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- Fix a problematic way in creating all-the-1 APInt.

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- Propagate "exact" bit of [l|a]shr instruction.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@169942 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Shuxin Yang 2012-12-12 00:29:03 +00:00
parent c244f38176
commit 5f70c2e934
2 changed files with 14 additions and 2 deletions
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6
lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
View File

@ -858,8 +858,8 @@ Value *InstCombiner::SimplifyShrShlDemandedBits(Instruction *Shr,
Value *VarX = Shr->getOperand(0);
Type *Ty = VarX->getType();
APInt BitMask1(Ty->getIntegerBitWidth(), (uint64_t)-1);
APInt BitMask2(Ty->getIntegerBitWidth(), (uint64_t)-1);
APInt BitMask1(APInt::getAllOnesValue(Ty->getIntegerBitWidth()));
APInt BitMask2(APInt::getAllOnesValue(Ty->getIntegerBitWidth()));
bool isLshr = (Shr->getOpcode() == Instruction::LShr);
BitMask1 = isLshr ? (BitMask1.lshr(ShrAmt) << ShlAmt) :
@ -891,6 +891,8 @@ Value *InstCombiner::SimplifyShrShlDemandedBits(Instruction *Shr,
Constant *Amt = ConstantInt::get(VarX->getType(), ShrAmt - ShlAmt);
New = isLshr ? BinaryOperator::CreateLShr(VarX, Amt) :
BinaryOperator::CreateAShr(VarX, Amt);
if (cast<BinaryOperator>(Shr)->isExact())
New->setIsExact(true);
}
return InsertNewInstWith(New, *Shl);

10
test/Transforms/InstCombine/shift.ll
View File

@ -735,3 +735,13 @@ define i32 @test61(i32 %x) {
; CHECK: @test61
; CHECK: ashr i32 %x, 4
}
; propagate "exact" trait
define i32 @test62(i32 %x) {
%shr = ashr exact i32 %x, 4
%shl = shl i32 %shr, 1
%or = or i32 %shl, 1
ret i32 %or
; CHECK: @test62
; CHECK: ashr exact i32 %x, 3
}