code-block:: llvm
+``DW_TAG_pointer_type``, ``DW_TAG_reference_type``, ``DW_TAG_const_type``,
+``DW_TAG_volatile_type`` and ``DW_TAG_restrict_type`` are used to qualify the
+``baseType:``.
- %a = load i8* %x, align 1, !range !0 ; Can only be 0 or 1
- %b = load i8* %y, align 1, !range !1 ; Can only be 255 (-1), 0 or 1
- %c = call i8 @foo(), !range !2 ; Can only be 0, 1, 3, 4 or 5
- %d = invoke i8 @bar() to label %cont
- unwind label %lpad, !range !3 ; Can only be -2, -1, 3, 4 or 5
- ...
- !0 = metadata !{ i8 0, i8 2 }
- !1 = metadata !{ i8 255, i8 2 }
- !2 = metadata !{ i8 0, i8 2, i8 3, i8 6 }
- !3 = metadata !{ i8 -2, i8 0, i8 3, i8 6 }
+Note that the ``void *`` type is expressed as a type derived from NULL.
-'``llvm.loop``'
-^^^^^^^^^^^^^^^
+.. _DICompositeType:
-It is sometimes useful to attach information to loop constructs. Currently,
-loop metadata is implemented as metadata attached to the branch instruction
-in the loop latch block. This type of metadata refer to a metadata node that is
-guaranteed to be separate for each loop. The loop identifier metadata is
-specified with the name ``llvm.loop``.
+DICompositeType
+"""""""""""""""
-The loop identifier metadata is implemented using a metadata that refers to
-itself to avoid merging it with any other identifier metadata, e.g.,
-during module linkage or function inlining. That is, each loop should refer
-to their own identification metadata even if they reside in separate functions.
-The following example contains loop identifier metadata for two separate loop
-constructs:
+``DICompositeType`` nodes represent types composed of other types, like
+structures and unions. ``elements:`` points to a tuple of the composed types.
+
+If the source language supports ODR, the ``identifier:`` field gives the unique
+identifier used for type merging between modules. When specified, other types
+can refer to composite types indirectly via a :ref:`metadata string
+<metadata-string>` that matches their identifier.
.. code-block:: llvm
- !0 = metadata !{ metadata !0 }
- !1 = metadata !{ metadata !1 }
+ !0 = !DIEnumerator(name: "SixKind", value: 7)
+ !1 = !DIEnumerator(name: "SevenKind", value: 7)
+ !2 = !DIEnumerator(name: "NegEightKind", value: -8)
+ !3 = !DICompositeType(tag: DW_TAG_enumeration_type, name: "Enum", file: !12,
+ line: 2, size: 32, align: 32, identifier: "_M4Enum",
+ elements: !{!0, !1, !2})
-The loop identifier metadata can be used to specify additional
-per-loop metadata. Any operands after the first operand can be treated
-as user-defined metadata. For example the ``llvm.loop.unroll.count``
-suggests an unroll factor to the loop unroller:
+The following ``tag:`` values are valid:
.. code-block:: llvm
- br i1 %exitcond, label %._crit_edge, label %.lr.ph, !llvm.loop !0
- ...
- !0 = metadata !{ metadata !0, metadata !1 }
- !1 = metadata !{ metadata !"llvm.loop.unroll.count", i32 4 }
+ DW_TAG_array_type = 1
+ DW_TAG_class_type = 2
+ DW_TAG_enumeration_type = 4
+ DW_TAG_structure_type = 19
+ DW_TAG_union_type = 23
+ DW_TAG_subroutine_type = 21
+ DW_TAG_inheritance = 28
-'``llvm.loop.vectorize``' and '``llvm.loop.interleave``'
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-Metadata prefixed with ``llvm.loop.vectorize`` or ``llvm.loop.interleave`` are
-used to control per-loop vectorization and interleaving parameters such as
-vectorization width and interleave count. These metadata should be used in
-conjunction with ``llvm.loop`` loop identification metadata. The
-``llvm.loop.vectorize`` and ``llvm.loop.interleave`` metadata are only
-optimization hints and the optimizer will only interleave and vectorize loops if
-it believes it is safe to do so. The ``llvm.mem.parallel_loop_access`` metadata
-which contains information about loop-carried memory dependencies can be helpful
-in determining the safety of these transformations.
+For ``DW_TAG_array_type``, the ``elements:`` should be :ref:`subrange
+descriptors <DISubrange>`, each representing the range of subscripts at that
+level of indexing. The ``DIFlagVector`` flag to ``flags:`` indicates that an
+array type is a native packed vector.
-'``llvm.loop.interleave.count``' Metadata
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+For ``DW_TAG_enumeration_type``, the ``elements:`` should be :ref:`enumerator
+descriptors <DIEnumerator>`, each representing the definition of an enumeration
+value for the set. All enumeration type descriptors are collected in the
+``enums:`` field of the :ref:`compile unit <DICompileUnit>`.
-This metadata suggests an interleave count to the loop interleaver.
-The first operand is the string ``llvm.loop.interleave.count`` and the
-second operand is an integer specifying the interleave count. For
-example:
+For ``DW_TAG_structure_type``, ``DW_TAG_class_type``, and
+``DW_TAG_union_type``, the ``elements:`` should be :ref:`derived types
+<DIDerivedType>` with ``tag: DW_TAG_member`` or ``tag: DW_TAG_inheritance``.
+
+.. _DISubrange:
+
+DISubrange
+""""""""""
+
+``DISubrange`` nodes are the elements for ``DW_TAG_array_type`` variants of
+:ref:`DICompositeType`. ``count: -1`` indicates an empty array.
.. code-block:: llvm
- !0 = metadata !{ metadata !"llvm.loop.interleave.count", i32 4 }
+ !0 = !DISubrange(count: 5, lowerBound: 0) ; array counting from 0
+ !1 = !DISubrange(count: 5, lowerBound: 1) ; array counting from 1
+ !2 = !DISubrange(count: -1) ; empty array.
-Note that setting ``llvm.loop.interleave.count`` to 1 disables interleaving
-multiple iterations of the loop. If ``llvm.loop.interleave.count`` is set to 0
-then the interleave count will be determined automatically.
+.. _DIEnumerator:
-'``llvm.loop.vectorize.enable``' Metadata
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+DIEnumerator
+""""""""""""
-This metadata selectively enables or disables vectorization for the loop. The
-first operand is the string ``llvm.loop.vectorize.enable`` and the second operand
-is a bit. If the bit operand value is 1 vectorization is enabled. A value of
-0 disables vectorization:
+``DIEnumerator`` nodes are the elements for ``DW_TAG_enumeration_type``
+variants of :ref:`DICompositeType`.
.. code-block:: llvm
- !0 = metadata !{ metadata !"llvm.loop.vectorize.enable", i1 0 }
- !1 = metadata !{ metadata !"llvm.loop.vectorize.enable", i1 1 }
+ !0 = !DIEnumerator(name: "SixKind", value: 7)
+ !1 = !DIEnumerator(name: "SevenKind", value: 7)
+ !2 = !DIEnumerator(name: "NegEightKind", value: -8)
-'``llvm.loop.vectorize.width``' Metadata
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+DITemplateTypeParameter
+"""""""""""""""""""""""
-This metadata sets the target width of the vectorizer. The first
-operand is the string ``llvm.loop.vectorize.width`` and the second
-operand is an integer specifying the width. For example:
+``DITemplateTypeParameter`` nodes represent type parameters to generic source
+language constructs. They are used (optionally) in :ref:`DICompositeType` and
+:ref:`DISubprogram` ``templateParams:`` fields.
.. code-block:: llvm
- !0 = metadata !{ metadata !"llvm.loop.vectorize.width", i32 4 }
+ !0 = !DITemplateTypeParameter(name: "Ty", type: !1)
-Note that setting ``llvm.loop.vectorize.width`` to 1 disables
-vectorization of the loop. If ``llvm.loop.vectorize.width`` is set to
-0 or if the loop does not have this metadata the width will be
-determined automatically.
+DITemplateValueParameter
+""""""""""""""""""""""""
-'``llvm.loop.unroll``'
-^^^^^^^^^^^^^^^^^^^^^^
+``DITemplateValueParameter`` nodes represent value parameters to generic source
+language constructs. ``tag:`` defaults to ``DW_TAG_template_value_parameter``,
+but if specified can also be set to ``DW_TAG_GNU_template_template_param`` or
+``DW_TAG_GNU_template_param_pack``. They are used (optionally) in
+:ref:`DICompositeType` and :ref:`DISubprogram` ``templateParams:`` fields.
-Metadata prefixed with ``llvm.loop.unroll`` are loop unrolling
-optimization hints such as the unroll factor. ``llvm.loop.unroll``
-metadata should be used in conjunction with ``llvm.loop`` loop
-identification metadata. The ``llvm.loop.unroll`` metadata are only
-optimization hints and the unrolling will only be performed if the
-optimizer believes it is safe to do so.
+.. code-block:: llvm
-'``llvm.loop.unroll.count``' Metadata
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+ !0 = !DITemplateValueParameter(name: "Ty", type: !1, value: i32 7)
-This metadata suggests an unroll factor to the loop unroller. The
-first operand is the string ``llvm.loop.unroll.count`` and the second
-operand is a positive integer specifying the unroll factor. For
-example:
+DINamespace
+"""""""""""
-.. code-block:: llvm
+``DINamespace`` nodes represent namespaces in the source language.
- !0 = metadata !{ metadata !"llvm.loop.unroll.count", i32 4 }
+.. code-block:: llvm
-If the trip count of the loop is less than the unroll count the loop
-will be partially unrolled.
+ !0 = !DINamespace(name: "myawesomeproject", scope: !1, file: !2, line: 7)
-'``llvm.loop.unroll.disable``' Metadata
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+DIGlobalVariable
+""""""""""""""""
-This metadata either disables loop unrolling. The metadata has a single operand
-which is the string ``llvm.loop.unroll.disable``. For example:
+``DIGlobalVariable`` nodes represent global variables in the source language.
.. code-block:: llvm
- !0 = metadata !{ metadata !"llvm.loop.unroll.disable" }
+ !0 = !DIGlobalVariable(name: "foo", linkageName: "foo", scope: !1,
+ file: !2, line: 7, type: !3, isLocal: true,
+ isDefinition: false, variable: i32* @foo,
+ declaration: !4)
-'``llvm.loop.unroll.full``' Metadata
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+All global variables should be referenced by the `globals:` field of a
+:ref:`compile unit <DICompileUnit>`.
-This metadata either suggests that the loop should be unrolled fully. The
-metadata has a single operand which is the string ``llvm.loop.unroll.disable``.
-For example:
+.. _DISubprogram:
+
+DISubprogram
+""""""""""""
+
+``DISubprogram`` nodes represent functions from the source language. The
+``variables:`` field points at :ref:`variables <DILocalVariable>` that must be
+retained, even if their IR counterparts are optimized out of the IR. The
+``type:`` field must point at an :ref:`DISubroutineType`.
.. code-block:: llvm
- !0 = metadata !{ metadata !"llvm.loop.unroll.full" }
+ !0 = !DISubprogram(name: "foo", linkageName: "_Zfoov", scope: !1,
+ file: !2, line: 7, type: !3, isLocal: true,
+ isDefinition: false, scopeLine: 8, containingType: !4,
+ virtuality: DW_VIRTUALITY_pure_virtual, virtualIndex: 10,
+ flags: DIFlagPrototyped, isOptimized: true,
+ function: void ()* @_Z3foov,
+ templateParams: !5, declaration: !6, variables: !7)
-'``llvm.mem``'
-^^^^^^^^^^^^^^^
+.. _DILexicalBlock:
-Metadata types used to annotate memory accesses with information helpful
-for optimizations are prefixed with ``llvm.mem``.
+DILexicalBlock
+""""""""""""""
-'``llvm.mem.parallel_loop_access``' Metadata
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+``DILexicalBlock`` nodes describe nested blocks within a :ref:`subprogram
+<DISubprogram>`. The line number and column numbers are used to dinstinguish
+two lexical blocks at same depth. They are valid targets for ``scope:``
+fields.
-The ``llvm.mem.parallel_loop_access`` metadata refers to a loop identifier,
-or metadata containing a list of loop identifiers for nested loops.
-The metadata is attached to memory accessing instructions and denotes that
-no loop carried memory dependence exist between it and other instructions denoted
-with the same loop identifier.
+.. code-block:: llvm
-Precisely, given two instructions ``m1`` and ``m2`` that both have the
-``llvm.mem.parallel_loop_access`` metadata, with ``L1`` and ``L2`` being the
-set of loops associated with that metadata, respectively, then there is no loop
-carried dependence between ``m1`` and ``m2`` for loops in both ``L1`` and
-``L2``.
+ !0 = distinct !DILexicalBlock(scope: !1, file: !2, line: 7, column: 35)
-As a special case, if all memory accessing instructions in a loop have
-``llvm.mem.parallel_loop_access`` metadata that refers to that loop, then the
-loop has no loop carried memory dependences and is considered to be a parallel
-loop.
+Usually lexical blocks are ``distinct`` to prevent node merging based on
+operands.
-Note that if not all memory access instructions have such metadata referring to
-the loop, then the loop is considered not being trivially parallel. Additional
-memory dependence analysis is required to make that determination. As a fail
-safe mechanism, this causes loops that were originally parallel to be considered
-sequential (if optimization passes that are unaware of the parallel semantics
-insert new memory instructions into the loop body).
+.. _DILexicalBlockFile:
-Example of a loop that is considered parallel due to its correct use of
-both ``llvm.loop`` and ``llvm.mem.parallel_loop_access``
-metadata types that refer to the same loop identifier metadata.
+DILexicalBlockFile
+""""""""""""""""""
-.. code-block:: llvm
+``DILexicalBlockFile`` nodes are used to discriminate between sections of a
+:ref:`lexical block <DILexicalBlock>`. The ``file:`` field can be changed to
+indicate textual inclusion, or the ``discriminator:`` field can be used to
+discriminate between control flow within a single block in the source language.
- for.body:
- ...
- %val0 = load i32* %arrayidx, !llvm.mem.parallel_loop_access !0
- ...
- store i32 %val0, i32* %arrayidx1, !llvm.mem.parallel_loop_access !0
- ...
- br i1 %exitcond, label %for.end, label %for.body, !llvm.loop !0
+.. code-block:: llvm
- for.end:
- ...
- !0 = metadata !{ metadata !0 }
+ !0 = !DILexicalBlock(scope: !3, file: !4, line: 7, column: 35)
+ !1 = !DILexicalBlockFile(scope: !0, file: !4, discriminator: 0)
+ !2 = !DILexicalBlockFile(scope: !0, file: !4, discriminator: 1)
-It is also possible to have nested parallel loops. In that case the
-memory accesses refer to a list of loop identifier metadata nodes instead of
-the loop identifier metadata node directly:
+.. _DILocation:
-.. code-block:: llvm
+DILocation
+""""""""""
- outer.for.body:
- ...
- %val1 = load i32* %arrayidx3, !llvm.mem.parallel_loop_access !2
- ...
- br label %inner.for.body
+``DILocation`` nodes represent source debug locations. The ``scope:`` field is
+mandatory, and points at an :ref:`DILexicalBlockFile`, an
+:ref:`DILexicalBlock`, or an :ref:`DISubprogram`.
- inner.for.body:
- ...
- %val0 = load i32* %arrayidx1, !llvm.mem.parallel_loop_access !0
- ...
- store i32 %val0, i32* %arrayidx2, !llvm.mem.parallel_loop_access !0
- ...
- br i1 %exitcond, label %inner.for.end, label %inner.for.body, !llvm.loop !1
+.. code-block:: llvm
- inner.for.end:
- ...
- store i32 %val1, i32* %arrayidx4, !llvm.mem.parallel_loop_access !2
- ...
- br i1 %exitcond, label %outer.for.end, label %outer.for.body, !llvm.loop !2
+ !0 = !DILocation(line: 2900, column: 42, scope: !1, inlinedAt: !2)
- outer.for.end: ; preds = %for.body
- ...
- !0 = metadata !{ metadata !1, metadata !2 } ; a list of loop identifiers
- !1 = metadata !{ metadata !1 } ; an identifier for the inner loop
- !2 = metadata !{ metadata !2 } ; an identifier for the outer loop
+.. _DILocalVariable:
-Module Flags Metadata
-=====================
+DILocalVariable
+"""""""""""""""
-Information about the module as a whole is difficult to convey to LLVM's
-subsystems. The LLVM IR isn't sufficient to transmit this information.
-The ``llvm.module.flags`` named metadata exists in order to facilitate
-this. These flags are in the form of key / value pairs --- much like a
-dictionary --- making it easy for any subsystem who cares about a flag to
-look it up.
+``DILocalVariable`` nodes represent local variables in the source language. If
+the ``arg:`` field is set to non-zero, then this variable is a subprogram
+parameter, and it will be included in the ``variables:`` field of its
+:ref:`DISubprogram`.
-The ``llvm.module.flags`` metadata contains a list of metadata triplets.
