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add an instcombine xform. This speeds up 462.libquantum from 9.78s to

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7.48s.  This regression is due to unforseen consequences of the cast patch.

llvm-svn: 32209
This commit is contained in:
Chris Lattner 2006-12-05 01:26:29 +00:00
parent ae17721f63
commit e0738f8f8b
1 changed files with 17 additions and 0 deletions
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17
lib/Transforms/Scalar/InstructionCombining.cpp
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@ -6023,6 +6023,23 @@ Instruction *InstCombiner::visitTrunc(CastInst &CI) {
Value *V = InsertCastBefore(SrcI->getOperand(0), Ty, CI);
return new ShiftInst(Instruction::LShr, V, SrcI->getOperand(1));
}
} else { // This is a variable shr.
// Turn 'trunc (lshr X, Y) to bool' into '(X & (1 << Y)) != 0'. This is
// more LLVM instructions, but allows '1 << Y' to be hoisted if
// loop-invariant and CSE'd.
if (CI.getType() == Type::BoolTy && SrcI->hasOneUse()) {
Value *One = ConstantInt::get(SrcI->getType(), 1);
Value *V = InsertNewInstBefore(new ShiftInst(Instruction::Shl, One,
SrcI->getOperand(1),
"tmp"), CI);
V = InsertNewInstBefore(BinaryOperator::createAnd(V,
SrcI->getOperand(0),
"tmp"), CI);
Value *Zero = Constant::getNullValue(V->getType());
return BinaryOperator::createSetNE(V, Zero);
}
}
break;
}