From 0f9fd5b0f820c57c88ea103ddeec44efbfd3345d Mon Sep 17 00:00:00 2001
From: Chris Lattner <sabre@nondot.org>
Date: Tue, 14 May 2002 19:57:25 +0000
Subject: [PATCH] * Fix bug:
 test/Regression/Transforms/GCSE/2002-05-14-OperandSwap.ll

By making sure to consider binary expressions identical if their operands
are backwards, but swappable.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@2629 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Transforms/Scalar/GCSE.cpp | 39 ++++++++++++++++++++++++++++------
 1 file changed, 32 insertions(+), 7 deletions(-)

diff --git a/lib/Transforms/Scalar/GCSE.cpp b/lib/Transforms/Scalar/GCSE.cpp
index d9f5f3ae169..27925509bd5 100644
--- a/lib/Transforms/Scalar/GCSE.cpp
+++ b/lib/Transforms/Scalar/GCSE.cpp
@@ -256,6 +256,37 @@ bool GCSE::visitUnaryOperator(Instruction *I) {
   return false;
 }
 
+// isIdenticalBinaryInst - Return true if the two binary instructions are
+// identical.
+//
+static inline bool isIdenticalBinaryInst(const Instruction *I1,
+                                         const Instruction *I2) {
+  // Is it embeded in the same function?  (This could be false if LHS
+  // is a constant or global!)
+  if (I1->getOpcode() != I2->getOpcode() ||
+      I1->getParent()->getParent() != I2->getParent()->getParent())
+    return false;
+  
+  // They are identical if both operands are the same!
+  if (I1->getOperand(0) == I2->getOperand(0) &&
+      I1->getOperand(1) == I2->getOperand(1))
+    return true;
+  
+  // If the instruction is commutative and associative, the instruction can
+  // match if the operands are swapped!
+  //
+  if ((I1->getOperand(0) == I2->getOperand(1) &&
+       I1->getOperand(1) == I2->getOperand(0)) &&
+      (I1->getOpcode() == Instruction::Add || 
+       I1->getOpcode() == Instruction::Mul ||
+       I1->getOpcode() == Instruction::And || 
+       I1->getOpcode() == Instruction::Or  ||
+       I1->getOpcode() == Instruction::Xor))
+    return true;
+
+  return false;
+}
+
 bool GCSE::visitBinaryOperator(Instruction *I) {
   Value *LHS = I->getOperand(0), *RHS = I->getOperand(1);
   Function *F = I->getParent()->getParent();
@@ -264,13 +295,7 @@ bool GCSE::visitBinaryOperator(Instruction *I) {
        UI != UE; ++UI)
     if (Instruction *Other = dyn_cast<Instruction>(*UI))
       // Check to see if this new binary operator is not I, but same operand...
-      if (Other != I && Other->getOpcode() == I->getOpcode() &&
-          // Are the LHS and RHS the same?
-          Other->getOperand(0) == LHS && Other->getOperand(1) == RHS &&
-          // Is it embeded in the same function?  (This could be false if LHS
-          // is a constant or global!)
-          Other->getParent()->getParent() == F) {
-        
+      if (Other != I && isIdenticalBinaryInst(I, Other)) {        
         // These instructions are identical.  Handle the situation.
         CommonSubExpressionFound(I, Other);
         return true;   // One instruction eliminated!