-Each triplet has the following form:
+.. code-block:: llvm
-- The first element is a *behavior* flag, which specifies the behavior
- when two (or more) modules are merged together, and it encounters two
- (or more) metadata with the same ID. The supported behaviors are
- described below.
-- The second element is a metadata string that is a unique ID for the
- metadata. Each module may only have one flag entry for each unique ID (not
- including entries with the **Require** behavior).
-- The third element is the value of the flag.
+ !0 = !DILocalVariable(name: "this", arg: 1, scope: !3, file: !2, line: 7,
+ type: !3, flags: DIFlagArtificial)
+ !1 = !DILocalVariable(name: "x", arg: 2, scope: !4, file: !2, line: 7,
+ type: !3)
+ !2 = !DILocalVariable(name: "y", scope: !5, file: !2, line: 7, type: !3)
-When two (or more) modules are merged together, the resulting
-``llvm.module.flags`` metadata is the union of the modules' flags. That is, for
-each unique metadata ID string, there will be exactly one entry in the merged
-modules ``llvm.module.flags`` metadata table, and the value for that entry will
-be determined by the merge behavior flag, as described below. The only exception
-is that entries with the *Require* behavior are always preserved.
+DIExpression
+""""""""""""
-The following behaviors are supported:
+``DIExpression`` nodes represent DWARF expression sequences. They are used in
+:ref:`debug intrinsics<dbg_intrinsics>` (such as ``llvm.dbg.declare``) to
+describe how the referenced LLVM variable relates to the source language
+variable.
-.. list-table::
- :header-rows: 1
- :widths: 10 90
+The current supported vocabulary is limited:
- * - Value
- - Behavior
+- ``DW_OP_deref`` dereferences the working expression.
+- ``DW_OP_plus, 93`` adds ``93`` to the working expression.
+- ``DW_OP_bit_piece, 16, 8`` specifies the offset and size (``16`` and ``8``
+ here, respectively) of the variable piece from the working expression.
- * - 1
- - **Error**
- Emits an error if two values disagree, otherwise the resulting value
- is that of the operands.
+.. code-block:: llvm
- * - 2
- - **Warning**
- Emits a warning if two values disagree. The result value will be the
- operand for the flag from the first module being linked.
+ !0 = !DIExpression(DW_OP_deref)
+ !1 = !DIExpression(DW_OP_plus, 3)
+ !2 = !DIExpression(DW_OP_bit_piece, 3, 7)
+ !3 = !DIExpression(DW_OP_deref, DW_OP_plus, 3, DW_OP_bit_piece, 3, 7)
- * - 3
- - **Require**
- Adds a requirement that another module flag be present and have a
- specified value after linking is performed. The value must be a
- metadata pair, where the first element of the pair is the ID of the
- module flag to be restricted, and the second element of the pair is
- the value the module flag should be restricted to. This behavior can
- be used to restrict the allowable results (via triggering of an
- error) of linking IDs with the **Override** behavior.
+DIObjCProperty
+""""""""""""""
- * - 4
- - **Override**
- Uses the specified value, regardless of the behavior or value of the
- other module. If both modules specify **Override**, but the values
- differ, an error will be emitted.
+``DIObjCProperty`` nodes represent Objective-C property nodes.
- * - 5
- - **Append**
- Appends the two values, which are required to be metadata nodes.
+.. code-block:: llvm
- * - 6
- - **AppendUnique**
- Appends the two values, which are required to be metadata
- nodes. However, duplicate entries in the second list are dropped
- during the append operation.
+ !3 = !DIObjCProperty(name: "foo", file: !1, line: 7, setter: "setFoo",
+ getter: "getFoo", attributes: 7, type: !2)
-It is an error for a particular unique flag ID to have multiple behaviors,
-except in the case of **Require** (which adds restrictions on another metadata
-value) or **Override**.
+DIImportedEntity
+""""""""""""""""
-An example of module flags:
+``DIImportedEntity`` nodes represent entities (such as modules) imported into a
+compile unit.
.. code-block:: llvm
- !0 = metadata !{ i32 1, metadata !"foo", i32 1 }
- !1 = metadata !{ i32 4, metadata !"bar", i32 37 }
- !2 = metadata !{ i32 2, metadata !"qux", i32 42 }
- !3 = metadata !{ i32 3, metadata !"qux",
- metadata !{
- metadata !"foo", i32 1
- }
- }
- !llvm.module.flags = !{ !0, !1, !2, !3 }
+ !2 = !DIImportedEntity(tag: DW_TAG_imported_module, name: "foo", scope: !0,
+ entity: !1, line: 7)
-- Metadata ``!0`` has the ID ``!"foo"`` and the value '1'. The behavior
- if two or more ``!"foo"`` flags are seen is to emit an error if their
- values are not equal.
+'``tbaa``' Metadata
+^^^^^^^^^^^^^^^^^^^
-- Metadata ``!1`` has the ID ``!"bar"`` and the value '37'. The
- behavior if two or more ``!"bar"`` flags are seen is to use the value
- '37'.
+In LLVM IR, memory does not have types, so LLVM's own type system is not
+suitable for doing TBAA. Instead, metadata is added to the IR to
+describe a type system of a higher level language. This can be used to
+implement typical C/C++ TBAA, but it can also be used to implement
+custom alias analysis behavior for other languages.
-- Metadata ``!2`` has the ID ``!"qux"`` and the value '42'. The
- behavior if two or more ``!"qux"`` flags are seen is to emit a
- warning if their values are not equal.
+The current metadata format is very simple. TBAA metadata nodes have up
+to three fields, e.g.:
-- Metadata ``!3`` has the ID ``!"qux"`` and the value:
+.. code-block:: llvm
- ::
+ !0 = !{ !"an example type tree" }
+ !1 = !{ !"int", !0 }
+ !2 = !{ !"float", !0 }
+ !3 = !{ !"const float", !2, i64 1 }
- metadata !{ metadata !"foo", i32 1 }
+The first field is an identity field. It can be any value, usually a
+metadata string, which uniquely identifies the type. The most important
+name in the tree is the name of the root node. Two trees with different
+root node names are entirely disjoint, even if they have leaves with
+common names.
- The behavior is to emit an error if the ``llvm.module.flags`` does not
- contain a flag with the ID ``!"foo"`` that has the value '1' after linking is
- performed.
+The second field identifies the type's parent node in the tree, or is
+null or omitted for a root node. A type is considered to alias all of
+its descendants and all of its ancestors in the tree. Also, a type is
+considered to alias all types in other trees, so that bitcode produced
+from multiple front-ends is handled conservatively.
-Objective-C Garbage Collection Module Flags Metadata
-----------------------------------------------------
+If the third field is present, it's an integer which if equal to 1
+indicates that the type is "constant" (meaning
+``pointsToConstantMemory`` should return true; see `other useful
+AliasAnalysis methods <AliasAnalysis.html#OtherItfs>`_).
-On the Mach-O platform, Objective-C stores metadata about garbage
-collection in a special section called "image info". The metadata
-consists of a version number and a bitmask specifying what types of
-garbage collection are supported (if any) by the file. If two or more
-modules are linked together their garbage collection metadata needs to
-be merged rather than appended together.
+'``tbaa.struct``' Metadata
+^^^^^^^^^^^^^^^^^^^^^^^^^^
-The Objective-C garbage collection module flags metadata consists of the
-following key-value pairs:
+The :ref:`llvm.memcpy <int_memcpy>` is often used to implement
+aggregate assignment operations in C and similar languages, however it
+is defined to copy a contiguous region of memory, which is more than
+strictly necessary for aggregate types which contain holes due to
+padding. Also, it doesn't contain any TBAA information about the fields
+of the aggregate.
-.. list-table::
- :header-rows: 1
- :widths: 30 70
+``!tbaa.struct`` metadata can describe which memory subregions in a
+memcpy are padding and what the TBAA tags of the struct are.
- * - Key
- - Value
+The current metadata format is very simple. ``!tbaa.struct`` metadata
+nodes are a list of operands which are in conceptual groups of three.
+For each group of three, the first operand gives the byte offset of a
+field in bytes, the second gives its size in bytes, and the third gives
+its tbaa tag. e.g.:
- * - ``Objective-C Version``
- - **[Required]** --- The Objective-C ABI version. Valid values are 1 and 2.
+.. code-block:: llvm
- * - ``Objective-C Image Info Version``
- - **[Required]** --- The version of the image info section. Currently
- always 0.
+ !4 = !{ i64 0, i64 4, !1, i64 8, i64 4, !2 }
- * - ``Objective-C Image Info Section``
- - **[Required]** --- The section to place the metadata. Valid values are
- ``"__OBJC, __image_info, regular"`` for Objective-C ABI version 1, and
- ``"__DATA,__objc_imageinfo, regular, no_dead_strip"`` for
- Objective-C ABI version 2.
+This describes a struct with two fields. The first is at offset 0 bytes
+with size 4 bytes, and has tbaa tag !1. The second is at offset 8 bytes
+and has size 4 bytes and has tbaa tag !2.
- * - ``Objective-C Garbage Collection``
+Note that the fields need not be contiguous. In this example, there is a
+4 byte gap between the two fields. This gap represents padding which
+does not carry useful data and need not be preserved.
+
+'``noalias``' and '``alias.scope``' Metadata
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+``noalias`` and ``alias.scope`` metadata provide the ability to specify generic
+noalias memory-access sets. This means that some collection of memory access
+instructions (loads, stores, memory-accessing calls, etc.) that carry
+``noalias`` metadata can specifically be specified not to alias with some other
+collection of memory access instructions that carry ``alias.scope`` metadata.
+Each type of metadata specifies a list of scopes where each scope has an id and
+a domain. When evaluating an aliasing query, if for some domain, the set
+of scopes with that domain in one instruction's ``alias.scope`` list is a
+subset of (or equal to) the set of scopes for that domain in another
+instruction's ``noalias`` list, then the two memory accesses are assumed not to
+alias.
+
+The metadata identifying each domain is itself a list containing one or two
+entries. The first entry is the name of the domain. Note that if the name is a
+string then it can be combined accross functions and translation units. A
+self-reference can be used to create globally unique domain names. A
+descriptive string may optionally be provided as a second list entry.
+
+The metadata identifying each scope is also itself a list containing two or
+three entries. The first entry is the name of the scope. Note that if the name
+is a string then it can be combined accross functions and translation units. A
+self-reference can be used to create globally unique scope names. A metadata
+reference to the scope's domain is the second entry. A descriptive string may
+optionally be provided as a third list entry.
+
+For example,
+
+.. code-block:: llvm
+
+ ; Two scope domains:
+ !0 = !{!0}
+ !1 = !{!1}
+
+ ; Some scopes in these domains:
+ !2 = !{!2, !0}
+ !3 = !{!3, !0}
+ !4 = !{!4, !1}
+
+ ; Some scope lists:
+ !5 = !{!4} ; A list containing only scope !4
+ !6 = !{!4, !3, !2}
+ !7 = !{!3}
+
+ ; These two instructions don't alias:
+ %0 = load float, float* %c, align 4, !alias.scope !5
+ store float %0, float* %arrayidx.i, align 4, !noalias !5
+
+ ; These two instructions also don't alias (for domain !1, the set of scopes
+ ; in the !alias.scope equals that in the !noalias list):
+ %2 = load float, float* %c, align 4, !alias.scope !5
+ store float %2, float* %arrayidx.i2, align 4, !noalias !6
+
+ ; These two instructions may alias (for domain !0, the set of scopes in
+ ; the !noalias list is not a superset of, or equal to, the scopes in the
+ ; !alias.scope list):
+ %2 = load float, float* %c, align 4, !alias.scope !6
+ store float %0, float* %arrayidx.i, align 4, !noalias !7
+
+'``fpmath``' Metadata
+^^^^^^^^^^^^^^^^^^^^^
+
+``fpmath`` metadata may be attached to any instruction of floating point
+type. It can be used to express the maximum acceptable error in the
+result of that instruction, in ULPs, thus potentially allowing the
+compiler to use a more efficient but less accurate method of computing
+it. ULP is defined as follows:
+
+ If ``x`` is a real number that lies between two finite consecutive
+ floating-point numbers ``a`` and ``b``, without being equal to one
+ of them, then ``ulp(x) = |b - a|``, otherwise ``ulp(x)`` is the
+ distance between the two non-equal finite floating-point numbers
+ nearest ``x``. Moreover, ``ulp(NaN)`` is ``NaN``.
+
+The metadata node shall consist of a single positive floating point
+number representing the maximum relative error, for example:
+
+.. code-block:: llvm
+
+ !0 = !{ float 2.5 } ; maximum acceptable inaccuracy is 2.5 ULPs
+
+.. _range-metadata:
+
+'``range``' Metadata
+^^^^^^^^^^^^^^^^^^^^
+
+``range`` metadata may be attached only to ``load``, ``call`` and ``invoke`` of
+integer types. It expresses the possible ranges the loaded value or the value
+returned by the called function at this call site is in. The ranges are
+represented with a flattened list of integers. The loaded value or the value
+returned is known to be in the union of the ranges defined by each consecutive
+pair. Each pair has the following properties:
+
+- The type must match the type loaded by the instruction.
+- The pair ``a,b`` represents the range ``[a,b)``.
+- Both ``a`` and ``b`` are constants.
+- The range is allowed to wrap.
+- The range should not represent the full or empty set. That is,
+ ``a!=b``.
+
+In addition, the pairs must be in signed order of the lower bound and
+they must be non-contiguous.
+
+Examples:
+
+.. code-block:: llvm
+
+ %a = load i8, i8* %x, align 1, !range !0 ; Can only be 0 or 1
+ %b = load i8, i8* %y, align 1, !range !1 ; Can only be 255 (-1), 0 or 1
+ %c = call i8 @foo(), !range !2 ; Can only be 0, 1, 3, 4 or 5
+ %d = invoke i8 @bar() to label %cont
+ unwind label %lpad, !range !3 ; Can only be -2, -1, 3, 4 or 5
+ ...
+ !0 = !{ i8 0, i8 2 }
+ !1 = !{ i8 255, i8 2 }
+ !2 = !{ i8 0, i8 2, i8 3, i8 6 }
+ !3 = !{ i8 -2, i8 0, i8 3, i8 6 }
+
+'``llvm.loop``'
+^^^^^^^^^^^^^^^
+
+It is sometimes useful to attach information to loop constructs. Currently,
+loop metadata is implemented as metadata attached to the branch instruction
+in the loop latch block. This type of metadata refer to a metadata node that is
+guaranteed to be separate for each loop. The loop identifier metadata is
+specified with the name ``llvm.loop``.
+
+The loop identifier metadata is implemented using a metadata that refers to
+itself to avoid merging it with any other identifier metadata, e.g.,
+during module linkage or function inlining. That is, each loop should refer
+to their own identification metadata even if they reside in separate functions.
+The following example contains loop identifier metadata for two separate loop
+constructs:
+
+.. code-block:: llvm
+
+ !0 = !{!0}
+ !1 = !{!1}
+
+The loop identifier metadata can be used to specify additional
+per-loop metadata. Any operands after the first operand can be treated
+as user-defined metadata. For example the ``llvm.loop.unroll.count``
+suggests an unroll factor to the loop unroller:
+
+.. code-block:: llvm
+
+ br i1 %exitcond, label %._crit_edge, label %.lr.ph, !llvm.loop !0
+ ...
+ !0 = !{!0, !1}
+ !1 = !{!"llvm.loop.unroll.count", i32 4}
+
+'``llvm.loop.vectorize``' and '``llvm.loop.interleave``'
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Metadata prefixed with ``llvm.loop.vectorize`` or ``llvm.loop.interleave`` are
+used to control per-loop vectorization and interleaving parameters such as
+vectorization width and interleave count. These metadata should be used in
+conjunction with ``llvm.loop`` loop identification metadata. The
+``llvm.loop.vectorize`` and ``llvm.loop.interleave`` metadata are only
+optimization hints and the optimizer will only interleave and vectorize loops if
+it believes it is safe to do so. The ``llvm.mem.parallel_loop_access`` metadata
+which contains information about loop-carried memory dependencies can be helpful
+in determining the safety of these transformations.
+
+'``llvm.loop.interleave.count``' Metadata
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+This metadata suggests an interleave count to the loop interleaver.
+The first operand is the string ``llvm.loop.interleave.count`` and the
+second operand is an integer specifying the interleave count. For
+example:
+
+.. code-block:: llvm
+
+ !0 = !{!"llvm.loop.interleave.count", i32 4}
+
+Note that setting ``llvm.loop.interleave.count`` to 1 disables interleaving
+multiple iterations of the loop. If ``llvm.loop.interleave.count`` is set to 0
+then the interleave count will be determined automatically.
+
+'``llvm.loop.vectorize.enable``' Metadata
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+This metadata selectively enables or disables vectorization for the loop. The
+first operand is the string ``llvm.loop.vectorize.enable`` and the second operand
+is a bit. If the bit operand value is 1 vectorization is enabled. A value of
+0 disables vectorization:
+
+.. code-block:: llvm
+
+ !0 = !{!"llvm.loop.vectorize.enable", i1 0}
+ !1 = !{!"llvm.loop.vectorize.enable", i1 1}
+
+'``llvm.loop.vectorize.width``' Metadata
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+This metadata sets the target width of the vectorizer. The first
+operand is the string ``llvm.loop.vectorize.width`` and the second
+operand is an integer specifying the width. For example:
+
+.. code-block:: llvm
+
+ !0 = !{!"llvm.loop.vectorize.width", i32 4}
+
+Note that setting ``llvm.loop.vectorize.width`` to 1 disables
+vectorization of the loop. If ``llvm.loop.vectorize.width`` is set to
+0 or if the loop does not have this metadata the width will be
+determined automatically.
