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//===- llvm/Analysis/ScalarEvolutionExpressions.h - SCEV Exprs --*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file defines the classes used to represent and build scalar expressions.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_ANALYSIS_SCALAREVOLUTIONEXPRESSIONS_H
#define LLVM_ANALYSIS_SCALAREVOLUTIONEXPRESSIONS_H
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/Analysis/ScalarEvolution.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/ValueHandle.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/ErrorHandling.h"
#include <cassert>
#include <cstddef>
namespace llvm {
class APInt;
class Constant;
class ConstantInt;
class ConstantRange;
class Loop;
class Type;
class Value;
enum SCEVTypes : unsigned short {
// These should be ordered in terms of increasing complexity to make the
// folders simpler.
scConstant,
scVScale,
scTruncate,
scZeroExtend,
scSignExtend,
scAddExpr,
scMulExpr,
scUDivExpr,
scAddRecExpr,
scUMaxExpr,
scSMaxExpr,
scUMinExpr,
scSMinExpr,
scSequentialUMinExpr,
scPtrToInt,
scUnknown,
scCouldNotCompute
};
/// This class represents a constant integer value.
class SCEVConstant : public SCEV {
friend class ScalarEvolution;
ConstantInt *V;
SCEVConstant(const FoldingSetNodeIDRef ID, ConstantInt *v)
: SCEV(ID, scConstant, 1), V(v) {}
public:
ConstantInt *getValue() const { return V; }
const APInt &getAPInt() const { return getValue()->getValue(); }
Type *getType() const { return V->getType(); }
/// Methods for support type inquiry through isa, cast, and dyn_cast:
static bool classof(const SCEV *S) { return S->getSCEVType() == scConstant; }
};
/// This class represents the value of vscale, as used when defining the length
/// of a scalable vector or returned by the llvm.vscale() intrinsic.
class SCEVVScale : public SCEV {
friend class ScalarEvolution;
SCEVVScale(const FoldingSetNodeIDRef ID, Type *ty)
: SCEV(ID, scVScale, 0), Ty(ty) {}
Type *Ty;
public:
Type *getType() const { return Ty; }
/// Methods for support type inquiry through isa, cast, and dyn_cast:
static bool classof(const SCEV *S) { return S->getSCEVType() == scVScale; }
};
inline unsigned short computeExpressionSize(ArrayRef<const SCEV *> Args) {
APInt Size(16, 1);
for (const auto *Arg : Args)
Size = Size.uadd_sat(APInt(16, Arg->getExpressionSize()));
return (unsigned short)Size.getZExtValue();
}
/// This is the base class for unary cast operator classes.
class SCEVCastExpr : public SCEV {
protected:
const SCEV *Op;
Type *Ty;
SCEVCastExpr(const FoldingSetNodeIDRef ID, SCEVTypes SCEVTy, const SCEV *op,
Type *ty);
public:
const SCEV *getOperand() const { return Op; }
const SCEV *getOperand(unsigned i) const {
assert(i == 0 && "Operand index out of range!");
return Op;
}
ArrayRef<const SCEV *> operands() const { return Op; }
size_t getNumOperands() const { return 1; }
Type *getType() const { return Ty; }
/// Methods for support type inquiry through isa, cast, and dyn_cast:
static bool classof(const SCEV *S) {
return S->getSCEVType() == scPtrToInt || S->getSCEVType() == scTruncate ||
S->getSCEVType() == scZeroExtend || S->getSCEVType() == scSignExtend;
}
};
/// This class represents a cast from a pointer to a pointer-sized integer
/// value.
class SCEVPtrToIntExpr : public SCEVCastExpr {
friend class ScalarEvolution;
SCEVPtrToIntExpr(const FoldingSetNodeIDRef ID, const SCEV *Op, Type *ITy);
public:
/// Methods for support type inquiry through isa, cast, and dyn_cast:
static bool classof(const SCEV *S) { return S->getSCEVType() == scPtrToInt; }
};
/// This is the base class for unary integral cast operator classes.
class SCEVIntegralCastExpr : public SCEVCastExpr {
protected:
SCEVIntegralCastExpr(const FoldingSetNodeIDRef ID, SCEVTypes SCEVTy,
const SCEV *op, Type *ty);
public:
/// Methods for support type inquiry through isa, cast, and dyn_cast:
static bool classof(const SCEV *S) {
return S->getSCEVType() == scTruncate || S->getSCEVType() == scZeroExtend ||
S->getSCEVType() == scSignExtend;
}
};
/// This class represents a truncation of an integer value to a
/// smaller integer value.
