[llvm-commits] [llvm] r60366 - /llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp

[Bill Wendling]

Author: void
Date: Mon Dec  1 13:46:27 2008
New Revision: 60366

URL: http://llvm.org/viewvc/llvm-project?rev=60366&view=rev
Log:
Use a simple comparison. Overflow on integer negation can only occur when the
integer is "minint".

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=60366&r1=60365&r2=60366&view=diff

==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp Mon Dec  1 13:46:27 2008
@@ -2934,20 +2934,9 @@
     if (Value *LHSNeg = dyn_castNegVal(Op0)) {
       if (ConstantInt *CI = dyn_cast<ConstantInt>(LHSNeg)) {
         ConstantInt *RHSNeg = cast<ConstantInt>(ConstantExpr::getNeg(RHS));
-        APInt RHSNegAPI(RHSNeg->getValue());
-
-        APInt NegOne = -APInt(RHSNeg->getBitWidth(), 1, true);
-        APInt TwoToExp(RHSNeg->getBitWidth(), 1 << (RHSNeg->getBitWidth() - 1));
-
-        if ((RHS->getValue().isNegative() &&
-             RHSNegAPI.slt(TwoToExp - 1)) ||
-            (RHS->getValue().isNonNegative() &&
-             RHSNegAPI.sgt(TwoToExp * NegOne))) {
+        if (RHS != RHSNeg) {
           ConstantInt *CINeg = cast<ConstantInt>(ConstantExpr::getNeg(CI));
-          APInt CINegAPI(CINeg->getValue());
-
-          if ((CI->getValue().isNegative() && CINegAPI.slt(TwoToExp - 1)) ||
-              (CI->getValue().isNonNegative() && CINegAPI.sgt(TwoToExp*NegOne)))
+          if (CI != CINeg)
             return BinaryOperator::CreateSDiv(LHSNeg,
                                               ConstantExpr::getNeg(RHS));
         }