+
+'``llvm.loop.unroll``'
+^^^^^^^^^^^^^^^^^^^^^^
+
+Metadata prefixed with ``llvm.loop.unroll`` are loop unrolling
+optimization hints such as the unroll factor. ``llvm.loop.unroll``
+metadata should be used in conjunction with ``llvm.loop`` loop
+identification metadata. The ``llvm.loop.unroll`` metadata are only
+optimization hints and the unrolling will only be performed if the
+optimizer believes it is safe to do so.
+
+'``llvm.loop.unroll.count``' Metadata
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+This metadata suggests an unroll factor to the loop unroller. The
+first operand is the string ``llvm.loop.unroll.count`` and the second
+operand is a positive integer specifying the unroll factor. For
+example:
+
+.. code-block:: llvm
+
+ !0 = !{!"llvm.loop.unroll.count", i32 4}
+
+If the trip count of the loop is less than the unroll count the loop
+will be partially unrolled.
+
+'``llvm.loop.unroll.disable``' Metadata
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+This metadata disables loop unrolling. The metadata has a single operand
+which is the string ``llvm.loop.unroll.disable``. For example:
+
+.. code-block:: llvm
+
+ !0 = !{!"llvm.loop.unroll.disable"}
+
+'``llvm.loop.unroll.runtime.disable``' Metadata
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+This metadata disables runtime loop unrolling. The metadata has a single
+operand which is the string ``llvm.loop.unroll.runtime.disable``. For example:
+
+.. code-block:: llvm
+
+ !0 = !{!"llvm.loop.unroll.runtime.disable"}
+
+'``llvm.loop.unroll.enable``' Metadata
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+This metadata suggests that the loop should be fully unrolled if the trip count
+is known at compile time and partially unrolled if the trip count is not known
+at compile time. The metadata has a single operand which is the string
+``llvm.loop.unroll.enable``. For example:
+
+.. code-block:: llvm
+
+ !0 = !{!"llvm.loop.unroll.enable"}
+
+'``llvm.loop.unroll.full``' Metadata
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+This metadata suggests that the loop should be unrolled fully. The
+metadata has a single operand which is the string ``llvm.loop.unroll.full``.
+For example:
+
+.. code-block:: llvm
+
+ !0 = !{!"llvm.loop.unroll.full"}
+
+'``llvm.mem``'
+^^^^^^^^^^^^^^^
+
+Metadata types used to annotate memory accesses with information helpful
+for optimizations are prefixed with ``llvm.mem``.
+
+'``llvm.mem.parallel_loop_access``' Metadata
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+The ``llvm.mem.parallel_loop_access`` metadata refers to a loop identifier,
+or metadata containing a list of loop identifiers for nested loops.
+The metadata is attached to memory accessing instructions and denotes that
+no loop carried memory dependence exist between it and other instructions denoted
+with the same loop identifier.
+
+Precisely, given two instructions ``m1`` and ``m2`` that both have the
+``llvm.mem.parallel_loop_access`` metadata, with ``L1`` and ``L2`` being the
+set of loops associated with that metadata, respectively, then there is no loop
+carried dependence between ``m1`` and ``m2`` for loops in both ``L1`` and
+``L2``.
+
+As a special case, if all memory accessing instructions in a loop have
+``llvm.mem.parallel_loop_access`` metadata that refers to that loop, then the
+loop has no loop carried memory dependences and is considered to be a parallel
+loop.
+
+Note that if not all memory access instructions have such metadata referring to
+the loop, then the loop is considered not being trivially parallel. Additional
+memory dependence analysis is required to make that determination. As a fail
+safe mechanism, this causes loops that were originally parallel to be considered
+sequential (if optimization passes that are unaware of the parallel semantics
+insert new memory instructions into the loop body).
+
+Example of a loop that is considered parallel due to its correct use of
+both ``llvm.loop`` and ``llvm.mem.parallel_loop_access``
+metadata types that refer to the same loop identifier metadata.
+
+.. code-block:: llvm
+
+ for.body:
+ ...
+ %val0 = load i32, i32* %arrayidx, !llvm.mem.parallel_loop_access !0
+ ...
+ store i32 %val0, i32* %arrayidx1, !llvm.mem.parallel_loop_access !0
+ ...
+ br i1 %exitcond, label %for.end, label %for.body, !llvm.loop !0
+
+ for.end:
+ ...
+ !0 = !{!0}
+
+It is also possible to have nested parallel loops. In that case the
+memory accesses refer to a list of loop identifier metadata nodes instead of
+the loop identifier metadata node directly:
+
+.. code-block:: llvm
+
+ outer.for.body:
+ ...
+ %val1 = load i32, i32* %arrayidx3, !llvm.mem.parallel_loop_access !2
+ ...
+ br label %inner.for.body
+
+ inner.for.body:
+ ...
+ %val0 = load i32, i32* %arrayidx1, !llvm.mem.parallel_loop_access !0
+ ...
+ store i32 %val0, i32* %arrayidx2, !llvm.mem.parallel_loop_access !0
+ ...
+ br i1 %exitcond, label %inner.for.end, label %inner.for.body, !llvm.loop !1
+
+ inner.for.end:
+ ...
+ store i32 %val1, i32* %arrayidx4, !llvm.mem.parallel_loop_access !2
+ ...
+ br i1 %exitcond, label %outer.for.end, label %outer.for.body, !llvm.loop !2
+
+ outer.for.end: ; preds = %for.body
+ ...
+ !0 = !{!1, !2} ; a list of loop identifiers
+ !1 = !{!1} ; an identifier for the inner loop
+ !2 = !{!2} ; an identifier for the outer loop
+
+'``llvm.bitsets``'
+^^^^^^^^^^^^^^^^^^
+
+The ``llvm.bitsets`` global metadata is used to implement
+:doc:`bitsets <BitSets>`.
+
+Module Flags Metadata
+=====================
+
+Information about the module as a whole is difficult to convey to LLVM's
+subsystems. The LLVM IR isn't sufficient to transmit this information.
+The ``llvm.module.flags`` named metadata exists in order to facilitate
+this. These flags are in the form of key / value pairs --- much like a
+dictionary --- making it easy for any subsystem who cares about a flag to
+look it up.
+
+The ``llvm.module.flags`` metadata contains a list of metadata triplets.
+Each triplet has the following form:
+
+- The first element is a *behavior* flag, which specifies the behavior
+ when two (or more) modules are merged together, and it encounters two
+ (or more) metadata with the same ID. The supported behaviors are
+ described below.
+- The second element is a metadata string that is a unique ID for the
+ metadata. Each module may only have one flag entry for each unique ID (not
+ including entries with the **Require** behavior).
+- The third element is the value of the flag.
+
+When two (or more) modules are merged together, the resulting
+``llvm.module.flags`` metadata is the union of the modules' flags. That is, for
+each unique metadata ID string, there will be exactly one entry in the merged
+modules ``llvm.module.flags`` metadata table, and the value for that entry will
+be determined by the merge behavior flag, as described below. The only exception
+is that entries with the *Require* behavior are always preserved.
+
+The following behaviors are supported:
+
+.. list-table::
+ :header-rows: 1
+ :widths: 10 90
+
+ * - Value
+ - Behavior
+
+ * - 1
+ - **Error**
+ Emits an error if two values disagree, otherwise the resulting value
+ is that of the operands.
+
+ * - 2
+ - **Warning**
+ Emits a warning if two values disagree. The result value will be the
+ operand for the flag from the first module being linked.
+
+ * - 3
+ - **Require**
+ Adds a requirement that another module flag be present and have a
+ specified value after linking is performed. The value must be a
+ metadata pair, where the first element of the pair is the ID of the
+ module flag to be restricted, and the second element of the pair is
+ the value the module flag should be restricted to. This behavior can
+ be used to restrict the allowable results (via triggering of an
+ error) of linking IDs with the **Override** behavior.
+
+ * - 4
+ - **Override**
+ Uses the specified value, regardless of the behavior or value of the
+ other module. If both modules specify **Override**, but the values
+ differ, an error will be emitted.
+
+ * - 5
+ - **Append**
+ Appends the two values, which are required to be metadata nodes.
+
+ * - 6
+ - **AppendUnique**
+ Appends the two values, which are required to be metadata
+ nodes. However, duplicate entries in the second list are dropped
+ during the append operation.
+
+It is an error for a particular unique flag ID to have multiple behaviors,
+except in the case of **Require** (which adds restrictions on another metadata
+value) or **Override**.
+
+An example of module flags:
+
+.. code-block:: llvm
+
+ !0 = !{ i32 1, !"foo", i32 1 }
+ !1 = !{ i32 4, !"bar", i32 37 }
+ !2 = !{ i32 2, !"qux", i32 42 }
+ !3 = !{ i32 3, !"qux",
+ !{
+ !"foo", i32 1
+ }
+ }
+ !llvm.module.flags = !{ !0, !1, !2, !3 }
+
+- Metadata ``!0`` has the ID ``!"foo"`` and the value '1'. The behavior
+ if two or more ``!"foo"`` flags are seen is to emit an error if their
+ values are not equal.
+
+- Metadata ``!1`` has the ID ``!"bar"`` and the value '37'. The
+ behavior if two or more ``!"bar"`` flags are seen is to use the value
+ '37'.
+
+- Metadata ``!2`` has the ID ``!"qux"`` and the value '42'. The
+ behavior if two or more ``!"qux"`` flags are seen is to emit a
+ warning if their values are not equal.
+
+- Metadata ``!3`` has the ID ``!"qux"`` and the value:
+
+ ::
+
+ !{ !"foo", i32 1 }
+
+ The behavior is to emit an error if the ``llvm.module.flags`` does not
+ contain a flag with the ID ``!"foo"`` that has the value '1' after linking is
+ performed.
+
+Objective-C Garbage Collection Module Flags Metadata
+----------------------------------------------------
+
+On the Mach-O platform, Objective-C stores metadata about garbage
+collection in a special section called "image info". The metadata
+consists of a version number and a bitmask specifying what types of
+garbage collection are supported (if any) by the file. If two or more
+modules are linked together their garbage collection metadata needs to
+be merged rather than appended together.
+
+The Objective-C garbage collection module flags metadata consists of the
+following key-value pairs:
+
+.. list-table::
+ :header-rows: 1
+ :widths: 30 70
+
+ * - Key
+ - Value
+
+ * - ``Objective-C Version``
+ - **[Required]** --- The Objective-C ABI version. Valid values are 1 and 2.
+
+ * - ``Objective-C Image Info Version``
+ - **[Required]** --- The version of the image info section. Currently
+ always 0.
+
+ * - ``Objective-C Image Info Section``
+ - **[Required]** --- The section to place the metadata. Valid values are
+ ``"__OBJC, __image_info, regular"`` for Objective-C ABI version 1, and
+ ``"__DATA,__objc_imageinfo, regular, no_dead_strip"`` for
+ Objective-C ABI version 2.
+
+ * - ``Objective-C Garbage Collection``
- **[Required]** --- Specifies whether garbage collection is supported or
not. Valid values are 0, for no garbage collection, and 2, for garbage
collection supported.
- * - ``Objective-C GC Only``
- - **[Optional]** --- Specifies that only garbage collection is supported.
- If present, its value must be 6. This flag requires that the
- ``Objective-C Garbage Collection`` flag have the value 2.
+ * - ``Objective-C GC Only``
+ - **[Optional]** --- Specifies that only garbage collection is supported.
+ If present, its value must be 6. This flag requires that the
+ ``Objective-C Garbage Collection`` flag have the value 2.
+
+Some important flag interactions:
+
+- If a module with ``Objective-C Garbage Collection`` set to 0 is
+ merged with a module with ``Objective-C Garbage Collection`` set to
+ 2, then the resulting module has the
+ ``Objective-C Garbage Collection`` flag set to 0.
+- A module with ``Objective-C Garbage Collection`` set to 0 cannot be
+ merged with a module with ``Objective-C GC Only`` set to 6.
+
+Automatic Linker Flags Module Flags Metadata
+--------------------------------------------
+
+Some targets support embedding flags to the linker inside individual object
+files. Typically this is used in conjunction with language extensions which
+allow source files to explicitly declare the libraries they depend on, and have
+these automatically be transmitted to the linker via object files.
+
+These flags are encoded in the IR using metadata in the module flags section,
+using the ``Linker Options`` key. The merge behavior for this flag is required
+to be ``AppendUnique``, and the value for the key is expected to be a metadata
+node which should be a list of other metadata nodes, each of which should be a
+list of metadata strings defining linker options.
+
+For example, the following metadata section specifies two separate sets of
+linker options, presumably to link against ``libz`` and the ``Cocoa``
+framework::
+
+ !0 = !{ i32 6, !"Linker Options",
+ !{
+ !{ !"-lz" },
+ !{ !"-framework", !"Cocoa" } } }
+ !llvm.module.flags = !{ !0 }
+
+The metadata encoding as lists of lists of options, as opposed to a collapsed
+list of options, is chosen so that the IR encoding can use multiple option
+strings to specify e.g., a single library, while still having that specifier be
+preserved as an atomic element that can be recognized by a target specific
+assembly writer or object file emitter.
+
+Each individual option is required to be either a valid option for the target's
+linker, or an option that is reserved by the target specific assembly writer or
+object file emitter. No other aspect of these options is defined by the IR.
+
+C type width Module Flags Metadata
+----------------------------------
+
+The ARM backend emits a section into each generated object file describing the
+options that it was compiled with (in a compiler-independent way) to prevent
+linking incompatible objects, and to allow automatic library selection. Some
+of these options are not visible at the IR level, namely wchar_t width and enum
+width.
+
+To pass this information to the backend, these options are encoded in module
+flags metadata, using the following key-value pairs:
+
+.. list-table::
+ :header-rows: 1
+ :widths: 30 70
+
+ * - Key
+ - Value
+
+ * - short_wchar
+ - * 0 --- sizeof(wchar_t) == 4
+ * 1 --- sizeof(wchar_t) == 2
+
+ * - short_enum
+ - * 0 --- Enums are at least as large as an ``int``.
+ * 1 --- Enums are stored in the smallest integer type which can
+ represent all of its values.
+
+For example, the following metadata section specifies that the module was
+compiled with a ``wchar_t`` width of 4 bytes, and the underlying type of an
+enum is the smallest type which can represent all of its values::
+
+ !llvm.module.flags = !{!0, !1}
+ !0 = !{i32 1, !"short_wchar", i32 1}
+ !1 = !{i32 1, !"short_enum", i32 0}
+
+.. _intrinsicglobalvariables:
+
+Intrinsic Global Variables
+==========================
+
+LLVM has a number of "magic" global variables that contain data that
+affect code generation or other IR semantics. These are documented here.
+All globals of this sort should have a section specified as
+"``llvm.metadata``". This section and all globals that start with
+"``llvm.``" are reserved for use by LLVM.
+
+.. _gv_llvmused:
+
+The '``llvm.used``' Global Variable
+-----------------------------------
+
+The ``@llvm.used`` global is an array which has
+:ref:`appending linkage <linkage_appending>`. This array contains a list of
+pointers to named global variables, functions and aliases which may optionally
+have a pointer cast formed of bitcast or getelementptr. For example, a legal
+use of it is:
+
+.. code-block:: llvm
+
+ @X = global i8 4
+ @Y = global i32 123
+
+ @llvm.used = appending global [2 x i8*] [
+ i8* @X,
+ i8* bitcast (i32* @Y to i8*)
+ ], section "llvm.metadata"
+
+If a symbol appears in the ``@llvm.used`` list, then the compiler, assembler,
+and linker are required to treat the symbol as if there is a reference to the
+symbol that it cannot see (which is why they have to be named). For example, if
+a variable has internal linkage and no references other than that from the
+``@llvm.used`` list, it cannot be deleted. This is commonly used to represent
+references from inline asms and other things the compiler cannot "see", and
+corresponds to "``attribute((used))``" in GNU C.
+
+On some targets, the code generator must emit a directive to the
+assembler or object file to prevent the assembler and linker from
+molesting the symbol.
+
+.. _gv_llvmcompilerused:
+
+The '``llvm.compiler.used``' Global Variable
+--------------------------------------------
+
+The ``@llvm.compiler.used`` directive is the same as the ``@llvm.used``
+directive, except that it only prevents the compiler from touching the
+symbol. On targets that support it, this allows an intelligent linker to
+optimize references to the symbol without being impeded as it would be
+by ``@llvm.used``.
+
+This is a rare construct that should only be used in rare circumstances,
+and should not be exposed to source languages.
