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//===---- llvm/Analysis/ScalarEvolutionExpander.h - SCEV Exprs --*- C++ -*-===//
// The LLVM Compiler Infrastructure
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
// This file defines the classes used to generate code from scalar expressions.
#include "llvm/Analysis/ScalarEvolutionExpressions.h"
#include "llvm/Analysis/ScalarEvolutionNormalization.h"
#include "llvm/Analysis/TargetFolder.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/IR/ValueHandle.h"
#include <set>
namespace llvm {
class TargetTransformInfo;
/// Return true if the given expression is safe to expand in the sense that
/// all materialized values are safe to speculate.
bool isSafeToExpand(const SCEV *S, ScalarEvolution &SE);
/// SCEVExpander - This class uses information about analyze scalars to
/// rewrite expressions in canonical form.
/// Clients should create an instance of this class when rewriting is needed,
/// and destroy it when finished to allow the release of the associated
/// memory.
class SCEVExpander : public SCEVVisitor<SCEVExpander, Value*> {
ScalarEvolution &SE;
// New instructions receive a name to identifies them with the current pass.
const char* IVName;
// InsertedExpressions caches Values for reuse, so must track RAUW.
std::map<std::pair<const SCEV *, Instruction *>, TrackingVH<Value> >
// InsertedValues only flags inserted instructions so needs no RAUW.
std::set<AssertingVH<Value> > InsertedValues;
std::set<AssertingVH<Value> > InsertedPostIncValues;
/// RelevantLoops - A memoization of the "relevant" loop for a given SCEV.
DenseMap<const SCEV *, const Loop *> RelevantLoops;
/// PostIncLoops - Addrecs referring to any of the given loops are expanded
/// in post-inc mode. For example, expanding {1,+,1}<L> in post-inc mode
/// returns the add instruction that adds one to the phi for {0,+,1}<L>,
/// as opposed to a new phi starting at 1. This is only supported in
/// non-canonical mode.
PostIncLoopSet PostIncLoops;
/// IVIncInsertPos - When this is non-null, addrecs expanded in the
/// loop it indicates should be inserted with increments at
/// IVIncInsertPos.
const Loop *IVIncInsertLoop;
/// IVIncInsertPos - When expanding addrecs in the IVIncInsertLoop loop,
/// insert the IV increment at this position.
Instruction *IVIncInsertPos;
/// Phis that complete an IV chain. Reuse
std::set<AssertingVH<PHINode> > ChainedPhis;
/// CanonicalMode - When true, expressions are expanded in "canonical"
/// form. In particular, addrecs are expanded as arithmetic based on
/// a canonical induction variable. When false, expression are expanded
/// in a more literal form.
bool CanonicalMode;
/// When invoked from LSR, the expander is in "strength reduction" mode. The
/// only difference is that phi's are only reused if they are already in
/// "expanded" form.
bool LSRMode;
typedef IRBuilder<true, TargetFolder> BuilderType;
BuilderType Builder;
#ifndef NDEBUG
const char *DebugType;
friend struct SCEVVisitor<SCEVExpander, Value*>;
/// SCEVExpander - Construct a SCEVExpander in "canonical" mode.
explicit SCEVExpander(ScalarEvolution &se, const char *name)
: SE(se), IVName(name), IVIncInsertLoop(nullptr), IVIncInsertPos(nullptr),
CanonicalMode(true), LSRMode(false),
Builder(se.getContext(), TargetFolder(se.DL)) {
#ifndef NDEBUG
DebugType = "";
#ifndef NDEBUG
void setDebugType(const char* s) { DebugType = s; }
/// clear - Erase the contents of the InsertedExpressions map so that users
/// trying to expand the same expression into multiple BasicBlocks or
/// different places within the same BasicBlock can do so.
void clear() {
/// getOrInsertCanonicalInductionVariable - This method returns the
/// canonical induction variable of the specified type for the specified
/// loop (inserting one if there is none). A canonical induction variable
/// starts at zero and steps by one on each iteration.
PHINode *getOrInsertCanonicalInductionVariable(const Loop *L, Type *Ty);
/// getIVIncOperand - Return the induction variable increment's IV operand.
Instruction *getIVIncOperand(Instruction *IncV, Instruction *InsertPos,
bool allowScale);
/// hoistIVInc - Utility for hoisting an IV increment.
bool hoistIVInc(Instruction *IncV, Instruction *InsertPos);
/// replaceCongruentIVs - replace congruent phis with their most canonical
/// representative. Return the number of phis eliminated.
unsigned replaceCongruentIVs(Loop *L, const DominatorTree *DT,
SmallVectorImpl<WeakVH> &DeadInsts,
const TargetTransformInfo *TTI = nullptr);
/// expandCodeFor - Insert code to directly compute the specified SCEV
/// expression into the program. The inserted code is inserted into the
/// specified block.
