From 5f70c2e934c8cf7814fc047f4824ac89b35dd72d Mon Sep 17 00:00:00 2001 From: Shuxin Yang Date: Wed, 12 Dec 2012 00:29:03 +0000 Subject: [PATCH] - Fix a problematic way in creating all-the-1 APInt. - 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 --- .../InstCombine/InstCombineSimplifyDemanded.cpp | 6 ++++-- test/Transforms/InstCombine/shift.ll | 10 ++++++++++ 2 files changed, 14 insertions(+), 2 deletions(-) diff --git a/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp b/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp index 08aedb3200a..13653183a79 100644 --- a/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp +++ b/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp @@ -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(Shr)->isExact()) + New->setIsExact(true); } return InsertNewInstWith(New, *Shl); diff --git a/test/Transforms/InstCombine/shift.ll b/test/Transforms/InstCombine/shift.ll index 32867761a3f..41f8aa9ee81 100644 --- a/test/Transforms/InstCombine/shift.ll +++ b/test/Transforms/InstCombine/shift.ll @@ -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 +}