X-Git-Url: http://plrg.eecs.uci.edu/git/?a=blobdiff_plain;f=docs%2FLangRef.rst;h=9820fd8a572328c643ffd3a98f7aabfb7d116ca3;hb=3b9afd308728feb1853596bbb8ccd57cf5f6b3b9;hp=91f2289d6bf4b50ff5e4f703f175728ffb99a608;hpb=d1066efaec118c4d21b6da19e0d42c0d5e32c82d;p=oota-llvm.git diff --git a/docs/LangRef.rst b/docs/LangRef.rst index 91f2289d6bf..9820fd8a572 100644 --- a/docs/LangRef.rst +++ b/docs/LangRef.rst @@ -4,7 +4,7 @@ LLVM Language Reference Manual .. contents:: :local: - :depth: 3 + :depth: 4 Abstract ======== @@ -128,7 +128,9 @@ lexical features of LLVM: #. Unnamed temporaries are created when the result of a computation is not assigned to a named value. #. Unnamed temporaries are numbered sequentially (using a per-function - incrementing counter, starting with 0). + incrementing counter, starting with 0). Note that basic blocks are + included in this numbering. For example, if the entry basic block is not + given a label name, then it will get number 0. It also shows a convention that we follow in this document. When demonstrating instructions, we will follow an instruction with a comment @@ -267,46 +269,13 @@ linkage: ``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. -``linkonce_odr_auto_hide`` - Similar to "``linkonce_odr``", but nothing in the translation unit - takes the address of this definition. For instance, functions that - had an inline definition, but the compiler decided not to inline it. - ``linkonce_odr_auto_hide`` may have only ``default`` visibility. The - symbols are removed by the linker from the final linked image - (executable or dynamic library). ``external`` If none of the above identifiers are used, the global is externally visible, meaning that it participates in linkage and can be used to resolve external symbol references. -The next two types of linkage are targeted for Microsoft Windows -platform only. They are designed to support importing (exporting) -symbols from (to) DLLs (Dynamic Link Libraries). - -``dllimport`` - "``dllimport``" linkage causes the compiler to reference a function - or variable via a global pointer to a pointer that is set up by the - DLL exporting the symbol. On Microsoft Windows targets, the pointer - name is formed by combining ``__imp_`` and the function or variable - name. -``dllexport`` - "``dllexport``" linkage causes the compiler to provide a global - pointer to a pointer in a DLL, so that it can be referenced with the - ``dllimport`` attribute. On Microsoft Windows targets, the pointer - name is formed by combining ``__imp_`` and the function or variable - name. - -For example, since the "``.LC0``" variable is defined to be internal, if -another module defined a "``.LC0``" variable and was linked with this -one, one of the two would be renamed, preventing a collision. Since -"``main``" and "``puts``" are external (i.e., lacking any linkage -declarations), they are accessible outside of the current module. - It is illegal for a function *declaration* to have any linkage type -other than ``external``, ``dllimport`` or ``extern_weak``. - -Aliases can have only ``external``, ``internal``, ``weak`` or -``weak_odr`` linkages. +other than ``external`` or ``extern_weak``. .. _callingconv: @@ -343,7 +312,8 @@ added in the future: so that the call does not break any live ranges in the caller side. This calling convention does not support varargs and requires the prototype of all callees to exactly match the prototype of the - function definition. + function definition. Furthermore the inliner doesn't consider such function + calls for inlining. "``cc 10``" - GHC convention This calling convention has been implemented specifically for use by the `Glasgow Haskell Compiler (GHC) `_. @@ -378,6 +348,72 @@ added in the future: accessed runtime components pinned to specific hardware registers. At the moment only X86 supports this convention (both 32 and 64 bit). +"``webkit_jscc``" - WebKit's JavaScript calling convention + This calling convention has been implemented for `WebKit FTL JIT + `_. It passes arguments on the + stack right to left (as cdecl does), and returns a value in the + platform's customary return register. +"``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 + 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` + 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 + call in the caller. If the arguments are passed in callee-saved registers, + then they will be preserved by the callee across the call. This doesn't + apply for values returned in callee-saved registers. + + - On X86-64 the callee preserves all general purpose registers, except for + R11. R11 can be used as a scratch register. Floating-point registers + (XMMs/YMMs) are not preserved and need to be saved by the caller. + + 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 + 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 + convention in terms of caller/callee-saved registers, but they are used for + different types of function calls. `coldcc` is for function calls that are + rarely executed, whereas `preserve_mostcc` function calls are intended to be + on the hot path and definitely executed a lot. Furthermore `preserve_mostcc` + doesn't prevent the inliner from inlining the function call. + + This calling convention will be used by a future version of the ObjectiveC + runtime and should therefore still be considered experimental at this time. + Although this