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Implement shift-and combinations, implementing InstCombine/and.ll:test19-21

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These combinations trigger 4 times in povray, 7x in gcc, 4x in gap, and 2x in bzip2.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@16508 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2004-09-24 15:21:34 +00:00
parent 71dd801055
commit 0c96766c90
1 changed files with 44 additions and 7 deletions
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51
lib/Transforms/Scalar/InstructionCombining.cpp
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@ -146,6 +146,17 @@ namespace {
return New;
}
/// InsertCastBefore - Insert a cast of V to TY before the instruction POS.
/// This also adds the cast to the worklist. Finally, this returns the
/// cast.
Value *InsertCastBefore(Value *V, const Type *Ty, Instruction &Pos) {
if (V->getType() == Ty) return V;
Instruction *C = new CastInst(V, Ty, V->getName(), &Pos);
WorkList.push_back(C);
return C;
}
// ReplaceInstUsesWith - This method is to be used when an instruction is
// found to be dead, replacable with another preexisting expression. Here
// we add all uses of I to the worklist, replace all uses of I with the new
@ -1088,9 +1099,12 @@ Instruction *InstCombiner::OptAndOp(Instruction *Op,
// the anded constant includes them, clear them now!
//
Constant *AllOne = ConstantIntegral::getAllOnesValue(AndRHS->getType());
Constant *CI = ConstantExpr::getAnd(AndRHS,
ConstantExpr::getShl(AllOne, OpRHS));
if (CI != AndRHS) {
Constant *ShlMask = ConstantExpr::getShl(AllOne, OpRHS);
Constant *CI = ConstantExpr::getAnd(AndRHS, ShlMask);
if (CI == ShlMask) { // Masking out bits that the shift already masks
return ReplaceInstUsesWith(TheAnd, Op); // No need for the and.
} else if (CI != AndRHS) { // Reducing bits set in and.
TheAnd.setOperand(1, CI);
return &TheAnd;
}
@ -1103,12 +1117,34 @@ Instruction *InstCombiner::OptAndOp(Instruction *Op,
//
if (AndRHS->getType()->isUnsigned()) {
Constant *AllOne = ConstantIntegral::getAllOnesValue(AndRHS->getType());
Constant *CI = ConstantExpr::getAnd(AndRHS,
ConstantExpr::getShr(AllOne, OpRHS));
if (CI != AndRHS) {
TheAnd.setOperand(1, CI);
Constant *ShrMask = ConstantExpr::getShr(AllOne, OpRHS);
Constant *CI = ConstantExpr::getAnd(AndRHS, ShrMask);
if (CI == ShrMask) { // Masking out bits that the shift already masks.
return ReplaceInstUsesWith(TheAnd, Op);
} else if (CI != AndRHS) {
TheAnd.setOperand(1, CI); // Reduce bits set in and cst.
return &TheAnd;
}
} else { // Signed shr.
// See if this is shifting in some sign extension, then masking it out
// with an and.
if (Op->hasOneUse()) {
Constant *AllOne = ConstantIntegral::getAllOnesValue(AndRHS->getType());
Constant *ShrMask = ConstantExpr::getUShr(AllOne, OpRHS);
Constant *CI = ConstantExpr::getAnd(AndRHS, ShrMask);
if (CI == ShrMask) { // Masking out bits shifted in.
// Make the argument unsigned.
Value *ShVal = Op->getOperand(0);
ShVal = InsertCastBefore(ShVal,
ShVal->getType()->getUnsignedVersion(),
TheAnd);
ShVal = InsertNewInstBefore(new ShiftInst(Instruction::Shr, ShVal,
OpRHS, Op->getName()),
TheAnd);
return new CastInst(ShVal, Op->getType());
}
}
}
break;
}
@ -1509,6 +1545,7 @@ Instruction *InstCombiner::visitSetCondInst(BinaryOperator &I) {
}
}
break;
case Instruction::Div:
if (0 && isa<ConstantInt>(LHSI->getOperand(1))) {
std::cerr << "COULD FOLD: " << *LHSI;