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Add a SCEV class and supporting code for sign-extend expressions. 

This created an ambiguity for expandInTy to decide when to use
sign-extension or zero-extension, but it turns out that most of its callers
don't actually need a type conversion, now that LLVM types don't have
explicit signedness. Drop expandInTy in favor of plain expand, and change
the few places that actually need a type conversion to do it themselves.

llvm-svn: 37591
This commit is contained in:
Dan Gohman 2007-06-15 14:38:12 +00:00
parent 92fb5453c3
commit cb9e09ad57
6 changed files with 139 additions and 58 deletions
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43
llvm/include/llvm/Analysis/ScalarEvolutionExpander.h
View File

@ -78,13 +78,10 @@ namespace llvm {
/// expandCodeFor - Insert code to directly compute the specified SCEV
/// expression into the program. The inserted code is inserted into the
/// specified block.
///
/// If a particular value sign is required, a type may be specified for the
/// result.
Value *expandCodeFor(SCEVHandle SH, Instruction *IP, const Type *Ty = 0) {
Value *expandCodeFor(SCEVHandle SH, Instruction *IP) {
// Expand the code for this SCEV.
this->InsertPt = IP;
return expandInTy(SH, Ty);
return expand(SH);
}
/// InsertCastOfTo - Insert a cast of V to the specified type, doing what
@ -107,25 +104,6 @@ namespace llvm {
return V;
}
Value *expandInTy(SCEV *S, const Type *Ty) {
Value *V = expand(S);
if (Ty && V->getType() != Ty) {
if (isa<PointerType>(Ty) && V->getType()->isInteger())
return InsertCastOfTo(Instruction::IntToPtr, V, Ty);
else if (Ty->isInteger() && isa<PointerType>(V->getType()))
return InsertCastOfTo(Instruction::PtrToInt, V, Ty);
else if (Ty->getPrimitiveSizeInBits() ==
V->getType()->getPrimitiveSizeInBits())
return InsertCastOfTo(Instruction::BitCast, V, Ty);
else if (Ty->getPrimitiveSizeInBits() >
V->getType()->getPrimitiveSizeInBits())
return InsertCastOfTo(Instruction::ZExt, V, Ty);
else
return InsertCastOfTo(Instruction::Trunc, V, Ty);
}
return V;
}
Value *visitConstant(SCEVConstant *S) {
return S->getValue();
}
@ -136,17 +114,21 @@ namespace llvm {
}
Value *visitZeroExtendExpr(SCEVZeroExtendExpr *S) {
Value *V = expandInTy(S->getOperand(), S->getType());
Value *V = expand(S->getOperand());
return CastInst::createZExtOrBitCast(V, S->getType(), "tmp.", InsertPt);
}
Value *visitSignExtendExpr(SCEVSignExtendExpr *S) {
Value *V = expand(S->getOperand());
return CastInst::createSExtOrBitCast(V, S->getType(), "tmp.", InsertPt);
}
Value *visitAddExpr(SCEVAddExpr *S) {
const Type *Ty = S->getType();
Value *V = expandInTy(S->getOperand(S->getNumOperands()-1), Ty);
Value *V = expand(S->getOperand(S->getNumOperands()-1));
// Emit a bunch of add instructions
for (int i = S->getNumOperands()-2; i >= 0; --i)
V = InsertBinop(Instruction::Add, V, expandInTy(S->getOperand(i), Ty),
V = InsertBinop(Instruction::Add, V, expand(S->getOperand(i)),
InsertPt);
return V;
}
@ -154,9 +136,8 @@ namespace llvm {
Value *visitMulExpr(SCEVMulExpr *S);
Value *visitSDivExpr(SCEVSDivExpr *S) {
const Type *Ty = S->getType();
Value *LHS = expandInTy(S->getLHS(), Ty);
Value *RHS = expandInTy(S->getRHS(), Ty);
Value *LHS = expand(S->getLHS());
Value *RHS = expand(S->getRHS());
return InsertBinop(Instruction::SDiv, LHS, RHS, InsertPt);
}

53
llvm/include/llvm/Analysis/ScalarEvolutionExpressions.h
View File

@ -24,8 +24,8 @@ namespace llvm {
enum SCEVTypes {
// These should be ordered in terms of increasing complexity to make the
// folders simpler.
scConstant, scTruncate, scZeroExtend, scAddExpr, scMulExpr, scSDivExpr,
scAddRecExpr, scUnknown, scCouldNotCompute
scConstant, scTruncate, scZeroExtend, scSignExtend, scAddExpr, scMulExpr,
scSDivExpr, scAddRecExpr, scUnknown, scCouldNotCompute
};
//===--------------------------------------------------------------------===//
@ -166,6 +166,53 @@ namespace llvm {
}
};
//===--------------------------------------------------------------------===//
/// SCEVSignExtendExpr - This class represents a sign extension of a small
/// integer value to a larger integer value.
///
class SCEVSignExtendExpr : public SCEV {
SCEVHandle Op;
const Type *Ty;
SCEVSignExtendExpr(const SCEVHandle &op, const Type *ty);
virtual ~SCEVSignExtendExpr();
public:
/// get method - This just gets and returns a new SCEVSignExtend object
///
static SCEVHandle get(const SCEVHandle &Op, const Type *Ty);
const SCEVHandle &getOperand() const { return Op; }
virtual const Type *getType() const { return Ty; }
virtual bool isLoopInvariant(const Loop *L) const {
return Op->isLoopInvariant(L);
}
virtual bool hasComputableLoopEvolution(const Loop *L) const {
return Op->hasComputableLoopEvolution(L);
}
/// getValueRange - Return the tightest constant bounds that this value is
/// known to have. This method is only valid on integer SCEV objects.
virtual ConstantRange getValueRange() const;
SCEVHandle replaceSymbolicValuesWithConcrete(const SCEVHandle &Sym,
const SCEVHandle &Conc) const {
SCEVHandle H = Op->replaceSymbolicValuesWithConcrete(Sym, Conc);
if (H == Op)
return this;
return get(H, Ty);
}
virtual void print(std::ostream &OS) const;
void print(std::ostream *OS) const { if (OS) print(*OS); }
/// Methods for support type inquiry through isa, cast, and dyn_cast:
static inline bool classof(const SCEVSignExtendExpr *S) { return true; }
static inline bool classof(const SCEV *S) {
return S->getSCEVType() == scSignExtend;
}
};
//===--------------------------------------------------------------------===//
/// SCEVCommutativeExpr - This node is the base class for n'ary commutative
@ -503,6 +550,8 @@ namespace llvm {
return ((SC*)this)->visitTruncateExpr((SCEVTruncateExpr*)S);
case scZeroExtend:
return ((SC*)this)->visitZeroExtendExpr((SCEVZeroExtendExpr*)S);
case scSignExtend:
return ((SC*)this)->visitSignExtendExpr((SCEVSignExtendExpr*)S);
case scAddExpr:
return ((SC*)this)->visitAddExpr((SCEVAddExpr*)S);
case scMulExpr:

47
llvm/lib/Analysis/ScalarEvolution.cpp
View File

@ -245,6 +245,32 @@ void SCEVZeroExtendExpr::print(std::ostream &OS) const {
OS << "(zeroextend " << *Op << " to " << *Ty << ")";
}
// SCEVSignExtends - Only allow the creation of one SCEVSignExtendExpr for any
// particular input. Don't use a SCEVHandle here, or else the object will never
// be deleted!
static ManagedStatic<std::map<std::pair<SCEV*, const Type*>,
SCEVSignExtendExpr*> > SCEVSignExtends;
SCEVSignExtendExpr::SCEVSignExtendExpr(const SCEVHandle &op, const Type *ty)
: SCEV(scSignExtend), Op(op), Ty(ty) {
assert(Op->getType()->isInteger() && Ty->isInteger() &&
"Cannot sign extend non-integer value!");
assert(Op->getType()->getPrimitiveSizeInBits() < Ty->getPrimitiveSizeInBits()
&& "This is not an extending conversion!");
}
SCEVSignExtendExpr::~SCEVSignExtendExpr() {
SCEVSignExtends->erase(std::make_pair(Op, Ty));
}
ConstantRange SCEVSignExtendExpr::getValueRange() const {
return getOperand()->getValueRange().signExtend(getBitWidth());
}
void SCEVSignExtendExpr::print(std::ostream &OS) const {
OS << "(signextend " << *Op << " to " << *Ty << ")";
}
// SCEVCommExprs - Only allow the creation of one SCEVCommutativeExpr for any
// particular input. Don't use a SCEVHandle here, or else the object will never
// be deleted!
@ -588,6 +614,21 @@ SCEVHandle SCEVZeroExtendExpr::get(const SCEVHandle &Op, const Type *Ty) {
return Result;
}
SCEVHandle SCEVSignExtendExpr::get(const SCEVHandle &Op, const Type *Ty) {
if (SCEVConstant *SC = dyn_cast<SCEVConstant>(Op))
return SCEVUnknown::get(
ConstantExpr::getSExt(SC->getValue(), Ty));
// FIXME: If the input value is a chrec scev, and we can prove that the value
// did not overflow the old, smaller, value, we can sign extend all of the
// operands (often constants). This would allow analysis of something like
// this: for (signed char X = 0; X < 100; ++X) { int Y = X; }
SCEVSignExtendExpr *&Result = (*SCEVSignExtends)[std::make_pair(Op, Ty)];
if (Result == 0) Result = new SCEVSignExtendExpr(Op, Ty);
return Result;
}
// get - Get a canonical add expression, or something simpler if possible.
SCEVHandle SCEVAddExpr::get(std::vector<SCEVHandle> &Ops) {
assert(!Ops.empty() && "Cannot get empty add!");
@ -1370,6 +1411,9 @@ static APInt GetConstantFactor(SCEVHandle S) {
if (SCEVZeroExtendExpr *E = dyn_cast<SCEVZeroExtendExpr>(S))
return GetConstantFactor(E->getOperand()).zext(
cast<IntegerType>(E->getType())->getBitWidth());
if (SCEVSignExtendExpr *E = dyn_cast<SCEVSignExtendExpr>(S))
return GetConstantFactor(E->getOperand()).sext(
cast<IntegerType>(E->getType())->getBitWidth());
if (SCEVAddExpr *A = dyn_cast<SCEVAddExpr>(S)) {
// The result is the min of all operands.
@ -1470,6 +1514,9 @@ SCEVHandle ScalarEvolutionsImpl::createSCEV(Value *V) {
case Instruction::ZExt:
return SCEVZeroExtendExpr::get(getSCEV(I->getOperand(0)), I->getType());
case Instruction::SExt:
return SCEVSignExtendExpr::get(getSCEV(I->getOperand(0)), I->getType());
case Instruction::BitCast:
// BitCasts are no-op casts so we just eliminate the cast.
if (I->getType()->isInteger() &&

13
llvm/lib/Analysis/ScalarEvolutionExpander.cpp
View File

@ -93,18 +93,17 @@ Value *SCEVExpander::InsertBinop(Instruction::BinaryOps Opcode, Value *LHS,
}
Value *SCEVExpander::visitMulExpr(SCEVMulExpr *S) {
const Type *Ty = S->getType();
int FirstOp = 0; // Set if we should emit a subtract.
if (SCEVConstant *SC = dyn_cast<SCEVConstant>(S->getOperand(0)))
if (SC->getValue()->isAllOnesValue())
FirstOp = 1;
int i = S->getNumOperands()-2;
Value *V = expandInTy(S->getOperand(i+1), Ty);
Value *V = expand(S->getOperand(i+1));
// Emit a bunch of multiply instructions
for (; i >= FirstOp; --i)
V = InsertBinop(Instruction::Mul, V, expandInTy(S->getOperand(i), Ty),
V = InsertBinop(Instruction::Mul, V, expand(S->getOperand(i)),
InsertPt);
// -1 * ... ---> 0 - ...
if (FirstOp == 1)
@ -122,10 +121,10 @@ Value *SCEVExpander::visitAddRecExpr(SCEVAddRecExpr *S) {
// {X,+,F} --> X + {0,+,F}
if (!isa<SCEVConstant>(S->getStart()) ||
!cast<SCEVConstant>(S->getStart())->getValue()->isZero()) {
Value *Start = expandInTy(S->getStart(), Ty);
Value *Start = expand(S->getStart());
std::vector<SCEVHandle> NewOps(S->op_begin(), S->op_end());
NewOps[0] = SCEVUnknown::getIntegerSCEV(0, Ty);
Value *Rest = expandInTy(SCEVAddRecExpr::get(NewOps, L), Ty);
Value *Rest = expand(SCEVAddRecExpr::get(NewOps, L));
// FIXME: look for an existing add to use.
return InsertBinop(Instruction::Add, Rest, Start, InsertPt);
@ -164,7 +163,7 @@ Value *SCEVExpander::visitAddRecExpr(SCEVAddRecExpr *S) {
// If this is a simple linear addrec, emit it now as a special case.
if (S->getNumOperands() == 2) { // {0,+,F} --> i*F
Value *F = expandInTy(S->getOperand(1), Ty);
Value *F = expand(S->getOperand(1));
// IF the step is by one, just return the inserted IV.
if (ConstantInt *CI = dyn_cast<ConstantInt>(F))
@ -201,5 +200,5 @@ Value *SCEVExpander::visitAddRecExpr(SCEVAddRecExpr *S) {
SCEVHandle V = S->evaluateAtIteration(IH);
//cerr << "Evaluated: " << *this << "\n to: " << *V << "\n";
return expandInTy(V, Ty);
return expand(V);
}

13
llvm/lib/Transforms/Scalar/IndVarSimplify.cpp
View File

@ -277,8 +277,7 @@ Instruction *IndVarSimplify::LinearFunctionTestReplace(Loop *L,
// Expand the code for the iteration count into the preheader of the loop.
BasicBlock *Preheader = L->getLoopPreheader();
Value *ExitCnt = RW.expandCodeFor(TripCount, Preheader->getTerminator(),
IndVar->getType());
Value *ExitCnt = RW.expandCodeFor(TripCount, Preheader->getTerminator());
// Insert a new icmp_ne or icmp_eq instruction before the branch.
ICmpInst::Predicate Opcode;
@ -383,7 +382,7 @@ void IndVarSimplify::RewriteLoopExitValues(Loop *L) {
// just reuse it.
Value *&ExitVal = ExitValues[Inst];
if (!ExitVal)
ExitVal = Rewriter.expandCodeFor(ExitValue, InsertPt,Inst->getType());
ExitVal = Rewriter.expandCodeFor(ExitValue, InsertPt);
DOUT << "INDVARS: RLEV: AfterLoopVal = " << *ExitVal
<< " LoopVal = " << *Inst << "\n";
@ -519,9 +518,12 @@ bool IndVarSimplify::runOnLoop(Loop *L, LPPassManager &LPM) {
Changed = true;
DOUT << "INDVARS: New CanIV: " << *IndVar;
if (!isa<SCEVCouldNotCompute>(IterationCount))
if (!isa<SCEVCouldNotCompute>(IterationCount)) {
if (IterationCount->getType() != LargestType)
IterationCount = SCEVZeroExtendExpr::get(IterationCount, LargestType);
if (Instruction *DI = LinearFunctionTestReplace(L, IterationCount,Rewriter))
DeadInsts.insert(DI);
}
// Now that we have a canonical induction variable, we can rewrite any
// recurrences in terms of the induction variable. Start with the auxillary
@ -555,8 +557,7 @@ bool IndVarSimplify::runOnLoop(Loop *L, LPPassManager &LPM) {
std::map<unsigned, Value*> InsertedSizes;
while (!IndVars.empty()) {
PHINode *PN = IndVars.back().first;
Value *NewVal = Rewriter.expandCodeFor(IndVars.back().second, InsertPt,
PN->getType());
Value *NewVal = Rewriter.expandCodeFor(IndVars.back().second, InsertPt);
DOUT << "INDVARS: Rewrote IV '" << *IndVars.back().second << "' " << *PN
<< " into = " << *NewVal << "\n";
NewVal->takeName(PN);

28
llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp
View File

@ -555,8 +555,7 @@ Value *BasedUser::InsertCodeForBaseAtPosition(const SCEVHandle &NewBase,
// If there is no immediate value, skip the next part.
if (SCEVConstant *SC = dyn_cast<SCEVConstant>(Imm))
if (SC->getValue()->isZero())
return Rewriter.expandCodeFor(NewBase, BaseInsertPt,
OperandValToReplace->getType());
return Rewriter.expandCodeFor(NewBase, BaseInsertPt);
Value *Base = Rewriter.expandCodeFor(NewBase, BaseInsertPt);
@ -567,8 +566,7 @@ Value *BasedUser::InsertCodeForBaseAtPosition(const SCEVHandle &NewBase,
// Always emit the immediate (if non-zero) into the same block as the user.
SCEVHandle NewValSCEV = SCEVAddExpr::get(SCEVUnknown::get(Base), Imm);
return Rewriter.expandCodeFor(NewValSCEV, IP,
OperandValToReplace->getType());
return Rewriter.expandCodeFor(NewValSCEV, IP);
}
@ -598,6 +596,11 @@ void BasedUser::RewriteInstructionToUseNewBase(const SCEVHandle &NewBase,
}
}
Value *NewVal = InsertCodeForBaseAtPosition(NewBase, Rewriter, InsertPt, L);
// Adjust the type back to match the Inst.
if (isa<PointerType>(OperandValToReplace->getType())) {
NewVal = new IntToPtrInst(NewVal, OperandValToReplace->getType(), "cast",
InsertPt);
}
// Replace the use of the operand Value with the new Phi we just created.
Inst->replaceUsesOfWith(OperandValToReplace, NewVal);
DOUT << " CHANGED: IMM =" << *Imm;
@ -644,6 +647,11 @@ void BasedUser::RewriteInstructionToUseNewBase(const SCEVHandle &NewBase,
// Insert the code into the end of the predecessor block.
Instruction *InsertPt = PN->getIncomingBlock(i)->getTerminator();
Code = InsertCodeForBaseAtPosition(NewBase, Rewriter, InsertPt, L);
// Adjust the type back to match the PHI.
if (isa<PointerType>(PN->getType())) {
Code = new IntToPtrInst(Code, PN->getType(), "cast", InsertPt);
}
}
// Replace the use of the operand Value with the new Phi we just created.
@ -1112,8 +1120,7 @@ void LoopStrengthReduce::StrengthReduceStridedIVUsers(const SCEVHandle &Stride,
// Emit the initial base value into the loop preheader.
Value *CommonBaseV
= PreheaderRewriter.expandCodeFor(CommonExprs, PreInsertPt,
ReplacedTy);
= PreheaderRewriter.expandCodeFor(CommonExprs, PreInsertPt);
if (RewriteFactor == 0) {
// Create a new Phi for this base, and stick it in the loop header.
@ -1131,8 +1138,7 @@ void LoopStrengthReduce::StrengthReduceStridedIVUsers(const SCEVHandle &Stride,
IncAmount = SCEV::getNegativeSCEV(Stride);
// Insert the stride into the preheader.
Value *StrideV = PreheaderRewriter.expandCodeFor(IncAmount, PreInsertPt,
ReplacedTy);
Value *StrideV = PreheaderRewriter.expandCodeFor(IncAmount, PreInsertPt);
if (!isa<ConstantInt>(StrideV)) ++NumVariable;
// Emit the increment of the base value before the terminator of the loop
@ -1142,8 +1148,7 @@ void LoopStrengthReduce::StrengthReduceStridedIVUsers(const SCEVHandle &Stride,
IncExp = SCEV::getNegativeSCEV(IncExp);
IncExp = SCEVAddExpr::get(SCEVUnknown::get(NewPHI), IncExp);
IncV = Rewriter.expandCodeFor(IncExp, LatchBlock->getTerminator(),
ReplacedTy);
IncV = Rewriter.expandCodeFor(IncExp, LatchBlock->getTerminator());
IncV->setName(NewPHI->getName()+".inc");
NewPHI->addIncoming(IncV, LatchBlock);
@ -1199,8 +1204,7 @@ void LoopStrengthReduce::StrengthReduceStridedIVUsers(const SCEVHandle &Stride,
SCEVHandle Base = UsersToProcess.back().Base;
// Emit the code for Base into the preheader.
Value *BaseV = PreheaderRewriter.expandCodeFor(Base, PreInsertPt,
ReplacedTy);
Value *BaseV = PreheaderRewriter.expandCodeFor(Base, PreInsertPt);
DOUT << " INSERTING code for BASE = " << *Base << ":";
if (BaseV->hasName())