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Add a new SCEV representing signed division. 

llvm-svn: 60407
This commit is contained in:
Nick Lewycky 2008-12-02 08:05:48 +00:00
parent 6e1c6ad127
commit 4d9966dd2d
5 changed files with 131 additions and 11 deletions
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1
llvm/include/llvm/Analysis/ScalarEvolution.h
View File

@ -225,6 +225,7 @@ namespace llvm {
return getMulExpr(Ops);
}
SCEVHandle getUDivExpr(const SCEVHandle &LHS, const SCEVHandle &RHS);
SCEVHandle getSDivExpr(const SCEVHandle &LHS, const SCEVHandle &RHS);
SCEVHandle getAddRecExpr(const SCEVHandle &Start, const SCEVHandle &Step,
const Loop *L);
SCEVHandle getAddRecExpr(std::vector<SCEVHandle> &Operands,

2
llvm/include/llvm/Analysis/ScalarEvolutionExpander.h
View File

@ -104,6 +104,8 @@ namespace llvm {
Value *visitUDivExpr(SCEVUDivExpr *S);
Value *visitSDivExpr(SCEVSDivExpr *S);
Value *visitAddRecExpr(SCEVAddRecExpr *S);
Value *visitSMaxExpr(SCEVSMaxExpr *S);

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

@ -25,7 +25,7 @@ namespace llvm {
// These should be ordered in terms of increasing complexity to make the
// folders simpler.
scConstant, scTruncate, scZeroExtend, scSignExtend, scAddExpr, scMulExpr,
scUDivExpr, scAddRecExpr, scUMaxExpr, scSMaxExpr, scUnknown,
scUDivExpr, scSDivExpr, scAddRecExpr, scUMaxExpr, scSMaxExpr, scUnknown,
scCouldNotCompute
};
@ -357,6 +357,55 @@ namespace llvm {
};
//===--------------------------------------------------------------------===//
/// SCEVSDivExpr - This class represents a binary signed division operation.
///
class SCEVSDivExpr : public SCEV {
friend class ScalarEvolution;
SCEVHandle LHS, RHS;
SCEVSDivExpr(const SCEVHandle &lhs, const SCEVHandle &rhs)
: SCEV(scSDivExpr), LHS(lhs), RHS(rhs) {}
virtual ~SCEVSDivExpr();
public:
const SCEVHandle &getLHS() const { return LHS; }
const SCEVHandle &getRHS() const { return RHS; }
virtual bool isLoopInvariant(const Loop *L) const {
return LHS->isLoopInvariant(L) && RHS->isLoopInvariant(L);
}
virtual bool hasComputableLoopEvolution(const Loop *L) const {
return LHS->hasComputableLoopEvolution(L) &&
RHS->hasComputableLoopEvolution(L);
}
SCEVHandle replaceSymbolicValuesWithConcrete(const SCEVHandle &Sym,
const SCEVHandle &Conc,
ScalarEvolution &SE) const {
SCEVHandle L = LHS->replaceSymbolicValuesWithConcrete(Sym, Conc, SE);
SCEVHandle R = RHS->replaceSymbolicValuesWithConcrete(Sym, Conc, SE);
if (L == LHS && R == RHS)
return this;
else
return SE.getSDivExpr(L, R);
}
virtual const Type *getType() const;
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 SCEVSDivExpr *S) { return true; }
static inline bool classof(const SCEV *S) {
return S->getSCEVType() == scSDivExpr;
}
};
//===--------------------------------------------------------------------===//
/// SCEVAddRecExpr - This node represents a polynomial recurrence on the trip
/// count of the specified loop.
@ -550,6 +599,8 @@ namespace llvm {
return ((SC*)this)->visitMulExpr((SCEVMulExpr*)S);
case scUDivExpr:
return ((SC*)this)->visitUDivExpr((SCEVUDivExpr*)S);
case scSDivExpr:
return ((SC*)this)->visitSDivExpr((SCEVSDivExpr*)S);
case scAddRecExpr:
return ((SC*)this)->visitAddRecExpr((SCEVAddRecExpr*)S);
case scSMaxExpr:

