forked from OSchip/llvm-project
621 lines
18 KiB
C++
621 lines
18 KiB
C++
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#include "polly/Support/SCEVValidator.h"
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#include "polly/ScopInfo.h"
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#include "llvm/Analysis/RegionInfo.h"
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#include "llvm/Analysis/ScalarEvolution.h"
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#include "llvm/Analysis/ScalarEvolutionExpressions.h"
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#include "llvm/Support/Debug.h"
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using namespace llvm;
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using namespace polly;
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#define DEBUG_TYPE "polly-scev-validator"
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namespace SCEVType {
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/// @brief The type of a SCEV
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///
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/// To check for the validity of a SCEV we assign to each SCEV a type. The
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/// possible types are INT, PARAM, IV and INVALID. The order of the types is
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/// important. The subexpressions of SCEV with a type X can only have a type
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/// that is smaller or equal than X.
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enum TYPE {
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// An integer value.
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INT,
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// An expression that is constant during the execution of the Scop,
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// but that may depend on parameters unknown at compile time.
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PARAM,
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// An expression that may change during the execution of the SCoP.
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IV,
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// An invalid expression.
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INVALID
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};
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}
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/// @brief The result the validator returns for a SCEV expression.
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class ValidatorResult {
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/// @brief The type of the expression
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SCEVType::TYPE Type;
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/// @brief The set of Parameters in the expression.
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ParameterSetTy Parameters;
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public:
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/// @brief The copy constructor
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ValidatorResult(const ValidatorResult &Source) {
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Type = Source.Type;
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Parameters = Source.Parameters;
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}
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/// @brief Construct a result with a certain type and no parameters.
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ValidatorResult(SCEVType::TYPE Type) : Type(Type) {
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assert(Type != SCEVType::PARAM && "Did you forget to pass the parameter");
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}
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/// @brief Construct a result with a certain type and a single parameter.
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ValidatorResult(SCEVType::TYPE Type, const SCEV *Expr) : Type(Type) {
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Parameters.insert(Expr);
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}
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/// @brief Get the type of the ValidatorResult.
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SCEVType::TYPE getType() { return Type; }
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/// @brief Is the analyzed SCEV constant during the execution of the SCoP.
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bool isConstant() { return Type == SCEVType::INT || Type == SCEVType::PARAM; }
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/// @brief Is the analyzed SCEV valid.
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bool isValid() { return Type != SCEVType::INVALID; }
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/// @brief Is the analyzed SCEV of Type IV.
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bool isIV() { return Type == SCEVType::IV; }
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/// @brief Is the analyzed SCEV of Type INT.
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bool isINT() { return Type == SCEVType::INT; }
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/// @brief Is the analyzed SCEV of Type PARAM.
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bool isPARAM() { return Type == SCEVType::PARAM; }
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/// @brief Get the parameters of this validator result.
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const ParameterSetTy &getParameters() { return Parameters; }
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/// @brief Add the parameters of Source to this result.
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void addParamsFrom(const ValidatorResult &Source) {
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Parameters.insert(Source.Parameters.begin(), Source.Parameters.end());
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}
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/// @brief Merge a result.
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///
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/// This means to merge the parameters and to set the Type to the most
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/// specific Type that matches both.
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void merge(const ValidatorResult &ToMerge) {
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Type = std::max(Type, ToMerge.Type);
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addParamsFrom(ToMerge);
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}
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void print(raw_ostream &OS) {
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switch (Type) {
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case SCEVType::INT:
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OS << "SCEVType::INT";
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break;
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case SCEVType::PARAM:
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OS << "SCEVType::PARAM";
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break;
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case SCEVType::IV:
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OS << "SCEVType::IV";
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break;
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case SCEVType::INVALID:
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OS << "SCEVType::INVALID";
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break;
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}
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}
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};
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raw_ostream &operator<<(raw_ostream &OS, class ValidatorResult &VR) {
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VR.print(OS);
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return OS;
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}
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/// Check if a SCEV is valid in a SCoP.
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struct SCEVValidator
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: public SCEVVisitor<SCEVValidator, class ValidatorResult> {
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private:
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const Region *R;
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Loop *Scope;
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ScalarEvolution &SE;
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InvariantLoadsSetTy *ILS;
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public:
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SCEVValidator(const Region *R, Loop *Scope, ScalarEvolution &SE,
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InvariantLoadsSetTy *ILS)
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: R(R), Scope(Scope), SE(SE), ILS(ILS) {}
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class ValidatorResult visitConstant(const SCEVConstant *Constant) {
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return ValidatorResult(SCEVType::INT);
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}
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class ValidatorResult visitTruncateExpr(const SCEVTruncateExpr *Expr) {
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ValidatorResult Op = visit(Expr->getOperand());
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switch (Op.getType()) {
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case SCEVType::INT:
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case SCEVType::PARAM:
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// We currently do not represent a truncate expression as an affine
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// expression. If it is constant during Scop execution, we treat it as a
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// parameter.
