Reassociate x + -0.1234 * y into x - 0.1234 * y

[oota-llvm.git] / lib / Transforms / Scalar / IndVarSimplify.cpp

diff --git a/lib/Transforms/Scalar/IndVarSimplify.cpp b/lib/Transforms/Scalar/IndVarSimplify.cpp
index bf19038b1ec0a92e32dd9716cd559470c0e506b2..9b653c6a232061a7ed31e9ee0043b4074780c2bb 100644 (file)
--- a/lib/Transforms/Scalar/IndVarSimplify.cpp
+++ b/lib/Transforms/Scalar/IndVarSimplify.cpp
@@ -757,6 +757,9 @@ protected:
 
   const SCEVAddRecExpr* GetExtendedOperandRecurrence(NarrowIVDefUse DU);
 
+  const SCEV *GetSCEVByOpCode(const SCEV *LHS, const SCEV *RHS,
+                              unsigned OpCode) const;
+
   Instruction *WidenIVUse(NarrowIVDefUse DU, SCEVExpander &Rewriter);
 
   void pushNarrowIVUsers(Instruction *NarrowDef, Instruction *WideDef);
@@ -833,13 +836,30 @@ Instruction *WidenIV::CloneIVUser(NarrowIVDefUse DU) {
   }
 }
 
+const SCEV *WidenIV::GetSCEVByOpCode(const SCEV *LHS, const SCEV *RHS,
+                                     unsigned OpCode) const {
+  if (OpCode == Instruction::Add)
+    return SE->getAddExpr(LHS, RHS);
+  if (OpCode == Instruction::Sub)
+    return SE->getMinusSCEV(LHS, RHS);
+  if (OpCode == Instruction::Mul)
+    return SE->getMulExpr(LHS, RHS);
+
+  llvm_unreachable("Unsupported opcode.");
+  return nullptr;
+}
+
 /// No-wrap operations can transfer sign extension of their result to their
 /// operands. Generate the SCEV value for the widened operation without
 /// actually modifying the IR yet. If the expression after extending the
 /// operands is an AddRec for this loop, return it.
 const SCEVAddRecExpr* WidenIV::GetExtendedOperandRecurrence(NarrowIVDefUse DU) {
+
   // Handle the common case of add<nsw/nuw>
-  if (DU.NarrowUse->getOpcode() != Instruction::Add)
+  const unsigned OpCode = DU.NarrowUse->getOpcode();
+  // Only Add/Sub/Mul instructions supported yet.
+  if (OpCode != Instruction::Add && OpCode != Instruction::Sub &&
+      OpCode != Instruction::Mul)
     return nullptr;
 
   // One operand (NarrowDef) has already been extended to WideDef. Now determine
@@ -859,14 +879,13 @@ const SCEVAddRecExpr* WidenIV::GetExtendedOperandRecurrence(NarrowIVDefUse DU) {
   else
     return nullptr;
 
-  // When creating this AddExpr, don't apply the current operations NSW or NUW
+  // When creating this SCEV expr, don't apply the current operations NSW or NUW
   // flags. This instruction may be guarded by control flow that the no-wrap
   // behavior depends on. Non-control-equivalent instructions can be mapped to
   // the same SCEV expression, and it would be incorrect to transfer NSW/NUW
   // semantics to those operations.
   const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(
-    SE->getAddExpr(SE->getSCEV(DU.WideDef), ExtendOperExpr));
-
+      GetSCEVByOpCode(SE->getSCEV(DU.WideDef), ExtendOperExpr, OpCode));
   if (!AddRec || AddRec->getLoop() != L)
     return nullptr;
   return AddRec;