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Use a memcpy so that type based alias analysis sees the change.

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The other option would be to do something like

if (that.isSingleWord())
  VAL = that.VAL;
else
  pVal = that.pVal

This bug was causing 86TTI::getIntImmCost to be miscompiled in a LTO
bootstrap in stage2, causing the build of stage3 to fail.

LLVM is getting quiet good at exploiting this. Not sure if there is anything
a sanitizer could do to help

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@222294 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Rafael Espindola 2014-11-19 01:02:22 +00:00
parent d8e31c73cd
commit 28b45aa83e
1 changed files with 3 additions and 1 deletions
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4
include/llvm/ADT/APInt.h
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@ -665,7 +665,9 @@ public:
delete[] pVal;
}
VAL = that.VAL;
// Use memcpy so that type based alias analysis sees both VAL and pVal
// as modified.
memcpy(&VAL, &that.VAL, sizeof(uint64_t));
// If 'this == &that', avoid zeroing our own bitwidth by storing to 'that'
// first.