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return ValidatorResult(SCEVType::PARAM, Expr);
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case SCEVType::IV:
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DEBUG(dbgs() << "INVALID: Truncation of SCEVType::IV expression");
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return ValidatorResult(SCEVType::INVALID);
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case SCEVType::INVALID:
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return Op;
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}
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llvm_unreachable("Unknown SCEVType");
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}
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class ValidatorResult visitZeroExtendExpr(const SCEVZeroExtendExpr *Expr) {
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return visit(Expr->getOperand());
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}
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class ValidatorResult visitSignExtendExpr(const SCEVSignExtendExpr *Expr) {
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// We currently allow only signed SCEV expressions. In the case of a
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// signed value, a sign extend is a noop.
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//
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// TODO: Reconsider this when we add support for unsigned values.
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return visit(Expr->getOperand());
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}
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class ValidatorResult visitAddExpr(const SCEVAddExpr *Expr) {
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ValidatorResult Return(SCEVType::INT);
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for (int i = 0, e = Expr->getNumOperands(); i < e; ++i) {
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ValidatorResult Op = visit(Expr->getOperand(i));
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Return.merge(Op);
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// Early exit.
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if (!Return.isValid())
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break;
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}
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// TODO: Check for NSW and NUW.
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return Return;
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}
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class ValidatorResult visitMulExpr(const SCEVMulExpr *Expr) {
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ValidatorResult Return(SCEVType::INT);
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bool HasMultipleParams = false;
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for (int i = 0, e = Expr->getNumOperands(); i < e; ++i) {
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ValidatorResult Op = visit(Expr->getOperand(i));
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if (Op.isINT())
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continue;
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if (Op.isPARAM() && Return.isPARAM()) {
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HasMultipleParams = true;
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continue;
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}
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if ((Op.isIV() || Op.isPARAM()) && !Return.isINT()) {
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DEBUG(dbgs() << "INVALID: More than one non-int operand in MulExpr\n"
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<< "\tExpr: " << *Expr << "\n"
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<< "\tPrevious expression type: " << Return << "\n"
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<< "\tNext operand (" << Op
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<< "): " << *Expr->getOperand(i) << "\n");
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return ValidatorResult(SCEVType::INVALID);
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}
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Return.merge(Op);
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}
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if (HasMultipleParams && Return.isValid())
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return ValidatorResult(SCEVType::PARAM, Expr);
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// TODO: Check for NSW and NUW.
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return Return;
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}
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class ValidatorResult visitUDivExpr(const SCEVUDivExpr *Expr) {
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ValidatorResult LHS = visit(Expr->getLHS());
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ValidatorResult RHS = visit(Expr->getRHS());
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// We currently do not represent an unsigned division as an affine
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// expression. If the division is constant during Scop execution we treat it
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// as a parameter, otherwise we bail out.
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if (LHS.isConstant() && RHS.isConstant())
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return ValidatorResult(SCEVType::PARAM, Expr);
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DEBUG(dbgs() << "INVALID: unsigned division of non-constant expressions");
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return ValidatorResult(SCEVType::INVALID);
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}
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class ValidatorResult visitAddRecExpr(const SCEVAddRecExpr *Expr) {
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if (!Expr->isAffine()) {
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DEBUG(dbgs() << "INVALID: AddRec is not affine");
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return ValidatorResult(SCEVType::INVALID);
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}
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ValidatorResult Start = visit(Expr->getStart());
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ValidatorResult Recurrence = visit(Expr->getStepRecurrence(SE));
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if (!Start.isValid())
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return Start;
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if (!Recurrence.isValid())
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return Recurrence;
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auto *L = Expr->getLoop();
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if (R->contains(L) && (!Scope || !L->contains(Scope))) {
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DEBUG(dbgs() << "INVALID: AddRec out of a loop whose exit value is not "
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"synthesizable");
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return ValidatorResult(SCEVType::INVALID);
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}
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if (R->contains(L)) {
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if (Recurrence.isINT()) {
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ValidatorResult Result(SCEVType::IV);
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Result.addParamsFrom(Start);
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return Result;
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}
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DEBUG(dbgs() << "INVALID: AddRec within scop has non-int"
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"recurrence part");
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return ValidatorResult(SCEVType::INVALID);
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}
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assert(Start.isConstant() && Recurrence.isConstant() &&
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"Expected 'Start' and 'Recurrence' to be constant");
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// Directly generate ValidatorResult for Expr if 'start' is zero.