class SCEVTruncateExpr : public SCEVIntegralCastExpr {
friend class ScalarEvolution;
SCEVTruncateExpr(const FoldingSetNodeIDRef ID, const SCEV *op, Type *ty);
public:
/// Methods for support type inquiry through isa, cast, and dyn_cast:
static bool classof(const SCEV *S) { return S->getSCEVType() == scTruncate; }
};
/// This class represents a zero extension of a small integer value
/// to a larger integer value.
class SCEVZeroExtendExpr : public SCEVIntegralCastExpr {
friend class ScalarEvolution;
SCEVZeroExtendExpr(const FoldingSetNodeIDRef ID, const SCEV *op, Type *ty);
public:
/// Methods for support type inquiry through isa, cast, and dyn_cast:
static bool classof(const SCEV *S) {
return S->getSCEVType() == scZeroExtend;
}
};
/// This class represents a sign extension of a small integer value
/// to a larger integer value.
class SCEVSignExtendExpr : public SCEVIntegralCastExpr {
friend class ScalarEvolution;
SCEVSignExtendExpr(const FoldingSetNodeIDRef ID, const SCEV *op, Type *ty);
public:
/// Methods for support type inquiry through isa, cast, and dyn_cast:
static bool classof(const SCEV *S) {
return S->getSCEVType() == scSignExtend;
}
};
/// This node is a base class providing common functionality for
/// n'ary operators.
class SCEVNAryExpr : public SCEV {
protected:
// Since SCEVs are immutable, ScalarEvolution allocates operand
// arrays with its SCEVAllocator, so this class just needs a simple
// pointer rather than a more elaborate vector-like data structure.
// This also avoids the need for a non-trivial destructor.
const SCEV *const *Operands;
size_t NumOperands;
SCEVNAryExpr(const FoldingSetNodeIDRef ID, enum SCEVTypes T,
const SCEV *const *O, size_t N)
: SCEV(ID, T, computeExpressionSize(ArrayRef(O, N))), Operands(O),
NumOperands(N) {}
public:
size_t getNumOperands() const { return NumOperands; }
const SCEV *getOperand(unsigned i) const {
assert(i < NumOperands && "Operand index out of range!");
return Operands[i];
}
ArrayRef<const SCEV *> operands() const {
return ArrayRef(Operands, NumOperands);
}
NoWrapFlags getNoWrapFlags(NoWrapFlags Mask = NoWrapMask) const {
return (NoWrapFlags)(SubclassData & Mask);
}
bool hasNoUnsignedWrap() const {
return getNoWrapFlags(FlagNUW) != FlagAnyWrap;
}
bool hasNoSignedWrap() const {
return getNoWrapFlags(FlagNSW) != FlagAnyWrap;
}
bool hasNoSelfWrap() const { return getNoWrapFlags(FlagNW) != FlagAnyWrap; }
/// Methods for support type inquiry through isa, cast, and dyn_cast:
static bool classof(const SCEV *S) {
return S->getSCEVType() == scAddExpr || S->getSCEVType() == scMulExpr ||
S->getSCEVType() == scSMaxExpr || S->getSCEVType() == scUMaxExpr ||
S->getSCEVType() == scSMinExpr || S->getSCEVType() == scUMinExpr ||
S->getSCEVType() == scSequentialUMinExpr ||
S->getSCEVType() == scAddRecExpr;
}
};
/// This node is the base class for n'ary commutative operators.
class SCEVCommutativeExpr : public SCEVNAryExpr {
protected:
SCEVCommutativeExpr(const FoldingSetNodeIDRef ID, enum SCEVTypes T,
const SCEV *const *O, size_t N)
: SCEVNAryExpr(ID, T, O, N) {}
public:
/// Methods for support type inquiry through isa, cast, and dyn_cast:
static bool classof(const SCEV *S) {
return S->getSCEVType() == scAddExpr || S->getSCEVType() == scMulExpr ||
S->getSCEVType() == scSMaxExpr || S->getSCEVType() == scUMaxExpr ||
S->getSCEVType() == scSMinExpr || S->getSCEVType() == scUMinExpr;
}
/// Set flags for a non-recurrence without clearing previously set flags.
void setNoWrapFlags(NoWrapFlags Flags) { SubclassData |= Flags; }
};
/// This node represents an addition of some number of SCEVs.
