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

[Chris Lattner]

Changes in directory llvm/lib/Transforms/Scalar:

InstructionCombining.cpp updated: 1.318 -> 1.319
---
Log message:

Implement InstCombine/add.ll:test28, transforming C1-(X+C2) --> (C1-C2)-X.
This occurs several dozen times in specint2k, particularly in crafty and gcc
apparently.


---
Diffs of the changes:  (+8 -2)

 InstructionCombining.cpp |   10 ++++++++--
 1 files changed, 8 insertions(+), 2 deletions(-)


Index: llvm/lib/Transforms/Scalar/InstructionCombining.cpp
diff -u llvm/lib/Transforms/Scalar/InstructionCombining.cpp:1.318 llvm/lib/Transforms/Scalar/InstructionCombining.cpp:1.319
--- llvm/lib/Transforms/Scalar/InstructionCombining.cpp:1.318	Thu Apr  7 11:15:25 2005
+++ llvm/lib/Transforms/Scalar/InstructionCombining.cpp	Thu Apr  7 11:28:01 2005
@@ -795,10 +795,16 @@
   if (BinaryOperator *Op1I = dyn_cast<BinaryOperator>(Op1)) {
     if (Op1I->getOpcode() == Instruction::Add &&
         !Op0->getType()->isFloatingPoint()) {
-      if (Op1I->getOperand(0) == Op0)             // X-(X+Y) == -Y
+      if (Op1I->getOperand(0) == Op0)              // X-(X+Y) == -Y
         return BinaryOperator::createNeg(Op1I->getOperand(1), I.getName());
-      else if (Op1I->getOperand(1) == Op0)        // X-(Y+X) == -Y
+      else if (Op1I->getOperand(1) == Op0)         // X-(Y+X) == -Y
         return BinaryOperator::createNeg(Op1I->getOperand(0), I.getName());
+      else if (ConstantInt *CI1 = dyn_cast<ConstantInt>(I.getOperand(0))) {
+        if (ConstantInt *CI2 = dyn_cast<ConstantInt>(Op1I->getOperand(1)))
+          // C1-(X+C2) --> (C1-C2)-X
+          return BinaryOperator::createSub(ConstantExpr::getSub(CI1, CI2),
+                                           Op1I->getOperand(0));
+      }
     }
 
     if (Op1I->hasOneUse()) {