.. code-block:: llvm
- %result = shl i32 %X, i8 3
+ %result = shl i32 %X, 3
And the hard way:
#. Comments are delimited with a '``;``' and go until the end of line.
#. Unnamed temporaries are created when the result of a computation is
not assigned to a named value.
-#. Unnamed temporaries are numbered sequentially
+#. Unnamed temporaries are numbered sequentially (using a per-function
+ incrementing counter, starting with 0).
It also shows a convention that we follow in this document. When
demonstrating instructions, we will follow an instruction with a comment
.. code-block:: llvm
- ; Declare the string constant as a global constant.
- @.str = private unnamed_addr constant [13 x i8] c"hello world\0A\00"
+ ; Declare the string constant as a global constant.
+ @.str = private unnamed_addr constant [13 x i8] c"hello world\0A\00"
- ; External declaration of the puts function
- declare i32 @puts(i8* nocapture) nounwind
+ ; External declaration of the puts function
+ declare i32 @puts(i8* nocapture) nounwind
; Definition of main function
- define i32 @main() { ; i32()*
- ; Convert [13 x i8]* to i8 *...
+ define i32 @main() { ; i32()*
+ ; Convert [13 x i8]* to i8 *...
%cast210 = getelementptr [13 x i8]* @.str, i64 0, i64 0
- ; Call puts function to write out the string to stdout.
+ ; Call puts function to write out the string to stdout.
call i32 @puts(i8* %cast210)
- ret i32 0
+ ret i32 0
}
; Named metadata
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.
support Pascal conventions or any other well-known target-independent
convention.
+.. _visibilitystyles:
+
Visibility Styles
-----------------
defining module will bind to the local symbol. That is, the symbol
cannot be overridden by another module.
+.. _namedtypes:
+
Named Types
-----------
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 variable may be defined as a global "constant," which indicates that
+A variable may be defined as a global ``constant``, which indicates that
the contents of the variable will **never** be modified (enabling better
optimization, allowing the global data to be placed in the read-only
section of an executable, etc). Note that variables that need runtime
-initialization cannot be marked "constant" as there is a store to the
+initialization cannot be marked ``constant`` as there is a store to the
variable.
LLVM explicitly allows *declarations* of global variables to be marked
LLVM allows an explicit section to be specified for globals. If the
target supports it, it will emit globals to the section specified.
+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
+true even for variables potentially accessible from outside the
+module, including those with external linkage or appearing in
+``@llvm.used``. This assumption may be suppressed by marking the
+variable with ``externally_initialized``.
+
An explicit alignment may be specified for a global, which must be a
power of 2. If not present, or if the alignment is set to zero, the
alignment of the global is set by the target to whatever it feels
name, a (possibly empty) argument list (each with optional :ref:`parameter
attributes <paramattrs>`), optional :ref:`function attributes <fnattrs>`,
an optional section, an optional alignment, an optional :ref:`garbage
-collector name <gc>`, an opening curly brace, a list of basic blocks,
-and a closing curly brace.
+collector name <gc>`, an optional :ref:`prefix <prefixdata>`, 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
style <visibility>`, an optional :ref:`calling convention <callingconv>`,
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, and an
-optional :ref:`garbage collector name <gc>`.
+name, a possibly empty list of arguments, an optional alignment, an optional
+:ref:`garbage collector name <gc>` and an optional :ref:`prefix <prefixdata>`.
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 (giving the basic block a symbol table entry),
contains a list of instructions, and ends with a
:ref:`terminator <terminators>` instruction (such as a branch or function
-return).
+return). If explicit label is not provided, a block is assigned an
+implicit numbered label, using a next value from the same counter as used
+for unnamed temporaries (:ref:`see above<identifiers>`). For example, if a
+function entry block does not have explicit label, it will be assigned
+label "%0", then first unnamed temporary in that block will be "%1", etc.
The first basic block in a function is special in two ways: it is
immediately executed on entrance to the function, and it is not allowed
[cconv] [ret attrs]
<ResultType> @<FunctionName> ([argument list])
[fn Attrs] [section "name"] [align N]
- [gc] { ... }
+ [gc] [prefix Constant] { ... }
+
+.. _langref_aliases:
Aliases
-------
This indicates that the pointer parameter specifies the address of a
structure that is the return value of the function in the source
program. This pointer must be guaranteed by the caller to be valid:
- loads and stores to the structure may be assumed by the callee to
+ loads and stores to the structure may be assumed by the callee
not to trap and to be properly aligned. This may only be applied to
the first parameter. This is not a valid attribute for return
values.
``noalias``
- This indicates that pointer values
`*based* <pointeraliasing>` on
+ This indicates that pointer values
:ref:`based <pointeraliasing>` on
the argument or return value do not alias pointer values which are
not *based* on it, ignoring certain "irrelevant" dependencies. For a
call to the parent function, dependencies between memory references
``nest``
This indicates that the pointer parameter can be excised using the
:ref:`trampoline intrinsics <int_trampoline>`. This is not a valid
- attribute for return values.
+ attribute for return values and can only be applied to one parameter.