+
+.. _gv_llvmglobalctors:
+
+The '``llvm.global_ctors``' Global Variable
+-------------------------------------------
+
+.. code-block:: llvm
+
+ %0 = type { i32, void ()*, i8* }
+ @llvm.global_ctors = appending global [1 x %0] [%0 { i32 65535, void ()* @ctor, i8* @data }]
+
+The ``@llvm.global_ctors`` array contains a list of constructor
+functions, priorities, and an optional associated global or function.
+The functions referenced by this array will be called in ascending order
+of priority (i.e. lowest first) when the module is loaded. The order of
+functions with the same priority is not defined.
+
+If the third field is present, non-null, and points to a global variable
+or function, the initializer function will only run if the associated
+data from the current module is not discarded.
+
+.. _llvmglobaldtors:
+
+The '``llvm.global_dtors``' Global Variable
+-------------------------------------------
+
+.. code-block:: llvm
+
+ %0 = type { i32, void ()*, i8* }
+ @llvm.global_dtors = appending global [1 x %0] [%0 { i32 65535, void ()* @dtor, i8* @data }]
+
+The ``@llvm.global_dtors`` array contains a list of destructor
+functions, priorities, and an optional associated global or function.
+The functions referenced by this array will be called in descending
+order of priority (i.e. highest first) when the module is unloaded. The
+order of functions with the same priority is not defined.
+
+If the third field is present, non-null, and points to a global variable
+or function, the destructor function will only run if the associated
+data from the current module is not discarded.
+
+Instruction Reference
+=====================
-Some important flag interactions:
+The LLVM instruction set consists of several different classifications
+of instructions: :ref:`terminator instructions <terminators>`, :ref:`binary
+instructions <binaryops>`, :ref:`bitwise binary
+instructions <bitwiseops>`, :ref:`memory instructions <memoryops>`, and
+:ref:`other instructions <otherops>`.
-- If a module with ``Objective-C Garbage Collection`` set to 0 is
- merged with a module with ``Objective-C Garbage Collection`` set to
- 2, then the resulting module has the
- ``Objective-C Garbage Collection`` flag set to 0.
-- A module with ``Objective-C Garbage Collection`` set to 0 cannot be
- merged with a module with ``Objective-C GC Only`` set to 6.
+.. _terminators:
-Automatic Linker Flags Module Flags Metadata
---------------------------------------------
+Terminator Instructions
+-----------------------
-Some targets support embedding flags to the linker inside individual object
-files. Typically this is used in conjunction with language extensions which
-allow source files to explicitly declare the libraries they depend on, and have
-these automatically be transmitted to the linker via object files.
+As mentioned :ref:`previously <functionstructure>`, every basic block in a
+program ends with a "Terminator" instruction, which indicates which
+block should be executed after the current block is finished. These
+terminator instructions typically yield a '``void``' value: they produce
+control flow, not values (the one exception being the
+':ref:`invoke <i_invoke>`' instruction).
-These flags are encoded in the IR using metadata in the module flags section,
-using the ``Linker Options`` key. The merge behavior for this flag is required
-to be ``AppendUnique``, and the value for the key is expected to be a metadata
-node which should be a list of other metadata nodes, each of which should be a
-list of metadata strings defining linker options.
+The terminator instructions are: ':ref:`ret <i_ret>`',
+':ref:`br <i_br>`', ':ref:`switch <i_switch>`',
+':ref:`indirectbr <i_indirectbr>`', ':ref:`invoke <i_invoke>`',
+':ref:`resume <i_resume>`', ':ref:`catchpad <i_catchpad>`',
+':ref:`catchendpad <i_catchendpad>`',
+':ref:`catchret <i_catchret>`',
+':ref:`cleanupret <i_cleanupret>`',
+':ref:`terminatepad <i_terminatepad>`',
+and ':ref:`unreachable <i_unreachable>`'.
-For example, the following metadata section specifies two separate sets of
-linker options, presumably to link against ``libz`` and the ``Cocoa``
-framework::
+.. _i_ret:
- !0 = metadata !{ i32 6, metadata !"Linker Options",
- metadata !{
- metadata !{ metadata !"-lz" },
- metadata !{ metadata !"-framework", metadata !"Cocoa" } } }
- !llvm.module.flags = !{ !0 }
+'``ret``' Instruction
+^^^^^^^^^^^^^^^^^^^^^
-The metadata encoding as lists of lists of options, as opposed to a collapsed
-list of options, is chosen so that the IR encoding can use multiple option
-strings to specify e.g., a single library, while still having that specifier be
-preserved as an atomic element that can be recognized by a target specific
-assembly writer or object file emitter.
+Syntax:
+"""""""
-Each individual option is required to be either a valid option for the target's
-linker, or an option that is reserved by the target specific assembly writer or
-object file emitter. No other aspect of these options is defined by the IR.
+::
-C type width Module Flags Metadata
-----------------------------------
+ ret <type> <value> ; Return a value from a non-void function
+ ret void ; Return from void function
-The ARM backend emits a section into each generated object file describing the
-options that it was compiled with (in a compiler-independent way) to prevent
-linking incompatible objects, and to allow automatic library selection. Some
-of these options are not visible at the IR level, namely wchar_t width and enum
-width.
+Overview:
+"""""""""
-To pass this information to the backend, these options are encoded in module
-flags metadata, using the following key-value pairs:
+The '``ret``' instruction is used to return control flow (and optionally
+a value) from a function back to the caller.
-.. list-table::
- :header-rows: 1
- :widths: 30 70
+There are two forms of the '``ret``' instruction: one that returns a
+value and then causes control flow, and one that just causes control
+flow to occur.
- * - Key
- - Value
+Arguments:
+""""""""""
- * - short_wchar
- - * 0 --- sizeof(wchar_t) == 4
- * 1 --- sizeof(wchar_t) == 2
+The '``ret``' instruction optionally accepts a single argument, the
+return value. The type of the return value must be a ':ref:`first
+class <t_firstclass>`' type.
- * - short_enum
- - * 0 --- Enums are at least as large as an ``int``.
- * 1 --- Enums are stored in the smallest integer type which can
- represent all of its values.
+A function is not :ref:`well formed <wellformed>` if it it has a non-void
+return type and contains a '``ret``' instruction with no return value or
+a return value with a type that does not match its type, or if it has a
+void return type and contains a '``ret``' instruction with a return
+value.
-For example, the following metadata section specifies that the module was
-compiled with a ``wchar_t`` width of 4 bytes, and the underlying type of an
-enum is the smallest type which can represent all of its values::
+Semantics:
+""""""""""
- !llvm.module.flags = !{!0, !1}
- !0 = metadata !{i32 1, metadata !"short_wchar", i32 1}
- !1 = metadata !{i32 1, metadata !"short_enum", i32 0}
+When the '``ret``' instruction is executed, control flow returns back to
+the calling function's context. If the caller is a
+":ref:`call <i_call>`" instruction, execution continues at the
+instruction after the call. If the caller was an
+":ref:`invoke <i_invoke>`" instruction, execution continues at the
+beginning of the "normal" destination block. If the instruction returns
+a value, that value shall set the call or invoke instruction's return
+value.
-.. _intrinsicglobalvariables:
+Example:
+""""""""
-Intrinsic Global Variables
-==========================
+.. code-block:: llvm
-LLVM has a number of "magic" global variables that contain data that
-affect code generation or other IR semantics. These are documented here.
-All globals of this sort should have a section specified as
-"``llvm.metadata``". This section and all globals that start with
-"``llvm.``" are reserved for use by LLVM.
+ ret i32 5 ; Return an integer value of 5
+ ret void ; Return from a void function
+ ret { i32, i8 } { i32 4, i8 2 } ; Return a struct of values 4 and 2
-.. _gv_llvmused:
+.. _i_br:
-The '``llvm.used``' Global Variable
------------------------------------
+'``br``' Instruction
+^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ br i1 <cond>, label <iftrue>, label <iffalse>
+ br label <dest> ; Unconditional branch
+
+Overview:
+"""""""""
+
+The '``br``' instruction is used to cause control flow to transfer to a
+different basic block in the current function. There are two forms of
+this instruction, corresponding to a conditional branch and an
+unconditional branch.
+
+Arguments:
+""""""""""
+
+The conditional branch form of the '``br``' instruction takes a single
+'``i1``' value and two '``label``' values. The unconditional form of the
+'``br``' instruction takes a single '``label``' value as a target.
+
+Semantics:
+""""""""""
+
+Upon execution of a conditional '``br``' instruction, the '``i1``'
+argument is evaluated. If the value is ``true``, control flows to the
+'``iftrue``' ``label`` argument. If "cond" is ``false``, control flows
+to the '``iffalse``' ``label`` argument.
+
+Example:
+""""""""
+
+.. code-block:: llvm
+
+ Test:
+ %cond = icmp eq i32 %a, %b
+ br i1 %cond, label %IfEqual, label %IfUnequal
+ IfEqual:
+ ret i32 1
+ IfUnequal:
+ ret i32 0
+
+.. _i_switch:
+
+'``switch``' Instruction
+^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ switch <intty> <value>, label <defaultdest> [ <intty> <val>, label <dest> ... ]
+
+Overview:
+"""""""""
+
+The '``switch``' instruction is used to transfer control flow to one of
+several different places. It is a generalization of the '``br``'
+instruction, allowing a branch to occur to one of many possible
+destinations.
+
+Arguments:
+""""""""""
+
+The '``switch``' instruction uses three parameters: an integer
+comparison value '``value``', a default '``label``' destination, and an
+array of pairs of comparison value constants and '``label``'s. The table
+is not allowed to contain duplicate constant entries.
+
+Semantics:
+""""""""""
+
+The ``switch`` instruction specifies a table of values and destinations.
+When the '``switch``' instruction is executed, this table is searched
+for the given value. If the value is found, control flow is transferred
+to the corresponding destination; otherwise, control flow is transferred
+to the default destination.
+
+Implementation:
+"""""""""""""""
+
+Depending on properties of the target machine and the particular
+``switch`` instruction, this instruction may be code generated in
+different ways. For example, it could be generated as a series of
+chained conditional branches or with a lookup table.
+
+Example:
+""""""""
+
+.. code-block:: llvm
+
+ ; Emulate a conditional br instruction
+ %Val = zext i1 %value to i32
+ switch i32 %Val, label %truedest [ i32 0, label %falsedest ]
+
+ ; Emulate an unconditional br instruction
+ switch i32 0, label %dest [ ]
+
+ ; Implement a jump table:
+ switch i32 %val, label %otherwise [ i32 0, label %onzero
+ i32 1, label %onone
+ i32 2, label %ontwo ]
+
+.. _i_indirectbr:
+
+'``indirectbr``' Instruction
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ indirectbr <somety>* <address>, [ label <dest1>, label <dest2>, ... ]
+
+Overview:
+"""""""""
+
+The '``indirectbr``' instruction implements an indirect branch to a
+label within the current function, whose address is specified by
+"``address``". Address must be derived from a
+:ref:`blockaddress <blockaddress>` constant.
-The ``@llvm.used`` global is an array which has
-:ref:`appending linkage <linkage_appending>`. This array contains a list of
-pointers to named global variables, functions and aliases which may optionally
-have a pointer cast formed of bitcast or getelementptr. For example, a legal
-use of it is:
+Arguments:
+""""""""""
-.. code-block:: llvm
+The '``address``' argument is the address of the label to jump to. The
+rest of the arguments indicate the full set of possible destinations
+that the address may point to. Blocks are allowed to occur multiple
+times in the destination list, though this isn't particularly useful.
- @X = global i8 4
- @Y = global i32 123
+This destination list is required so that dataflow analysis has an
+accurate understanding of the CFG.
- @llvm.used = appending global [2 x i8*] [
- i8* @X,
- i8* bitcast (i32* @Y to i8*)
- ], section "llvm.metadata"
+Semantics:
+""""""""""
-If a symbol appears in the ``@llvm.used`` list, then the compiler, assembler,
-and linker are required to treat the symbol as if there is a reference to the
-symbol that it cannot see (which is why they have to be named). For example, if
-a variable has internal linkage and no references other than that from the
-``@llvm.used`` list, it cannot be deleted. This is commonly used to represent
-references from inline asms and other things the compiler cannot "see", and
-corresponds to "``attribute((used))``" in GNU C.
+Control transfers to the block specified in the address argument. All
+possible destination blocks must be listed in the label list, otherwise
+this instruction has undefined behavior. This implies that jumps to
+labels defined in other functions have undefined behavior as well.
-On some targets, the code generator must emit a directive to the
-assembler or object file to prevent the assembler and linker from
-molesting the symbol.
+Implementation:
+"""""""""""""""
-.. _gv_llvmcompilerused:
+This is typically implemented with a jump through a register.
-The '``llvm.compiler.used``' Global Variable
---------------------------------------------
+Example:
+""""""""
-The ``@llvm.compiler.used`` directive is the same as the ``@llvm.used``
-directive, except that it only prevents the compiler from touching the
-symbol. On targets that support it, this allows an intelligent linker to
-optimize references to the symbol without being impeded as it would be
-by ``@llvm.used``.
+.. code-block:: llvm
-This is a rare construct that should only be used in rare circumstances,
-and should not be exposed to source languages.
+ indirectbr i8* %Addr, [ label %bb1, label %bb2, label %bb3 ]
-.. _gv_llvmglobalctors:
+.. _i_invoke:
-The '``llvm.global_ctors``' Global Variable
--------------------------------------------
+'``invoke``' Instruction
+^^^^^^^^^^^^^^^^^^^^^^^^
-.. code-block:: llvm
+Syntax:
+"""""""
- %0 = type { i32, void ()*, i8* }
- @llvm.global_ctors = appending global [1 x %0] [%0 { i32 65535, void ()* @ctor, i8* @data }]
+::
-The ``@llvm.global_ctors`` array contains a list of constructor
-functions, priorities, and an optional associated global or function.
-The functions referenced by this array will be called in ascending order
-of priority (i.e. lowest first) when the module is loaded. The order of
-functions with the same priority is not defined.
+ <result> = invoke [cconv] [ret attrs] <ptr to function ty> <function ptr val>(<function args>) [fn attrs]
+ to label <normal label> unwind label <exception label>
-If the third field is present, non-null, and points to a global variable
-or function, the initializer function will only run if the associated
-data from the current module is not discarded.
+Overview:
+"""""""""
-.. _llvmglobaldtors:
+The '``invoke``' instruction causes control to transfer to a specified
+function, with the possibility of control flow transfer to either the
+'``normal``' label or the '``exception``' label. If the callee function
+returns with the "``ret``" instruction, control flow will return to the
+"normal" label. If the callee (or any indirect callees) returns via the
+":ref:`resume <i_resume>`" instruction or other exception handling
+mechanism, control is interrupted and continued at the dynamically
+nearest "exception" label.
-The '``llvm.global_dtors``' Global Variable
--------------------------------------------
+The '``exception``' label is a `landing
+pad <ExceptionHandling.html#overview>`_ for the exception. As such,
+'``exception``' label is required to have the
+":ref:`landingpad <i_landingpad>`" instruction, which contains the
+information about the behavior of the program after unwinding happens,
+as its first non-PHI instruction. The restrictions on the
+"``landingpad``" instruction's tightly couples it to the "``invoke``"
+instruction, so that the important information contained within the
+"``landingpad``" instruction can't be lost through normal code motion.
-.. code-block:: llvm
+Arguments:
+""""""""""
- %0 = type { i32, void ()*, i8* }
- @llvm.global_dtors = appending global [1 x %0] [%0 { i32 65535, void ()* @dtor, i8* @data }]
+This instruction requires several arguments:
-The ``@llvm.global_dtors`` array contains a list of destructor
-functions, priorities, and an optional associated global or function.
-The functions referenced by this array will be called in descending
-order of priority (i.e. highest first) when the module is unloaded. The
-order of functions with the same priority is not defined.
+#. The optional "cconv" marker indicates which :ref:`calling
+ convention <callingconv>` the call should use. If none is
+ specified, the call defaults to using C calling conventions.
+#. The optional :ref:`Parameter Attributes <paramattrs>` list for return
+ values. Only '``zeroext``', '``signext``', and '``inreg``' attributes
+ are valid here.
+#. '``ptr to function ty``': shall be the signature of the pointer to
+ function value being invoked. In most cases, this is a direct
+ function invocation, but indirect ``invoke``'s are just as possible,
+ branching off an arbitrary pointer to function value.
+#. '``function ptr val``': An LLVM value containing a pointer to a
+ function to be invoked.
+#. '``function args``': argument list whose types match the function
+ signature argument types and parameter attributes. All arguments must
+ be of :ref:`first class <t_firstclass>` type. If the function signature
+ indicates the function accepts a variable number of arguments, the
+ extra arguments can be specified.
+#. '``normal label``': the label reached when the called function
+ executes a '``ret``' instruction.
+#. '``exception label``': the label reached when a callee returns via
+ the :ref:`resume <i_resume>` instruction or other exception handling
+ mechanism.
+#. The optional :ref:`function attributes <fnattrs>` list. Only
+ '``noreturn``', '``nounwind``', '``readonly``' and '``readnone``'
+ attributes are valid here.
-If the third field is present, non-null, and points to a global variable
-or function, the destructor function will only run if the associated
-data from the current module is not discarded.
