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preserve NUW/NSW when transforming add x,x

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@125711 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner
2011-02-17 02:23:02 +00:00
parent 3e468e1efa
commit 41429e3f1e
2 changed files with 15 additions and 2 deletions
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9
lib/Transforms/InstCombine/InstCombineAddSub.cpp
View File

@@ -147,8 +147,13 @@ Instruction *InstCombiner::visitAdd(BinaryOperator &I) {
return BinaryOperator::CreateXor(LHS, RHS); return BinaryOperator::CreateXor(LHS, RHS);
// X + X --> X << 1 // X + X --> X << 1
if (LHS == RHS && I.getType()->isIntegerTy()) if (LHS == RHS && I.getType()->isIntegerTy()) {
return BinaryOperator::CreateShl(LHS, ConstantInt::get(I.getType(), 1)); BinaryOperator *New =
BinaryOperator::CreateShl(LHS, ConstantInt::get(I.getType(), 1));
New->setHasNoSignedWrap(I.hasNoSignedWrap());
New->setHasNoUnsignedWrap(I.hasNoUnsignedWrap());
return New;
}
// -A + B --> B - A // -A + B --> B - A
// -A + -B --> -(A + B) // -A + -B --> -(A + B)

8
test/Transforms/InstCombine/add2.ll
View File

@@ -33,3 +33,11 @@ define i32 @test3(i32 %A) {
; CHECK-NEXT: ret i32 ; CHECK-NEXT: ret i32
} }
define i32 @test4(i32 %A) {
%B = add nuw i32 %A, %A
ret i32 %B
; CHECK: @test4
; CHECK-NEXT: %B = shl nuw i32 %A, 1
; CHECK-NEXT: ret i32 %B
}