class SCEVAddExpr : public SCEVCommutativeExpr {
friend class ScalarEvolution;
Type *Ty;
SCEVAddExpr(const FoldingSetNodeIDRef ID, const SCEV *const *O, size_t N)
: SCEVCommutativeExpr(ID, scAddExpr, O, N) {
auto *FirstPointerTypedOp = find_if(operands(), [](const SCEV *Op) {
return Op->getType()->isPointerTy();
});
if (FirstPointerTypedOp != operands().end())
Ty = (*FirstPointerTypedOp)->getType();
else
Ty = getOperand(0)->getType();
}
public:
Type *getType() const { return Ty; }
/// Methods for support type inquiry through isa, cast, and dyn_cast:
static bool classof(const SCEV *S) { return S->getSCEVType() == scAddExpr; }
};
/// This node represents multiplication of some number of SCEVs.
class SCEVMulExpr : public SCEVCommutativeExpr {
friend class ScalarEvolution;
SCEVMulExpr(const FoldingSetNodeIDRef ID, const SCEV *const *O, size_t N)
: SCEVCommutativeExpr(ID, scMulExpr, O, N) {}
public:
Type *getType() const { return getOperand(0)->getType(); }
/// Methods for support type inquiry through isa, cast, and dyn_cast:
static bool classof(const SCEV *S) { return S->getSCEVType() == scMulExpr; }
};
/// This class represents a binary unsigned division operation.
class SCEVUDivExpr : public SCEV {
friend class ScalarEvolution;
std::array<const SCEV *, 2> Operands;
SCEVUDivExpr(const FoldingSetNodeIDRef ID, const SCEV *lhs, const SCEV *rhs)
: SCEV(ID, scUDivExpr, computeExpressionSize({lhs, rhs})) {
Operands[0] = lhs;
Operands[1] = rhs;
}
public:
const SCEV *getLHS() const { return Operands[0]; }
const SCEV *getRHS() const { return Operands[1]; }
size_t getNumOperands() const { return 2; }
const SCEV *getOperand(unsigned i) const {
assert((i == 0 || i == 1) && "Operand index out of range!");
return i == 0 ? getLHS() : getRHS();
}
ArrayRef<const SCEV *> operands() const { return Operands; }
Type *getType() const {
// In most cases the types of LHS and RHS will be the same, but in some
// crazy cases one or the other may be a pointer. ScalarEvolution doesn't
// depend on the type for correctness, but handling types carefully can
// avoid extra casts in the SCEVExpander. The LHS is more likely to be
// a pointer type than the RHS, so use the RHS' type here.
return getRHS()->getType();
}
/// Methods for support type inquiry through isa, cast, and dyn_cast:
static bool classof(const SCEV *S) { return S->getSCEVType() == scUDivExpr; }
};
/// This node represents a polynomial recurrence on the trip count
/// of the specified loop. This is the primary focus of the
/// ScalarEvolution framework; all the other SCEV subclasses are
/// mostly just supporting infrastructure to allow SCEVAddRecExpr
/// expressions to be created and analyzed.
///
/// All operands of an AddRec are required to be loop invariant.
///
class SCEVAddRecExpr : public SCEVNAryExpr {
friend class ScalarEvolution;
const Loop *L;
SCEVAddRecExpr(const FoldingSetNodeIDRef ID, const SCEV *const *O, size_t N,
const Loop *l)
: SCEVNAryExpr(ID, scAddRecExpr, O, N), L(l) {}
public:
Type *getType() const { return getStart()->getType(); }
const SCEV *getStart() const { return Operands[0]; }
const Loop *getLoop() const { return L; }
/// Constructs and returns the recurrence indicating how much this
/// expression steps by. If this is a polynomial of degree N, it
/// returns a chrec of degree N-1. We cannot determine whether
/// the step recurrence has self-wraparound.
const SCEV *getStepRecurrence(ScalarEvolution &SE) const {
if (isAffine())
return getOperand(1);
return SE.getAddRecExpr(
SmallVector<const SCEV *, 3>(operands().drop_front()), getLoop(),
FlagAnyWrap);
}
/// Return true if this represents an expression A + B*x where A
/// and B are loop invariant values.
bool isAffine() const {
// We know that the start value is invariant. This expression is thus
// affine iff the step is also invariant.
return getNumOperands() == 2;
}
/// Return true if this represents an expression A + B*x + C*x^2
/// where A, B and C are loop invariant values. This corresponds
/// to an addrec of the form {L,+,M,+,N}
bool isQuadratic() const { return getNumOperands() == 3; }
/// Set flags for a recurrence without clearing any previously set flags.