convention was created to optimize certain runtime calls to + the ObjectiveC runtime, it is not limited to this runtime and might be used + by other runtimes in the future too. The current implementation only + supports X86-64, but the intention is to support more architectures in the + future. +"``preserve_allcc``" - The `PreserveAll` calling convention + This calling convention attempts to make the code in the caller even less + intrusive than the `PreserveMost` calling convention. This calling + convention also behaves identical 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 removes the burden of saving and + recovering a large register set before and after the call in the caller. If + the arguments are passed in callee-saved registers, then they will be + preserved by the callee across the call. This doesn't apply for values + returned in callee-saved registers. + + - On X86-64 the callee preserves all general purpose registers, except for + R11. R11 can be used as a scratch register. Furthermore it also preserves + all floating-point registers (XMMs/YMMs). + + The idea behind this convention is to support calls to runtime functions + that don't need to call out to any other functions. + + This calling convention, like the `PreserveMost` calling convention, will be + used by a future version of the ObjectiveC runtime and should be considered + experimental at this time. "``cc ``" - Numbered convention Any calling convention may be specified by number, allowing target-specific calling conventions to be used. Target specific @@ -416,31 +452,41 @@ styles: .. _namedtypes: -Named Types ------------ +DLL Storage Classes +------------------- + +All Global Variables, Functions and Aliases can have one of the following +DLL storage class: + +``dllimport`` + "``dllimport``" causes the compiler to reference a function or variable via + a global pointer to a pointer that is set up by the DLL exporting the + symbol. On Microsoft Windows targets, the pointer name is formed by + combining ``__imp_`` and the function or variable name. +``dllexport`` + "``dllexport``" causes the compiler to provide a global pointer to a pointer + in a DLL, so that it can be referenced with the ``dllimport`` attribute. On + Microsoft Windows targets, the pointer name is formed by combining + ``__imp_`` and the function or variable name. Since this storage class + exists for defining a dll interface, the compiler, assembler and linker know + it is externally referenced and must refrain from deleting the symbol. + +Structure Types +--------------- + +LLVM IR allows you to specify both "identified" and "literal" :ref:`structure +types `. Literal types are uniqued structurally, but identified types +are never uniqued. An :ref:`opaque structural type ` can also be used +to forward declare a type which is not yet available. -LLVM IR allows you to specify name aliases for certain types. This can -make it easier to read the IR and make the IR more condensed -(particularly when recursive types are involved). An example of a name -specification is: +An example of a identified structure specification is: .. code-block:: llvm %mytype = type { %mytype*, i32 } -You may give a name to any :ref:`type ` except -":ref:`void `". Type name aliases may be used anywhere a type is -expected with the syntax "%mytype". - -Note that type names are aliases for the structural type that they -indicate, and that you can therefore specify multiple names for the same -type. This often leads to confusing behavior when dumping out a .ll -file. Since LLVM IR uses structural typing, the name is not part of the -type. When printing out LLVM IR, the printer will pick *one name* to -render all types of a particular shape. This means that if you have code -where two different source types end up having the same LLVM type, that -the dumper will sometimes print the "wrong" or unexpected type. This is -an important design point and isn't going to change. +Prior to the LLVM 3.0 release, identified types were structurally uniqued. Only +literal types are uniqued in recent versions of LLVM. .. _globalvars: @@ -448,9 +494,13 @@ Global Variables ---------------- Global variables define regions of memory allocated at compilation time -instead of run-time. Global variables may optionally be initialized, may -have an explicit section to be placed in, and may have an optional -explicit alignment specified. +instead of run-time. + +Global variables definitions must be initialized, may have an explicit section +to be placed in, and may have an optional explicit alignment specified. + +Global variables in other translation units can also be declared, in which +case they don't have an initializer. A variable may be defined as ``thread_local``, which means that it will not be shared by threads (each thread will have a separated copy of the @@ -511,8 +561,8 @@ 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``. +``@llvm.used`` or dllexported variables. 