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Diffstat (limited to 'docs/LangRef.rst')
| -rw-r--r-- | docs/LangRef.rst | 37 |
1 files changed, 37 insertions, 0 deletions
diff --git a/docs/LangRef.rst b/docs/LangRef.rst index 2faa15692b..86b5a15f25 100644 --- a/docs/LangRef.rst +++ b/docs/LangRef.rst @@ -697,6 +697,39 @@ 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 get the + address of an outgoing argument to a ``call`` or ``invoke`` before + it executes. It is similar to ``byval`` in that it is used to pass + arguments by value, but it guarantees that the argument will not be + copied. + + To be :ref:`well formed <wellformed>`, the caller must pass in an + alloca value into an ``inalloca`` parameter, and an alloca may be + used as an ``inalloca`` argument at most once. The attribute can + only be applied to parameters that would be passed in memory and not + registers. The ``inalloca`` attribute cannot be used in conjunction + with other attributes that affect argument storage, like ``inreg``, + ``nest``, ``sret``, or ``byval``. The ``inalloca`` stack space is + considered to be clobbered by any call that uses it, so any + ``inalloca`` parameters cannot be marked ``readonly``. + + Allocas passed with ``inalloca`` to a call must be in the opposite + order of the parameter list, meaning that the rightmost argument + must be allocated first. If a call has inalloca arguments, no other + allocas can occur between the first alloca used by the call and the + call site, unless they are are cleared by calls to + :ref:`llvm.stackrestore <int_stackrestore>`. Violating these rules + results in undefined behavior at runtime. + + 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 @@ -8419,6 +8452,8 @@ 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 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ @@ -8450,6 +8485,8 @@ 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 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ |