Changes in directory llvm/lib/Transforms/Scalar:
InstructionCombining.cpp updated: 1.445 -> 1.446
---
Log message:
Generalize the REM folding code to handle another case Nick Lewycky
pointed out: realize the AND can provide factors and look through Casts.
---
Diffs of the changes: (+43 -13)
InstructionCombining.cpp | 56 ++++++++++++++++++++++++++++++++++++-----------
1 files changed, 43 insertions(+), 13 deletions(-)
Index: llvm/lib/Transforms/Scalar/InstructionCombining.cpp
diff -u llvm/lib/Transforms/Scalar/InstructionCombining.cpp:1.445
llvm/lib/Transforms/Scalar/InstructionCombining.cpp:1.446
--- llvm/lib/Transforms/Scalar/InstructionCombining.cpp:1.445 Tue Feb 28
13:47:20 2006
+++ llvm/lib/Transforms/Scalar/InstructionCombining.cpp Thu Mar 2 00:50:58 2006
@@ -1812,6 +1812,45 @@
}
+/// GetFactor - If we can prove that the specified value is at least a multiple
+/// of some factor, return that factor.
+static Constant *GetFactor(Value *V) {
+ if (ConstantInt *CI = dyn_cast<ConstantInt>(V))
+ return CI;
+
+ // Unless we can be tricky, we know this is a multiple of 1.
+ Constant *Result = ConstantInt::get(V->getType(), 1);
+
+ Instruction *I = dyn_cast<Instruction>(V);
+ if (!I) return Result;
+
+ if (I->getOpcode() == Instruction::Mul) {
+ // Handle multiplies by a constant, etc.
+ return ConstantExpr::getMul(GetFactor(I->getOperand(0)),
+ GetFactor(I->getOperand(1)));
+ } else if (I->getOpcode() == Instruction::Shl) {
+ // (X<<C) -> X * (1 << C)
+ if (Constant *ShRHS = dyn_cast<Constant>(I->getOperand(1))) {
+ ShRHS = ConstantExpr::getShl(Result, ShRHS);
+ return ConstantExpr::getMul(GetFactor(I->getOperand(0)), ShRHS);
+ }
+ } else if (I->getOpcode() == Instruction::And) {
+ if (ConstantInt *RHS = dyn_cast<ConstantInt>(I->getOperand(1))) {
+ // X & 0xFFF0 is known to be a multiple of 16.
+ unsigned Zeros = CountTrailingZeros_64(RHS->getZExtValue());
+ if (Zeros != V->getType()->getPrimitiveSizeInBits())
+ return ConstantExpr::getShl(Result,
+ ConstantUInt::get(Type::UByteTy, Zeros));
+ }
+ } else if (I->getOpcode() == Instruction::Cast) {
+ Value *Op = I->getOperand(0);
+ // Only handle int->int casts.
+ if (!Op->getType()->isInteger()) return Result;
+ return ConstantExpr::getCast(GetFactor(Op), V->getType());
+ }
+ return Result;
+}
+
Instruction *InstCombiner::visitRem(BinaryOperator &I) {
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
@@ -1874,20 +1913,11 @@
} else if (isa<PHINode>(Op0I)) {
if (Instruction *NV = FoldOpIntoPhi(I))
return NV;
- } else if (Op0I->getOpcode() == Instruction::Mul) {
- // X*C1%C2 --> 0 iff C1%C2 == 0
- if (ConstantInt *MulRHS = dyn_cast<ConstantInt>(Op0I->getOperand(1))) {
- if (ConstantExpr::getRem(MulRHS, RHS)->isNullValue())
- return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
- }
- } else if (Op0I->getOpcode() == Instruction::Shl) {
- // (X<<C1)%C2 --> 0 iff (1<<C1)%C2 == 0
- if (Constant *ShRHS = dyn_cast<Constant>(Op0I->getOperand(1))) {
- ShRHS = ConstantExpr::getShl(ConstantInt::get(I.getType(), 1),
ShRHS);
- if (ConstantExpr::getRem(ShRHS, RHS)->isNullValue())
- return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
- }
}
+
+ // X*C1%C2 --> 0 iff C1%C2 == 0
+ if (ConstantExpr::getRem(GetFactor(Op0I), RHS)->isNullValue())
+ return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
}
}
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