+
+``returned``
+ This indicates that the function always returns the argument as its return
+ value. This is an optimization hint to the code generator when generating
+ the caller, allowing tail call optimization and omission of register saves
+ and restores in some cases; it is not checked or enforced when generating
+ the callee. The parameter and the function return type must be valid
+ operands for the :ref:`bitcast instruction <i_bitcast>`. This is not a
+ valid attribute for return values and can only be applied to one parameter.
.. _gc:
collector which will cause the compiler to alter its output in order to
support the named garbage collection algorithm.
+.. _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
+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 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.
+
+A trivial example of valid prefix data for the x86 architecture is ``i8 144``,
+which encodes the ``nop`` instruction:
+
+.. code-block:: llvm
+
+ define void @f() prefix 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
+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}> { ... }
+
+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.
+
+.. _attrgrp:
+
+Attribute Groups
+----------------
+
+Attribute groups are groups of attributes that are referenced by objects within
+the IR. They are important for keeping ``.ll`` files readable, because a lot of
+functions will use the same set of attributes. In the degenerative case of a
+``.ll`` file that corresponds to a single ``.c`` file, the single attribute
+group will capture the important command line flags used to build that file.
+
+An attribute group is a module-level object. To use an attribute group, an
+object references the attribute group's ID (e.g. ``#37``). An object may refer
+to more than one attribute group. In that situation, the attributes from the
+different groups are merged.
+
+Here is an example of attribute groups for a function that should always be
+inlined, has a stack alignment of 4, and which shouldn't use SSE instructions:
+
+.. code-block:: llvm
+
+ ; Target-independent attributes:
+ attributes #0 = { alwaysinline alignstack=4 }
+
+ ; Target-dependent attributes:
+ attributes #1 = { "no-sse" }
+
+ ; Function @f has attributes: alwaysinline, alignstack=4, and "no-sse".
+ define void @f() #0 #1 { ... }
+
.. _fnattrs:
Function Attributes
define void @f() alwaysinline optsize { ... }
define void @f() optsize { ... }
-``address_safety``
- This attribute indicates that the address safety analysis is enabled
- for this function.
``alignstack(<n>)``
This attribute indicates that, when emitting the prologue and
epilogue, the backend should forcibly align the stack pointer.
This attribute indicates that the inliner should attempt to inline
this function into callers whenever possible, ignoring any active
inlining size threshold for this caller.
-``nonlazybind``
- This attribute suppresses lazy symbol binding for the function. This
- may make calls to the function faster, at the cost of extra program
- startup time if the function is not called during program startup.
+``builtin``
+ This indicates that the callee function at a call site should be
+ recognized as a built-in function, even though the function's declaration
+ uses the ``nobuiltin`` attribute. This is only valid at call sites for
+ direct calls to functions which are declared with the ``nobuiltin``
+ attribute.
+``cold``
+ This attribute indicates that this function is rarely called. When
+ computing edge weights, basic blocks post-dominated by a cold
+ function call are also considered to be cold; and, thus, given low
+ weight.
``inlinehint``
This attribute indicates that the source code contained a hint that
inlining this function is desirable (such as the "inline" keyword in
C/C++). It is just a hint; it imposes no requirements on the
inliner.
+``minsize``
+ This attribute suggests that optimization passes and code generator
+ passes make choices that keep the code size of this function as small
+ as possible and perform optimizations that may sacrifice runtime
+ performance in order to minimize the size of the generated code.
``naked``
This attribute disables prologue / epilogue emission for the
function. This can have very system-specific consequences.
+``nobuiltin``
+ This indicates that the callee function at a call site is not recognized as
+ a built-in function. LLVM will retain the original call and not replace it
+ with equivalent code based on the semantics of the built-in function, unless
+ the call site uses the ``builtin`` attribute. This is valid at call sites
+ and on function declarations and definitions.
+``noduplicate``
+ This attribute indicates that calls to the function cannot be
+ duplicated. A call to a ``noduplicate`` function may be moved
+ within its parent function, but may not be duplicated within
+ its parent function.
+
+ A function containing a ``noduplicate`` call may still
+ be an inlining candidate, provided that the call is not
+ duplicated by inlining. That implies that the function has
+ internal linkage and only has one call site, so the original
+ call is dead after inlining.
``noimplicitfloat``
This attributes disables implicit floating point instructions.
``noinline``
This attribute indicates that the inliner should never inline this
function in any situation. This attribute may not be used together
with the ``alwaysinline`` attribute.
+``nonlazybind``
+ This attribute suppresses lazy symbol binding for the function. This
+ may make calls to the function faster, at the cost of extra program
+ startup time if the function is not called during program startup.
``noredzone``
This attribute indicates that the code generator should not use a
red zone, even if the target-specific ABI normally permits it.
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.
+``optnone``
+ This function attribute indicates that the function is not optimized
+ by any optimization or code generator passes with the
+ exception of interprocedural optimization passes.
+ This attribute cannot be used together with the ``alwaysinline``
+ attribute; this attribute is also incompatible
+ with the ``minsize`` attribute and the ``optsize`` attribute.
+
+ The inliner should never inline this function in any situation.
+ Only functions with the ``alwaysinline`` attribute are valid
+ candidates for inlining inside the body of this function.
``optsize``
This attribute suggests that optimization passes and code generator
passes make choices that keep the code size of this function low,
- and otherwise do optimizations specifically to reduce code size.