/// For AddRec, either NUW or NSW implies NW. Keep track of this fact here
/// to make it easier to propagate flags.
void setNoWrapFlags(NoWrapFlags Flags) {
if (Flags & (FlagNUW | FlagNSW))
Flags = ScalarEvolution::setFlags(Flags, FlagNW);
SubclassData |= Flags;
}
/// Return the value of this chain of recurrences at the specified
/// iteration number.
const SCEV *evaluateAtIteration(const SCEV *It, ScalarEvolution &SE) const;
/// Return the value of this chain of recurrences at the specified iteration
/// number. Takes an explicit list of operands to represent an AddRec.
static const SCEV *evaluateAtIteration(ArrayRef<const SCEV *> Operands,
const SCEV *It, ScalarEvolution &SE);
/// Return the number of iterations of this loop that produce
/// values in the specified constant range. Another way of
/// looking at this is that it returns the first iteration number
/// where the value is not in the condition, thus computing the
/// exit count. If the iteration count can't be computed, an
/// instance of SCEVCouldNotCompute is returned.
const SCEV *getNumIterationsInRange(const ConstantRange &Range,
ScalarEvolution &SE) const;
/// Return an expression representing the value of this expression
/// one iteration of the loop ahead.
const SCEVAddRecExpr *getPostIncExpr(ScalarEvolution &SE) const;
/// Methods for support type inquiry through isa, cast, and dyn_cast:
static bool classof(const SCEV *S) {
return S->getSCEVType() == scAddRecExpr;
}
};
/// This node is the base class min/max selections.
class SCEVMinMaxExpr : public SCEVCommutativeExpr {
friend class ScalarEvolution;
static bool isMinMaxType(enum SCEVTypes T) {
return T == scSMaxExpr || T == scUMaxExpr || T == scSMinExpr ||
T == scUMinExpr;
}
protected:
/// Note: Constructing subclasses via this constructor is allowed
SCEVMinMaxExpr(const FoldingSetNodeIDRef ID, enum SCEVTypes T,
const SCEV *const *O, size_t N)
: SCEVCommutativeExpr(ID, T, O, N) {
assert(isMinMaxType(T));
// Min and max never overflow
setNoWrapFlags((NoWrapFlags)(FlagNUW | FlagNSW));
}
public:
Type *getType() const { return getOperand(0)->getType(); }
static bool classof(const SCEV *S) { return isMinMaxType(S->getSCEVType()); }
static enum SCEVTypes negate(enum SCEVTypes T) {
switch (T) {
case scSMaxExpr:
return scSMinExpr;
case scSMinExpr:
return scSMaxExpr;
case scUMaxExpr:
return scUMinExpr;
case scUMinExpr:
return scUMaxExpr;
default:
llvm_unreachable("Not a min or max SCEV type!");
}
}
};
/// This class represents a signed maximum selection.
class SCEVSMaxExpr : public SCEVMinMaxExpr {
friend class ScalarEvolution;
SCEVSMaxExpr(const FoldingSetNodeIDRef ID, const SCEV *const *O, size_t N)
: SCEVMinMaxExpr(ID, scSMaxExpr, O, N) {}
public:
/// Methods for support type inquiry through isa, cast, and dyn_cast:
static bool classof(const SCEV *S) { return S->getSCEVType() == scSMaxExpr; }
};
/// This class represents an unsigned maximum selection.
class SCEVUMaxExpr : public SCEVMinMaxExpr {
friend class ScalarEvolution;
SCEVUMaxExpr(const FoldingSetNodeIDRef ID, const SCEV *const *O, size_t N)
: SCEVMinMaxExpr(ID, scUMaxExpr, O, N) {}
public:
/// Methods for support type inquiry through isa, cast, and dyn_cast:
static bool classof(const SCEV *S) { return S->getSCEVType() == scUMaxExpr; }
};
/// This class represents a signed minimum selection.
class SCEVSMinExpr : public SCEVMinMaxExpr {
friend class ScalarEvolution;
SCEVSMinExpr(const FoldingSetNodeIDRef ID, const SCEV *const *O, size_t N)
: SCEVMinMaxExpr(ID, scSMinExpr, O, N) {}
public:
/// Methods for support type inquiry through isa, cast, and dyn_cast:
static bool classof(const SCEV *S) { return S->getSCEVType() == scSMinExpr; }
};
/// This class represents an unsigned minimum selection.