+Semantics:
+""""""""""
-Instruction Reference
-=====================
+This instruction is designed to operate as a standard '``call``'
+instruction in most regards. The primary difference is that it
+establishes an association with a label, which is used by the runtime
+library to unwind the stack.
-The LLVM instruction set consists of several different classifications
-of instructions: :ref:`terminator instructions <terminators>`, :ref:`binary
-instructions <binaryops>`, :ref:`bitwise binary
-instructions <bitwiseops>`, :ref:`memory instructions <memoryops>`, and
-:ref:`other instructions <otherops>`.
+This instruction is used in languages with destructors to ensure that
+proper cleanup is performed in the case of either a ``longjmp`` or a
+thrown exception. Additionally, this is important for implementation of
+'``catch``' clauses in high-level languages that support them.
-.. _terminators:
+For the purposes of the SSA form, the definition of the value returned
+by the '``invoke``' instruction is deemed to occur on the edge from the
+current block to the "normal" label. If the callee unwinds then no
+return value is available.
-Terminator Instructions
------------------------
+Example:
+""""""""
-As mentioned :ref:`previously <functionstructure>`, every basic block in a
-program ends with a "Terminator" instruction, which indicates which
-block should be executed after the current block is finished. These
-terminator instructions typically yield a '``void``' value: they produce
-control flow, not values (the one exception being the
-':ref:`invoke <i_invoke>`' instruction).
+.. code-block:: llvm
-The terminator instructions are: ':ref:`ret <i_ret>`',
-':ref:`br <i_br>`', ':ref:`switch <i_switch>`',
-':ref:`indirectbr <i_indirectbr>`', ':ref:`invoke <i_invoke>`',
-':ref:`resume <i_resume>`', and ':ref:`unreachable <i_unreachable>`'.
+ %retval = invoke i32 @Test(i32 15) to label %Continue
+ unwind label %TestCleanup ; i32:retval set
+ %retval = invoke coldcc i32 %Testfnptr(i32 15) to label %Continue
+ unwind label %TestCleanup ; i32:retval set
-.. _i_ret:
+.. _i_resume:
-'``ret``' Instruction
-^^^^^^^^^^^^^^^^^^^^^
+'``resume``' Instruction
+^^^^^^^^^^^^^^^^^^^^^^^^
Syntax:
"""""""
::
- ret <type> <value> ; Return a value from a non-void function
- ret void ; Return from void function
+ resume <type> <value>
Overview:
"""""""""
-The '``ret``' instruction is used to return control flow (and optionally
-a value) from a function back to the caller.
-
-There are two forms of the '``ret``' instruction: one that returns a
-value and then causes control flow, and one that just causes control
-flow to occur.
+The '``resume``' instruction is a terminator instruction that has no
+successors.
Arguments:
""""""""""
-The '``ret``' instruction optionally accepts a single argument, the
-return value. The type of the return value must be a ':ref:`first
-class <t_firstclass>`' type.
-
-A function is not :ref:`well formed <wellformed>` if it it has a non-void
-return type and contains a '``ret``' instruction with no return value or
-a return value with a type that does not match its type, or if it has a
-void return type and contains a '``ret``' instruction with a return
-value.
+The '``resume``' instruction requires one argument, which must have the
+same type as the result of any '``landingpad``' instruction in the same
+function.
Semantics:
""""""""""
-When the '``ret``' instruction is executed, control flow returns back to
-the calling function's context. If the caller is a
-":ref:`call <i_call>`" instruction, execution continues at the
-instruction after the call. If the caller was an
-":ref:`invoke <i_invoke>`" instruction, execution continues at the
-beginning of the "normal" destination block. If the instruction returns
-a value, that value shall set the call or invoke instruction's return
-value.
+The '``resume``' instruction resumes propagation of an existing
+(in-flight) exception whose unwinding was interrupted with a
+:ref:`landingpad <i_landingpad>` instruction.
Example:
""""""""
.. code-block:: llvm
- ret i32 5 ; Return an integer value of 5
- ret void ; Return from a void function
- ret { i32, i8 } { i32 4, i8 2 } ; Return a struct of values 4 and 2
+ resume { i8*, i32 } %exn
-.. _i_br:
+.. _i_catchpad:
-'``br``' Instruction
-^^^^^^^^^^^^^^^^^^^^
+'``catchpad``' Instruction
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Syntax:
"""""""
::
- br i1 <cond>, label <iftrue>, label <iffalse>
- br label <dest> ; Unconditional branch
+ <resultval> = catchpad [<args>*]
+ to label <normal label> unwind label <exception label>
Overview:
"""""""""
-The '``br``' instruction is used to cause control flow to transfer to a
-different basic block in the current function. There are two forms of
-this instruction, corresponding to a conditional branch and an
-unconditional branch.
+The '``catchpad``' instruction is used by `LLVM's exception handling
+system <ExceptionHandling.html#overview>`_ to specify that a basic block
+is a catch block --- one where a personality routine attempts to transfer
+control to catch an exception.
+The ``args`` correspond to whatever information the personality
+routine requires to know if this is an appropriate place to catch the
+exception. Control is tranfered to the ``exception`` label if the
+``catchpad`` is not an appropriate handler for the in-flight exception.
+The ``normal`` label should contain the code found in the ``catch``
+portion of a ``try``/``catch`` sequence. The ``resultval`` has the type
+:ref:`token <t_token>` and is used to match the ``catchpad`` to
+corresponding :ref:`catchrets <i_catchret>`.
Arguments:
""""""""""
-The conditional branch form of the '``br``' instruction takes a single
-'``i1``' value and two '``label``' values. The unconditional form of the
-'``br``' instruction takes a single '``label``' value as a target.
+The instruction takes a list of arbitrary values which are interpreted
+by the :ref:`personality function <personalityfn>`.
+
+The ``catchpad`` must be provided a ``normal`` label to transfer control
+to if the ``catchpad`` matches the exception and an ``exception``
+label to transfer control to if it doesn't.
Semantics:
""""""""""
-Upon execution of a conditional '``br``' instruction, the '``i1``'
-argument is evaluated. If the value is ``true``, control flows to the
-'``iftrue``' ``label`` argument. If "cond" is ``false``, control flows
-to the '``iffalse``' ``label`` argument.
+When the call stack is being unwound due to an exception being thrown,
+the exception is compared against the ``args``. If it doesn't match,
+then control is transfered to the ``exception`` basic block.
+As with calling conventions, how the personality function results are
+represented in LLVM IR is target specific.
+
+The ``catchpad`` instruction has several restrictions:
+
+- A catch block is a basic block which is the unwind destination of
+ an exceptional instruction.
+- A catch block must have a '``catchpad``' instruction as its
+ first non-PHI instruction.
+- A catch block's ``exception`` edge must refer to a catch block or a
+ catch-end block.
+- There can be only one '``catchpad``' instruction within the
+ catch block.
+- A basic block that is not a catch block may not include a
+ '``catchpad``' instruction.
+- A catch block which has another catch block as a predecessor may not have
+ any other predecessors.
+- It is undefined behavior for control to transfer from a ``catchpad`` to a
+ ``ret`` without first executing a ``catchret`` that consumes the
+ ``catchpad`` or unwinding through its ``catchendpad``.
+- It is undefined behavior for control to transfer from a ``catchpad`` to
+ itself without first executing a ``catchret`` that consumes the
+ ``catchpad`` or unwinding through its ``catchendpad``.
Example:
""""""""
-.. code-block:: llvm
-
- Test:
- %cond = icmp eq i32 %a, %b
- br i1 %cond, label %IfEqual, label %IfUnequal
- IfEqual:
- ret i32 1
- IfUnequal:
- ret i32 0
+.. code-block:: llvm
-.. _i_switch:
+ ;; A catch block which can catch an integer.
+ %tok = catchpad [i8** @_ZTIi]
+ to label %int.handler unwind label %terminate
-'``switch``' Instruction
-^^^^^^^^^^^^^^^^^^^^^^^^
+.. _i_catchendpad:
+
+'``catchendpad``' Instruction
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Syntax:
"""""""
::
- switch <intty> <value>, label <defaultdest> [ <intty> <val>, label <dest> ... ]
+ catchendpad unwind label <nextaction>
+ catchendpad unwind to caller
Overview:
"""""""""
-The '``switch``' instruction is used to transfer control flow to one of
-several different places. It is a generalization of the '``br``'
-instruction, allowing a branch to occur to one of many possible
-destinations.
+The '``catchendpad``' instruction is used by `LLVM's exception handling
+system <ExceptionHandling.html#overview>`_ to communicate to the
+:ref:`personality function <personalityfn>` which invokes are associated
+with a chain of :ref:`catchpad <i_catchpad>` instructions.
+
+The ``nextaction`` label indicates where control should transfer to if
+none of the ``catchpad`` instructions are suitable for catching the
+in-flight exception.
+
+If a ``nextaction`` label is not present, the instruction unwinds out of
+its parent function. The
+:ref:`personality function <personalityfn>` will continue processing
+exception handling actions in the caller.
Arguments:
""""""""""
-The '``switch``' instruction uses three parameters: an integer
-comparison value '``value``', a default '``label``' destination, and an
-array of pairs of comparison value constants and '``label``'s. The table
-is not allowed to contain duplicate constant entries.
+The instruction optionally takes a label, ``nextaction``, indicating
+where control should transfer to if none of the preceding
+``catchpad`` instructions are suitable for the in-flight exception.
Semantics:
""""""""""
-The ``switch`` instruction specifies a table of values and destinations.
-When the '``switch``' instruction is executed, this table is searched
-for the given value. If the value is found, control flow is transferred
-to the corresponding destination; otherwise, control flow is transferred
-to the default destination.
+When the call stack is being unwound due to an exception being thrown
+and none of the constituent ``catchpad`` instructions match, then
+control is transfered to ``nextaction`` if it is present. If it is not
+present, control is transfered to the caller.
-Implementation:
-"""""""""""""""
+The ``catchendpad`` instruction has several restrictions:
-Depending on properties of the target machine and the particular
-``switch`` instruction, this instruction may be code generated in
-different ways. For example, it could be generated as a series of
-chained conditional branches or with a lookup table.
+- A catch-end block is a basic block which is the unwind destination of
+ an exceptional instruction.
+- A catch-end block must have a '``catchendpad``' instruction as its
+ first non-PHI instruction.
+- There can be only one '``catchendpad``' instruction within the
+ catch block.
+- A basic block that is not a catch-end block may not include a
+ '``catchendpad``' instruction.
+- Exactly one catch block may unwind to a ``catchendpad``.
+- The unwind target of invokes between a ``catchpad`` and a
+ corresponding ``catchret`` must be its ``catchendpad`` or
+ an inner EH pad.
Example:
""""""""
.. code-block:: llvm
- ; Emulate a conditional br instruction
- %Val = zext i1 %value to i32
- switch i32 %Val, label %truedest [ i32 0, label %falsedest ]
-
- ; Emulate an unconditional br instruction
- switch i32 0, label %dest [ ]
-
- ; Implement a jump table:
- switch i32 %val, label %otherwise [ i32 0, label %onzero
- i32 1, label %onone
- i32 2, label %ontwo ]
+ catchendpad unwind label %terminate
+ catchendpad unwind to caller
-.. _i_indirectbr:
+.. _i_catchret:
-'``indirectbr``' Instruction
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+'``catchret``' Instruction
+^^^^^^^^^^^^^^^^^^^^^^^^^^
Syntax:
"""""""
::
- indirectbr <somety>* <address>, [ label <dest1>, label <dest2>, ... ]
+ catchret <value> to label <normal>
Overview:
"""""""""
-The '``indirectbr``' instruction implements an indirect branch to a
-label within the current function, whose address is specified by
-"``address``". Address must be derived from a
-:ref:`blockaddress <blockaddress>` constant.
+The '``catchret``' instruction is a terminator instruction that has a
+single successor.
+
Arguments:
""""""""""
-The '``address``' argument is the address of the label to jump to. The
-rest of the arguments indicate the full set of possible destinations
-that the address may point to. Blocks are allowed to occur multiple
-times in the destination list, though this isn't particularly useful.
-
-This destination list is required so that dataflow analysis has an
-accurate understanding of the CFG.
+The first argument to a '``catchret``' indicates which ``catchpad`` it
+exits. It must be a :ref:`catchpad <i_catchpad>`.
+The second argument to a '``catchret``' specifies where control will
+transfer to next.
Semantics:
""""""""""
-Control transfers to the block specified in the address argument. All
-possible destination blocks must be listed in the label list, otherwise
-this instruction has undefined behavior. This implies that jumps to
-labels defined in other functions have undefined behavior as well.
-
-Implementation:
-"""""""""""""""
+The '``catchret``' instruction ends the existing (in-flight) exception
+whose unwinding was interrupted with a
+:ref:`catchpad <i_catchpad>` instruction.
+The :ref:`personality function <personalityfn>` gets a chance to execute
+arbitrary code to, for example, run a C++ destructor.
+Control then transfers to ``normal``.
+It may be passed an optional, personality specific, value.
+It is undefined behavior to execute a ``catchret`` whose ``catchpad`` has
+not been executed.
+It is undefined behavior to execute a ``catchret`` if any ``catchpad`` or
+``cleanuppad`` has been executed, without subsequently executing a
+corresponding ``catchret``/``cleanupret`` or unwinding out of the inner
+pad, following the most recent execution of the ``catchret``'s corresponding
+``catchpad``.
-This is typically implemented with a jump through a register.
Example:
""""""""
.. code-block:: llvm
- indirectbr i8* %Addr, [ label %bb1, label %bb2, label %bb3 ]
+ catchret %catch label %continue
-.. _i_invoke:
+.. _i_cleanupret:
-'``invoke``' Instruction
-^^^^^^^^^^^^^^^^^^^^^^^^
+'``cleanupret``' Instruction
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Syntax:
"""""""
::
- <result> = invoke [cconv] [ret attrs] <ptr to function ty> <function ptr val>(<function args>) [fn attrs]
- to label <normal label> unwind label <exception label>
+ cleanupret <value> unwind label <continue>
+ cleanupret <value> unwind to caller
Overview:
"""""""""
-The '``invoke``' instruction causes control to transfer to a specified
-function, with the possibility of control flow transfer to either the
-'``normal``' label or the '``exception``' label. If the callee function
-returns with the "``ret``" instruction, control flow will return to the
-"normal" label. If the callee (or any indirect callees) returns via the
-":ref:`resume <i_resume>`" instruction or other exception handling
-mechanism, control is interrupted and continued at the dynamically
-nearest "exception" label.
+The '``cleanupret``' instruction is a terminator instruction that has
+an optional successor.
-The '``exception``' label is a `landing
-pad <ExceptionHandling.html#overview>`_ for the exception. As such,
-'``exception``' label is required to have the
-":ref:`landingpad <i_landingpad>`" instruction, which contains the
-information about the behavior of the program after unwinding happens,
-as its first non-PHI instruction. The restrictions on the
-"``landingpad``" instruction's tightly couples it to the "``invoke``"
-instruction, so that the important information contained within the
-"``landingpad``" instruction can't be lost through normal code motion.
Arguments:
""""""""""
-This instruction requires several arguments:
-
-#. The optional "cconv" marker indicates which :ref:`calling
- convention <callingconv>` the call should use. If none is
- specified, the call defaults to using C calling conventions.
-#. The optional :ref:`Parameter Attributes <paramattrs>` list for return
- values. Only '``zeroext``', '``signext``', and '``inreg``' attributes
- are valid here.
-#. '``ptr to function ty``': shall be the signature of the pointer to
- function value being invoked. In most cases, this is a direct
- function invocation, but indirect ``invoke``'s are just as possible,
- branching off an arbitrary pointer to function value.
-#. '``function ptr val``': An LLVM value containing a pointer to a
- function to be invoked.
-#. '``function args``': argument list whose types match the function
- signature argument types and parameter attributes. All arguments must
- be of :ref:`first class <t_firstclass>` type. If the function signature
- indicates the function accepts a variable number of arguments, the
- extra arguments can be specified.
-#. '``normal label``': the label reached when the called function
- executes a '``ret``' instruction.
-#. '``exception label``': the label reached when a callee returns via
- the :ref:`resume <i_resume>` instruction or other exception handling
- mechanism.
-#. The optional :ref:`function attributes <fnattrs>` list. Only
- '``noreturn``', '``nounwind``', '``readonly``' and '``readnone``'
- attributes are valid here.
+The '``cleanupret``' instruction requires one argument, which indicates
+which ``cleanuppad`` it exits, and must be a :ref:`cleanuppad <i_cleanuppad>`.
+It also has an optional successor, ``continue``.
Semantics:
""""""""""
-This instruction is designed to operate as a standard '``call``'
-instruction in most regards. The primary difference is that it
-establishes an association with a label, which is used by the runtime
-library to unwind the stack.
-
-This instruction is used in languages with destructors to ensure that
-proper cleanup is performed in the case of either a ``longjmp`` or a
-thrown exception. Additionally, this is important for implementation of
-'``catch``' clauses in high-level languages that support them.
-
-For the purposes of the SSA form, the definition of the value returned
-by the '``invoke``' instruction is deemed to occur on the edge from the
-current block to the "normal" label. If the callee unwinds then no
-return value is available.
+The '``cleanupret``' instruction indicates to the
+:ref:`personality function <personalityfn>` that one
+:ref:`cleanuppad <i_cleanuppad>` it transferred control to has ended.
+It transfers control to ``continue`` or unwinds out of the function.
+It is undefined behavior to execute a ``cleanupret`` whose ``cleanuppad`` has
+not been executed.
+It is undefined behavior to execute a ``cleanupret`` if any ``catchpad`` or
+``cleanuppad`` has been executed, without subsequently executing a
+corresponding ``catchret``/``cleanupret`` or unwinding out of the inner pad,
+following the most recent execution of the ``cleanupret``'s corresponding
+``cleanuppad``.
Example:
""""""""
.. code-block:: llvm
- %retval = invoke i32 @Test(i32 15) to label %Continue
- unwind label %TestCleanup ; i32:retval set
- %retval = invoke coldcc i32 %Testfnptr(i32 15) to label %Continue
- unwind label %TestCleanup ; i32:retval set
+ cleanupret %cleanup unwind to caller
+ cleanupret %cleanup unwind label %continue
-.. _i_resume:
+.. _i_terminatepad:
-'``resume``' Instruction
-^^^^^^^^^^^^^^^^^^^^^^^^
+'``terminatepad``' Instruction
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Syntax:
"""""""
::
- resume <type> <value>
+ terminatepad [<args>*] unwind label <exception label>
+ terminatepad [<args>*] unwind to caller
Overview:
"""""""""
-The '``resume``' instruction is a terminator instruction that has no
-successors.
+The '``terminatepad``' instruction is used by `LLVM's exception handling
+system <ExceptionHandling.html#overview>`_ to specify that a basic block
+is a terminate block --- one where a personality routine may decide to
+terminate the program.
+The ``args`` correspond to whatever information the personality
+routine requires to know if this is an appropriate place to terminate the
+program. Control is transferred to the ``exception`` label if the
+personality routine decides not to terminate the program for the
+in-flight exception.
Arguments:
""""""""""
-The '``resume``' instruction requires one argument, which must have the
-same type as the result of any '``landingpad``' instruction in the same
-function.
+The instruction takes a list of arbitrary values which are interpreted
+by the :ref:`personality function <personalityfn>`.
+
+The ``terminatepad`` may be given an ``exception`` label to
+transfer control to if the in-flight exception matches the ``args``.
Semantics:
""""""""""
-The '``resume``' instruction resumes propagation of an existing
-(in-flight) exception whose unwinding was interrupted with a
-:ref:`landingpad <i_landingpad>` instruction.
+When the call stack is being unwound due to an exception being thrown,
+the exception is compared against the ``args``. If it matches,
+then control is transfered to the ``exception`` basic block. Otherwise,
+the program is terminated via personality-specific means. Typically,
+the first argument to ``terminatepad`` specifies what function the
+personality should defer to in order to terminate the program.
+
+The ``terminatepad`` instruction has several restrictions:
+
+- A terminate block is a basic block which is the unwind destination of
+ an exceptional instruction.
+- A terminate block must have a '``terminatepad``' instruction as its
+ first non-PHI instruction.
+- There can be only one '``terminatepad``' instruction within the
+ terminate block.
+- A basic block that is not a terminate block may not include a
+ '``terminatepad``' instruction.
Example:
""""""""
.. code-block:: llvm
- resume { i8*, i32 } %exn
+ ;; A terminate block which only permits integers.
+ terminatepad [i8** @_ZTIi] unwind label %continue
.. _i_unreachable:
The value produced is ``op1`` \* 2\ :sup:`op2` mod 2\ :sup:`n`,
where ``n`` is the width of the result. If ``op2`` is (statically or
-dynamically) negative or equal to or larger than the number of bits in
+dynamically) equal to or larger than the number of bits in
``op1``, the result is undefined. If the arguments are vectors, each
vector element of ``op1`` is shifted by the corresponding shift amount
in ``op2``.
::
- <result> = load [volatile] <ty>* <pointer>[, align <alignment>][, !nontemporal !<index>][, !invariant.load !<index>][, !nonnull !<index>]
+ <result> = load [volatile] <ty>, <ty>* <pointer>[, align <alignment>][, !nontemporal !<index>][, !invariant.load !<index>][, !nonnull !<index>][, !dereferenceable !<index>][, !dereferenceable_or_null !<index>]
<result> = load atomic [volatile] <ty>* <pointer> [singlethread] <ordering>, align <alignment>
!<index> = !{ i32 1 }
""""""""""
The argument to the ``load`` instruction specifies the memory address
-from which to load. The pointer must point to a :ref:`first
+from which to load. The type specified must be a :ref:`first
class <t_firstclass>` type. If the ``load`` is marked as ``volatile``,
then the optimizer is not allowed to modify the number or order of
execution of this ``load`` with other :ref:`volatile
The optional ``!invariant.load`` metadata must reference a single
metadata name ``<index>`` corresponding to a metadata node with no
entries. The existence of the ``!invariant.load`` metadata on the
-instruction tells the optimizer and code generator that this load
-address points to memory which does not change value during program
-execution. The optimizer may then move this load around, for example, by
-hoisting it out of loops using loop invariant code motion.
+instruction tells the optimizer and code generator that the address
+operand to this load points to memory which can be assumed unchanged.
+Being invariant does not imply that a location is dereferenceable,
+but it does imply that once the location is known dereferenceable
+its value is henceforth unchanging.
The optional ``!nonnull`` metadata must reference a single
metadata name ``<index>`` corresponding to a metadata node with no
entries. The existence of the ``!nonnull`` metadata on the
instruction tells the optimizer that the value loaded is known to
-never be null. This is analogous to the ''nonnull'' attribute
-on parameters and return values. This metadata can only be applied
-to loads of a pointer type.
+never be null. This is analogous to the ''nonnull'' attribute
+on parameters and return values. This metadata can only be applied
+to loads of a pointer type.
+
+The optional ``!dereferenceable`` metadata must reference a single
+metadata name ``<index>`` corresponding to a metadata node with one ``i64``
+entry. The existence of the ``!dereferenceable`` metadata on the instruction
+tells the optimizer that the value loaded is known to be dereferenceable.
+The number of bytes known to be dereferenceable is specified by the integer
+value in the metadata node. This is analogous to the ''dereferenceable''
+attribute on parameters and return values. This metadata can only be applied
+to loads of a pointer type.
+
+The optional ``!dereferenceable_or_null`` metadata must reference a single
+metadata name ``<index>`` corresponding to a metadata node with one ``i64``
+entry. The existence of the ``!dereferenceable_or_null`` metadata on the
+instruction tells the optimizer that the value loaded is known to be either
+dereferenceable or null.
+The number of bytes known to be dereferenceable is specified by the integer
+value in the metadata node. This is analogous to the ''dereferenceable_or_null''
+attribute on parameters and return values. This metadata can only be applied
+to loads of a pointer type.
Semantics:
""""""""""
%ptr = alloca i32 ; yields i32*:ptr
store i32 3, i32* %ptr ; yields void
- %val = load i32* %ptr ; yields i32:val = i32 3
+ %val = load i32, i32* %ptr ; yields i32:val = i32 3
.. _i_store:
%ptr = alloca i32 ; yields i32*:ptr
store i32 3, i32* %ptr ; yields void
- %val = load i32* %ptr ; yields i32:val = i32 3
+ %val = load i32, i32* %ptr ; yields i32:val = i32 3
.. _i_fence:
.. code-block:: llvm
entry:
- %orig = atomic load i32* %ptr unordered ; yields i32
+ %orig = atomic load i32, i32* %ptr unordered ; yields i32
br label %loop
loop:
::
- <result> = getelementptr <
pty>* <ptrval>{, <ty> <idx>}*
- <result> = getelementptr inbounds <
pty>* <ptrval>{, <ty> <idx>}*
- <result> = getelementptr <ptr vector> ptrval, <vector index type> idx
+ <result> = getelementptr <
ty>, <ty>* <ptrval>{, <ty> <idx>}*
+ <result> = getelementptr inbounds <
ty>, <ty>* <ptrval>{, <ty> <idx>}*
+ <result> = getelementptr <ty>, <ptr vector> <ptrval>, <vector index type> <idx>
Overview:
"""""""""
The '``getelementptr``' instruction is used to get the address of a
subelement of an :ref:`aggregate <t_aggregate>` data structure. It performs
-address calculation only and does not access memory.
+address calculation only and does not access memory. The instruction can also
+be used to calculate a vector of such addresses.
Arguments:
""""""""""
-The first argument is always a pointer or a vector of pointers, and
-forms the basis of the calculation. The remaining arguments are indices
+The first argument is always a type used as the basis for the calculations.
+The second argument is always a pointer or a vector of pointers, and is the
+base address to start from. The remaining arguments are indices
that indicate which of the elements of the aggregate object are indexed.
The interpretation of each index is dependent on the type being indexed
into. The first index always indexes the pointer value given as the
define i32* @foo(%struct.ST* %s) nounwind uwtable readnone optsize ssp {
entry:
- %arrayidx = getelementptr inbounds %struct.ST* %s, i64 1, i32 2, i32 1, i64 5, i64 13
+ %arrayidx = getelementptr inbounds %struct.ST, %struct.ST* %s, i64 1, i32 2, i32 1, i64 5, i64 13
ret i32* %arrayidx
}
.. code-block:: llvm
define i32* @foo(%struct.ST* %s) {
- %t1 = getelementptr %struct.ST* %s, i32 1 ; yields %struct.ST*:%t1
- %t2 = getelementptr %struct.ST* %t1, i32 0, i32 2 ; yields %struct.RT*:%t2
- %t3 = getelementptr %struct.RT* %t2, i32 0, i32 1 ; yields [10 x [20 x i32]]*:%t3
- %t4 = getelementptr [10 x [20 x i32]]* %t3, i32 0, i32 5 ; yields [20 x i32]*:%t4
- %t5 = getelementptr [20 x i32]* %t4, i32 0, i32 13 ; yields i32*:%t5
+ %t1 = getelementptr %struct.ST, %struct.ST* %s, i32 1 ; yields %struct.ST*:%t1
+ %t2 = getelementptr %struct.ST, %struct.ST* %t1, i32 0, i32 2 ; yields %struct.RT*:%t2
+ %t3 = getelementptr %struct.RT, %struct.RT* %t2, i32 0, i32 1 ; yields [10 x [20 x i32]]*:%t3
+ %t4 = getelementptr [10 x [20 x i32]], [10 x [20 x i32]]* %t3, i32 0, i32 5 ; yields [20 x i32]*:%t4
+ %t5 = getelementptr [20 x i32], [20 x i32]* %t4, i32 0, i32 13 ; yields i32*:%t5
ret i32* %t5
}
.. code-block:: llvm
; yields [12 x i8]*:aptr
- %aptr = getelementptr {i32, [12 x i8]}* %saptr, i64 0, i32 1
+ %aptr = getelementptr {i32, [12 x i8]}, {i32, [12 x i8]}* %saptr, i64 0, i32 1
; yields i8*:vptr
- %vptr = getelementptr {i32, <2 x i8>}* %svptr, i64 0, i32 1, i32 1
+ %vptr = getelementptr {i32, <2 x i8>}, {i32, <2 x i8>}* %svptr, i64 0, i32 1, i32 1
; yields i8*:eptr
- %eptr = getelementptr [12 x i8]* %aptr, i64 0, i32 1
+ %eptr = getelementptr [12 x i8], [12 x i8]* %aptr, i64 0, i32 1
; yields i32*:iptr
- %iptr = getelementptr [10 x i32]* @arr, i16 0, i16 0
+ %iptr = getelementptr [10 x i32], [10 x i32]* @arr, i16 0, i16 0
+
+Vector of pointers:
+"""""""""""""""""""
+
+The ``getelementptr`` returns a vector of pointers, instead of a single address,
+when one or more of its arguments is a vector. In such cases, all vector
+arguments should have the same number of elements, and every scalar argument
+will be effectively broadcast into a vector during address calculation.
+
+.. code-block:: llvm
+
+ ; All arguments are vectors:
+ ; A[i] = ptrs[i] + offsets[i]*sizeof(i8)
+ %A = getelementptr i8, <4 x i8*> %ptrs, <4 x i64> %offsets
+
+ ; Add the same scalar offset to each pointer of a vector:
+ ; A[i] = ptrs[i] + offset*sizeof(i8)
+ %A = getelementptr i8, <4 x i8*> %ptrs, i64 %offset
-In cases where the pointer argument is a vector of pointers, each index
-must be a vector with the same number of elements. For example:
+ ; Add distinct offsets to the same pointer:
+ ; A[i] = ptr + offsets[i]*sizeof(i8)
+ %A = getelementptr i8, i8* %ptr, <4 x i64> %offsets
+
+ ; In all cases described above the type of the result is <4 x i8*>
+
+The two following instructions are equivalent:
+
+.. code-block:: llvm
+
+ getelementptr %struct.ST, <4 x %struct.ST*> %s, <4 x i64> %ind1,
+ <4 x i32> <i32 2, i32 2, i32 2, i32 2>,
+ <4 x i32> <i32 1, i32 1, i32 1, i32 1>,
+ <4 x i32> %ind4,
+ <4 x i64> <i64 13, i64 13, i64 13, i64 13>
+
+ getelementptr %struct.ST, <4 x %struct.ST*> %s, <4 x i64> %ind1,
+ i32 2, i32 1, <4 x i32> %ind4, i64 13
+
+Let's look at the C code, where the vector version of ``getelementptr``
+makes sense:
+
+.. code-block:: c
+
+ // Let's assume that we vectorize the following loop:
+ double *A, B; int *C;
+ for (int i = 0; i < size; ++i) {
+ A[i] = B[C[i]];
+ }
.. code-block:: llvm
- %A = getelementptr <4 x i8*> %ptrs, <4 x i64> %offsets,
+ ; get pointers for 8 elements from array B
+ %ptrs = getelementptr double, double* %B, <8 x i32> %C
+ ; load 8 elements from array B into A
+ %A = call <8 x double> @llvm.masked.gather.v8f64(<8 x double*> %ptrs,
+ i32 8, <8 x i1> %mask, <8 x double> %passthru)
Conversion Operations
---------------------
""""""""""
The '``ptrtoint``' instruction takes a ``value`` to cast, which must be
-a a value of type :ref:`pointer <t_pointer>` or a vector of pointers, and a
+a value of type :ref:`pointer <t_pointer>` or a vector of pointers, and a
type to cast it to ``ty2``, which must be an :ref:`integer <t_integer>` or
a vector of integers type.
non-aggregate first class value, and a type to cast it to, which must
also be a non-aggregate :ref:`first class <t_firstclass>` type. The
bit sizes of ``value`` and the destination type, ``ty2``, must be
-identical. If the source type is a pointer, the destination type must
+identical. If the source type is a pointer, the destination type must
also be a pointer of the same size. This instruction supports bitwise
conversion of vectors to integers and to vectors of other types (as
long as they have the same size).
::
- <result> = fcmp <cond> <ty> <op1>, <op2> ; yields i1 or <N x i1>:result
+ <result> = fcmp [fast-math flags]* <cond> <ty> <op1>, <op2> ; yields i1 or <N x i1>:result
Overview:
"""""""""
#. ``uno``: yields ``true`` if either operand is a QNAN.
#. ``true``: always yields ``true``, regardless of operands.
+The ``fcmp`` instruction can also optionally take any number of
+:ref:`fast-math flags <fastmath>`, which are optimization hints to enable
+otherwise unsafe floating point optimizations.
+
+Any set of fast-math flags are legal on an ``fcmp`` instruction, but the
+only flags that have any effect on its semantics are those that allow
+assumptions to be made about the values of input arguments; namely
+``nnan``, ``ninf``, and ``nsz``. See :ref:`fastmath` for more information.
+
Example:
""""""""
The '``select``' instruction requires an 'i1' value or a vector of 'i1'
values indicating the condition, and two values of the same :ref:`first
-class <t_firstclass>` type. If the val1/val2 are vectors and the
-condition is a scalar, then entire vectors are selected, not individual
-elements.
+class <t_firstclass>` type.
Semantics:
""""""""""
If the condition is a vector of i1, then the value arguments must be
vectors of the same size, and the selection is done element by element.
+If the condition is an i1 and the value arguments are vectors of the
+same size, then an entire vector is selected.
+
Example:
""""""""
This instruction requires several arguments:
#. The optional ``tail`` and ``musttail`` markers indicate that the optimizers
- should perform tail call optimization. The ``tail`` marker is a hint that
- `can be ignored <CodeGenerator.html#sibcallopt>`_. The ``musttail`` marker
+ should perform tail call optimization. The ``tail`` marker is a hint that
+ `can be ignored <CodeGenerator.html#sibcallopt>`_. The ``musttail`` marker
means that the call must be tail call optimized in order for the program to
- be correct. The ``musttail`` marker provides these guarantees:
+ be correct. The ``musttail`` marker provides these guarantees:
#. The call will not cause unbounded stack growth if it is part of a
recursive cycle in the call graph.
forwarded in place.