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 @@ -525,6 +575,15 @@ assume that the globals are densely packed in their section and try to iterate over them as an array, alignment padding would break this iteration. +Globals can also have a :ref:`DLL storage class `. + +Syntax:: + + [@ =] [Linkage] [Visibility] [DLLStorageClass] [ThreadLocal] + [AddrSpace] [unnamed_addr] [ExternallyInitialized] + + [, section "name"] [, align ] + For example, the following defines a global in a numbered address space with an initializer, section, and alignment: @@ -532,6 +591,12 @@ with an initializer, section, and alignment: @G = addrspace(5) constant float 1.0, section "foo", align 4 +The following example just declares a global variable + +.. code-block:: llvm + + @G = external global i32 + The following example defines a thread-local global with the ``initialexec`` TLS model: @@ -546,33 +611,34 @@ Functions LLVM function definitions consist of the "``define``" keyword, an optional :ref:`linkage type `, an optional :ref:`visibility -style `, an optional :ref:`calling convention `, +style `, an optional :ref:`DLL storage class `, +an optional :ref:`calling convention `, an optional ``unnamed_addr`` attribute, a return type, an optional :ref:`parameter attribute ` for the return type, a function name, a (possibly empty) argument list (each with optional :ref:`parameter attributes `), optional :ref:`function attributes `, an optional section, an optional alignment, an optional :ref:`garbage -collector name `, an opening curly brace, a list of basic blocks, -and a closing curly brace. +collector name `, an optional :ref:`prefix `, 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 `, an optional :ref:`visibility -style `, an optional :ref:`calling convention `, +style `, an optional :ref:`DLL storage class `, +an optional :ref:`calling convention `, an optional ``unnamed_addr`` attribute, a return type, an optional :ref:`parameter attribute ` for the return type, a function -name, a possibly empty list of arguments, an optional alignment, and an -optional :ref:`garbage collector name `. - -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 ` instruction (such as a branch or function -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`). 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. +name, a possibly empty list of arguments, an optional alignment, an optional +:ref:`garbage collector name ` and an optional :ref:`prefix `. + +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 ` instruction (such as a branch or +function return). If an explicit label is not provided, a block is assigned an +implicit numbered label, using the next value from the same counter as used for +unnamed temporaries (:ref:`see above`). For example, if a function +entry block does not have an explicit label, it will be assigned label "%0", +then the 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 @@ -594,11 +660,11 @@ be significant and two identical functions can be merged. Syntax:: - define [linkage] [visibility] + define [linkage] [visibility] [DLLStorageClass] [cconv] [ret attrs] @ ([argument list]) [fn Attrs] [section "name"] [align N] - [gc] { ... } + [gc] [prefix Constant] { ... } .. _langref_aliases: @@ -607,12 +673,19 @@ Aliases Aliases act as "second name" for the aliasee value (which can be either function, global variable, another alias or bitcast of global value). -Aliases may have an optional :ref:`linkage type `, and an optional -:ref:`visibility style `. +Aliases may have an optional :ref:`linkage type `, an optional +:ref:`visibility style `, and an optional :ref:`DLL storage class +`. Syntax:: - @ = alias [Linkage] [Visibility] @ + @ = [Visibility] [DLLStorageClass] alias [Linkage] @ + +The linkage must be one of ``private``, ``linker_private``, +``linker_private_weak``, ``internal``, ``linkonce``, ``weak``, +``linkonce_odr``, ``weak_odr``, ``external``. Note that some system linkers +might not correctly handle dropping a weak symbol that is aliased by a non-weak +alias. .. _namedmetadatastructure: @@ -694,6 +767,37 @@ Currently, only the following parameter attributes are defined: site. If the alignment is not specified, then the code generator makes a target-specific assumption. +.. _attr_inalloca: + +``inalloca`` + +.. Warning:: This feature is unstable and not fully implemented. + + The ``inalloca`` argument attribute allows the caller to take the + 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 past 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 + used in conjunction with other attributes that affect argument + 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 + space after an argument allocation and before its call site, but it + must be cleared off with :ref:`llvm.stackrestore + `. + + See :doc:`InAlloca` for more information on how to use this + attribute. + ``sret`` This indicates that the pointer parameter specifies the address of a structure that is the return value of the function in the source @@ -757,6 +861,55 @@ The compiler declares the supported values of *name*. Specifying a 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 @@ -828,15 +981,16 @@ example: computing edge weights, basic blocks post-dominated by a cold function call are also considered to be cold; and, thus, given low weight. -``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. ``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. @@ -863,6 +1017,10 @@ example: 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. @@ -874,10 +1032,23 @@ example: 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. + + This attribute requires the ``noinline`` attribute to be specified on + the function as well, so the function is never inlined into any caller. + Only functions with the ``alwaysinline`` attribute are valid + candidates