class SCEVUMinExpr : public SCEVMinMaxExpr {
friend class ScalarEvolution;
SCEVUMinExpr(const FoldingSetNodeIDRef ID, const SCEV *const *O, size_t N)
: SCEVMinMaxExpr(ID, scUMinExpr, O, N) {}
public:
/// Methods for support type inquiry through isa, cast, and dyn_cast:
static bool classof(const SCEV *S) { return S->getSCEVType() == scUMinExpr; }
};
/// This node is the base class for sequential/in-order min/max selections.
/// Note that their fundamental difference from SCEVMinMaxExpr's is that they
/// are early-returning upon reaching saturation point.
/// I.e. given `0 umin_seq poison`, the result will be `0`,
/// while the result of `0 umin poison` is `poison`.
class SCEVSequentialMinMaxExpr : public SCEVNAryExpr {
friend class ScalarEvolution;
static bool isSequentialMinMaxType(enum SCEVTypes T) {
return T == scSequentialUMinExpr;
}
/// Set flags for a non-recurrence without clearing previously set flags.
void setNoWrapFlags(NoWrapFlags Flags) { SubclassData |= Flags; }
protected:
/// Note: Constructing subclasses via this constructor is allowed
SCEVSequentialMinMaxExpr(const FoldingSetNodeIDRef ID, enum SCEVTypes T,
const SCEV *const *O, size_t N)
: SCEVNAryExpr(ID, T, O, N) {
assert(isSequentialMinMaxType(T));
// Min and max never overflow
setNoWrapFlags((NoWrapFlags)(FlagNUW | FlagNSW));
}
public:
Type *getType() const { return getOperand(0)->getType(); }
static SCEVTypes getEquivalentNonSequentialSCEVType(SCEVTypes Ty) {
assert(isSequentialMinMaxType(Ty));
switch (Ty) {
case scSequentialUMinExpr:
return scUMinExpr;
default:
llvm_unreachable("Not a sequential min/max type.");
}
}
SCEVTypes getEquivalentNonSequentialSCEVType() const {
return getEquivalentNonSequentialSCEVType(getSCEVType());
}
static bool classof(const SCEV *S) {
return isSequentialMinMaxType(S->getSCEVType());
}
};
/// This class represents a sequential/in-order unsigned minimum selection.
class SCEVSequentialUMinExpr : public SCEVSequentialMinMaxExpr {
friend class ScalarEvolution;
SCEVSequentialUMinExpr(const FoldingSetNodeIDRef ID, const SCEV *const *O,
size_t N)
: SCEVSequentialMinMaxExpr(ID, scSequentialUMinExpr, O, N) {}
public:
/// Methods for support type inquiry through isa, cast, and dyn_cast:
static bool classof(const SCEV *S) {
return S->getSCEVType() == scSequentialUMinExpr;
}
};
/// This means that we are dealing with an entirely unknown SCEV
/// value, and only represent it as its LLVM Value. This is the
/// "bottom" value for the analysis.
class SCEVUnknown final : public SCEV, private CallbackVH {
friend class ScalarEvolution;
/// The parent ScalarEvolution value. This is used to update the
/// parent's maps when the value associated with a SCEVUnknown is
/// deleted or RAUW'd.
ScalarEvolution *SE;
/// The next pointer in the linked list of all SCEVUnknown
/// instances owned by a ScalarEvolution.
SCEVUnknown *Next;
SCEVUnknown(const FoldingSetNodeIDRef ID, Value *V, ScalarEvolution *se,
SCEVUnknown *next)
: SCEV(ID, scUnknown, 1), CallbackVH(V), SE(se), Next(next) {}
// Implement CallbackVH.
void deleted() override;
void allUsesReplacedWith(Value *New) override;
public:
Value *getValue() const { return getValPtr(); }
Type *getType() const { return getValPtr()->getType(); }
/// Methods for support type inquiry through isa, cast, and dyn_cast:
static bool classof(const SCEV *S) { return S->getSCEVType() == scUnknown; }
};
/// This class defines a simple visitor class that may be used for
/// various SCEV analysis purposes.
