Author: nicholas
Date: Sun Feb 3 01:42:09 2008
New Revision: 46683
URL: http://llvm.org/viewvc/llvm-project?rev=46683&view=rev
Log:
Fold away one multiply in instcombine. This would normally be caught in
reassociate anyways, but they could be generated during instcombine's run.
Modified:
llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp
Modified: llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp
URL:
http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp?rev=46683&r1=46682&r2=46683&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp Sun Feb 3
01:42:09 2008
@@ -2123,6 +2123,30 @@
if (Instruction *R = AssociativeOpt(I, AddMaskingAnd(C2)))
return R;
+ // W*X + Y*Z --> W * (X+Z) iff W == Y
+ if (I.getType()->isInteger()) {
+ Value *W, *X, *Y, *Z;
+ if (match(LHS, m_Mul(m_Value(W), m_Value(X))) &&
+ match(RHS, m_Mul(m_Value(Y), m_Value(Z)))) {
+ if (W != Y) {
+ if (W == Z) {
+ std::swap(Y, Z);
+ } else if (Y == X) {
+ std::swap(W, X);
+ } else if (X == Z) {
+ std::swap(Y, Z);
+ std::swap(W, X);
+ }
+ }
+
+ if (W == Y) {
+ Value *NewAdd = InsertNewInstBefore(BinaryOperator::createAdd(X, Z,
+ LHS->getName()),
I);
+ return BinaryOperator::createMul(W, NewAdd);
+ }
+ }
+ }
+
if (ConstantInt *CRHS = dyn_cast<ConstantInt>(RHS)) {
Value *X = 0;
if (match(LHS, m_Not(m_Value(X)))) // ~X + C --> (C-1) - X
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