for inlining into 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`` On a function, this attribute indicates that the function computes its result (or decides to unwind an exception) based strictly on its arguments, @@ -887,7 +1058,7 @@ example: (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. @@ -901,7 +1072,7 @@ example: 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. @@ -932,6 +1103,9 @@ example: - Calls to alloca() with variable sizes or constant sizes greater than ``ssp-buffer-size``. + Variables that are identified as requiring a protector will be arranged + on the stack such that they are adjacent to the stack protector guard. + If a function that has an ``ssp`` attribute is inlined into a function that doesn't have an ``ssp`` attribute, then the resulting function will have an ``ssp`` attribute. @@ -940,6 +1114,17 @@ example: stack smashing protector. This overrides the ``ssp`` function attribute. + Variables that are identified as requiring a protector will be arranged + on the stack such that they are adjacent to the stack protector guard. + The specific layout rules are: + + #. Large arrays and structures containing large arrays + (``>= ssp-buffer-size``) are closest to the stack protector. + #. Small arrays and structures containing small arrays + (``< ssp-buffer-size``) are 2nd closest to the protector. + #. Variables that have had their address taken are 3rd closest to the + protector. + 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`` or ``sspstrong`` attribute, then the resulting function will have @@ -955,6 +1140,17 @@ example: - Calls to alloca(). - Local variables that have had their address taken. + Variables that are identified as requiring a protector will be arranged + on the stack such that they are adjacent to the stack protector guard. + The specific layout rules are: + + #. Large arrays and structures containing large arrays + (``>= ssp-buffer-size``) are closest to the stack protector. + #. Small arrays and structures containing small arrays + (``< ssp-buffer-size``) are 2nd closest to the protector. + #. Variables that have had their address taken are 3rd closest to the + protector. + This overrides the ``ssp`` function attribute. If a function that has an ``sspstrong`` attribute is inlined into a @@ -1026,10 +1222,9 @@ as follows: ``p[n]:::`` This specifies the *size* of a pointer and its ```` and ````\erred alignments for address space ``n``. All sizes are in - bits. Specifying the ```` alignment is optional. If omitted, the - preceding ``:`` should be omitted too. 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). + 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::`` This specifies the alignment for an integer type of a given bit ````. The value of ```` must be in the range [1,2^23). @@ -1042,12 +1237,18 @@ as follows: will work. 32 (float) and 64 (double) are supported on all targets; 80 or 128 (different flavors of long double) are also supported on some targets. -``a::`` - This specifies the alignment for an aggregate type of a given bit - ````. -``s::`` - This specifies the alignment for a stack object of a given bit - ````. +``a::`` + This specifies the alignment for an object of aggregate type. +``m:`` + If present, specifies that llvm names are mangled in the output. The + options are + + * ``e``: ELF mangling: Private symbols get a ``.L`` prefix. + * ``m``: Mips mangling: Private symbols get a ``$`` prefix. + * ``o``: Mach-O mangling: Private symbols get ``L`` prefix. Other + symbols get a ``_`` prefix. + * ``w``: Windows COFF prefix: Similar to Mach-O, but stdcall and fastcall + functions also get a suffix based on the frame size. ``n::...`` This specifies a set of native integer widths for the target CPU in bits. For example, it might contain ``n32`` for 32-bit PowerPC, @@ -1055,13 +1256,19 @@ as follows: this set are considered to support most general arithmetic operations efficiently. +On every specification that takes a ``:``, specifying the +```` alignment is optional. If omitted, the preceding ``:`` +should be omitted too and ```` will be equal to ````. + When constructing the data layout for a given target, LLVM starts with a default set of specifications which are then (possibly) overridden by the specifications in the ``datalayout`` keyword. The default specifications are given in this list: - ``E`` - big endian -- ``p:64:64:64`` - 64-bit pointers with 64-bit alignment +- ``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 @@ -1075,7 +1282,7 @@ specifications are given in this list: - ``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 -- ``a0:0:64`` - aggregates are 64-bit aligned +- ``a:0:64`` - aggregates are 64-bit aligned When LLVM is determining the alignment for a given type, it uses the following rules: @@ -1107,6 +1314,30 @@ 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. +.. _langref_triple: + +Target Triple +------------- + +A module may specify a target triple string that describes the target +host. The syntax for the target triple is simply: + +.. code-block:: llvm + + target triple = "x86_64-apple-macosx10.7.0" + +The *target triple* string consists of a series of identifiers delimited +by the minus sign character ('-'). The canonical forms are: + +:: + + ARCHITECTURE-VENDOR-OPERATING_SYSTEM + ARCHITECTURE-VENDOR-OPERATING_SYSTEM-ENVIRONMENT + +This information is passed along to the backend