Changes in directory llvm/lib/Transforms/Scalar:
InstructionCombining.cpp updated: 1.403 -> 1.404
---
Log message:
Turn srem -> urem when neither input has their sign bit set. This triggers
8 times in vortex, allowing the srems to be turned into shrs:
OLD: %tmp.104 = rem int %tmp.5.i37, 16 ; <int> [#uses=1]
NEW: %tmp.104 = rem uint %tmp.5.i37, 16 ; <uint> [#uses=0]
OLD: %tmp.98 = rem int %tmp.5.i24, 16 ; <int> [#uses=1]
NEW: %tmp.98 = rem uint %tmp.5.i24, 16 ; <uint> [#uses=0]
OLD: %tmp.91 = rem int %tmp.5.i19, 8 ; <int> [#uses=1]
NEW: %tmp.91 = rem uint %tmp.5.i19, 8 ; <uint> [#uses=0]
OLD: %tmp.88 = rem int %tmp.5.i14, 8 ; <int> [#uses=1]
NEW: %tmp.88 = rem uint %tmp.5.i14, 8 ; <uint> [#uses=0]
OLD: %tmp.85 = rem int %tmp.5.i9, 1024 ; <int> [#uses=2]
NEW: %tmp.85 = rem uint %tmp.5.i9, 1024 ; <uint> [#uses=0]
OLD: %tmp.82 = rem int %tmp.5.i, 512 ; <int> [#uses=2]
NEW: %tmp.82 = rem uint %tmp.5.i1, 512 ; <uint> [#uses=0]
OLD: %tmp.48.i = rem int %tmp.5.i.i161, 4 ; <int> [#uses=1]
NEW: %tmp.48.i = rem uint %tmp.5.i.i161, 4 ; <uint> [#uses=0]
OLD: %tmp.20.i2 = rem int %tmp.5.i.i, 4 ; <int> [#uses=1]
NEW: %tmp.20.i2 = rem uint %tmp.5.i.i, 4 ; <uint> [#uses=0]
it also occurs 9 times in gcc, but with odd constant divisors (1009 and 61)
so the payoff isn't as great.
---
Diffs of the changes: (+19 -1)
InstructionCombining.cpp | 20 +++++++++++++++++++-
1 files changed, 19 insertions(+), 1 deletion(-)
Index: llvm/lib/Transforms/Scalar/InstructionCombining.cpp
diff -u llvm/lib/Transforms/Scalar/InstructionCombining.cpp:1.403
llvm/lib/Transforms/Scalar/InstructionCombining.cpp:1.404
--- llvm/lib/Transforms/Scalar/InstructionCombining.cpp:1.403 Wed Nov 2
12:35:40 2005
+++ llvm/lib/Transforms/Scalar/InstructionCombining.cpp Sat Nov 5 01:28:37 2005
@@ -1246,7 +1246,7 @@
Instruction *InstCombiner::visitRem(BinaryOperator &I) {
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
- if (I.getType()->isSigned())
+ if (I.getType()->isSigned()) {
if (Value *RHSNeg = dyn_castNegVal(Op1))
if (!isa<ConstantSInt>(RHSNeg) ||
cast<ConstantSInt>(RHSNeg)->getValue() > 0) {
@@ -1255,6 +1255,24 @@
I.setOperand(1, RHSNeg);
return &I;
}
+
+ // If the top bits of both operands are zero (i.e. we can prove they are
+ // unsigned inputs), turn this into a urem.
+ 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 *Rem = BinaryOperator::createRem(LHS, RHS, I.getName());
+ InsertNewInstBefore(Rem, I);
+ return new CastInst(Rem, I.getType());
+ }
+ }
if (isa<UndefValue>(Op0)) // undef % X -> 0
return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
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