template <typename SC, typename RetVal = void> struct SCEVVisitor {
RetVal visit(const SCEV *S) {
switch (S->getSCEVType()) {
case scConstant:
return ((SC *)this)->visitConstant((const SCEVConstant *)S);
case scVScale:
return ((SC *)this)->visitVScale((const SCEVVScale *)S);
case scPtrToInt:
return ((SC *)this)->visitPtrToIntExpr((const SCEVPtrToIntExpr *)S);
case scTruncate:
return ((SC *)this)->visitTruncateExpr((const SCEVTruncateExpr *)S);
case scZeroExtend:
return ((SC *)this)->visitZeroExtendExpr((const SCEVZeroExtendExpr *)S);
case scSignExtend:
return ((SC *)this)->visitSignExtendExpr((const SCEVSignExtendExpr *)S);
case scAddExpr:
return ((SC *)this)->visitAddExpr((const SCEVAddExpr *)S);
case scMulExpr:
return ((SC *)this)->visitMulExpr((const SCEVMulExpr *)S);
case scUDivExpr:
return ((SC *)this)->visitUDivExpr((const SCEVUDivExpr *)S);
case scAddRecExpr:
return ((SC *)this)->visitAddRecExpr((const SCEVAddRecExpr *)S);
case scSMaxExpr:
return ((SC *)this)->visitSMaxExpr((const SCEVSMaxExpr *)S);
case scUMaxExpr:
return ((SC *)this)->visitUMaxExpr((const SCEVUMaxExpr *)S);
case scSMinExpr:
return ((SC *)this)->visitSMinExpr((const SCEVSMinExpr *)S);
case scUMinExpr:
return ((SC *)this)->visitUMinExpr((const SCEVUMinExpr *)S);
case scSequentialUMinExpr:
return ((SC *)this)
->visitSequentialUMinExpr((const SCEVSequentialUMinExpr *)S);
case scUnknown:
return ((SC *)this)->visitUnknown((const SCEVUnknown *)S);
case scCouldNotCompute:
return ((SC *)this)->visitCouldNotCompute((const SCEVCouldNotCompute *)S);
}
llvm_unreachable("Unknown SCEV kind!");
}
RetVal visitCouldNotCompute(const SCEVCouldNotCompute *S) {
llvm_unreachable("Invalid use of SCEVCouldNotCompute!");
}
};
/// Visit all nodes in the expression tree using worklist traversal.
///
/// Visitor implements:
/// // return true to follow this node.
/// bool follow(const SCEV *S);
/// // return true to terminate the search.
/// bool isDone();
template <typename SV> class SCEVTraversal {
SV &Visitor;
SmallVector<const SCEV *, 8> Worklist;
SmallPtrSet<const SCEV *, 8> Visited;
void push(const SCEV *S) {
if (Visited.insert(S).second && Visitor.follow(S))
Worklist.push_back(S);
}
public:
SCEVTraversal(SV &V) : Visitor(V) {}
void visitAll(const SCEV *Root) {
push(Root);
while (!Worklist.empty() && !Visitor.isDone()) {
const SCEV *S = Worklist.pop_back_val();
switch (S->getSCEVType()) {
case scConstant:
case scVScale:
case scUnknown:
continue;
case scPtrToInt:
case scTruncate:
case scZeroExtend:
case scSignExtend:
case scAddExpr:
case scMulExpr:
case scUDivExpr:
case scSMaxExpr:
case scUMaxExpr:
case scSMinExpr:
case scUMinExpr:
case scSequentialUMinExpr:
case scAddRecExpr:
for (const auto *Op : S->operands()) {
push(Op);
if (Visitor.isDone())
break;
}
continue;
case scCouldNotCompute:
llvm_unreachable("Attempt to use a SCEVCouldNotCompute object!");
}
llvm_unreachable("Unknown SCEV kind!");
}
}
};
/// Use SCEVTraversal to visit all nodes in the given expression tree.
template <typename SV> void visitAll(const SCEV *Root, SV &Visitor) {
SCEVTraversal<SV> T(Visitor);
T.visitAll(Root);
}
/// Return true if any node in \p Root satisfies the predicate \p Pred.
template <typename PredTy>
bool SCEVExprContains(const SCEV *Root, PredTy Pred) {
struct FindClosure {
bool Found = false;
PredTy Pred;
FindClosure(PredTy Pred) : Pred(Pred) {}
bool follow(const SCEV *S) {
if (!Pred(S))
return true;
Found = true;
return false;
}
bool isDone() const { return Found; }
};
FindClosure FC(Pred);
visitAll(Root, FC);
return FC.Found;
}
/// This visitor recursively visits a SCEV expression and re-writes it.