+ and otherwise do optimizations specifically to reduce code size as
+ long as they do not significantly impact runtime performance.
``readnone``
- This attribute indicates that the function computes its result (or
- decides to unwind an exception) based strictly on its arguments,
+ On a function, this attribute indicates that the function computes its
+ result (or decides to unwind an exception) based strictly on its arguments,
without dereferencing any pointer arguments or otherwise accessing
any mutable state (e.g. memory, control registers, etc) visible to
caller functions. It does not write through any pointer arguments
(including ``byval`` arguments) and never changes any state visible
to callers. This means that it cannot unwind exceptions by calling
the ``C++`` exception throwing methods.
+
+ On an argument, this attribute indicates that the function does not
+ dereference that pointer argument, even though it may read or write the
+ memory that the pointer points to if accessed through other pointers.
``readonly``
- This attribute indicates that the function does not write through
- any pointer arguments (including ``byval`` arguments) or otherwise
+ On a function, this attribute indicates that the function does not write
+ through any pointer arguments (including ``byval`` arguments) or otherwise
modify any state (e.g. memory, control registers, etc) visible to
caller functions. It may dereference pointer arguments and read
state that may be set in the caller. A readonly function always
called with the same set of arguments and global state. It cannot
unwind an exception by calling the ``C++`` exception throwing
methods.
+
+ 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.
``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.
+``sanitize_address``
+ This attribute indicates that AddressSanitizer checks
+ (dynamic address safety analysis) are enabled for this function.
+``sanitize_memory``
+ This attribute indicates that MemorySanitizer checks (dynamic detection
+ of accesses to uninitialized memory) are enabled for this function.
+``sanitize_thread``
+ This attribute indicates that ThreadSanitizer checks
+ (dynamic thread safety analysis) are enabled for this function.
``ssp``
This attribute indicates that the function should emit a stack
- smashing protector. It is in the form of a "canary"—a random value
+ smashing protector. It is in the form of a "canary" --- a random value
placed on the stack before the local variables that's checked upon
return from the function to see if it has been overwritten. A
heuristic is used to determine if a function needs stack protectors
- or not.
+ or not. The heuristic used will enable protectors for functions with:
+
+ - Character arrays larger than ``ssp-buffer-size`` (default 8).
+ - Aggregates containing character arrays larger than ``ssp-buffer-size``.
+ - Calls to alloca() with variable sizes or constant sizes greater than
+ ``ssp-buffer-size``.
If a function that has an ``ssp`` attribute is inlined into a
function that doesn't have an ``ssp`` attribute, then the resulting
If a function that has an ``sspreq`` attribute is inlined into a
function that doesn't have an ``sspreq`` attribute or which has an
- ``ssp`` attribute, then the resulting function will have an
- ``sspreq`` attribute.
+ ``ssp`` or ``sspstrong`` attribute, then the resulting function will have
+ an ``sspreq`` attribute.
+``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
+ will enable protectors for functions with:
+
+ - Arrays of any size and type
+ - Aggregates containing an array of any size and type.
+ - Calls to alloca().
+ - Local variables that have had their address taken.
+
+ This overrides the ``ssp`` function attribute.
+
+ 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.
``uwtable``
This attribute indicates that the ABI being targeted requires that
an unwind table entry be produce 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.
-``noduplicate``
- This attribute indicates that calls to the function cannot be
- duplicated. A call to a ``noduplicate`` function may be moved
- within its parent function, but may not be duplicated within
- its parent function.
-
- A function containing a ``noduplicate`` call may still
- be an inlining candidate, provided that the call is not
- duplicated by inlining. That implies that the function has
- internal linkage and only has one call site, so the original
- call is dead after inlining.
.. _moduleasm:
The inline asm code is simply printed to the machine code .s file when
assembly code is generated.
+.. _langref_datalayout:
+
Data Layout
-----------
specifications are given in this list:
- ``E`` - big endian
-- ``p:64:64:64`` - 64-bit pointers with 64-bit alignment
-- ``p1:32:32:32`` - 32-bit pointers with 32-bit alignment for address
- space 1
-- ``p2:16:32:32`` - 16-bit pointers with 32-bit alignment for address
- space 2
+- ``p:64:64:64`` - 64-bit pointers with 64-bit alignment.
+- ``p[n]:64:64:64`` - Other address spaces are assumed to be the
+ same as the default address space.
+- ``S0`` - natural stack alignment is unspecified
- ``i1:8:8`` - i1 is 8-bit (byte) aligned
- ``i8:8:8`` - i8 is 8-bit (byte) aligned
- ``i16:16:16`` - i16 is 16-bit aligned
- ``i32:32:32`` - i32 is 32-bit aligned
- ``i64:32:64`` - i64 has ABI alignment of 32-bits but preferred
alignment of 64-bits
+- ``f16:16:16`` - half is 16-bit aligned
- ``f32:32:32`` - float is 32-bit aligned
- ``f64:64:64`` - double is 64-bit aligned
+- ``f128:128:128`` - quad is 128-bit aligned
- ``v64:64:64`` - 64-bit vector is 64-bit aligned
- ``v128:128:128`` - 128-bit vector is 128-bit aligned
-- ``a0:0:1`` - aggregates are 8-bit aligned
-- ``s0:64:64`` - stack objects are 64-bit aligned
+- ``a0:0:64`` - aggregates are 64-bit aligned
When LLVM is determining the alignment for a given type, it uses the
following rules:
operations relative to non-volatile operations. This is not Java's
"volatile" and has no cross-thread synchronization behavior.