77
llvm/lib/Analysis/ScalarEvolution.cpp
View File

@ -324,6 +324,26 @@ const Type *SCEVUDivExpr::getType() const {
return LHS->getType();
}
// SCEVSDivs - Only allow the creation of one SCEVSDivExpr 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*, SCEV*>,
SCEVSDivExpr*> > SCEVSDivs;
SCEVSDivExpr::~SCEVSDivExpr() {
SCEVSDivs->erase(std::make_pair(LHS, RHS));
}
void SCEVSDivExpr::print(std::ostream &OS) const {
OS << "(" << *LHS << " /s " << *RHS << ")";
}
const Type *SCEVSDivExpr::getType() const {
return LHS->getType();
}
// SCEVAddRecExprs - Only allow the creation of one SCEVAddRecExpr for any
// particular input. Don't use a SCEVHandle here, or else the object will never
// be deleted!
@ -1109,9 +1129,12 @@ SCEVHandle ScalarEvolution::getMulExpr(std::vector<SCEVHandle> &Ops) {
}
SCEVHandle ScalarEvolution::getUDivExpr(const SCEVHandle &LHS, const SCEVHandle &RHS) {
if (LHS == RHS)
return getIntegerSCEV(1, LHS->getType()); // X udiv X --> 1
if (SCEVConstant *RHSC = dyn_cast<SCEVConstant>(RHS)) {
if (RHSC->getValue()->equalsInt(1))
return LHS; // X udiv 1 --> x
return LHS; // X udiv 1 --> X
if (SCEVConstant *LHSC = dyn_cast<SCEVConstant>(LHS)) {
Constant *LHSCV = LHSC->getValue();
@ -1120,13 +1143,34 @@ SCEVHandle ScalarEvolution::getUDivExpr(const SCEVHandle &LHS, const SCEVHandle
}
}
// FIXME: implement folding of (X*4)/4 when we know X*4 doesn't overflow.
SCEVUDivExpr *&Result = (*SCEVUDivs)[std::make_pair(LHS, RHS)];
if (Result == 0) Result = new SCEVUDivExpr(LHS, RHS);
return Result;
}
SCEVHandle ScalarEvolution::getSDivExpr(const SCEVHandle &LHS, const SCEVHandle &RHS) {
if (LHS == RHS)
return getIntegerSCEV(1, LHS->getType()); // X sdiv X --> 1
if (SCEVConstant *RHSC = dyn_cast<SCEVConstant>(RHS)) {
if (RHSC->getValue()->equalsInt(1))
return LHS; // X sdiv 1 --> X
if (RHSC->getValue()->isAllOnesValue())
return getNegativeSCEV(LHS); // X sdiv -1 --> -X
if (SCEVConstant *LHSC = dyn_cast<SCEVConstant>(LHS)) {
Constant *LHSCV = LHSC->getValue();
Constant *RHSCV = RHSC->getValue();
return getUnknown(ConstantExpr::getSDiv(LHSCV, RHSCV));
}
}
SCEVSDivExpr *&Result = (*SCEVSDivs)[std::make_pair(LHS, RHS)];
if (Result == 0) Result = new SCEVSDivExpr(LHS, RHS);
return Result;
}
/// SCEVAddRecExpr::get - Get a add recurrence expression for the
/// specified loop. Simplify the expression as much as possible.
@ -1732,7 +1776,7 @@ static uint32_t GetMinTrailingZeros(SCEVHandle S) {
return MinOpRes;
}
// SCEVUDivExpr, SCEVUnknown
// SCEVUDivExpr, SCEVSDivExpr, SCEVUnknown
return 0;
}
@ -1762,6 +1806,9 @@ SCEVHandle ScalarEvolutionsImpl::createSCEV(Value *V) {
case Instruction::UDiv:
return SE.getUDivExpr(getSCEV(U->getOperand(0)),
getSCEV(U->getOperand(1)));
case Instruction::SDiv:
return SE.getSDivExpr(getSCEV(U->getOperand(0)),
getSCEV(U->getOperand(1)));
case Instruction::Sub:
return SE.getMinusSCEV(getSCEV(U->getOperand(0)),
getSCEV(U->getOperand(1)));
@ -1805,7 +1852,7 @@ SCEVHandle ScalarEvolutionsImpl::createSCEV(Value *V) {
break;
case Instruction::LShr:
// Turn logical shift right of a constant into a unsigned divide.
// Turn logical shift right of a constant into an unsigned divide.
if (ConstantInt *SA = dyn_cast<ConstantInt>(U->getOperand(1))) {
uint32_t BitWidth = cast<IntegerType>(V->getType())->getBitWidth();
Constant *X = ConstantInt::get(
@ -2505,16 +2552,26 @@ SCEVHandle ScalarEvolutionsImpl::getSCEVAtScope(SCEV *V, const Loop *L) {
return Comm;
}
if (SCEVUDivExpr *Div = dyn_cast<SCEVUDivExpr>(V)) {
SCEVHandle LHS = getSCEVAtScope(Div->getLHS(), L);
if (SCEVUDivExpr *UDiv = dyn_cast<SCEVUDivExpr>(V)) {
SCEVHandle LHS = getSCEVAtScope(UDiv->getLHS(), L);
if (LHS == UnknownValue) return LHS;
SCEVHandle RHS = getSCEVAtScope(Div->getRHS(), L);
SCEVHandle RHS = getSCEVAtScope(UDiv->getRHS(), L);
if (RHS == UnknownValue) return RHS;
if (LHS == Div->getLHS() && RHS == Div->getRHS())
return Div; // must be loop invariant
if (LHS == UDiv->getLHS() && RHS == UDiv->getRHS())
return UDiv; // must be loop invariant
return SE.getUDivExpr(LHS, RHS);
}
if (SCEVSDivExpr *SDiv = dyn_cast<SCEVSDivExpr>(V)) {
SCEVHandle LHS = getSCEVAtScope(SDiv->getLHS(), L);
if (LHS == UnknownValue) return LHS;
SCEVHandle RHS = getSCEVAtScope(SDiv->getRHS(), L);
if (RHS == UnknownValue) return RHS;
if (LHS == SDiv->getLHS() && RHS == SDiv->getRHS())
return SDiv; // must be loop invariant
return SE.getSDivExpr(LHS, RHS);
}
// If this is a loop recurrence for a loop that does not contain L, then we
// are dealing with the final value computed by the loop.
if (SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(V)) {

9
llvm/lib/Analysis/ScalarEvolutionExpander.cpp
View File

@ -143,6 +143,15 @@ Value *SCEVExpander::visitUDivExpr(SCEVUDivExpr *S) {
return InsertBinop(Instruction::UDiv, LHS, RHS, InsertPt);
}
Value *SCEVExpander::visitSDivExpr(SCEVSDivExpr *S) {
// Do not fold sdiv into ashr, unless you know that LHS is positive. On
// negative values, it rounds the wrong way.
Value *LHS = expand(S->getLHS());
Value *RHS = expand(S->getRHS());
return InsertBinop(Instruction::SDiv, LHS, RHS, InsertPt);
}
Value *SCEVExpander::visitAddRecExpr(SCEVAddRecExpr *S) {
const Type *Ty = S->getType();
const Loop *L = S->getLoop();