[InstCombine] Fold Select with binary op - non-commutative opcodes

Summary:
Basic version was merged - https://reviews.llvm.org/D49954

This adds support for FP & non-commutative opcodes

Precommited tests: https://reviews.llvm.org/rL338727

Reviewers: spatel, lebedev.ri

Reviewed By: spatel

Subscribers: jfb

Differential Revision: https://reviews.llvm.org/D50190

llvm-svn: 339520

1 files changed, 3 insertions, 2 deletions

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp b/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
index 61e917fd4f8..dc8e8df421e 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
@@ -68,15 +68,16 @@ static Instruction *foldSelectBinOpIdentity(SelectInst &Sel) {
 
   // A select operand must be a binop, and the compare constant must be the
   // identity constant for that binop.
-  // TODO: Support non-commutative binops.
   bool IsEq = Pred == ICmpInst::ICMP_EQ;
   BinaryOperator *BO;
   if (!match(Sel.getOperand(IsEq ? 1 : 2), m_BinOp(BO)) ||
-      ConstantExpr::getBinOpIdentity(BO->getOpcode(), BO->getType(), false) != C)
+      ConstantExpr::getBinOpIdentity(BO->getOpcode(), BO->getType(), true) != C)
     return nullptr;
 
   // Last, match the compare variable operand with a binop operand.
   Value *Y;
+  if (!BO->isCommutative() && !match(BO, m_BinOp(m_Value(Y), m_Specific(X))))
+    return nullptr;
   if (!match(BO, m_c_BinOp(m_Value(Y), m_Specific(X))))
     return nullptr;