+IR-level volatile loads and stores cannot safely be optimized into
+llvm.memcpy or llvm.memmove intrinsics even when those intrinsics are
+flagged volatile. Likewise, the backend should never split or merge
+target-legal volatile load/store instructions.
+
+.. admonition:: Rationale
+
+ Platforms may rely on volatile loads and stores of natively supported
+ data width to be executed as single instruction. For example, in C
+ 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
+ do not violate the frontend's contract with the language.
+
.. _memmodel:
Memory Model for Concurrent Operations
generated code and enables novel analyses and transformations that are
not feasible to perform on normal three address code representations.
+.. _typeclassifications:
+
Type Classifications
--------------------
+---------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| ``i32 (i32)`` | function taking an ``i32``, returning an ``i32`` |
+---------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------+
-| ``float (i16, i32 *) *`` | :ref:`Pointer <t_pointer>` to a function that takes an ``i16`` and a :ref:`pointer <t_pointer>` to ``i32``, returning ``float``. |
+| ``float (i16, i32 *) *`` | :ref:`Pointer <t_pointer>` to a function that takes an ``i16`` and a :ref:`pointer <t_pointer>` to ``i32``, returning ``float``. |
+---------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| ``i32 (i8*, ...)`` | A vararg function that takes at least one :ref:`pointer <t_pointer>` to ``i8`` (char in C), which returns an integer. This is the signature for ``printf`` in LLVM. |
+---------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------+
+------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| ``{ i32, i32, i32 }`` | A triple of three ``i32`` values |
+------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
-| ``{ float, i32 (i32) * }`` | A pair, where the first element is a ``float`` and the second element is a :ref:`pointer <t_pointer>` to a :ref:`function <t_function>` that takes an ``i32``, returning an ``i32``. |
+| ``{ float, i32 (i32) * }`` | A pair, where the first element is a ``float`` and the second element is a :ref:`pointer <t_pointer>` to a :ref:`function <t_function>` that takes an ``i32``, returning an ``i32``. |
+------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| ``<{ i8, i32 }>`` | A packed struct known to be 5 bytes in size. |
+------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
When using the hexadecimal form, constants of types half, float, and
double are represented using the 16-digit form shown above (which
matches the IEEE754 representation for double); half and float values
-must, however, be exactly representable as IEE754 half and single
+must, however, be exactly representable as IEEE 754 half and single
precision, respectively. Hexadecimal format is always used for long
double, and there are three forms of long double. The 80-bit format used
by x86 is represented as ``0xK`` followed by 20 hexadecimal digits. The
128-bit format used by PowerPC (two adjacent doubles) is represented by
``0xM`` followed by 32 hexadecimal digits. The IEEE 128-bit format is
-represented by ``0xL`` followed by 32 hexadecimal digits; no currently
-supported target uses this format. Long doubles will only work if they
-match the long double format on your target. The IEEE 16-bit format
-(half precision) is represented by ``0xH`` followed by 4 hexadecimal
-digits. All hexadecimal formats are big-endian (sign bit at the left).
+represented by ``0xL`` followed by 32 hexadecimal digits. Long doubles
+will only work if they match the long double format on your target.
+The IEEE 16-bit format (half precision) is represented by ``0xH``
+followed by 4 hexadecimal digits. All hexadecimal formats are big-endian
+(sign bit at the left).
There are no constants of type x86mmx.
+.. _complexconstants:
+
Complex Constants
-----------------
This value only has defined behavior when used as an operand to the
':ref:`indirectbr <i_indirectbr>`' instruction, or for comparisons
against null. Pointer equality tests between labels addresses results in
-undefined behavior — though, again, comparison against null is ok, and
+undefined behavior --- though, again, comparison against null is ok, and
no label is equal to the null pointer. This may be passed around as an
opaque pointer sized value as long as the bits are not inspected. This
allows ``ptrtoint`` and arithmetic to be performed on these values so
Finally, some targets may provide defined semantics when using the value
as the operand to an inline assembly, but that is target specific.
+.. _constantexprs:
+
Constant Expressions
--------------------
won't fit in the floating point type, the results are undefined.
``ptrtoint (CST to TYPE)``
Convert a pointer typed constant to the corresponding integer
- constant ``TYPE`` must be an integer type. ``CST`` must be of
+ constant. ``TYPE`` must be an integer type. ``CST`` must be of
pointer type. The ``CST`` value is zero extended, truncated, or
unchanged to make it fit in ``TYPE``.
