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[SelectionDAG] Don't inspect !range metadata for extended loads

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Summary:
Don't call `computeKnownBitsFromRangeMetadata` for extended loads --
this can cause a mismatch between the width of the !range metadata and
the width of the APInt's accumulating `KnownZero` (and `KnownOne` in the
future).  This isn't a problem now, but will be after a future change.

Note: this can be made more aggressive in the future.

Reviewers: nlewycky

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D14107

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@251486 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Sanjoy Das 2015-10-28 03:20:10 +00:00
parent e7c323a364
commit 0c67849a49
2 changed files with 14 additions and 1 deletions
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3
lib/CodeGen/SelectionDAG/SelectionDAG.cpp
View File

@ -2284,7 +2284,8 @@ void SelectionDAG::computeKnownBits(SDValue Op, APInt &KnownZero,
unsigned MemBits = VT.getScalarType().getSizeInBits();
KnownZero |= APInt::getHighBitsSet(BitWidth, BitWidth - MemBits);
} else if (const MDNode *Ranges = LD->getRanges()) {
computeKnownBitsFromRangeMetadata(*Ranges, KnownZero);
if (LD->getExtensionType() == ISD::NON_EXTLOAD)
computeKnownBitsFromRangeMetadata(*Ranges, KnownZero);
}
break;
}

12
test/CodeGen/PowerPC/selectiondag-extload-computeknownbits.ll Normal file
View File

@ -0,0 +1,12 @@
; RUN: llc -mtriple=powerpc64-bgq-linux < %s
; Check that llc does not crash due to an illegal APInt operation
define i1 @f(i8* %ptr) {
entry:
%val = load i8, i8* %ptr, align 8, !range !0
%tobool = icmp eq i8 %val, 0
ret i1 %tobool
}
!0 = !{i8 0, i8 2}