[llvm] 24dd041 - [LangRef] Memset/memcpy/memmove can take undef/poison pointer if the size is 0
Juneyoung Lee via llvm-commits
llvm-commits at lists.llvm.org
Wed Aug 26 14:19:46 PDT 2020
Author: Juneyoung Lee
Date: 2020-08-27T06:19:28+09:00
New Revision: 24dd04116db34e97271a520b6ab2397c67c627cb
URL: https://github.com/llvm/llvm-project/commit/24dd04116db34e97271a520b6ab2397c67c627cb
DIFF: https://github.com/llvm/llvm-project/commit/24dd04116db34e97271a520b6ab2397c67c627cb.diff
LOG: [LangRef] Memset/memcpy/memmove can take undef/poison pointer if the size is 0
According to the current LangRef, Memset/memcpy/memmove can take a
null/dangling pointer if the size is zero.
(Relevant thread: http://lists.llvm.org/pipermail/llvm-dev/2017-July/115665.html )
This patch expands it and allows the functions to take undef/poison pointers
too.
This required the updates in the align attribute since it isn't specified
what is the alignment of undef/poison pointers.
This patch states that their alignment is 1.
Reviewed By: efriedma
Differential Revision: https://reviews.llvm.org/D86643
Added:
Modified:
llvm/docs/LangRef.rst
Removed:
################################################################################
diff --git a/llvm/docs/LangRef.rst b/llvm/docs/LangRef.rst
index 8e3befad3d5a..1dfb19555380 100644
--- a/llvm/docs/LangRef.rst
+++ b/llvm/docs/LangRef.rst
@@ -1157,10 +1157,11 @@ Currently, only the following parameter attributes are defined:
``align <n>`` or ``align(<n>)``
This indicates that the pointer value may be assumed by the optimizer to
have the specified alignment. If the pointer value does not have the
- specified alignment, behavior is undefined.
+ specified alignment, behavior is undefined. ``align 1`` has no effect on
+ non-byval, non-preallocated arguments.
Note that this attribute has additional semantics when combined with the
- ``byval`` attribute, which are documented there.
+ ``byval`` or ``preallocated`` attribute, which are documented there.
.. _noalias:
@@ -12478,8 +12479,8 @@ overlap. It copies "len" bytes of memory over. If the argument is known
to be aligned to some boundary, this can be specified as an attribute on
the argument.
-If "len" is 0, the pointers may be NULL or dangling. However, they must still
-be appropriately aligned.
+If "len" is 0, the pointers may be NULL, dangling, ``undef``, or ``poison``
+pointers. However, they must still be appropriately aligned.
.. _int_memcpy_inline:
@@ -12535,8 +12536,8 @@ overlap. It copies "len" bytes of memory over. If the argument is known
to be aligned to some boundary, this can be specified as an attribute on
the argument.
-If "len" is 0, the pointers may be NULL or dangling. However, they must still
-be appropriately aligned.
+If "len" is 0, the pointers may be NULL, dangling, ``undef``, or ``poison``
+pointers. However, they must still be appropriately aligned.
The generated code is guaranteed not to call any external functions.
@@ -12595,8 +12596,8 @@ copies "len" bytes of memory over. If the argument is known to be
aligned to some boundary, this can be specified as an attribute on
the argument.
-If "len" is 0, the pointers may be NULL or dangling. However, they must still
-be appropriately aligned.
+If "len" is 0, the pointers may be NULL, dangling, ``undef``, or ``poison``
+pointers. However, they must still be appropriately aligned.
.. _int_memset:
@@ -12650,8 +12651,8 @@ at the destination location. If the argument is known to be
aligned to some boundary, this can be specified as an attribute on
the argument.
-If "len" is 0, the pointers may be NULL or dangling. However, they must still
-be appropriately aligned.
+If "len" is 0, the pointer may be NULL, dangling, ``undef``, or ``poison``
+pointer. However, it must still be appropriately aligned.
'``llvm.sqrt.*``' Intrinsic
^^^^^^^^^^^^^^^^^^^^^^^^^^^
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