Both markers imply that the callee does not access allocas or varargs from
- the caller. Calls marked ``musttail`` must obey the following additional
+ the caller. Calls marked ``musttail`` must obey the following additional
rules:
- The call must immediately precede a :ref:`ret <i_ret>` instruction,
or a pointer bitcast followed by a ret instruction.
- The ret instruction must return the (possibly bitcasted) value
produced by the call or void.
- - The caller and callee prototypes must match. Pointer types of
+ - The caller and callee prototypes must match. Pointer types of
parameters or return types may differ in pointee type, but not
in address space.
- The calling conventions of the caller and callee must match.
::
- <resultval> = landingpad <resultty> personality <type> <pers_fn> <clause>+
- <resultval> = landingpad <resultty> personality <type> <pers_fn> cleanup <clause>*
+ <resultval> = landingpad <resultty> <clause>+
+ <resultval> = landingpad <resultty> cleanup <clause>*
<clause> := catch <type> <value>
<clause> := filter <array constant type> <array constant>
system <ExceptionHandling.html#overview>`_ to specify that a basic block
is a landing pad --- one where the exception lands, and corresponds to the
code found in the ``catch`` portion of a ``try``/``catch`` sequence. It
-defines values supplied by the personality function (``pers_fn``) upon
+defines values supplied by the :ref:`personality function <personalityfn>` upon
re-entry to the function. The ``resultval`` has the type ``resultty``.
Arguments:
""""""""""
-This instruction takes a ``pers_fn`` value. This is the personality
-function associated with the unwinding mechanism. The optional
+The optional
``cleanup`` flag indicates that the landing pad block is a cleanup.
A ``clause`` begins with the clause type --- ``catch`` or ``filter`` --- and
""""""""""
The '``landingpad``' instruction defines the values which are set by the
-personality function (``pers_fn``) upon re-entry to the function, and
+:ref:`personality function <personalityfn>` upon re-entry to the function, and
therefore the "result type" of the ``landingpad`` instruction. As with
calling conventions, how the personality function results are
represented in LLVM IR is target specific.
pad block.
- A basic block that is not a landing pad block may not include a
'``landingpad``' instruction.
-- All '``landingpad``' instructions in a function must have the same
- personality function.
Example:
""""""""
.. code-block:: llvm
;; A landing pad which can catch an integer.
- %res = landingpad { i8*, i32 } personality i32 (...)* @__gxx_personality_v0
+ %res = landingpad { i8*, i32 }
catch i8** @_ZTIi
;; A landing pad that is a cleanup.
- %res = landingpad { i8*, i32 } personality i32 (...)* @__gxx_personality_v0
+ %res = landingpad { i8*, i32 }
cleanup
;; A landing pad which can catch an integer and can only throw a double.
- %res = landingpad { i8*, i32 } personality i32 (...)* @__gxx_personality_v0
+ %res = landingpad { i8*, i32 }
catch i8** @_ZTIi
filter [1 x i8**] [@_ZTId]
+.. _i_cleanuppad:
+
+'``cleanuppad``' Instruction
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ <resultval> = cleanuppad [<args>*]
+
+Overview:
+"""""""""
+
+The '``cleanuppad``' instruction is used by `LLVM's exception handling
+system <ExceptionHandling.html#overview>`_ to specify that a basic block
+is a cleanup block --- one where a personality routine attempts to
+transfer control to run cleanup actions.
+The ``args`` correspond to whatever additional
+information the :ref:`personality function <personalityfn>` requires to
+execute the cleanup.
+The ``resultval`` has the type :ref:`token <t_token>` and is used to
+match the ``cleanuppad`` to corresponding :ref:`cleanuprets <i_cleanupret>`.
+
+Arguments:
+""""""""""
+
+The instruction takes a list of arbitrary values which are interpreted
+by the :ref:`personality function <personalityfn>`.
+
+Semantics:
+""""""""""
+
+The '``cleanuppad``' instruction defines the values which are set by the
+:ref:`personality function <personalityfn>` upon re-entry to the function.
+As with calling conventions, how the personality function results are
+represented in LLVM IR is target specific.
+
+When the call stack is being unwound due to an exception being thrown,
+the :ref:`personality function <personalityfn>` transfers control to the
+``cleanuppad`` with the aid of the personality-specific arguments.
+
+The ``cleanuppad`` instruction has several restrictions:
+
+- A cleanup block is a basic block which is the unwind destination of
+ an exceptional instruction.
+- A cleanup block must have a '``cleanuppad``' instruction as its
+ first non-PHI instruction.
+- There can be only one '``cleanuppad``' instruction within the
+ cleanup block.
+- A basic block that is not a cleanup block may not include a
+ '``cleanuppad``' instruction.
+- All '``cleanupret``'s which exit a ``cleanuppad`` must have the same
+ exceptional successor.
+- It is undefined behavior for control to transfer from a ``cleanuppad`` to a
+ ``ret`` without first executing a ``cleanupret`` that consumes the
+ ``cleanuppad`` or unwinding out of the ``cleanuppad``.
+- It is undefined behavior for control to transfer from a ``cleanuppad`` to
+ itself without first executing a ``cleanupret`` that consumes the
+ ``cleanuppad`` or unwinding out of the ``cleanuppad``.
+
+Example:
+""""""""
+
+.. code-block:: llvm
+
+ %tok = cleanuppad []
+
.. _intrinsics:
Intrinsic Functions
.. code-block:: llvm
+ ; This struct is different for every platform. For most platforms,
+ ; it is merely an i8*.
+ %struct.va_list = type { i8* }
+
+ ; For Unix x86_64 platforms, va_list is the following struct:
+ ; %struct.va_list = type { i32, i32, i8*, i8* }
+
define i32 @test(i32 %X, ...) {
; Initialize variable argument processing
- %ap = alloca i8*
- %ap2 = bitcast i8** %ap to i8*
+ %ap = alloca %struct.va_list
+ %ap2 = bitcast %struct.va_list* %ap to i8*
call void @llvm.va_start(i8* %ap2)
; Read a single integer argument
- %tmp = va_arg i8** %ap, i32
+ %tmp = va_arg i8* %ap2, i32
; Demonstrate usage of llvm.va_copy and llvm.va_end
%aq = alloca i8*
Accurate Garbage Collection Intrinsics
--------------------------------------
-LLVM support for `Accurate Garbage Collection <GarbageCollection.html>`_
-(GC) requires the implementation and generation of these intrinsics.
+LLVM's support for `Accurate Garbage Collection <GarbageCollection.html>`_
+(GC) requires the frontend to generate code containing appropriate intrinsic
+calls and select an appropriate GC strategy which knows how to lower these
+intrinsics in a manner which is appropriate for the target collector.
+
These intrinsics allow identification of :ref:`GC roots on the
stack <int_gcroot>`, as well as garbage collector implementations that
require :ref:`read <int_gcread>` and :ref:`write <int_gcwrite>` barriers.
-Front-ends for type-safe garbage collected languages should generate
+Frontends for type-safe garbage collected languages should generate
these intrinsics to make use of the LLVM garbage collectors. For more
-details, see `Accurate Garbage Collection with
-LLVM <GarbageCollection.html>`_.
+details, see `Garbage Collection with LLVM <GarbageCollection.html>`_.
+
+Experimental Statepoint Intrinsics
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-The garbage collection intrinsics only operate on objects in the generic
-address space (address space zero).
+LLVM provides an second experimental set of intrinsics for describing garbage
+collection safepoints in compiled code. These intrinsics are an alternative
+to the ``llvm.gcroot`` intrinsics, but are compatible with the ones for
+:ref:`read <int_gcread>` and :ref:`write <int_gcwrite>` barriers. The
+differences in approach are covered in the `Garbage Collection with LLVM
+<GarbageCollection.html>`_ documentation. The intrinsics themselves are
+described in :doc:`Statepoints`.
.. _int_gcroot:
other aggressive transformations, so the value returned may not be that
of the obvious source-language caller.
+'``llvm.localescape``' and '``llvm.localrecover``' Intrinsics
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ declare void @llvm.localescape(...)
+ declare i8* @llvm.localrecover(i8* %func, i8* %fp, i32 %idx)
+
+Overview:
+"""""""""
+
+The '``llvm.localescape``' intrinsic escapes offsets of a collection of static
+allocas, and the '``llvm.localrecover``' intrinsic applies those offsets to a
+live frame pointer to recover the address of the allocation. The offset is
+computed during frame layout of the caller of ``llvm.localescape``.
+
+Arguments:
+""""""""""
+
+All arguments to '``llvm.localescape``' must be pointers to static allocas or
+casts of static allocas. Each function can only call '``llvm.localescape``'
+once, and it can only do so from the entry block.
+
+The ``func`` argument to '``llvm.localrecover``' must be a constant
+bitcasted pointer to a function defined in the current module. The code
+generator cannot determine the frame allocation offset of functions defined in
+other modules.
+
+The ``fp`` argument to '``llvm.localrecover``' must be a frame pointer of a
+call frame that is currently live. The return value of '``llvm.localaddress``'
+is one way to produce such a value, but various runtimes also expose a suitable
+pointer in platform-specific ways.
+
+The ``idx`` argument to '``llvm.localrecover``' indicates which alloca passed to
+'``llvm.localescape``' to recover. It is zero-indexed.
+
+Semantics:
+""""""""""
+
+These intrinsics allow a group of functions to share access to a set of local
+stack allocations of a one parent function. The parent function may call the
+'``llvm.localescape``' intrinsic once from the function entry block, and the
+child functions can use '``llvm.localrecover``' to access the escaped allocas.
+The '``llvm.localescape``' intrinsic blocks inlining, as inlining changes where
+the escaped allocas are allocated, which would break attempts to use
+'``llvm.localrecover``'.
+
.. _int_read_register:
.. _int_write_register:
declare i64 @llvm.read_register.i64(metadata)
declare void @llvm.write_register.i32(metadata, i32 @value)
declare void @llvm.write_register.i64(metadata, i64 @value)
- !0 = metadata !{metadata !"sp\00"}
+ !0 = !{!"sp\00"}
Overview:
"""""""""
The default behavior is to emit a call to ``__clear_cache`` from the run
time library.
-This instrinsic does *not* empty the instruction pipeline. Modifications
-of the current function are outside the scope of the intrinsic.
+This instrinsic does *not* empty the instruction pipeline. Modifications
+of the current function are outside the scope of the intrinsic.
+
+'``llvm.instrprof_increment``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ declare void @llvm.instrprof_increment(i8* <name>, i64 <hash>,
+ i32 <num-counters>, i32 <index>)
+
+Overview:
+"""""""""
+
+The '``llvm.instrprof_increment``' intrinsic can be emitted by a
+frontend for use with instrumentation based profiling. These will be
+lowered by the ``-instrprof`` pass to generate execution counts of a
+program at runtime.
+
+Arguments:
+""""""""""
+
+The first argument is a pointer to a global variable containing the
+name of the entity being instrumented. This should generally be the
+(mangled) function name for a set of counters.
+
+The second argument is a hash value that can be used by the consumer
+of the profile data to detect changes to the instrumented source, and
+the third is the number of counters associated with ``name``. It is an
+error if ``hash`` or ``num-counters`` differ between two instances of
+``instrprof_increment`` that refer to the same name.
+
+The last argument refers to which of the counters for ``name`` should
+be incremented. It should be a value between 0 and ``num-counters``.
+
+Semantics:
+""""""""""
+
+This intrinsic represents an increment of a profiling counter. It will
+cause the ``-instrprof`` pass to generate the appropriate data
+structures and the code to increment the appropriate value, in a
+format that can be written out by a compiler runtime and consumed via
+the ``llvm-profdata`` tool.
Standard C Library Intrinsics
-----------------------------
declare float @llvm.fabs.f32(float %Val)
declare double @llvm.fabs.f64(double %Val)
- declare x86_fp80 @llvm.fabs.f80(x86_fp80 %Val)
+ declare x86_fp80 @llvm.fabs.f80(x86_fp80 %Val)
declare fp128 @llvm.fabs.f128(fp128 %Val)
- declare ppc_fp128 @llvm.fabs.ppcf128(ppc_fp128 %Val)
+ declare ppc_fp128 @llvm.fabs.ppcf128(ppc_fp128 %Val)
Overview:
"""""""""
This function returns the same values as the libm ``fabs`` functions
would, and handles error conditions in the same way.
+'``llvm.minnum.*``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+This is an overloaded intrinsic. You can use ``llvm.minnum`` on any
+floating point or vector of floating point type. Not all targets support
+all types however.
+
+::
+
+ declare float @llvm.minnum.f32(float %Val0, float %Val1)
+ declare double @llvm.minnum.f64(double %Val0, double %Val1)
+ declare x86_fp80 @llvm.minnum.f80(x86_fp80 %Val0, x86_fp80 %Val1)
+ declare fp128 @llvm.minnum.f128(fp128 %Val0, fp128 %Val1)
+ declare ppc_fp128 @llvm.minnum.ppcf128(ppc_fp128 %Val0, ppc_fp128 %Val1)
+
+Overview:
+"""""""""
+
+The '``llvm.minnum.*``' intrinsics return the minimum of the two
+arguments.
+
+
+Arguments:
+""""""""""
+
+The arguments and return value are floating point numbers of the same
+type.
+
+Semantics:
+""""""""""
+
+Follows the IEEE-754 semantics for minNum, which also match for libm's
+fmin.
+
+If either operand is a NaN, returns the other non-NaN operand. Returns
+NaN only if both operands are NaN. If the operands compare equal,
+returns a value that compares equal to both operands. This means that
+fmin(+/-0.0, +/-0.0) could return either -0.0 or 0.0.
+
+'``llvm.maxnum.*``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+This is an overloaded intrinsic. You can use ``llvm.maxnum`` on any
+floating point or vector of floating point type. Not all targets support
+all types however.
+
+::
+
+ declare float @llvm.maxnum.f32(float %Val0, float %Val1l)
+ declare double @llvm.maxnum.f64(double %Val0, double %Val1)
+ declare x86_fp80 @llvm.maxnum.f80(x86_fp80 %Val0, x86_fp80 %Val1)
+ declare fp128 @llvm.maxnum.f128(fp128 %Val0, fp128 %Val1)
+ declare ppc_fp128 @llvm.maxnum.ppcf128(ppc_fp128 %Val0, ppc_fp128 %Val1)
+
+Overview:
+"""""""""
+
+The '``llvm.maxnum.*``' intrinsics return the maximum of the two
+arguments.
+
+
+Arguments:
+""""""""""
+
+The arguments and return value are floating point numbers of the same
+type.
+
+Semantics:
+""""""""""
+Follows the IEEE-754 semantics for maxNum, which also match for libm's
+fmax.
+
+If either operand is a NaN, returns the other non-NaN operand. Returns
+NaN only if both operands are NaN. If the operands compare equal,
+returns a value that compares equal to both operands. This means that
+fmax(+/-0.0, +/-0.0) could return either -0.0 or 0.0.
+
'``llvm.copysign.*``' Intrinsic
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
""""""""""
The first argument is the value to be counted. This argument may be of
-any integer type, or a vectory with integer element type. The return
+any integer type, or a vector with integer element type. The return
type must match the first argument type.
The second argument must be a constant and is a flag to indicate whether
""""""""""
The first argument is the value to be counted. This argument may be of
-any integer type, or a vectory with integer element type. The return
+any integer type, or a vector with integer element type. The return
type must match the first argument type.
The second argument must be a constant and is a flag to indicate whether
``is_zero_undef == 0`` and ``undef`` otherwise. For example,
``llvm.cttz(2) = 1``.
+.. _int_overflow:
+
Arithmetic with Overflow Intrinsics
-----------------------------------
Specialised Arithmetic Intrinsics
---------------------------------
+'``llvm.canonicalize.*``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ declare float @llvm.canonicalize.f32(float %a)
+ declare double @llvm.canonicalize.f64(double %b)
+
+Overview:
+"""""""""
+
+The '``llvm.canonicalize.*``' intrinsic returns the platform specific canonical
+encoding of a floating point number. This canonicalization is useful for
+implementing certain numeric primitives such as frexp. The canonical encoding is
+defined by IEEE-754-2008 to be:
+
+::
+
+ 2.1.8 canonical encoding: The preferred encoding of a floating-point
+ representation in a format. Applied to declets, significands of finite
+ numbers, infinities, and NaNs, especially in decimal formats.
+
+This operation can also be considered equivalent to the IEEE-754-2008
+conversion of a floating-point value to the same format. NaNs are handled
+according to section 6.2.
+
+Examples of non-canonical encodings:
+
+- x87 pseudo denormals, pseudo NaNs, pseudo Infinity, Unnormals. These are
+ converted to a canonical representation per hardware-specific protocol.
+- Many normal decimal floating point numbers have non-canonical alternative
+ encodings.
+- Some machines, like GPUs or ARMv7 NEON, do not support subnormal values.
+ These are treated as non-canonical encodings of zero and with be flushed to
+ a zero of the same sign by this operation.
+
+Note that per IEEE-754-2008 6.2, systems that support signaling NaNs with
+default exception handling must signal an invalid exception, and produce a
+quiet NaN result.