/// The result from each visit is cached, so it will return the same
/// SCEV for the same input.
template <typename SC>
class SCEVRewriteVisitor : public SCEVVisitor<SC, const SCEV *> {
protected:
ScalarEvolution &SE;
// Memoize the result of each visit so that we only compute once for
// the same input SCEV. This is to avoid redundant computations when
// a SCEV is referenced by multiple SCEVs. Without memoization, this
// visit algorithm would have exponential time complexity in the worst
// case, causing the compiler to hang on certain tests.
SmallDenseMap<const SCEV *, const SCEV *> RewriteResults;
public:
SCEVRewriteVisitor(ScalarEvolution &SE) : SE(SE) {}
const SCEV *visit(const SCEV *S) {
auto It = RewriteResults.find(S);
if (It != RewriteResults.end())
return It->second;
auto *Visited = SCEVVisitor<SC, const SCEV *>::visit(S);
auto Result = RewriteResults.try_emplace(S, Visited);
assert(Result.second && "Should insert a new entry");
return Result.first->second;
}
const SCEV *visitConstant(const SCEVConstant *Constant) { return Constant; }
const SCEV *visitVScale(const SCEVVScale *VScale) { return VScale; }
const SCEV *visitPtrToIntExpr(const SCEVPtrToIntExpr *Expr) {
const SCEV *Operand = ((SC *)this)->visit(Expr->getOperand());
return Operand == Expr->getOperand()
? Expr
: SE.getPtrToIntExpr(Operand, Expr->getType());
}
const SCEV *visitTruncateExpr(const SCEVTruncateExpr *Expr) {
const SCEV *Operand = ((SC *)this)->visit(Expr->getOperand());
return Operand == Expr->getOperand()
? Expr
: SE.getTruncateExpr(Operand, Expr->getType());
}
const SCEV *visitZeroExtendExpr(const SCEVZeroExtendExpr *Expr) {
const SCEV *Operand = ((SC *)this)->visit(Expr->getOperand());
return Operand == Expr->getOperand()
? Expr
: SE.getZeroExtendExpr(Operand, Expr->getType());
}
const SCEV *visitSignExtendExpr(const SCEVSignExtendExpr *Expr) {
const SCEV *Operand = ((SC *)this)->visit(Expr->getOperand());
return Operand == Expr->getOperand()
? Expr
: SE.getSignExtendExpr(Operand, Expr->getType());
}
const SCEV *visitAddExpr(const SCEVAddExpr *Expr) {
SmallVector<const SCEV *, 2> Operands;
bool Changed = false;
for (const auto *Op : Expr->operands()) {
Operands.push_back(((SC *)this)->visit(Op));
Changed |= Op != Operands.back();
}
return !Changed ? Expr : SE.getAddExpr(Operands);
}
const SCEV *visitMulExpr(const SCEVMulExpr *Expr) {
SmallVector<const SCEV *, 2> Operands;
bool Changed = false;
for (const auto *Op : Expr->operands()) {
Operands.push_back(((SC *)this)->visit(Op));
Changed |= Op != Operands.back();
}
return !Changed ? Expr : SE.getMulExpr(Operands);
}
const SCEV *visitUDivExpr(const SCEVUDivExpr *Expr) {
auto *LHS = ((SC *)this)->visit(Expr->getLHS());
auto *RHS = ((SC *)this)->visit(Expr->getRHS());
bool Changed = LHS != Expr->getLHS() || RHS != Expr->getRHS();
return !Changed ? Expr : SE.getUDivExpr(LHS, RHS);
}
const SCEV *visitAddRecExpr(const SCEVAddRecExpr *Expr) {
SmallVector<const SCEV *, 2> Operands;
bool Changed = false;
for (const auto *Op : Expr->operands()) {
Operands.push_back(((SC *)this)->visit(Op));
Changed |= Op != Operands.back();
}
return !Changed ? Expr
: SE.getAddRecExpr(Operands, Expr->getLoop(),
Expr->getNoWrapFlags());
}
const SCEV *visitSMaxExpr(const SCEVSMaxExpr *Expr) {
SmallVector<const SCEV *, 2> Operands;
bool Changed = false;
for (const auto *Op : Expr->operands()) {