``inttoptr (CST to TYPE)``
Other Values
============
+.. _inlineasmexprs:
+
Inline Assembler Expressions
----------------------------
!2 = metadata !{ i8 0, i8 2, i8 3, i8 6 }
!3 = metadata !{ 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 = metadata !{ metadata !0 }
+ !1 = metadata !{ metadata !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.vectorizer.unroll`` metadata is understood
+by the loop vectorizer to indicate how many times to unroll the loop:
+
+.. 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.vectorizer.unroll", i32 2 }
+
+'``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
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+For a loop to be parallel, in addition to using
+the ``llvm.loop`` metadata to mark the loop latch branch instruction,
+also all of the memory accessing instructions in the loop body need to be
+marked with the ``llvm.mem.parallel_loop_access`` metadata. If there
+is at least one memory accessing instruction not marked with the metadata,
+the loop must be considered a sequential loop. This causes parallel loops to be
+converted to sequential loops due to optimization passes that are unaware of
+the parallel semantics and that insert new memory instructions to 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:
+ ...
+ %0 = load i32* %arrayidx, align 4, !llvm.mem.parallel_loop_access !0
+ ...
+ store i32 %0, i32* %arrayidx4, align 4, !llvm.mem.parallel_loop_access !0
+ ...
+ br i1 %exitcond, label %for.end, label %for.body, !llvm.loop !0
+
+ for.end:
+ ...
+ !0 = metadata !{ metadata !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:
+ ...
+
+ inner.for.body:
+ ...
+ %0 = load i32* %arrayidx, align 4, !llvm.mem.parallel_loop_access !0
+ ...
+ store i32 %0, i32* %arrayidx4, align 4, !llvm.mem.parallel_loop_access !0
+ ...
+ br i1 %exitcond, label %inner.for.end, label %inner.for.body, !llvm.loop !1
+
+ inner.for.end:
+ ...
+ %0 = load i32* %arrayidx, align 4, !llvm.mem.parallel_loop_access !0
+ ...
+ store i32 %0, i32* %arrayidx4, align 4, !llvm.mem.parallel_loop_access !0
+ ...
+ br i1 %exitcond, label %outer.for.end, label %outer.for.body, !llvm.loop !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
+
+'``llvm.vectorizer``'
+^^^^^^^^^^^^^^^^^^^^^
+
+Metadata prefixed with ``llvm.vectorizer`` is used to control per-loop
+vectorization parameters such as vectorization factor and unroll factor.
+
+``llvm.vectorizer`` metadata should be used in conjunction with ``llvm.loop``
+loop identification metadata.
+
+'``llvm.vectorizer.unroll``' Metadata
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+This metadata instructs the loop vectorizer to unroll the specified
+loop exactly ``N`` times.
+
+The first operand is the string ``llvm.vectorizer.unroll`` and the second
+operand is an integer specifying the unroll factor. For example:
+
+.. code-block:: llvm
+
+ !0 = metadata !{ metadata !"llvm.vectorizer.unroll", i32 4 }
+
+Note that setting ``llvm.vectorizer.unroll`` to 1 disables unrolling of the
+loop.
+
+If ``llvm.vectorizer.unroll`` is set to 0 then the amount of unrolling will be
+determined automatically.
+
+'``llvm.vectorizer.width``' Metadata
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+This metadata sets the target width of the vectorizer to ``N``. Without
+this metadata, the vectorizer will choose a width automatically.
+Regardless of this metadata, the vectorizer will only vectorize loops if
+it believes it is valid to do so.
+
+The first operand is the string ``llvm.vectorizer.width`` and the second
+operand is an integer specifying the width. For example:
+
+.. code-block:: llvm
+
+ !0 = metadata !{ metadata !"llvm.vectorizer.width", i32 4 }
+
+Note that setting ``llvm.vectorizer.width`` to 1 disables vectorization of the
+loop.
+
+If ``llvm.vectorizer.width`` is set to 0 then the width will be determined
+automatically.
+
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
+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.
(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. How each ID is interpreted is documented below.
+ 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'
-``llvm.module.flags`` metadata. The only exception being a flag with the
-*Override* behavior, which may override another flag's value (see
-below).
+``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:
* - 1
- **Error**
- Emits an error if two values disagree. It is an error to have an
- ID with both an Error and a Warning behavior.
+ 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.
+ 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**
- Emits an error when the specified value is not present or doesn't
- have the specified value. It is an error for two (or more)
- ``llvm.module.flags`` with the same ID to have the Require behavior
- but different values. There may be multiple Require flags per ID.
+ 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 if the two values disagree. It is an
- error for two (or more) ``llvm.module.flags`` with the same ID
- to have the Override behavior but different values.
+ 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:
- 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' if their values are not equal.
+ '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
metadata !{ metadata !"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'. If
- two or more ``!"qux"`` flags exist, then they must have the same
- value or an error will be issued.
+ 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
----------------------------------------------------
* - Key
- Value
- * - ``Objective-C Version``
- - **[Required]** — The Objective-C ABI version. Valid values are 1 and 2.
+ * - ``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
+ * - ``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
+ * - ``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
+ * - ``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.
+ * - ``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.
- 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 = metadata !{ i32 6, metadata !"Linker Options",
+ metadata !{
+ metadata !{ metadata !"-lz" },
+ metadata !{ metadata !"-framework", metadata !"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.
+
+.. _intrinsicglobalvariables:
+
Intrinsic Global Variables
==========================
"``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 with i8\* element type which has
+The ``@llvm.used`` global is an array which has
:ref:`appending linkage <linkage_appending>`. This array contains a list of
-pointers to global variables and functions which may optionally have a
-pointer cast formed of bitcast or getelementptr. For example, a legal
+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
i8* bitcast (i32* @Y to i8*)
], section "llvm.metadata"
-If a global variable 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 global that it cannot see. 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.