so that it generates +code for the proper architecture. It's possible to override this on the +command line with the ``-mtriple`` command line option. + .. _pointeraliasing: Pointer Aliasing Rules @@ -1380,80 +1611,90 @@ transformation. A strong type system makes it easier to read the generated code and enables novel analyses and transformations that are not feasible to perform on normal three address code representations. -.. _typeclassifications: +.. _t_void: -Type Classifications --------------------- +Void Type +--------- -The types fall into a few useful classifications: +:Overview: -.. list-table:: - :header-rows: 1 +The void type does not represent any value and has no size. + +:Syntax: + + +:: + + void + + +.. _t_function: - * - Classification - - Types +Function Type +------------- - * - :ref:`integer ` - - ``i1``, ``i2``, ``i3``, ... ``i8``, ... ``i16``, ... ``i32``, ... - ``i64``, ... +:Overview: - * - :ref:`floating point ` - - ``half``, ``float``, ``double``, ``x86_fp80``, ``fp128``, - ``ppc_fp128`` +The function type can be thought of as a function signature. It consists of a +return type and a list of formal parameter types. The return type of a function +type is a void type or first class type --- except for :ref:`label ` +and :ref:`metadata ` types. - * - first class +:Syntax: + +:: - .. _t_firstclass: + () + +...where '````' 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 +argument functions can access their arguments with the :ref:`variable argument +handling intrinsic ` functions. '````' is any type +except :ref:`label ` and :ref:`metadata `. - - :ref:`integer `, :ref:`floating point `, - :ref:`pointer `, :ref:`vector `, - :ref:`structure `, :ref:`array `, - :ref:`label `, :ref:`metadata `. +:Examples: + ++---------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------+ +| ``i32 (i32)`` | function taking an ``i32``, returning an ``i32`` | ++---------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------+ +| ``float (i16, i32 *) *`` | :ref:`Pointer ` to a function that takes an ``i16`` and a :ref:`pointer ` to ``i32``, returning ``float``. | ++---------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------+ +| ``i32 (i8*, ...)`` | A vararg function that takes at least one :ref:`pointer ` to ``i8`` (char in C), which returns an integer. This is the signature for ``printf`` in LLVM. | ++---------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------+ +| ``{i32, i32} (i32)`` | A function taking an ``i32``, returning a :ref:`structure ` containing two ``i32`` values | ++---------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------+ - * - :ref:`primitive ` - - :ref:`label `, - :ref:`void `, - :ref:`integer `, - :ref:`floating point `, - :ref:`x86mmx `, - :ref:`metadata `. +.. _t_firstclass: - * - :ref:`derived ` - - :ref:`array `, - :ref:`function `, - :ref:`pointer `, - :ref:`structure `, - :ref:`vector `, - :ref:`opaque `. +First Class Types +----------------- The :ref:`first class ` types are perhaps the most important. Values of these types are the only ones which can be produced by instructions. -.. _t_primitive: +.. _t_single_value: -Primitive Types ---------------- +Single Value Types +^^^^^^^^^^^^^^^^^^ -The primitive types are the fundamental building blocks of the LLVM -system. +These are the types that are valid in registers from CodeGen's perspective. .. _t_integer: Integer Type -^^^^^^^^^^^^ +"""""""""""" -Overview: -""""""""" +:Overview: The integer type is a very simple type that simply specifies an arbitrary bit width for the integer type desired. Any bit width from 1 bit to 2\ :sup:`23`\ -1 (about 8 million) can be specified. -Syntax: -""""""" +:Syntax: :: @@ -1463,7 +1704,7 @@ The number of bits the integer will occupy is specified by the ``N`` value. Examples: -""""""""" +********* +----------------+------------------------------------------------+ | ``i1`` | a single-bit integer. | @@ -1476,7 +1717,7 @@ Examples: .. _t_floating: Floating Point Types -^^^^^^^^^^^^^^^^^^^^ +"""""""""""""""""""" .. list-table:: :header-rows: 1 @@ -1502,57 +1743,104 @@ Floating Point Types * - ``ppc_fp128`` - 128-bit floating point value (two 64-bits) -.. _t_x86mmx: +X86_mmx Type +"""""""""""" -X86mmx Type -^^^^^^^^^^^ +:Overview: -Overview: -""""""""" - -The x86mmx type represents a value held in an MMX register on an x86 +The x86_mmx type represents a value held in an MMX register on an x86 machine. The operations allowed on it are quite limited: parameters and return values, load and store, and bitcast. User-specified MMX instructions are represented as intrinsic or asm calls with arguments and/or results of this type. There are no arrays, vectors or constants of this type. -Syntax: -""""""" +:Syntax: :: - x86mmx + x86_mmx -.. _t_void: -Void Type -^^^^^^^^^ +.. _t_pointer: -Overview: -""""""""" +Pointer Type +"""""""""""" -The void type does not represent any value and has no size. +:Overview: -Syntax: -""""""" +The pointer type is used to specify memory locations. Pointers are +commonly used to reference objects in memory. + +Pointer types may have an optional address space attribute defining the +numbered address space where the pointed-to object resides. The default +address space is number zero. The semantics of non-zero address spaces +are target-specific. + +Note that LLVM does not permit pointers to void (``void*``) nor does it +permit pointers to