Operands.push_back(((SC *)this)->visit(Op));
Changed |= Op != Operands.back();
}
return !Changed ? Expr : SE.getSMaxExpr(Operands);
}
const SCEV *visitUMaxExpr(const SCEVUMaxExpr *Expr) {
SmallVector<const SCEV *, 2> Operands;
bool Changed = false;
for (const auto *Op : Expr->operands()) {
Operands.push_back(((SC *)this)->visit(Op));
Changed |= Op != Operands.back();
}
return !Changed ? Expr : SE.getUMaxExpr(Operands);
}
const SCEV *visitSMinExpr(const SCEVSMinExpr *Expr) {
SmallVector<const SCEV *, 2> Operands;
bool Changed = false;
for (const auto *Op : Expr->operands()) {
Operands.push_back(((SC *)this)->visit(Op));
Changed |= Op != Operands.back();
}
return !Changed ? Expr : SE.getSMinExpr(Operands);
}
const SCEV *visitUMinExpr(const SCEVUMinExpr *Expr) {
SmallVector<const SCEV *, 2> Operands;
bool Changed = false;
for (const auto *Op : Expr->operands()) {
Operands.push_back(((SC *)this)->visit(Op));
Changed |= Op != Operands.back();
}
return !Changed ? Expr : SE.getUMinExpr(Operands);
}
const SCEV *visitSequentialUMinExpr(const SCEVSequentialUMinExpr *Expr) {
SmallVector<const SCEV *, 2> Operands;
bool Changed = false;
for (const auto *Op : Expr->operands()) {
Operands.push_back(((SC *)this)->visit(Op));
Changed |= Op != Operands.back();
}
return !Changed ? Expr : SE.getUMinExpr(Operands, /*Sequential=*/true);
}
const SCEV *visitUnknown(const SCEVUnknown *Expr) { return Expr; }
const SCEV *visitCouldNotCompute(const SCEVCouldNotCompute *Expr) {
return Expr;
}
};
using ValueToValueMap = DenseMap<const Value *, Value *>;
using ValueToSCEVMapTy = DenseMap<const Value *, const SCEV *>;
/// The SCEVParameterRewriter takes a scalar evolution expression and updates
/// the SCEVUnknown components following the Map (Value -> SCEV).
class SCEVParameterRewriter : public SCEVRewriteVisitor<SCEVParameterRewriter> {
public:
static const SCEV *rewrite(const SCEV *Scev, ScalarEvolution &SE,
ValueToSCEVMapTy &Map) {
SCEVParameterRewriter Rewriter(SE, Map);
return Rewriter.visit(Scev);
}
SCEVParameterRewriter(ScalarEvolution &SE, ValueToSCEVMapTy &M)
: SCEVRewriteVisitor(SE), Map(M) {}
const SCEV *visitUnknown(const SCEVUnknown *Expr) {
auto I = Map.find(Expr->getValue());
if (I == Map.end())
return Expr;
return I->second;
}
private:
ValueToSCEVMapTy ⤅
};
using LoopToScevMapT = DenseMap<const Loop *, const SCEV *>;
/// The SCEVLoopAddRecRewriter takes a scalar evolution expression and applies
/// the Map (Loop -> SCEV) to all AddRecExprs.
class SCEVLoopAddRecRewriter
: public SCEVRewriteVisitor<SCEVLoopAddRecRewriter> {
public:
SCEVLoopAddRecRewriter(ScalarEvolution &SE, LoopToScevMapT &M)
: SCEVRewriteVisitor(SE), Map(M) {}
static const SCEV *rewrite(const SCEV *Scev, LoopToScevMapT &Map,
ScalarEvolution &SE) {
SCEVLoopAddRecRewriter Rewriter(SE, Map);
return Rewriter.visit(Scev);
}
const SCEV *visitAddRecExpr(const SCEVAddRecExpr *Expr) {
SmallVector<const SCEV *, 2> Operands;
for (const SCEV *Op : Expr->operands())
Operands.push_back(visit(Op));
const Loop *L = Expr->getLoop();
if (0 == Map.count(L))
return SE.getAddRecExpr(Operands, L, Expr->getNoWrapFlags());
return SCEVAddRecExpr::evaluateAtIteration(Operands, Map[L], SE);
}
private:
LoopToScevMapT ⤅
};
} // end namespace llvm
#endif // LLVM_ANALYSIS_SCALAREVOLUTIONEXPRESSIONS_H
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