+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
--------------------------------------------
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
-------------------------------------------
when the module is loaded. The order of functions with the same priority
is not defined.
+.. _llvmglobaldtors:
+
The '``llvm.global_dtors``' Global Variable
-------------------------------------------
<result> = lshr i32 4, 1 ; yields {i32}:result = 2
<result> = lshr i32 4, 2 ; yields {i32}:result = 1
<result> = lshr i8 4, 3 ; yields {i8}:result = 0
- <result> = lshr i8 -2, 1 ; yields {i8}:result = 0x7FFFFFFF
+ <result> = lshr i8 -2, 1 ; yields {i8}:result = 0x7F
<result> = lshr i32 1, 32 ; undefined
<result> = lshr <2 x i32> < i32 -2, i32 4>, < i32 1, i32 2> ; yields: result=<2 x i32> < i32 0x7FFFFFFF, i32 1>
Arguments:
""""""""""
-The argument to the '``load``' instruction specifies the memory address
+The argument to the ``load`` instruction specifies the memory address
from which to load. The pointer must point to 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
The optional constant ``align`` argument specifies the alignment of the
operation (that is, the alignment of the memory address). A value of 0
-or an omitted ``align`` argument means that the operation has the abi
+or an omitted ``align`` argument means that the operation has the ABI
alignment for the target. It is the responsibility of the code emitter
to ensure that the alignment information is correct. Overestimating the
alignment results in undefined behavior. Underestimating the alignment
may produce less efficient code. An alignment of 1 is always safe.
The optional ``!nontemporal`` metadata must reference a single
-metatadata name <index> corresponding to a metadata node with one
+metadata name ``<index>`` corresponding to a metadata node with one
``i32`` entry of value 1. The existence of the ``!nontemporal``
-metatadata on the instruction tells the optimizer and code generator
+metadata on the instruction tells the optimizer and code generator
that this load is not expected to be reused in the cache. The code
generator may select special instructions to save cache bandwidth, such
as the ``MOVNT`` instruction on x86.
The optional ``!invariant.load`` metadata must reference a single
-metatadata name <index> corresponding to a metadata node with no
-entries. The existence of the ``!invariant.load`` metatadata on the
+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
Arguments:
""""""""""
-There are two arguments to the '``store``' instruction: a value to store
-and an address at which to store it. The type of the '``<pointer>``'
+There are two arguments to the ``store`` instruction: a value to store
+and an address at which to store it. The type of the ``<pointer>``
operand must be a pointer to the :ref:`first class <t_firstclass>` type of
-the '``<value>``' operand. If the ``store`` is marked as ``volatile``,
+the ``<value>`` operand. If the ``store`` is marked as ``volatile``,
then the optimizer is not allowed to modify the number or order of
execution of this ``store`` with other :ref:`volatile
operations <volatile>`.
at least the size in bytes of the pointee. ``!nontemporal`` does not
have any defined semantics for atomic stores.
-The optional constant "align" argument specifies the alignment of the
+The optional constant ``align`` argument specifies the alignment of the
operation (that is, the alignment of the memory address). A value of 0
-or an omitted "align" argument means that the operation has the abi
+or an omitted ``align`` argument means that the operation has the ABI
alignment for the target. It is the responsibility of the code emitter
to ensure that the alignment information is correct. Overestimating the
-alignment results in an undefined behavior. Underestimating the
+alignment results in undefined behavior. Underestimating the
alignment may produce less efficient code. An alignment of 1 is always
safe.
-The optional !nontemporal metadata must reference a single metatadata
-name <index> corresponding to a metadata node with one i32 entry of
-value 1. The existence of the !nontemporal metatadata on the instruction
+The optional ``!nontemporal`` metadata must reference a single metadata
+name ``<index>`` corresponding to a metadata node with one ``i32`` entry of
+value 1. The existence of the ``!nontemporal`` metadata on the instruction
tells the optimizer and code generator that this load is not expected to
be reused in the cache. The code generator may select special
instructions to save cache bandwidth, such as the MOVNT instruction on
Semantics:
""""""""""
-The contents of memory are updated to contain '``<value>``' at the
-location specified by the '``<pointer>``' operand. If '``<value>``' is
+The contents of memory are updated to contain ``<value>`` at the
+location specified by the ``<pointer>`` operand. If ``<value>`` is
of scalar type then the number of bytes written does not exceed the
minimum number of bytes needed to hold all bits of the type. For
example, storing an ``i24`` writes at most three bytes. When writing a
The '``bitcast``' instruction takes a value to cast, which must be a
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 also be a
-pointer. This instruction supports bitwise conversion of vectors to
-integers and to vectors of other types (as long as they have the same
-size).
+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
+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).
Semantics:
""""""""""
-The '``bitcast``' instruction converts ``value`` to type ``ty2``. It is
-always a *no-op cast* because no bits change with this conversion. The
-conversion is done as if the ``value`` had been stored to memory and
-read back as type ``ty2``. Pointer (or vector of pointers) types may
-only be converted to other pointer (or vector of pointers) types with
-this instruction. To convert pointers to other types, use the
-:ref:`inttoptr <i_inttoptr>` or :ref:`ptrtoint <i_ptrtoint>` instructions
-first.
