- 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

diff --git a/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp b/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
index 08aedb3200a0c79c2d841450dbc7de2bc112d66a..13653183a791af68da610953859109e3942effe7 100644 (file)
--- 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<BinaryOperator>(Shr)->isExact())
+        New->setIsExact(true);
     }
 
     return InsertNewInstWith(New, *Shl);

diff --git a/test/Transforms/InstCombine/shift.ll b/test/Transforms/InstCombine/shift.ll
index 32867761a3f0ba9609268c7dddda5cd1b9179e48..41f8aa9ee8124ddcc05e3fa3340104369faea608 100644 (file)
--- 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
+}