labels (``label*``). Use ``i8*`` instead. + +:Syntax: :: - void + * + +:Examples: + ++-------------------------+--------------------------------------------------------------------------------------------------------------+ +| ``[4 x i32]*`` | A :ref:`pointer ` to :ref:`array ` of four ``i32`` values. | ++-------------------------+--------------------------------------------------------------------------------------------------------------+ +| ``i32 (i32*) *`` | A :ref:`pointer ` to a :ref:`function ` that takes an ``i32*``, returning an ``i32``. | ++-------------------------+--------------------------------------------------------------------------------------------------------------+ +| ``i32 addrspace(5)*`` | A :ref:`pointer ` to an ``i32`` value that resides in address space #5. | ++-------------------------+--------------------------------------------------------------------------------------------------------------+ + +.. _t_vector: + +Vector Type +""""""""""" + +:Overview: + +A vector type is a simple derived type that represents a vector of +elements. Vector types are used when multiple primitive data are +operated in parallel using a single instruction (SIMD). A vector type +requires a size (number of elements) and an underlying primitive data +type. Vector types are considered :ref:`first class `. + +:Syntax: + +:: + + < <# elements> x > + +The number of elements is a constant integer value larger than 0; +elementtype may be any integer or floating point type, or a pointer to +these types. Vectors of size zero are not allowed. + +:Examples: + ++-------------------+--------------------------------------------------+ +| ``<4 x i32>`` | Vector of 4 32-bit integer values. | ++-------------------+--------------------------------------------------+ +| ``<8 x float>`` | Vector of 8 32-bit floating-point values. | ++-------------------+--------------------------------------------------+ +| ``<2 x i64>`` | Vector of 2 64-bit integer values. | ++-------------------+--------------------------------------------------+ +| ``<4 x i64*>`` | Vector of 4 pointers to 64-bit integer values. | ++-------------------+--------------------------------------------------+ .. _t_label: Label Type ^^^^^^^^^^ -Overview: -""""""""" +:Overview: The label type represents code labels. -Syntax: -""""""" +:Syntax: :: @@ -1563,31 +1851,17 @@ Syntax: Metadata Type ^^^^^^^^^^^^^ -Overview: -""""""""" +:Overview: The metadata type represents embedded metadata. No derived types may be created from metadata except for :ref:`function ` arguments. -Syntax: -""""""" +:Syntax: :: metadata -.. _t_derived: - -Derived Types -------------- - -The real power in LLVM comes from the derived types in the system. This -is what allows a programmer to represent arrays, functions, pointers, -and other useful types. Each of these types contain one or more element -types which may be a primitive type, or another derived type. For -example, it is possible to have a two dimensional array, using an array -as the element type of another array. - .. _t_aggregate: Aggregate Types @@ -1601,17 +1875,15 @@ aggregate types. .. _t_array: Array Type -^^^^^^^^^^ +"""""""""" -Overview: -""""""""" +:Overview: The array type is a very simple derived type that arranges elements sequentially in memory. The array type requires a size (number of elements) and an underlying data type. -Syntax: -""""""" +:Syntax: :: @@ -1620,8 +1892,7 @@ Syntax: The number of elements is a constant integer value; ``elementtype`` may be any type with a size. -Examples: -""""""""" +:Examples: +------------------+--------------------------------------+ | ``[40 x i32]`` | Array of 40 32-bit integer values. | @@ -1649,52 +1920,12 @@ LLVM with a zero length array type. An implementation of 'pascal style arrays' in LLVM could use the type "``{ i32, [0 x float]}``", for example. -.. _t_function: - -Function Type -^^^^^^^^^^^^^ - -Overview: -""""""""" - -The function type can be thought of as a function signature. It consists -of a return type and a list of formal parameter types. The return type -of a function type is a first class type or a void type. - -Syntax: -""""""" - -:: - - () - -...where '````' 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 argument functions can access their arguments with the -:ref:`variable argument handling intrinsic ` functions. -'````' is any type except :ref:`label `. - -Examples: -""""""""" - -+---------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------+ -| ``i32 (i32)`` | function taking an ``i32``, returning an ``i32`` | -+---------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------+ -| ``float (i16, i32 *) *`` | :ref:`Pointer ` to a function that takes an ``i16`` and a :ref:`pointer ` to ``i32``, returning ``float``. | -+---------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------+ -| ``i32 (i8*, ...)