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PR9346: Prevent SimplifyDemandedBits from incorrectly introducing

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INT_MIN % -1.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@127306 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Eli Friedman 2011-03-09 01:28:35 +00:00
parent d7f3e7d046
commit c6b018b737
2 changed files with 16 additions and 0 deletions
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4
lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
View File

@ -684,6 +684,10 @@ Value *InstCombiner::SimplifyDemandedUseBits(Value *V, APInt DemandedMask,
break;
case Instruction::SRem:
if (ConstantInt *Rem = dyn_cast<ConstantInt>(I->getOperand(1))) {
// X % -1 demands all the bits because we don't want to introduce
// INT_MIN % -1 (== undef) by accident.
if (Rem->isAllOnesValue())
break;
APInt RA = Rem->getValue().abs();
if (RA.isPowerOf2()) {
if (DemandedMask.ult(RA)) // srem won't affect demanded bits

12
test/Transforms/InstCombine/2011-03-08-SRemMinusOneBadOpt.ll Normal file
View File

@ -0,0 +1,12 @@
; RUN: opt < %s -instcombine -S | FileCheck %s
; PR9346
define i32 @test(i64 %x) nounwind {
; CHECK: ret i32 0
entry:
%or = or i64 %x, 4294967294
%conv = trunc i64 %or to i32
%rem.i = srem i32 %conv, -1
ret i32 %rem.i
}