[InstCombine] use pattern matchers for fsub --> fadd folds
This allows folding for vectors with undef elements.
llvm-svn: 329316
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp b/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
index 1f04a8b..578ba23 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
@@ -1708,10 +1708,15 @@
if (Instruction *NV = FoldOpIntoSelect(I, SI))
return NV;
- // If this is a 'B = x-(-A)', change to B = x+A, potentially looking
- // through FP extensions/truncations along the way.
- if (Value *V = dyn_castFNegVal(Op1))
- return BinaryOperator::CreateFAddFMF(Op0, V, &I);
+ // X - C --> X + (-C)
+ Constant *C;
+ if (match(Op1, m_Constant(C)))
+ return BinaryOperator::CreateFAddFMF(Op0, ConstantExpr::getFNeg(C), &I);
+
+ // X - (-Y) --> X + Y
+ Value *Y;
+ if (match(Op1, m_FNeg(m_Value(Y))))
+ return BinaryOperator::CreateFAddFMF(Op0, Y, &I);
if (FPTruncInst *FPTI = dyn_cast<FPTruncInst>(Op1)) {
if (Value *V = dyn_castFNegVal(FPTI->getOperand(0))) {