+
+This function should always be implementable as multiplication by 1.0, provided
+that the compiler does not constant fold the operation. Likewise, division by
+1.0 and ``llvm.minnum(x, x)`` are possible implementations. Addition with
+-0.0 is also sufficient provided that the rounding mode is not -Infinity.
+
+``@llvm.canonicalize`` must preserve the equality relation. That is:
+
+- ``(@llvm.canonicalize(x) == x)`` is equivalent to ``(x == x)``
+- ``(@llvm.canonicalize(x) == @llvm.canonicalize(y))`` is equivalent to
+ to ``(x == y)``
+
+Additionally, the sign of zero must be conserved:
+``@llvm.canonicalize(-0.0) = -0.0`` and ``@llvm.canonicalize(+0.0) = +0.0``
+
+The payload bits of a NaN must be conserved, with two exceptions.
+First, environments which use only a single canonical representation of NaN
+must perform said canonicalization. Second, SNaNs must be quieted per the
+usual methods.
+
+The canonicalization operation may be optimized away if:
+
+- The input is known to be canonical. For example, it was produced by a
+ floating-point operation that is required by the standard to be canonical.
+- The result is consumed only by (or fused with) other floating-point
+ operations. That is, the bits of the floating point value are not examined.
+
'``llvm.fmuladd.*``' Intrinsic
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
%r2 = call float @llvm.fmuladd.f32(float %a, float %b, float %c) ; yields float:r2 = (a * b) + c
+
+'``llvm.uabsdiff.*``' and '``llvm.sabsdiff.*``' Intrinsics
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+This is an overloaded intrinsic. The loaded data is a vector of any integer bit width.
+
+.. code-block:: llvm
+
+ declare <4 x integer> @llvm.uabsdiff.v4i32(<4 x integer> %a, <4 x integer> %b)
+
+
+Overview:
+"""""""""
+
+The ``llvm.uabsdiff`` intrinsic returns a vector result of the absolute difference of
+the two operands, treating them both as unsigned integers.
+
+The ``llvm.sabsdiff`` intrinsic returns a vector result of the absolute difference of
+the two operands, treating them both as signed integers.
+
+.. note::
+
+ These intrinsics are primarily used during the code generation stage of compilation.
+ They are generated by compiler passes such as the Loop and SLP vectorizers.it is not
+ recommended for users to create them manually.
+
+Arguments:
+""""""""""
+
+Both intrinsics take two integer of the same bitwidth.
+
+Semantics:
+""""""""""
+
+The expression::
+
+ call <4 x i32> @llvm.uabsdiff.v4i32(<4 x i32> %a, <4 x i32> %b)
+
+is equivalent to::
+
+ %sub = sub <4 x i32> %a, %b
+ %ispos = icmp ugt <4 x i32> %sub, <i32 -1, i32 -1, i32 -1, i32 -1>
+ %neg = sub <4 x i32> zeroinitializer, %sub
+ %1 = select <4 x i1> %ispos, <4 x i32> %sub, <4 x i32> %neg
+
+Similarly the expression::
+
+ call <4 x i32> @llvm.sabsdiff.v4i32(<4 x i32> %a, <4 x i32> %b)
+
+is equivalent to::
+
+ %sub = sub nsw <4 x i32> %a, %b
+ %ispos = icmp sgt <4 x i32> %sub, <i32 -1, i32 -1, i32 -1, i32 -1>
+ %neg = sub nsw <4 x i32> zeroinitializer, %sub
+ %1 = select <4 x i1> %ispos, <4 x i32> %sub, <4 x i32> %neg
+
+
Half Precision Floating Point Intrinsics
----------------------------------------
.. code-block:: llvm
- %a = load i16* @x, align 2
+ %a = load i16, i16* @x, align 2
%res = call float @llvm.convert.from.fp16(i16 %a)
+.. _dbg_intrinsics:
+
Debugger Intrinsics
-------------------
.. code-block:: llvm
%tramp = alloca [10 x i8], align 4 ; size and alignment only correct for X86
- %tramp1 = getelementptr [10 x i8]* %tramp, i32 0, i32 0
+ %tramp1 = getelementptr [10 x i8], [10 x i8]* %tramp, i32 0, i32 0
call i8* @llvm.init.trampoline(i8* %tramp1, i8* bitcast (i32 (i8*, i32, i32)* @f to i8*), i8* %nval)
%p = call i8* @llvm.adjust.trampoline(i8* %tramp1)
%fp = bitcast i8* %p to i32 (i32, i32)*
after performing the required machine specific adjustments. The pointer
returned can then be :ref:`bitcast and executed <int_trampoline>`.
+.. _int_mload_mstore:
+
+Masked Vector Load and Store Intrinsics
+---------------------------------------
+
+LLVM provides intrinsics for predicated vector load and store operations. The predicate is specified by a mask operand, which holds one bit per vector element, switching the associated vector lane on or off. The memory addresses corresponding to the "off" lanes are not accessed. When all bits of the mask are on, the intrinsic is identical to a regular vector load or store. When all bits are off, no memory is accessed.
+
+.. _int_mload:
+
+'``llvm.masked.load.*``' Intrinsics
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+This is an overloaded intrinsic. The loaded data is a vector of any integer or floating point data type.
+
+::
+
+ declare <16 x float> @llvm.masked.load.v16f32 (<16 x float>* <ptr>, i32 <alignment>, <16 x i1> <mask>, <16 x float> <passthru>)
+ declare <2 x double> @llvm.masked.load.v2f64 (<2 x double>* <ptr>, i32 <alignment>, <2 x i1> <mask>, <2 x double> <passthru>)
+
+Overview:
+"""""""""
+
+Reads a vector from memory according to the provided mask. The mask holds a bit for each vector lane, and is used to prevent memory accesses to the masked-off lanes. The masked-off lanes in the result vector are taken from the corresponding lanes of the '``passthru``' operand.
+
+
+Arguments:
+""""""""""
+
+The first operand is the base pointer for the load. The second operand is the alignment of the source location. It must be a constant integer value. The third operand, mask, is a vector of boolean values with the same number of elements as the return type. The fourth is a pass-through value that is used to fill the masked-off lanes of the result. The return type, underlying type of the base pointer and the type of the '``passthru``' operand are the same vector types.
+
+
+Semantics:
+""""""""""
+
+The '``llvm.masked.load``' intrinsic is designed for conditional reading of selected vector elements in a single IR operation. It is useful for targets that support vector masked loads and allows vectorizing predicated basic blocks on these targets. Other targets may support this intrinsic differently, for example by lowering it into a sequence of branches that guard scalar load operations.
+The result of this operation is equivalent to a regular vector load instruction followed by a 'select' between the loaded and the passthru values, predicated on the same mask. However, using this intrinsic prevents exceptions on memory access to masked-off lanes.
+
+
+::
+
+ %res = call <16 x float> @llvm.masked.load.v16f32 (<16 x float>* %ptr, i32 4, <16 x i1>%mask, <16 x float> %passthru)
+
+ ;; The result of the two following instructions is identical aside from potential memory access exception
+ %loadlal = load <16 x float>, <16 x float>* %ptr, align 4
+ %res = select <16 x i1> %mask, <16 x float> %loadlal, <16 x float> %passthru
+
+.. _int_mstore:
+
+'``llvm.masked.store.*``' Intrinsics
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+This is an overloaded intrinsic. The data stored in memory is a vector of any integer or floating point data type.
+
+::
+
+ declare void @llvm.masked.store.v8i32 (<8 x i32> <value>, <8 x i32> * <ptr>, i32 <alignment>, <8 x i1> <mask>)
+ declare void @llvm.masked.store.v16f32(<16 x i32> <value>, <16 x i32>* <ptr>, i32 <alignment>, <16 x i1> <mask>)
+
+Overview:
+"""""""""
+
+Writes a vector to memory according to the provided mask. The mask holds a bit for each vector lane, and is used to prevent memory accesses to the masked-off lanes.
+
+Arguments:
+""""""""""
+
+The first operand is the vector value to be written to memory. The second operand is the base pointer for the store, it has the same underlying type as the value operand. The third operand is the alignment of the destination location. The fourth operand, mask, is a vector of boolean values. The types of the mask and the value operand must have the same number of vector elements.
+
+
+Semantics:
+""""""""""
+
+The '``llvm.masked.store``' intrinsics is designed for conditional writing of selected vector elements in a single IR operation. It is useful for targets that support vector masked store and allows vectorizing predicated basic blocks on these targets. Other targets may support this intrinsic differently, for example by lowering it into a sequence of branches that guard scalar store operations.
+The result of this operation is equivalent to a load-modify-store sequence. However, using this intrinsic prevents exceptions and data races on memory access to masked-off lanes.
+
+::
+
+ call void @llvm.masked.store.v16f32(<16 x float> %value, <16 x float>* %ptr, i32 4, <16 x i1> %mask)
+
+ ;; The result of the following instructions is identical aside from potential data races and memory access exceptions
+ %oldval = load <16 x float>, <16 x float>* %ptr, align 4
+ %res = select <16 x i1> %mask, <16 x float> %value, <16 x float> %oldval
+ store <16 x float> %res, <16 x float>* %ptr, align 4
+
+
+Masked Vector Gather and Scatter Intrinsics
+-------------------------------------------
+
+LLVM provides intrinsics for vector gather and scatter operations. They are similar to :ref:`Masked Vector Load and Store <int_mload_mstore>`, except they are designed for arbitrary memory accesses, rather than sequential memory accesses. Gather and scatter also employ a mask operand, which holds one bit per vector element, switching the associated vector lane on or off. The memory addresses corresponding to the "off" lanes are not accessed. When all bits are off, no memory is accessed.
+
+.. _int_mgather:
+
+'``llvm.masked.gather.*``' Intrinsics
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+This is an overloaded intrinsic. The loaded data are multiple scalar values of any integer or floating point data type gathered together into one vector.
+
+::
+
+ declare <16 x float> @llvm.masked.gather.v16f32 (<16 x float*> <ptrs>, i32 <alignment>, <16 x i1> <mask>, <16 x float> <passthru>)
+ declare <2 x double> @llvm.masked.gather.v2f64 (<2 x double*> <ptrs>, i32 <alignment>, <2 x i1> <mask>, <2 x double> <passthru>)
+
+Overview:
+"""""""""
+
+Reads scalar values from arbitrary memory locations and gathers them into one vector. The memory locations are provided in the vector of pointers '``ptrs``'. The memory is accessed according to the provided mask. The mask holds a bit for each vector lane, and is used to prevent memory accesses to the masked-off lanes. The masked-off lanes in the result vector are taken from the corresponding lanes of the '``passthru``' operand.
+
+
+Arguments:
+""""""""""
+
+The first operand is a vector of pointers which holds all memory addresses to read. The second operand is an alignment of the source addresses. It must be a constant integer value. The third operand, mask, is a vector of boolean values with the same number of elements as the return type. The fourth is a pass-through value that is used to fill the masked-off lanes of the result. The return type, underlying type of the vector of pointers and the type of the '``passthru``' operand are the same vector types.
+
+
+Semantics:
+""""""""""
+
+The '``llvm.masked.gather``' intrinsic is designed for conditional reading of multiple scalar values from arbitrary memory locations in a single IR operation. It is useful for targets that support vector masked gathers and allows vectorizing basic blocks with data and control divergence. Other targets may support this intrinsic differently, for example by lowering it into a sequence of scalar load operations.
+The semantics of this operation are equivalent to a sequence of conditional scalar loads with subsequent gathering all loaded values into a single vector. The mask restricts memory access to certain lanes and facilitates vectorization of predicated basic blocks.
+
+
+::
+
+ %res = call <4 x double> @llvm.masked.gather.v4f64 (<4 x double*> %ptrs, i32 8, <4 x i1>%mask, <4 x double> <true, true, true, true>)
+
+ ;; The gather with all-true mask is equivalent to the following instruction sequence
+ %ptr0 = extractelement <4 x double*> %ptrs, i32 0
+ %ptr1 = extractelement <4 x double*> %ptrs, i32 1
+ %ptr2 = extractelement <4 x double*> %ptrs, i32 2
+ %ptr3 = extractelement <4 x double*> %ptrs, i32 3
+
+ %val0 = load double, double* %ptr0, align 8
+ %val1 = load double, double* %ptr1, align 8
+ %val2 = load double, double* %ptr2, align 8
+ %val3 = load double, double* %ptr3, align 8
+
+ %vec0 = insertelement <4 x double>undef, %val0, 0
+ %vec01 = insertelement <4 x double>%vec0, %val1, 1
+ %vec012 = insertelement <4 x double>%vec01, %val2, 2
+ %vec0123 = insertelement <4 x double>%vec012, %val3, 3
+
+.. _int_mscatter:
+
+'``llvm.masked.scatter.*``' Intrinsics
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+This is an overloaded intrinsic. The data stored in memory is a vector of any integer or floating point data type. Each vector element is stored in an arbitrary memory addresses. Scatter with overlapping addresses is guaranteed to be ordered from least-significant to most-significant element.
+
+::
+
+ declare void @llvm.masked.scatter.v8i32 (<8 x i32> <value>, <8 x i32*> <ptrs>, i32 <alignment>, <8 x i1> <mask>)
+ declare void @llvm.masked.scatter.v16f32(<16 x i32> <value>, <16 x i32*> <ptrs>, i32 <alignment>, <16 x i1> <mask>)
+
+Overview:
+"""""""""
+
+Writes each element from the value vector to the corresponding memory address. The memory addresses are represented as a vector of pointers. Writing is done according to the provided mask. The mask holds a bit for each vector lane, and is used to prevent memory accesses to the masked-off lanes.
+
+Arguments:
+""""""""""
+
+The first operand is a vector value to be written to memory. The second operand is a vector of pointers, pointing to where the value elements should be stored. It has the same underlying type as the value operand. The third operand is an alignment of the destination addresses. The fourth operand, mask, is a vector of boolean values. The types of the mask and the value operand must have the same number of vector elements.
+
+
+Semantics:
+""""""""""
+
+The '``llvm.masked.scatter``' intrinsics is designed for writing selected vector elements to arbitrary memory addresses in a single IR operation. The operation may be conditional, when not all bits in the mask are switched on. It is useful for targets that support vector masked scatter and allows vectorizing basic blocks with data and control divergency. Other targets may support this intrinsic differently, for example by lowering it into a sequence of branches that guard scalar store operations.
+
+::
+
+ ;; This instruction unconditionaly stores data vector in multiple addresses
+ call @llvm.masked.scatter.v8i32 (<8 x i32> %value, <8 x i32*> %ptrs, i32 4, <8 x i1> <true, true, .. true>)
+
+ ;; It is equivalent to a list of scalar stores
+ %val0 = extractelement <8 x i32> %value, i32 0
+ %val1 = extractelement <8 x i32> %value, i32 1
+ ..
+ %val7 = extractelement <8 x i32> %value, i32 7
+ %ptr0 = extractelement <8 x i32*> %ptrs, i32 0
+ %ptr1 = extractelement <8 x i32*> %ptrs, i32 1
+ ..
+ %ptr7 = extractelement <8 x i32*> %ptrs, i32 7
+ ;; Note: the order of the following stores is important when they overlap:
+ store i32 %val0, i32* %ptr0, align 4
+ store i32 %val1, i32* %ptr1, align 4
+ ..
+ store i32 %val7, i32* %ptr7, align 4
+
+
Memory Use Markers
------------------
This intrinsic is lowered to the ``val``.
+.. _int_assume:
+
'``llvm.assume``' Intrinsic
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
provided condition are not used for code generation. If the condition is
violated during execution, the behavior is undefined.
-Please note that optimizer might limit the transformations performed on values
+Note that the optimizer might limit the transformations performed on values
used by the ``llvm.assume`` intrinsic in order to preserve the instructions
only used to form the intrinsic's input argument. This might prove undesirable
-if the extra information provided by the ``llvm.assume`` intrinsic does cause
+if the extra information provided by the ``llvm.assume`` intrinsic does not cause
sufficient overall improvement in code quality. For this reason,
``llvm.assume`` should not be used to document basic mathematical invariants
that the optimizer can otherwise deduce or facts that are of little use to the
optimizer.
+.. _bitset.test:
+
+'``llvm.bitset.test``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ declare i1 @llvm.bitset.test(i8* %ptr, metadata %bitset) nounwind readnone
+
+
+Arguments:
+""""""""""
+
+The first argument is a pointer to be tested. The second argument is a
+metadata string containing the name of a :doc:`bitset <BitSets>`.
+
+Overview:
+"""""""""
+
+The ``llvm.bitset.test`` intrinsic tests whether the given pointer is a
+member of the given bitset.
+
'``llvm.donothing``' Intrinsic
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Overview:
"""""""""
-The ``llvm.donothing`` intrinsic doesn't perform any operation. It's the
-only intrinsic that can be called with an invoke instruction.
+The ``llvm.donothing`` intrinsic doesn't perform any operation. It's one of only
+two intrinsics (besides ``llvm.experimental.patchpoint``) that can be called
+with an invoke instruction.
Arguments:
""""""""""
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