`` | A vararg function that takes at least one :ref:`pointer ` to ``i8`` (char in C), which returns an integer. This is the signature for ``printf`` in LLVM. | -+---------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------+ -| ``{i32, i32} (i32)`` | A function taking an ``i32``, returning a :ref:`structure ` containing two ``i32`` values | -+---------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------+ - .. _t_struct: Structure Type -^^^^^^^^^^^^^^ +"""""""""""""" -Overview: -""""""""" +:Overview: The structure type is used to represent a collection of data members together in memory. The elements of a structure may be any type that has @@ -1718,16 +1949,14 @@ Literal types are uniqued by their contents and can never be recursive or opaque since there is no way to write one. Identified types can be recursive, can be opaqued, and are never uniqued. -Syntax: -""""""" +:Syntax: :: %T1 = type { } ; Identified normal struct type %T2 = type <{ }> ; Identified packed struct type -Examples: -""""""""" +:Examples: +------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ | ``{ i32, i32, i32 }`` | A triple of three ``i32`` values | @@ -1740,105 +1969,27 @@ Examples: .. _t_opaque: Opaque Structure Types -^^^^^^^^^^^^^^^^^^^^^^ +"""""""""""""""""""""" -Overview: -""""""""" +:Overview: Opaque structure types are used to represent named structure types that do not have a body specified. This corresponds (for example) to the C notion of a forward declared structure. -Syntax: -""""""" +:Syntax: :: %X = type opaque %52 = type opaque -Examples: -""""""""" +:Examples: +--------------+-------------------+ | ``opaque`` | An opaque type. | +--------------+-------------------+ -.. _t_pointer: - -Pointer Type -^^^^^^^^^^^^ - -Overview: -""""""""" - -The pointer type is used to specify memory locations. Pointers are -commonly used to reference objects in memory. - -Pointer types may have an optional address space attribute defining the -numbered address space where the pointed-to object resides. The default -address space is number zero. The semantics of non-zero address spaces -are target-specific. - -Note that LLVM does not permit pointers to void (``void*``) nor does it -permit pointers to labels (``label*``). Use ``i8*`` instead. - -Syntax: -""""""" - -:: - - * - -Examples: -""""""""" - -+-------------------------+--------------------------------------------------------------------------------------------------------------+ -| ``[4 x i32]*`` | A :ref:`pointer ` to :ref:`array ` of four ``i32`` values. | -+-------------------------+--------------------------------------------------------------------------------------------------------------+ -| ``i32 (i32*) *`` | A :ref:`pointer ` to a :ref:`function ` that takes an ``i32*``, returning an ``i32``. | -+-------------------------+--------------------------------------------------------------------------------------------------------------+ -| ``i32 addrspace(5)*`` | A :ref:`pointer ` to an ``i32`` value that resides in address space #5. | -+-------------------------+--------------------------------------------------------------------------------------------------------------+ - -.. _t_vector: - -Vector Type -^^^^^^^^^^^ - -Overview: -""""""""" - -A vector type is a simple derived type that represents a vector of -elements. Vector types are used when multiple primitive data are -operated in parallel using a single instruction (SIMD). A vector type -requires a size (number of elements) and an underlying primitive data -type. Vector types are considered :ref:`first class `. - -Syntax: -""""""" - -:: - - < <# elements> x > - -The number of elements is a constant integer value larger than 0; -elementtype may be any integer or floating point type, or a pointer to -these types. Vectors of size zero are not allowed. - -Examples: -""""""""" - -+-------------------+--------------------------------------------------+ -| ``<4 x i32>`` | Vector of 4 32-bit integer values. | -+-------------------+--------------------------------------------------+ -| ``<8 x float>`` | Vector of 8 32-bit floating-point values. | -+-------------------+--------------------------------------------------+ -| ``<2 x i64>`` | Vector of 2 64-bit integer values. | -+-------------------+--------------------------------------------------+ -| ``<4 x i64*>`` | Vector of 4 pointers to 64-bit integer values. | -+-------------------+--------------------------------------------------+ - Constants ========= @@ -1893,7 +2044,7 @@ 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. +There are no constants of type x86_mmx. .. _complexconstants: @@ -2284,6 +2435,10 @@ The following is the syntax for constant expressions: Convert a constant, CST, to another TYPE. The constraints of the operands are the same as those for the :ref:`bitcast instruction `. +``addrspacecast (CST to TYPE)`` + 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 `. ``getelementptr (CSTPTR, IDX0, IDX1, ...)``, ``getelementptr inbounds (CSTPTR, IDX0, IDX1, ...)`` Perform the :ref:`getelementptr operation ` on constants. As with the :ref:`getelementptr ` @@ -2583,7 +2738,7 @@ Examples: 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 +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 @@ -4557,7 +4712,7 @@ Syntax: :: - = alloca [, ][, align ] ; yields {type*}:result + = alloca [, inalloca][, ][, align ] ; yields {type*}:result Overview: """"""""" @@ -5613,24 +5768,24 @@ Arguments: 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 ` 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 ` 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 ` or :ref:`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 the same address space through this instruction. +To convert pointers to other types, use the :ref:`inttoptr ` +or :ref:`ptrtoint ` instructions first. Example: """""""" @@ -5642,6 +5797,51 @@ Example: %Z = bitcast <2 x int> %V to i64; ; yields i64: %V %Z = bitcast <2 x i32*> %V to <2 x i64*> ; yields <2 x i64*> +.. _i_addrspacecast: + +'``addrspacecast .. to``' Instruction +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +Syntax: +""""""" + +:: + + = addrspacecast to ; yields pty2 + +Overview: +""""""""" + +The '``addrspacecast``' instruction converts ``ptrval`` from ``pty`` in +address space ``n`` to type ``pty2`` in address space ``m``. + +Arguments: +"""""""""" + +The '``addrspacecast``' instruction takes a pointer or vector of pointer value +to cast and a pointer type to cast it to, which must have a different +address space. + +Semantics: +"""""""""" + +The '``addrspacecast``' instruction converts the pointer value +``ptrval`` to type ``pty2``. It can be a *no-op cast* or a complex +value modification, depending on the target and the address space +pair. Pointer conversions within the same address space must be +performed with the ``bitcast`` instruction. Note that if the address space +conversion is legal then both result and operand refer to the same memory +location. + +Example: +"""""""" + +.. code-block:: llvm + + %X = addrspacecast i32* %x to i32 addrspace(1)* ; yields i32 addrspace(1)*:%x + %Y = addrspacecast i32 addrspace(1)* %y to i64 addrspace(2)* ; yields i64 addrspace(2)*:%y + %Z = addrspacecast <4 x i32*> %z to <4 x float addrspace(3)*> ; yields <4 x float addrspace(3)*>:%z + .. _otherops: Other Operations @@ -6291,7 +6491,7 @@ Syntax: :: - declare void %llvm.va_start(i8* ) + declare void @llvm.va_start(i8* ) Overview: """"""""" @@ -6803,7 +7003,7 @@ The '``llvm.memcpy.*``' intrinsics copy a block of memory from the source location to the destination location, which are not allowed to overlap. It copies "len" bytes of memory over. If the argument is known to be aligned to some boundary, this can be specified as the fourth -argument, otherwise it should be set to 0 or 1. +argument, otherwise it should be set to 0 or 1 (both meaning no alignment). '``llvm.memmove``' Intrinsic ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ @@ -6858,7 +7058,7 @@ The '``llvm.memmove.*``' intrinsics copy a block of memory from the source location to the destination location, which may overlap. It copies "len" bytes of memory over. If the argument is known to be aligned to some boundary, this can be specified as the fourth argument, -otherwise it should be set to 0 or 1. +otherwise it should be set to 0 or 1 (both meaning no alignment). '``llvm.memset.*``' Intrinsics ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ @@ -6909,7 +7109,7 @@ Semantics: The '``llvm.memset.*``' intrinsics fill "len" bytes of memory starting at the destination location. If the argument is known to be aligned to some boundary, this can be specified as the fourth argument, otherwise -it should be set to 0 or 1. +it should be set to 0 or 1 (both meaning no alignment). '``llvm.sqrt.*``' Intrinsic ^^^^^^^^^^^^^^^^^^^^^^^^^^^ @@ -7307,7 +7507,7 @@ Semantics: """""""""" This function returns the same values as the libm ``fma`` functions -would. +would, and does not set errno. '``llvm.fabs.*``' Intrinsic ^^^^^^^^^^^^^^^^^^^^^^^^^^^ @@ -7345,6 +7545,42 @@ Semantics: 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 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ @@ -7524,6 +7760,42 @@ Semantics: 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 --------------------------- @@ -8043,7 +8315,8 @@ is equivalent to the expression a \* b + c, except that rounding will not be performed between the multiplication and addition steps if the code generator fuses the operations. Fusion is not guaranteed, even if the target platform supports it. If a fused multiply-add is required the -corresponding llvm.fma.\* intrinsic function should be used instead. +corresponding llvm.fma.\* intrinsic function should be used +instead. This never sets errno, just as '``llvm.fma.*``'. Examples: """"""""" @@ -8280,6 +8553,8 @@ Memory Use Markers This class of intrinsics exists to information about the lifetime of memory objects and ranges where variables are immutable. +.. _int_lifestart: + '``llvm.lifetime.start``' Intrinsic ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ @@ -8311,6 +8586,8 @@ of the memory pointed to by ``ptr`` is dead. This means that it is known to never be used and has an undefined value. A load from the pointer that precedes this intrinsic can be replaced with ``'undef'``. +.. _int_lifeend: + '``llvm.lifetime.end``' Intrinsic ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ @@ -8597,14 +8874,52 @@ enough space to hold the value of the guard. 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** ) + +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 occurred. + '``llvm.objectsize``' Intrinsic ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ @@ -8649,8 +8964,12 @@ on the ``min`` argument). Syntax: """"""" +This is an overloaded intrinsic. You can use ``llvm.expect`` on any +integer bit width. + :: + declare i1 @llvm.expect.i1(i1 , i1 ) declare i32 @llvm.expect.i32(i32 , i32 ) declare i64 @llvm.expect.i64(i64 , i64 ) @@ -8698,3 +9017,10 @@ Semantics: This intrinsic does nothing, and it's removed by optimizers and ignored by codegen. + +Stack Map Intrinsics +-------------------- + +LLVM provides experimental intrinsics to support runtime patching +mechanisms commonly desired in dynamic language JITs. These intrinsics +are described in :doc:`StackMaps`.