forked from OSchip/llvm-project
497 lines
14 KiB
C++
497 lines
14 KiB
C++
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#include "polly/Support/SCEVValidator.h"
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#include "polly/ScopInfo.h"
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#define DEBUG_TYPE "polly-scev-validator"
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#include "llvm/Support/Debug.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/Analysis/RegionInfo.h"
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#include <vector>
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using namespace llvm;
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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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std::vector<const SCEV *> 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.push_back(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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std::vector<const SCEV *> getParameters() { return Parameters; }
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/// @brief Add the parameters of Source to this result.
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void addParamsFrom(class ValidatorResult &Source) {
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Parameters.insert(Parameters.end(), Source.Parameters.begin(),
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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(class 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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ScalarEvolution &SE;
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const Value *BaseAddress;
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public:
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SCEVValidator(const Region *R, ScalarEvolution &SE, const Value *BaseAddress)
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: R(R), SE(SE), BaseAddress(BaseAddress) {}
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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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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: ZeroExtend 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 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)
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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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if (R->contains(Expr->getLoop())) {
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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(), SCEV::FlagAnyWrap);
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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, Expr);
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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 visitUnknown(const SCEVUnknown *Expr) {
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Value *V = Expr->getValue();
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// We currently only support integer types. It may be useful to support
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// pointer types, e.g. to support code like:
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//
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// if (A)
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// A[i] = 1;
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//
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// See test/CodeGen/20120316-InvalidCast.ll
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if (!Expr->getType()->isIntegerTy()) {
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DEBUG(dbgs() << "INVALID: UnknownExpr is not an integer type");
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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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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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if (BaseAddress == V) {
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DEBUG(dbgs() << "INVALID: UnknownExpr references BaseAddress\n");
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return ValidatorResult(SCEVType::INVALID);
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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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///
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struct SCEVInRegionDependences
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: public SCEVVisitor<SCEVInRegionDependences, bool> {
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public:
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/// Returns true when the SCEV has SSA names defined in region R.
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static bool hasDependences(const SCEV *S, const Region *R) {
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SCEVInRegionDependences Ignore(R);
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return Ignore.visit(S);
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}
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SCEVInRegionDependences(const Region *R) : R(R) {}
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bool visit(const SCEV *Expr) {
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return SCEVVisitor<SCEVInRegionDependences, bool>::visit(Expr);
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}
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bool visitConstant(const SCEVConstant *Constant) { return false; }
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bool visitTruncateExpr(const SCEVTruncateExpr *Expr) {
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return visit(Expr->getOperand());
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}
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bool visitZeroExtendExpr(const SCEVZeroExtendExpr *Expr) {
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return visit(Expr->getOperand());
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}
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bool visitSignExtendExpr(const SCEVSignExtendExpr *Expr) {
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return visit(Expr->getOperand());
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}
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bool visitAddExpr(const SCEVAddExpr *Expr) {
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for (int i = 0, e = Expr->getNumOperands(); i < e; ++i)
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if (visit(Expr->getOperand(i)))
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return true;
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return false;
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}
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bool visitMulExpr(const SCEVMulExpr *Expr) {
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for (int i = 0, e = Expr->getNumOperands(); i < e; ++i)
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if (visit(Expr->getOperand(i)))
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return true;
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return false;
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}
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bool visitUDivExpr(const SCEVUDivExpr *Expr) {
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if (visit(Expr->getLHS()))
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return true;
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if (visit(Expr->getRHS()))
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return true;
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return false;
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}
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bool visitAddRecExpr(const SCEVAddRecExpr *Expr) {
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if (visit(Expr->getStart()))
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return true;
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for (size_t i = 0; i < Expr->getNumOperands(); ++i)
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if (visit(Expr->getOperand(i)))
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return true;
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return false;
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}
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bool visitSMaxExpr(const SCEVSMaxExpr *Expr) {
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for (size_t i = 0; i < Expr->getNumOperands(); ++i)
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if (visit(Expr->getOperand(i)))
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return true;
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return false;
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}
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bool visitUMaxExpr(const SCEVUMaxExpr *Expr) {
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for (size_t i = 0; i < Expr->getNumOperands(); ++i)
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if (visit(Expr->getOperand(i)))
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return true;
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return false;
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}
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bool visitUnknown(const SCEVUnknown *Expr) {
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Instruction *Inst = dyn_cast<Instruction>(Expr->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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return true;
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return false;
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}
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private:
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const Region *R;
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};
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namespace polly {
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bool hasScalarDepsInsideRegion(const SCEV *Expr, const Region *R) {
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return SCEVInRegionDependences::hasDependences(Expr, R);
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}
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bool isAffineExpr(const Region *R, const SCEV *Expr, ScalarEvolution &SE,
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const Value *BaseAddress) {
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if (isa<SCEVCouldNotCompute>(Expr))
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return false;
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SCEVValidator Validator(R, SE, BaseAddress);
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DEBUG(dbgs() << "\n"; dbgs() << "Expr: " << *Expr << "\n";
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dbgs() << "Region: " << R->getNameStr() << "\n"; dbgs() << " -> ");
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ValidatorResult Result = Validator.visit(Expr);
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DEBUG(if (Result.isValid()) dbgs() << "VALID\n"; dbgs() << "\n";);
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return Result.isValid();
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}
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std::vector<const SCEV *> getParamsInAffineExpr(const Region *R,
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const SCEV *Expr,
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ScalarEvolution &SE,
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const Value *BaseAddress) {
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if (isa<SCEVCouldNotCompute>(Expr))
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return std::vector<const SCEV *>();
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SCEVValidator Validator(R, SE, BaseAddress);
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ValidatorResult Result = Validator.visit(Expr);
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return Result.getParameters();
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}
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}
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