Value *expandCodeFor(const SCEV *SH, Type *Ty, Instruction *I);
/// setIVIncInsertPos - Set the current IV increment loop and position.
void setIVIncInsertPos(const Loop *L, Instruction *Pos) {
assert(!CanonicalMode &&
"IV increment positions are not supported in CanonicalMode");
IVIncInsertLoop = L;
IVIncInsertPos = Pos;
/// setPostInc - Enable post-inc expansion for addrecs referring to the
/// given loops. Post-inc expansion is only supported in non-canonical
/// mode.
void setPostInc(const PostIncLoopSet &L) {
assert(!CanonicalMode &&
"Post-inc expansion is not supported in CanonicalMode");
PostIncLoops = L;
/// clearPostInc - Disable all post-inc expansion.
void clearPostInc() {
// When we change the post-inc loop set, cached expansions may no
// longer be valid.
/// disableCanonicalMode - Disable the behavior of expanding expressions in
/// canonical form rather than in a more literal form. Non-canonical mode
/// is useful for late optimization passes.
void disableCanonicalMode() { CanonicalMode = false; }
void enableLSRMode() { LSRMode = true; }
/// clearInsertPoint - Clear the current insertion point. This is useful
/// if the instruction that had been serving as the insertion point may
/// have been deleted.
void clearInsertPoint() {
/// isInsertedInstruction - Return true if the specified instruction was
/// inserted by the code rewriter. If so, the client should not modify the
/// instruction.
bool isInsertedInstruction(Instruction *I) const {
return InsertedValues.count(I) || InsertedPostIncValues.count(I);
void setChainedPhi(PHINode *PN) { ChainedPhis.insert(PN); }
LLVMContext &getContext() const { return SE.getContext(); }
/// InsertBinop - Insert the specified binary operator, doing a small amount
/// of work to avoid inserting an obviously redundant operation.
Value *InsertBinop(Instruction::BinaryOps Opcode, Value *LHS, Value *RHS);
/// ReuseOrCreateCast - Arange for there to be a cast of V to Ty at IP,
/// reusing an existing cast if a suitable one exists, moving an existing
/// cast if a suitable one exists but isn't in the right place, or
/// or creating a new one.
Value *ReuseOrCreateCast(Value *V, Type *Ty,
Instruction::CastOps Op,
BasicBlock::iterator IP);
/// InsertNoopCastOfTo - Insert a cast of V to the specified type,
/// which must be possible with a noop cast, doing what we can to
/// share the casts.
Value *InsertNoopCastOfTo(Value *V, Type *Ty);
/// expandAddToGEP - Expand a SCEVAddExpr with a pointer type into a GEP
/// instead of using ptrtoint+arithmetic+inttoptr.
Value *expandAddToGEP(const SCEV *const *op_begin,
const SCEV *const *op_end,
PointerType *PTy, Type *Ty, Value *V);
Value *expand(const SCEV *S);
/// expandCodeFor - Insert code to directly compute the specified SCEV
/// expression into the program. The inserted code is inserted into the
/// SCEVExpander's current insertion point. If a type is specified, the
/// result will be expanded to have that type, with a cast if necessary.
Value *expandCodeFor(const SCEV *SH, Type *Ty = nullptr);
/// getRelevantLoop - Determine the most "relevant" loop for the given SCEV.
const Loop *getRelevantLoop(const SCEV *);
Value *visitConstant(const SCEVConstant *S) {
return S->getValue();
Value *visitTruncateExpr(const SCEVTruncateExpr *S);
Value *visitZeroExtendExpr(const SCEVZeroExtendExpr *S);
Value *visitSignExtendExpr(const SCEVSignExtendExpr *S);
Value *visitAddExpr(const SCEVAddExpr *S);
Value *visitMulExpr(const SCEVMulExpr *S);
Value *visitUDivExpr(const SCEVUDivExpr *S);
Value *visitAddRecExpr(const SCEVAddRecExpr *S);
Value *visitSMaxExpr(const SCEVSMaxExpr *S);
Value *visitUMaxExpr(const SCEVUMaxExpr *S);
Value *visitUnknown(const SCEVUnknown *S) {
return S->getValue();
void rememberInstruction(Value *I);
bool isNormalAddRecExprPHI(PHINode *PN, Instruction *IncV, const Loop *L);
bool isExpandedAddRecExprPHI(PHINode *PN, Instruction *IncV, const Loop *L);
Value *expandAddRecExprLiterally(const SCEVAddRecExpr *);
PHINode *getAddRecExprPHILiterally(const SCEVAddRecExpr *Normalized,
const Loop *L,
Type *ExpandTy,
Type *IntTy,
Type *&TruncTy,
bool &InvertStep);
Value *expandIVInc(PHINode *PN, Value *StepV, const Loop *L,
Type *ExpandTy, Type *IntTy, bool useSubtract);