diff options
Diffstat (limited to 'docs/LangRef.rst')
| -rw-r--r-- | docs/LangRef.rst | 25 |
1 files changed, 11 insertions, 14 deletions
diff --git a/docs/LangRef.rst b/docs/LangRef.rst index a767700636..8bb834b45e 100644 --- a/docs/LangRef.rst +++ b/docs/LangRef.rst @@ -778,19 +778,16 @@ Currently, only the following parameter attributes are defined: .. Warning:: This feature is unstable and not fully implemented. The ``inalloca`` argument attribute allows the caller to take the - address of all stack-allocated arguments 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>`, an alloca may be used as an - ``inalloca`` argument at most once. The attribute can only be - applied to the last parameter, and it guarantees that they are - passed in memory. 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``. + 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``. When the call site is reached, the argument allocation must have been the most recent stack allocation that is still live, or the @@ -4693,7 +4690,7 @@ Syntax: :: - <result> = alloca <type>[, <ty> <NumElements>][, align <alignment>] ; yields {type*}:result + <result> = alloca <type>[, inalloca][, <ty> <NumElements>][, align <alignment>] ; yields {type*}:result Overview: """"""""" |