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if (Expr->getStart()->isZero())
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return ValidatorResult(SCEVType::PARAM, Expr);
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// Translate AddRecExpr from '{start, +, inc}' into 'start + {0, +, inc}'
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// if 'start' is not zero.
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const SCEV *ZeroStartExpr = SE.getAddRecExpr(
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SE.getConstant(Expr->getStart()->getType(), 0),
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Expr->getStepRecurrence(SE), Expr->getLoop(), Expr->getNoWrapFlags());
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ValidatorResult ZeroStartResult =
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ValidatorResult(SCEVType::PARAM, ZeroStartExpr);
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ZeroStartResult.addParamsFrom(Start);
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return ZeroStartResult;
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}
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class ValidatorResult visitSMaxExpr(const SCEVSMaxExpr *Expr) {
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ValidatorResult Return(SCEVType::INT);
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for (int i = 0, e = Expr->getNumOperands(); i < e; ++i) {
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ValidatorResult Op = visit(Expr->getOperand(i));
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if (!Op.isValid())
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return Op;
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Return.merge(Op);
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}
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return Return;
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}
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class ValidatorResult visitUMaxExpr(const SCEVUMaxExpr *Expr) {
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// We do not support unsigned operations. If 'Expr' is constant during Scop
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// execution we treat this as a parameter, otherwise we bail out.
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for (int i = 0, e = Expr->getNumOperands(); i < e; ++i) {
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ValidatorResult Op = visit(Expr->getOperand(i));
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if (!Op.isConstant()) {
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DEBUG(dbgs() << "INVALID: UMaxExpr has a non-constant operand");
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return ValidatorResult(SCEVType::INVALID);
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}
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}
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return ValidatorResult(SCEVType::PARAM, Expr);
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}
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ValidatorResult visitGenericInst(Instruction *I, const SCEV *S) {
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if (R->contains(I)) {
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DEBUG(dbgs() << "INVALID: UnknownExpr references an instruction "
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"within the region\n");
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return ValidatorResult(SCEVType::INVALID);
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}
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return ValidatorResult(SCEVType::PARAM, S);
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}
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ValidatorResult visitLoadInstruction(Instruction *I, const SCEV *S) {
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if (R->contains(I) && ILS) {
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ILS->insert(cast<LoadInst>(I));
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return ValidatorResult(SCEVType::PARAM, S);
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}
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return visitGenericInst(I, S);
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}
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ValidatorResult visitSDivInstruction(Instruction *SDiv, const SCEV *S) {
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assert(SDiv->getOpcode() == Instruction::SDiv &&
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"Assumed SDiv instruction!");
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auto *Divisor = SDiv->getOperand(1);
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auto *CI = dyn_cast<ConstantInt>(Divisor);
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if (!CI)
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return visitGenericInst(SDiv, S);
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auto *Dividend = SDiv->getOperand(0);
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auto *DividendSCEV = SE.getSCEV(Dividend);
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return visit(DividendSCEV);
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}
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ValidatorResult visitSRemInstruction(Instruction *SRem, const SCEV *S) {
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assert(SRem->getOpcode() == Instruction::SRem &&
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"Assumed SRem instruction!");
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auto *Divisor = SRem->getOperand(1);
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auto *CI = dyn_cast<ConstantInt>(Divisor);
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if (!CI)
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return visitGenericInst(SRem, S);
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auto *Dividend = SRem->getOperand(0);
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auto *DividendSCEV = SE.getSCEV(Dividend);
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return visit(DividendSCEV);
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}
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ValidatorResult visitUnknown(const SCEVUnknown *Expr) {
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Value *V = Expr->getValue();
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if (!Expr->getType()->isIntegerTy() && !Expr->getType()->isPointerTy()) {
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DEBUG(dbgs() << "INVALID: UnknownExpr is not an integer or pointer");
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return ValidatorResult(SCEVType::INVALID);
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}
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if (isa<UndefValue>(V)) {
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DEBUG(dbgs() << "INVALID: UnknownExpr references an undef value");
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return ValidatorResult(SCEVType::INVALID);
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}
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if (Instruction *I = dyn_cast<Instruction>(Expr->getValue())) {
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switch (I->getOpcode()) {
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case Instruction::Load:
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return visitLoadInstruction(I, Expr);
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case Instruction::SDiv:
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return visitSDivInstruction(I, Expr);
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case Instruction::SRem:
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return visitSRemInstruction(I, Expr);
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default:
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return visitGenericInst(I, Expr);
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}
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}
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return ValidatorResult(SCEVType::PARAM, Expr);
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}
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};
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/// @brief Check whether a SCEV refers to an SSA name defined inside a region.