+The '``bitcast``' instruction converts ``value`` to type ``ty2``. It
+is always a *no-op cast* because no bits change with this
+conversion. The conversion is done as if the ``value`` had been stored
+to memory and read back as type ``ty2``. Pointer (or vector of
+pointers) types may only be converted to other pointer (or vector of
+pointers) types with this instruction if the pointer sizes are
+equal. To convert pointers to other types, use the :ref:`inttoptr
+<i_inttoptr>` or :ref:`ptrtoint <i_ptrtoint>` instructions first.
Example:
""""""""
The '``landingpad``' instruction is used by `LLVM's exception handling
system <ExceptionHandling.html#overview>`_ to specify that a basic block
-is a landing pad — one where the exception lands, and corresponds to the
+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
re-entry to the function. The ``resultval`` has the type ``resultty``.
function associated with the unwinding mechanism. The optional
``cleanup`` flag indicates that the landing pad block is a cleanup.
-A ``clause`` begins with the clause type — ``catch`` or ``filter`` — and
+A ``clause`` begins with the clause type --- ``catch`` or ``filter`` --- and
contains the global variable representing the "type" that may be caught
or filtered respectively. Unlike the ``catch`` clause, the ``filter``
clause takes an array constant as its argument. Use
::
- declare void
%llvm.va_start(i8* <arglist>)
+ declare void
@llvm.va_start(i8* <arglist>)
Overview:
"""""""""
specific value or a system wide value. On backends without support, this
is lowered to a constant 0.
+Note that runtime support may be conditional on the privilege-level code is
+running at and the host platform.
+
Standard C Library Intrinsics
-----------------------------
This function returns the same values as the libm ``fabs`` functions
would, and handles error conditions in the same way.
+'``llvm.copysign.*``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+This is an overloaded intrinsic. You can use ``llvm.copysign`` on any
+floating point or vector of floating point type. Not all targets support
+all types however.
+
+::
+
+ declare float @llvm.copysign.f32(float %Mag, float %Sgn)
+ declare double @llvm.copysign.f64(double %Mag, double %Sgn)
+ declare x86_fp80 @llvm.copysign.f80(x86_fp80 %Mag, x86_fp80 %Sgn)
+ declare fp128 @llvm.copysign.f128(fp128 %Mag, fp128 %Sgn)
+ declare ppc_fp128 @llvm.copysign.ppcf128(ppc_fp128 %Mag, ppc_fp128 %Sgn)
+
+Overview:
+"""""""""
+
+The '``llvm.copysign.*``' intrinsics return a value with the magnitude of the
+first operand and the sign of the second operand.
+
+Arguments:
+""""""""""
+
+The arguments and return value are floating point numbers of the same
+type.
+
+Semantics:
+""""""""""
+
+This function returns the same values as the libm ``copysign``
+functions would, and handles error conditions in the same way.
+
'``llvm.floor.*``' Intrinsic
^^^^^^^^^^^^^^^^^^^^^^^^^^^^
This function returns the same values as the libm ``nearbyint``
functions would, and handles error conditions in the same way.
+'``llvm.round.*``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+This is an overloaded intrinsic. You can use ``llvm.round`` on any
+floating point or vector of floating point type. Not all targets support
+all types however.
+
+::
+
+ declare float @llvm.round.f32(float %Val)
+ declare double @llvm.round.f64(double %Val)
+ declare x86_fp80 @llvm.round.f80(x86_fp80 %Val)
+ declare fp128 @llvm.round.f128(fp128 %Val)
+ declare ppc_fp128 @llvm.round.ppcf128(ppc_fp128 %Val)
+
+Overview:
+"""""""""
+
+The '``llvm.round.*``' intrinsics returns the operand rounded to the
+nearest integer.
+
+Arguments:
+""""""""""
+
+The argument and return value are floating point numbers of the same
+type.
+
+Semantics:
+""""""""""
+
+This function returns the same values as the libm ``round``
+functions would, and handles error conditions in the same way.
+
Bit Manipulation Intrinsics
---------------------------
""""""""""
The '``llvm.sadd.with.overflow``' family of intrinsic functions perform
-a signed addition of the two variables. They return a structure — the
+a signed addition of the two variables. They return a structure --- the
first element of which is the signed summation, and the second element
of which is a bit specifying if the signed summation resulted in an
overflow.
""""""""""
The '``llvm.uadd.with.overflow``' family of intrinsic functions perform
-an unsigned addition of the two arguments. They return a structure — the
+an unsigned addition of the two arguments. They return a structure --- the
first element of which is the sum, and the second element of which is a
bit specifying if the unsigned summation resulted in a carry.
""""""""""
The '``llvm.ssub.with.overflow``' family of intrinsic functions perform
-a signed subtraction of the two arguments. They return a structure — the
+a signed subtraction of the two arguments. They return a structure --- the
first element of which is the subtraction, and the second element of
which is a bit specifying if the signed subtraction resulted in an
overflow.
