[all-commits] [llvm/llvm-project] 178318: Respect integer overflow handling in abs builtin
Artem Labazov via All-commits
all-commits at lists.llvm.org
Thu Aug 17 11:36:20 PDT 2023
Branch: refs/heads/main
Home: https://github.com/llvm/llvm-project
Commit: 1783185790de29b24d3850d33d9a9d586e6bbd39
https://github.com/llvm/llvm-project/commit/1783185790de29b24d3850d33d9a9d586e6bbd39
Author: Artem Labazov <123321artyom at gmail.com>
Date: 2023-08-17 (Thu, 17 Aug 2023)
Changed paths:
M clang/docs/ReleaseNotes.rst
M clang/lib/CodeGen/CGBuiltin.cpp
A clang/test/CodeGen/abs-overflow.c
A clang/test/ubsan/TestCases/Misc/abs.cpp
Log Message:
-----------
Respect integer overflow handling in abs builtin
Currenly both Clang and GCC support the following set of flags that
control code gen of signed overflow:
* -fwrapv: overflow is defined as in two-complement
* -ftrapv: overflow traps
* -fsanitize=signed-integer-overflow: if undefined (no -fwrapv), then
overflow behaviour is controlled by UBSan runtime, overrides -ftrapv.
However, clang ignores these flags for __builtin_abs(int) and its
higher-width versions, so passing minimum integer value always causes
poison.
The same holds for *abs(), which are not handled in frontend at all but
folded to llvm.abs.* intrinsics during InstCombinePass. The intrinsics
are not instrumented by UBSan, so the functions need special handling
as well.
This patch does a few things:
* Handle *abs() in CGBuiltin the same way as __builtin_*abs()
* -fsanitize=signed-integer-overflow now properly instruments abs() with
UBSan
* -fwrapv and -ftrapv handling for abs() is made consistent with GCC
Fixes https://github.com/llvm/llvm-project/issues/45129
Fixes https://github.com/llvm/llvm-project/issues/45794
Differential Revision: https://reviews.llvm.org/D156821
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