[llvm-commits] CVS: llvm/lib/Transforms/Scalar/InstructionCombining.cpp

[Chris Lattner]

Changes in directory llvm/lib/Transforms/Scalar:

InstructionCombining.cpp updated: 1.152 -> 1.153

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Log message:

Implement Transforms/InstCombine/xor.ll:test19


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Diffs of the changes:  (+13 -2)

Index: llvm/lib/Transforms/Scalar/InstructionCombining.cpp
diff -u llvm/lib/Transforms/Scalar/InstructionCombining.cpp:1.152 llvm/lib/Transforms/Scalar/InstructionCombining.cpp:1.153
--- llvm/lib/Transforms/Scalar/InstructionCombining.cpp:1.152	Sat Feb 14 23:55:10 2004
+++ llvm/lib/Transforms/Scalar/InstructionCombining.cpp	Sun Feb 15 19:20:27 2004
@@ -1002,15 +1002,26 @@
   return Changed ? &I : 0;
 }
 
+// XorSelf - Implements: X ^ X --> 0
+struct XorSelf {
+  Value *RHS;
+  XorSelf(Value *rhs) : RHS(rhs) {}
+  bool shouldApply(Value *LHS) const { return LHS == RHS; }
+  Instruction *apply(BinaryOperator &Xor) const {
+    return &Xor;
+  }
+};
 
 
 Instruction *InstCombiner::visitXor(BinaryOperator &I) {
   bool Changed = SimplifyCommutative(I);
   Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
 
-  // xor X, X = 0
-  if (Op0 == Op1)
+  // xor X, X = 0, even if X is nested in a sequence of Xor's.
+  if (Instruction *Result = AssociativeOpt(I, XorSelf(Op1))) {
+    assert(Result == &I && "AssociativeOpt didn't work?");
     return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
+  }
 
   if (ConstantIntegral *RHS = dyn_cast<ConstantIntegral>(Op1)) {
     // xor X, 0 == X