""""""""""
The '``llvm.usub.with.overflow``' family of intrinsic functions perform
-an unsigned subtraction of the two arguments. They return a structure —
+an unsigned subtraction of the two arguments. They return a structure ---
the first element of which is the subtraction, and the second element of
which is a bit specifying if the unsigned subtraction resulted in an
overflow.
""""""""""
The '``llvm.smul.with.overflow``' family of intrinsic functions perform
-a signed multiplication of the two arguments. They return a structure —
+a signed multiplication of the two arguments. They return a structure ---
the first element of which is the multiplication, and the second element
of which is a bit specifying if the signed multiplication resulted in an
overflow.
""""""""""
The '``llvm.umul.with.overflow``' family of intrinsic functions perform
-an unsigned multiplication of the two arguments. They return a structure
-— the first element of which is the multiplication, and the second
+an unsigned multiplication of the two arguments. They return a structure ---
+the first element of which is the multiplication, and the second
element of which is a bit specifying if the unsigned multiplication
resulted in an overflow.
"""""""""
The '``llvm.fmuladd.*``' intrinsic functions represent multiply-add
-expressions that can be fused if the code generator determines that the
-fused expression would be legal and efficient.
+expressions that can be fused if the code generator determines that (a) the
+target instruction set has support for a fused operation, and (b) that the
+fused operation is more efficient than the equivalent, separate pair of mul
+and add instructions.
Arguments:
""""""""""
to look for these annotations. These have no other defined use; they are
ignored by code generation and optimization.
+'``llvm.ptr.annotation.*``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+This is an overloaded intrinsic. You can use '``llvm.ptr.annotation``' on a
+pointer to an integer of any width. *NOTE* you must specify an address space for
+the pointer. The identifier for the default address space is the integer
+'``0``'.
+
+::
+
+ declare i8* @llvm.ptr.annotation.p<address space>i8(i8* <val>, i8* <str>, i8* <str>, i32 <int>)
+ declare i16* @llvm.ptr.annotation.p<address space>i16(i16* <val>, i8* <str>, i8* <str>, i32 <int>)
+ declare i32* @llvm.ptr.annotation.p<address space>i32(i32* <val>, i8* <str>, i8* <str>, i32 <int>)
+ declare i64* @llvm.ptr.annotation.p<address space>i64(i64* <val>, i8* <str>, i8* <str>, i32 <int>)
+ declare i256* @llvm.ptr.annotation.p<address space>i256(i256* <val>, i8* <str>, i8* <str>, i32 <int>)
+
+Overview:
+"""""""""
+
+The '``llvm.ptr.annotation``' intrinsic.
+
+Arguments:
+""""""""""
+
+The first argument is a pointer to an integer value of arbitrary bitwidth
+(result of some expression), the second is a pointer to a global string, the
+third is a pointer to a global string which is the source file name, and the
+last argument is the line number. It returns the value of the first argument.
+
+Semantics:
+""""""""""
+
+This intrinsic allows annotation of a pointer to an integer with arbitrary
+strings. This can be useful for special purpose optimizations that want to look
+for these annotations. These have no other defined use; they are ignored by code
+generation and optimization.
+
'``llvm.annotation.*``' Intrinsic
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Semantics:
""""""""""
-This intrinsic causes the prologue/epilogue inserter to force the
-position of the ``AllocaInst`` stack slot to be before local variables
-on the stack. This is to ensure that if a local variable on the stack is
-overwritten, it will destroy the value of the guard. When the function
-exits, the guard on the stack is checked against the original guard. If
-they are different, then the program aborts by calling the
+This intrinsic causes the prologue/epilogue inserter to force the position of
+the ``AllocaInst`` stack slot to be before local variables on the stack. This is
+to ensure that if a local variable on the stack is overwritten, it will destroy
+the value of the guard. When the function exits, the guard on the stack is
+checked against the original guard by ``llvm.stackprotectorcheck``. If they are
+different, then ``llvm.stackprotectorcheck`` causes the program to abort by
+calling the ``__stack_chk_fail()`` function.
+
+'``llvm.stackprotectorcheck``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ declare void @llvm.stackprotectorcheck(i8** <guard>)
+
+Overview:
+"""""""""
+
+The ``llvm.stackprotectorcheck`` intrinsic compares ``guard`` against an already
+created stack protector and if they are not equal calls the
``__stack_chk_fail()`` function.
+Arguments:
+""""""""""
+
+The ``llvm.stackprotectorcheck`` intrinsic requires one pointer argument, the
+the variable ``@__stack_chk_guard``.
+
+Semantics:
+""""""""""
+
+This intrinsic is provided to perform the stack protector check by comparing
+``guard`` with the stack slot created by ``llvm.stackprotector`` and if the
+values do not match call the ``__stack_chk_fail()`` function.
+
+The reason to provide this as an IR level intrinsic instead of implementing it
+via other IR operations is that in order to perform this operation at the IR
+level without an intrinsic, one would need to create additional basic blocks to
+handle the success/failure cases. This makes it difficult to stop the stack
+protector check from disrupting sibling tail calls in Codegen. With this
+intrinsic, we are able to generate the stack protector basic blocks late in
+codegen after the tail call decision has occured.
+
'``llvm.objectsize``' Intrinsic
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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