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class SCEVInRegionDependences {
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const Region *R;
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Loop *Scope;
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bool AllowLoops;
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bool HasInRegionDeps = false;
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public:
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SCEVInRegionDependences(const Region *R, Loop *Scope, bool AllowLoops)
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: R(R), Scope(Scope), AllowLoops(AllowLoops) {}
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bool follow(const SCEV *S) {
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if (auto Unknown = dyn_cast<SCEVUnknown>(S)) {
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Instruction *Inst = dyn_cast<Instruction>(Unknown->getValue());
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// Return true when Inst is defined inside the region R.
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if (Inst && R->contains(Inst)) {
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HasInRegionDeps = true;
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return false;
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}
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} else if (auto AddRec = dyn_cast<SCEVAddRecExpr>(S)) {
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if (!AllowLoops) {
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if (!Scope) {
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HasInRegionDeps = true;
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return false;
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}
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auto *L = AddRec->getLoop();
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if (R->contains(L) && !L->contains(Scope)) {
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HasInRegionDeps = true;
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return false;
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}
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}
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}
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return true;
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}
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bool isDone() { return false; }
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bool hasDependences() { return HasInRegionDeps; }
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};
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namespace polly {
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/// Find all loops referenced in SCEVAddRecExprs.
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class SCEVFindLoops {
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SetVector<const Loop *> &Loops;
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public:
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SCEVFindLoops(SetVector<const Loop *> &Loops) : Loops(Loops) {}
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bool follow(const SCEV *S) {
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if (const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(S))
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Loops.insert(AddRec->getLoop());
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return true;
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}
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bool isDone() { return false; }
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};
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void findLoops(const SCEV *Expr, SetVector<const Loop *> &Loops) {
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SCEVFindLoops FindLoops(Loops);
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SCEVTraversal<SCEVFindLoops> ST(FindLoops);
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ST.visitAll(Expr);
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}
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/// Find all values referenced in SCEVUnknowns.
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class SCEVFindValues {
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ScalarEvolution &SE;
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SetVector<Value *> &Values;
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public:
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SCEVFindValues(ScalarEvolution &SE, SetVector<Value *> &Values)
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: SE(SE), Values(Values) {}
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bool follow(const SCEV *S) {
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const SCEVUnknown *Unknown = dyn_cast<SCEVUnknown>(S);
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if (!Unknown)
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return true;
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Values.insert(Unknown->getValue());
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Instruction *Inst = dyn_cast<Instruction>(Unknown->getValue());
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if (!Inst || (Inst->getOpcode() != Instruction::SRem &&
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Inst->getOpcode() != Instruction::SDiv))
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return false;
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auto *Dividend = SE.getSCEV(Inst->getOperand(1));
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if (!isa<SCEVConstant>(Dividend))
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return false;
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auto *Divisor = SE.getSCEV(Inst->getOperand(0));
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SCEVFindValues FindValues(SE, Values);
