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authorNick Lewycky <nicholas@mxc.ca>2011-02-28 08:31:40 +0000
committerNick Lewycky <nicholas@mxc.ca>2011-02-28 08:31:40 +0000
commitb042f8e9699dd15d7ac48bb9b9475122b1673687 (patch)
treeb4f6931415cb55575b9c575ecf700f970dc7ee2b
parent3dfd98744c1f6e6c5d13e419b63ac69894ae84cf (diff)
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Teach InstCombine to fold "(shr exact X, Y) == 0" --> X == 0, fixing #1 from
PR9343. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@126643 91177308-0d34-0410-b5e6-96231b3b80d8
-rw-r--r--lib/Transforms/InstCombine/InstCombineCompares.cpp18
-rw-r--r--test/Transforms/InstCombine/icmp.ll17
2 files changed, 30 insertions, 5 deletions
diff --git a/lib/Transforms/InstCombine/InstCombineCompares.cpp b/lib/Transforms/InstCombine/InstCombineCompares.cpp
index 7c67bf6..79c5d88 100644
--- a/lib/Transforms/InstCombine/InstCombineCompares.cpp
+++ b/lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -1289,13 +1289,21 @@ Instruction *InstCombiner::visitICmpInstWithInstAndIntCst(ICmpInst &ICI,
}
case Instruction::LShr: // (icmp pred (shr X, ShAmt), CI)
- case Instruction::AShr:
- // Only handle equality comparisons of shift-by-constant.
- if (ConstantInt *ShAmt = dyn_cast<ConstantInt>(LHSI->getOperand(1)))
- if (Instruction *Res = FoldICmpShrCst(ICI, cast<BinaryOperator>(LHSI),
- ShAmt))
+ case Instruction::AShr: {
+ // Handle equality comparisons of shift-by-constant.
+ BinaryOperator *BO = cast<BinaryOperator>(LHSI);
+ if (ConstantInt *ShAmt = dyn_cast<ConstantInt>(LHSI->getOperand(1))) {
+ if (Instruction *Res = FoldICmpShrCst(ICI, BO, ShAmt))
return Res;
+ }
+
+ // Handle exact shr's.
+ if (ICI.isEquality() && BO->isExact() && BO->hasOneUse()) {
+ if (RHSV.isMinValue())
+ return new ICmpInst(ICI.getPredicate(), BO->getOperand(0), RHS);
+ }
break;
+ }
case Instruction::SDiv:
case Instruction::UDiv:
diff --git a/test/Transforms/InstCombine/icmp.ll b/test/Transforms/InstCombine/icmp.ll
index c11dea5..f6a18fa 100644
--- a/test/Transforms/InstCombine/icmp.ll
+++ b/test/Transforms/InstCombine/icmp.ll
@@ -387,3 +387,20 @@ define i1 @test39(i31 %X, i32 %Y) {
%C = icmp slt i32 %B, 0
ret i1 %C
}
+
+; PR9343 #1
+; CHECK: test40
+; CHECK %B = icmp eq i32 %X, 0
+define i1 @test40(i32 %X, i32 %Y) {
+ %A = ashr exact i32 %X, %Y
+ %B = icmp eq i32 %A, 0
+ ret i1 %B
+}
+
+; CHECK: test41
+; CHECK %B = icmp ne i32 %X, 0
+define i1 @test41(i32 %X, i32 %Y) {
+ %A = lshr exact i32 %X, %Y
+ %B = icmp ne i32 %A, 0
+ ret i1 %B
+}