[InstCombine] allow fsub+fmul FMF folds for vectors

llvm-svn: 339368

1 files changed, 11 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp b/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
index 16e3d742ce0..e3391345ac0 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
@@ -1914,6 +1914,17 @@ Instruction *InstCombiner::visitFSub(BinaryOperator &I) {
     if (match(Op1, m_c_FAdd(m_Specific(Op0), m_Value(X))))
       return BinaryOperator::CreateFNegFMF(X, &I);
 
+    // (X * C) - X --> X * (C - 1.0)
+    if (match(Op0, m_FMul(m_Specific(Op1), m_Constant(C)))) {
+      Constant *CSubOne = ConstantExpr::getFSub(C, ConstantFP::get(Ty, 1.0));
+      return BinaryOperator::CreateFMulFMF(Op1, CSubOne, &I);
+    }
+    // X - (X * C) --> X * (1.0 - C)
+    if (match(Op1, m_FMul(m_Specific(Op0), m_Constant(C)))) {
+      Constant *OneSubC = ConstantExpr::getFSub(ConstantFP::get(Ty, 1.0), C);
+      return BinaryOperator::CreateFMulFMF(Op0, OneSubC, &I);
+    }
+
     // TODO: This performs reassociative folds for FP ops. Some fraction of the
     // functionality has been subsumed by simple pattern matching here and in
     // InstSimplify. We should let a dedicated reassociation pass handle more