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Fold (-x + -y) -> -(x+y) which promotes better association, fixing
the second half of PR2047 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@47244 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -2090,8 +2090,16 @@ Instruction *InstCombiner::visitAdd(BinaryOperator &I) {
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}
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// -A + B --> B - A
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if (Value *V = dyn_castNegVal(LHS))
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return BinaryOperator::createSub(RHS, V);
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// -A + -B --> -(A + B)
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if (Value *LHSV = dyn_castNegVal(LHS)) {
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if (Value *RHSV = dyn_castNegVal(RHS)) {
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Instruction *NewAdd = BinaryOperator::createAdd(LHSV, RHSV, "sum");
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InsertNewInstBefore(NewAdd, I);
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return BinaryOperator::createNeg(NewAdd);
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}
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return BinaryOperator::createSub(RHS, LHSV);
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}
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// A + -B --> A - B
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if (!isa<Constant>(RHS))
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12
test/Transforms/InstCombine/addnegneg.ll
Normal file
12
test/Transforms/InstCombine/addnegneg.ll
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@ -0,0 +1,12 @@
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; RUN: llvm-as < %s | opt -instcombine | llvm-dis | grep { sub } | count 1
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; PR2047
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define i32 @l(i32 %a, i32 %b, i32 %c, i32 %d) {
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entry:
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%b.neg = sub i32 0, %b ; <i32> [#uses=1]
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%c.neg = sub i32 0, %c ; <i32> [#uses=1]
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%sub4 = add i32 %c.neg, %b.neg ; <i32> [#uses=1]
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%sub6 = add i32 %sub4, %d ; <i32> [#uses=1]
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ret i32 %sub6
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}
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