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Refactor some code. In the mul - setcc folding case, we really care about 

whether this is the sign bit or not, so check unsigned comparisons as well.

llvm-svn: 11740
This commit is contained in:
Chris Lattner 2004-02-23 06:38:22 +00:00
parent 6ddaa24dd9
commit e79e854c5c
1 changed files with 63 additions and 32 deletions
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95
llvm/lib/Transforms/Scalar/InstructionCombining.cpp
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@ -116,12 +116,13 @@ namespace {
// InsertNewInstBefore - insert an instruction New before instruction Old
// in the program. Add the new instruction to the worklist.
//
void InsertNewInstBefore(Instruction *New, Instruction &Old) {
Value *InsertNewInstBefore(Instruction *New, Instruction &Old) {
assert(New && New->getParent() == 0 &&
"New instruction already inserted into a basic block!");
BasicBlock *BB = Old.getParent();
BB->getInstList().insert(&Old, New); // Insert inst
WorkList.push_back(New); // Add to worklist
return New;
}
public:
@ -173,6 +174,31 @@ static bool isOnlyUse(Value *V) {
return V->hasOneUse() || isa<Constant>(V);
}
// getSignedIntegralType - Given an unsigned integral type, return the signed
// version of it that has the same size.
static const Type *getSignedIntegralType(const Type *Ty) {
switch (Ty->getPrimitiveID()) {
default: assert(0 && "Invalid unsigned integer type!"); abort();
case Type::UByteTyID: return Type::SByteTy;
case Type::UShortTyID: return Type::ShortTy;
case Type::UIntTyID: return Type::IntTy;
case Type::ULongTyID: return Type::LongTy;
}
}
// getPromotedType - Return the specified type promoted as it would be to pass
// though a va_arg area...
static const Type *getPromotedType(const Type *Ty) {
switch (Ty->getPrimitiveID()) {
case Type::SByteTyID:
case Type::ShortTyID: return Type::IntTy;
case Type::UByteTyID:
case Type::UShortTyID: return Type::UIntTy;
case Type::FloatTyID: return Type::DoubleTy;
default: return Ty;
}
}
// SimplifyCommutative - This performs a few simplifications for commutative
// operators:
//
@ -557,6 +583,26 @@ Instruction *InstCombiner::visitSub(BinaryOperator &I) {
return 0;
}
/// isSignBitCheck - Given an exploded setcc instruction, return true if it is
/// really just returns true if the most significant (sign) bit is set.
static bool isSignBitCheck(unsigned Opcode, Value *LHS, ConstantInt *RHS) {
if (RHS->getType()->isSigned()) {
// True if source is LHS < 0 or LHS <= -1
return Opcode == Instruction::SetLT && RHS->isNullValue() ||
Opcode == Instruction::SetLE && RHS->isAllOnesValue();
} else {
ConstantUInt *RHSC = cast<ConstantUInt>(RHS);
// True if source is LHS > 127 or LHS >= 128, where the constants depend on
// the size of the integer type.
if (Opcode == Instruction::SetGE)
return RHSC->getValue() == 1ULL<<(RHS->getType()->getPrimitiveSize()*8-1);
if (Opcode == Instruction::SetGT)
return RHSC->getValue() ==
(1ULL << (RHS->getType()->getPrimitiveSize()*8-1))-1;
}
return false;
}
Instruction *InstCombiner::visitMul(BinaryOperator &I) {
bool Changed = SimplifyCommutative(I);
Value *Op0 = I.getOperand(0);
@ -616,23 +662,28 @@ Instruction *InstCombiner::visitMul(BinaryOperator &I) {
Value *SCIOp0 = SCI->getOperand(0), *SCIOp1 = SCI->getOperand(1);
const Type *SCOpTy = SCIOp0->getType();
// If the source is X < 0 or X <= -1, and X is a signed integer type,
// convert this multiply into a shift/and combination.
if (SCOpTy->isSigned() && isa<ConstantInt>(SCIOp1) &&
((SCI->getOpcode() == Instruction::SetLT &&
cast<Constant>(SCIOp1)->isNullValue()) ||
(SCI->getOpcode() == Instruction::SetLE &&
cast<ConstantInt>(SCIOp1)->isAllOnesValue()))) {
// If the setcc is true iff the sign bit of X is set, then convert this
// multiply into a shift/and combination.
if (isa<ConstantInt>(SCIOp1) &&
isSignBitCheck(SCI->getOpcode(), SCIOp0, cast<ConstantInt>(SCIOp1))) {
// Shift the X value right to turn it into "all signbits".
Constant *Amt = ConstantUInt::get(Type::UByteTy,
SCOpTy->getPrimitiveSize()*8-1);
Value *V = new ShiftInst(Instruction::Shr, SCIOp0, Amt,
BoolCast->getName()+".mask", &I);
if (SCIOp0->getType()->isUnsigned()) {
const Type *NewTy = getSignedIntegralType(SCIOp0->getType());
SCIOp0 = InsertNewInstBefore(new CastInst(SCIOp0, NewTy,
SCIOp0->getName()), I);
}
Value *V =
InsertNewInstBefore(new ShiftInst(Instruction::Shr, SCIOp0, Amt,
BoolCast->getOperand(0)->getName()+
".mask"), I);
// If the multiply type is not the same as the source type, sign extend
// or truncate to the multiply type.
if (I.getType() != V->getType())
V = new CastInst(V, I.getType(), V->getName(), &I);
V = InsertNewInstBefore(new CastInst(V, I.getType(), V->getName()),I);
Value *OtherOp = Op0 == BoolCast ? I.getOperand(1) : Op0;
return BinaryOperator::create(Instruction::And, V, OtherOp);
@ -1314,14 +1365,7 @@ Instruction *InstCombiner::visitSetCondInst(BinaryOperator &I) {
Value *X = BO->getOperand(0);
// If 'X' is not signed, insert a cast now...
if (!BOC->getType()->isSigned()) {
const Type *DestTy;
switch (BOC->getType()->getPrimitiveID()) {
case Type::UByteTyID: DestTy = Type::SByteTy; break;
case Type::UShortTyID: DestTy = Type::ShortTy; break;
case Type::UIntTyID: DestTy = Type::IntTy; break;
case Type::ULongTyID: DestTy = Type::LongTy; break;
default: assert(0 && "Invalid unsigned integer type!"); abort();
}
const Type *DestTy = getSignedIntegralType(BOC->getType());
CastInst *NewCI = new CastInst(X,DestTy,X->getName()+".signed");
InsertNewInstBefore(NewCI, I);
X = NewCI;
@ -1829,19 +1873,6 @@ Instruction *InstCombiner::visitInvokeInst(InvokeInst &II) {
return visitCallSite(&II);
}
// getPromotedType - Return the specified type promoted as it would be to pass
// though a va_arg area...
static const Type *getPromotedType(const Type *Ty) {
switch (Ty->getPrimitiveID()) {
case Type::SByteTyID:
case Type::ShortTyID: return Type::IntTy;
case Type::UByteTyID:
case Type::UShortTyID: return Type::UIntTy;
case Type::FloatTyID: return Type::DoubleTy;
default: return Ty;
}
}
// visitCallSite - Improvements for call and invoke instructions.
//
Instruction *InstCombiner::visitCallSite(CallSite CS) {