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Fix an overaggressive SimplifyDemandedBits optimization on urem. This 

fixes the 254.gap regression on x86 and the 403.gcc regression on x86-64.

llvm-svn: 50537
This commit is contained in:
Dan Gohman 2008-05-01 19:13:24 +00:00
parent fb4191cc04
commit 4be6ae4e6c
2 changed files with 37 additions and 4 deletions
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9
llvm/lib/Transforms/Scalar/InstructionCombining.cpp
View File

@ -1762,11 +1762,12 @@ bool InstCombiner::SimplifyDemandedBits(Value *V, APInt DemandedMask,
APInt KnownZero2(BitWidth, 0), KnownOne2(BitWidth, 0);
APInt AllOnes = APInt::getAllOnesValue(BitWidth);
ComputeMaskedBits(I->getOperand(0), AllOnes,
KnownZero2, KnownOne2, Depth+1);
if (SimplifyDemandedBits(I->getOperand(0), AllOnes,
KnownZero2, KnownOne2, Depth+1))
return true;
uint32_t Leaders = KnownZero2.countLeadingOnes();
APInt HighZeros = APInt::getHighBitsSet(BitWidth, Leaders);
if (SimplifyDemandedBits(I->getOperand(1), ~HighZeros,
if (SimplifyDemandedBits(I->getOperand(1), AllOnes,
KnownZero2, KnownOne2, Depth+1))
return true;

32
llvm/test/Transforms/InstCombine/urem-simplify-bug.ll Normal file
View File

@ -0,0 +1,32 @@
; RUN: llvm-as < %s | opt -instcombine | llvm-dis | grep {= or i32 %x, -5 }
@.str = internal constant [5 x i8] c"foo\0A\00" ; <[5 x i8]*> [#uses=1]
@.str1 = internal constant [5 x i8] c"bar\0A\00" ; <[5 x i8]*> [#uses=1]
define i32 @main() nounwind {
entry:
%x = call i32 @func_11( ) nounwind ; <i32> [#uses=1]
%tmp3 = or i32 %x, -5 ; <i32> [#uses=1]
%tmp5 = urem i32 251, %tmp3 ; <i32> [#uses=1]
%tmp6 = icmp ne i32 %tmp5, 0 ; <i1> [#uses=1]
%tmp67 = zext i1 %tmp6 to i32 ; <i32> [#uses=1]
%tmp9 = urem i32 %tmp67, 95 ; <i32> [#uses=1]
%tmp10 = and i32 %tmp9, 1 ; <i32> [#uses=1]
%tmp12 = icmp eq i32 %tmp10, 0 ; <i1> [#uses=1]
br i1 %tmp12, label %bb14, label %bb
bb: ; preds = %entry
br label %bb15
bb14: ; preds = %entry
br label %bb15
bb15: ; preds = %bb14, %bb
%iftmp.0.0 = phi i8* [ getelementptr ([5 x i8]* @.str1, i32 0, i32 0), %bb14 ], [ getelementptr ([5 x i8]* @.str, i32 0, i32 0), %bb ] ; <i8*> [#uses=1]
%tmp17 = call i32 (i8*, ...)* @printf( i8* %iftmp.0.0 ) nounwind ; <i32> [#uses=0]
ret i32 0
}
declare i32 @func_11()
declare i32 @printf(i8*, ...) nounwind