Reenable the transform "(X*Y)/Y->X" when the multiplication is known not to

overflow (nsw flag), which was disabled because it breaks 254.gap.  I have
informed the GAP authors of the mistake in their code, and arranged for the
testsuite to use -fwrapv when compiling this benchmark.

llvm-svn: 124746

1 files changed, 5 insertions, 5 deletions

diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp
index 6ca4dddcf36..4b9b648aa6c 100644
--- a/llvm/lib/Analysis/InstructionSimplify.cpp
+++ b/llvm/lib/Analysis/InstructionSimplify.cpp
@@ -798,11 +798,11 @@ static Value *SimplifyDiv(unsigned Opcode, Value *Op0, Value *Op1,
   Value *X = 0, *Y = 0;
   if (match(Op0, m_Mul(m_Value(X), m_Value(Y))) && (X == Op1 || Y == Op1)) {
     if (Y != Op1) std::swap(X, Y); // Ensure expression is (X * Y) / Y, Y = Op1
-//    BinaryOperator *Mul = cast<BinaryOperator>(Op0);
-//    // If the Mul knows it does not overflow, then we are good to go.
-//    if ((isSigned && Mul->hasNoSignedWrap()) ||
-//        (!isSigned && Mul->hasNoUnsignedWrap()))
-//      return X;
+    BinaryOperator *Mul = cast<BinaryOperator>(Op0);
+    // If the Mul knows it does not overflow, then we are good to go.
+    if ((isSigned && Mul->hasNoSignedWrap()) ||
+        (!isSigned && Mul->hasNoUnsignedWrap()))
+      return X;
     // If X has the form X = A / Y then X * Y cannot overflow.
     if (BinaryOperator *Div = dyn_cast<BinaryOperator>(X))
       if (Div->getOpcode() == Opcode && Div->getOperand(1) == Y)