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SCEVTraversal<SCEVFindValues> ST(FindValues);
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ST.visitAll(Dividend);
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ST.visitAll(Divisor);
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return false;
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}
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bool isDone() { return false; }
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};
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void findValues(const SCEV *Expr, ScalarEvolution &SE,
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SetVector<Value *> &Values) {
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SCEVFindValues FindValues(SE, Values);
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SCEVTraversal<SCEVFindValues> ST(FindValues);
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ST.visitAll(Expr);
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}
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bool hasScalarDepsInsideRegion(const SCEV *Expr, const Region *R,
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llvm::Loop *Scope, bool AllowLoops) {
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SCEVInRegionDependences InRegionDeps(R, Scope, AllowLoops);
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SCEVTraversal<SCEVInRegionDependences> ST(InRegionDeps);
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ST.visitAll(Expr);
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return InRegionDeps.hasDependences();
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}
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bool isAffineExpr(const Region *R, llvm::Loop *Scope, const SCEV *Expr,
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ScalarEvolution &SE, InvariantLoadsSetTy *ILS) {
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if (isa<SCEVCouldNotCompute>(Expr))
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return false;
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SCEVValidator Validator(R, Scope, SE, ILS);
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DEBUG({
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dbgs() << "\n";
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dbgs() << "Expr: " << *Expr << "\n";
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dbgs() << "Region: " << R->getNameStr() << "\n";
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dbgs() << " -> ";
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});
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ValidatorResult Result = Validator.visit(Expr);
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DEBUG({
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if (Result.isValid())
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dbgs() << "VALID\n";
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|
dbgs() << "\n";
|
|
});
|
|
|
|
return Result.isValid();
|
|
}
|
|
|
|
static bool isAffineParamExpr(Value *V, const Region *R, Loop *Scope,
|
|
ScalarEvolution &SE, ParameterSetTy &Params) {
|
|
auto *E = SE.getSCEV(V);
|
|
if (isa<SCEVCouldNotCompute>(E))
|
|
return false;
|
|
|
|
SCEVValidator Validator(R, Scope, SE, nullptr);
|
|
ValidatorResult Result = Validator.visit(E);
|
|
if (!Result.isConstant())
|
|
return false;
|
|
|
|
auto ResultParams = Result.getParameters();
|
|
Params.insert(ResultParams.begin(), ResultParams.end());
|
|
|
|
return true;
|
|
}
|
|
|
|
bool isAffineParamConstraint(Value *V, const Region *R, llvm::Loop *Scope,
|
|
ScalarEvolution &SE, ParameterSetTy &Params,
|
|
bool OrExpr) {
|
|
if (auto *ICmp = dyn_cast<ICmpInst>(V)) {
|
|
return isAffineParamConstraint(ICmp->getOperand(0), R, Scope, SE, Params,
|
|
true) &&
|
|
isAffineParamConstraint(ICmp->getOperand(1), R, Scope, SE, Params,
|
|
true);
|
|
} else if (auto *BinOp = dyn_cast<BinaryOperator>(V)) {
|
|
auto Opcode = BinOp->getOpcode();
|
|
if (Opcode == Instruction::And || Opcode == Instruction::Or)
|
|
return isAffineParamConstraint(BinOp->getOperand(0), R, Scope, SE, Params,
|
|
false) &&
|
|
isAffineParamConstraint(BinOp->getOperand(1), R, Scope, SE, Params,
|
|
false);
|
|
/* Fall through */
|
|
}
|
|
|
|
if (!OrExpr)
|
|
return false;
|
|
|
|
return isAffineParamExpr(V, R, Scope, SE, Params);
|
|
}
|
|
|
|
ParameterSetTy getParamsInAffineExpr(const Region *R, Loop *Scope,
|
|
const SCEV *Expr, ScalarEvolution &SE) {
|
|
if (isa<SCEVCouldNotCompute>(Expr))
|
|
return ParameterSetTy();
|
|
|
|
InvariantLoadsSetTy ILS;
|
|
SCEVValidator Validator(R, Scope, SE, &ILS);
|
|
ValidatorResult Result = Validator.visit(Expr);
|
|
assert(Result.isValid() && "Requested parameters for an invalid SCEV!");
|
|
|
|
return Result.getParameters();
|
|
}
|
|
|
|
std::pair<const SCEVConstant *, const SCEV *>
|
|
extractConstantFactor(const SCEV *S, ScalarEvolution &SE) {
|
|
|
|
auto *LeftOver = SE.getConstant(S->getType(), 1);
|
|
auto *ConstPart = cast<SCEVConstant>(SE.getConstant(S->getType(), 1));
|
|
|
|
if (auto *Constant = dyn_cast<SCEVConstant>(S))
|
|
return std::make_pair(Constant, LeftOver);
|
|
|
|
auto *AddRec = dyn_cast<SCEVAddRecExpr>(S);
|
|
if (AddRec) {
|
|
auto *StartExpr = AddRec->getStart();
|
|
if (StartExpr->isZero()) {
|
|
auto StepPair = extractConstantFactor(AddRec->getStepRecurrence(SE), SE);
|
|
auto *LeftOverAddRec =
|
|
SE.getAddRecExpr(StartExpr, StepPair.second, AddRec->getLoop(),
|
|
AddRec->getNoWrapFlags());
|
|
return std::make_pair(StepPair.first, LeftOverAddRec);
|
|
}
|
|
return std::make_pair(ConstPart, S);
|
|
}
|
|
|
|
auto *Mul = dyn_cast<SCEVMulExpr>(S);
|
|
if (!Mul)
|
|
return std::make_pair(ConstPart, S);
|
|
|
|
for (auto *Op : Mul->operands())
|
|
if (isa<SCEVConstant>(Op))
|
|
ConstPart = cast<SCEVConstant>(SE.getMulExpr(ConstPart, Op));
|
|
else
|
|
LeftOver = SE.getMulExpr(LeftOver, Op);
|
|
|
|
return std::make_pair(ConstPart, LeftOver);
|
|
}
|
|
}
|