Changes in directory llvm/lib/Transforms/Scalar:
InstructionCombining.cpp updated: 1.404 -> 1.405
---
Log message:
Turn sdiv into udiv if both operands have a clear sign bit. This occurs
a few times in crafty:
OLD: %tmp.36 = div int %tmp.35, 8 ; <int> [#uses=1]
NEW: %tmp.36 = div uint %tmp.35, 8 ; <uint> [#uses=0]
OLD: %tmp.19 = div int %tmp.18, 8 ; <int> [#uses=1]
NEW: %tmp.19 = div uint %tmp.18, 8 ; <uint> [#uses=0]
OLD: %tmp.117 = div int %tmp.116, 8 ; <int> [#uses=1]
NEW: %tmp.117 = div uint %tmp.116, 8 ; <uint> [#uses=0]
OLD: %tmp.92 = div int %tmp.91, 8 ; <int> [#uses=1]
NEW: %tmp.92 = div uint %tmp.91, 8 ; <uint> [#uses=0]
Which all turn into shrs.
---
Diffs of the changes: (+19 -0)
InstructionCombining.cpp | 19 +++++++++++++++++++
1 files changed, 19 insertions(+)
Index: llvm/lib/Transforms/Scalar/InstructionCombining.cpp
diff -u llvm/lib/Transforms/Scalar/InstructionCombining.cpp:1.404
llvm/lib/Transforms/Scalar/InstructionCombining.cpp:1.405
--- llvm/lib/Transforms/Scalar/InstructionCombining.cpp:1.404 Sat Nov 5
01:28:37 2005
+++ llvm/lib/Transforms/Scalar/InstructionCombining.cpp Sat Nov 5 01:40:31 2005
@@ -1240,6 +1240,25 @@
if (LHS->equalsInt(0))
return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
+ if (I.getType()->isSigned()) {
+ // If the top bits of both operands are zero (i.e. we can prove they are
+ // unsigned inputs), turn this into a udiv.
+ ConstantIntegral *MaskV = ConstantSInt::getMinValue(I.getType());
+ if (MaskedValueIsZero(Op1, MaskV) && MaskedValueIsZero(Op0, MaskV)) {
+ const Type *NTy = Op0->getType()->getUnsignedVersion();
+ Instruction *LHS = new CastInst(Op0, NTy, Op0->getName());
+ InsertNewInstBefore(LHS, I);
+ Value *RHS;
+ if (Constant *R = dyn_cast<Constant>(Op1))
+ RHS = ConstantExpr::getCast(R, NTy);
+ else
+ RHS = InsertNewInstBefore(new CastInst(Op1, NTy, Op1->getName()), I);
+ Instruction *Div = BinaryOperator::createDiv(LHS, RHS, I.getName());
+ InsertNewInstBefore(Div, I);
+ return new CastInst(Div, I.getType());
+ }
+ }
+
return 0;
}
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