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llvm-6502/lib/Analysis/ScalarEvolutionExpander.cpp
Dan Gohman 4d8414f420 Teach SCEVExpander's visitAddRecExpr to reuse an existing canonical 
induction variable when the addrec to be expanded does not require
a wider type. This eliminates the need for IndVarSimplify to
micro-manage SCEV expansions, because SCEVExpander now
automatically expands them in the form that IndVarSimplify considers
to be canonical. (LSR still micro-manages its SCEV expansions,
because it's optimizing for the target, rather than for
other optimizations.)

Also, this uses the new getAnyExtendExpr, which has more clever
expression simplification logic than the IndVarSimplify code it
replaces, and this cleans up some ugly expansions in code such as
the included masked-iv.ll testcase.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@73294 91177308-0d34-0410-b5e6-96231b3b80d8
2009-06-13 16:25:49 +00:00

692 lines
27 KiB
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//===- ScalarEvolutionExpander.cpp - Scalar Evolution Analysis --*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file contains the implementation of the scalar evolution expander,
// which is used to generate the code corresponding to a given scalar evolution
// expression.
//
//===----------------------------------------------------------------------===//
#include "llvm/Analysis/ScalarEvolutionExpander.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Target/TargetData.h"
#include "llvm/ADT/STLExtras.h"
using namespace llvm;
/// InsertCastOfTo - Insert a cast of V to the specified type, doing what
/// we can to share the casts.
Value *SCEVExpander::InsertCastOfTo(Instruction::CastOps opcode, Value *V,
const Type *Ty) {
// Short-circuit unnecessary bitcasts.
if (opcode == Instruction::BitCast && V->getType() == Ty)
return V;
// Short-circuit unnecessary inttoptr<->ptrtoint casts.
if ((opcode == Instruction::PtrToInt || opcode == Instruction::IntToPtr) &&
SE.getTypeSizeInBits(Ty) == SE.getTypeSizeInBits(V->getType())) {
if (CastInst *CI = dyn_cast<CastInst>(V))
if ((CI->getOpcode() == Instruction::PtrToInt ||
CI->getOpcode() == Instruction::IntToPtr) &&
SE.getTypeSizeInBits(CI->getType()) ==
SE.getTypeSizeInBits(CI->getOperand(0)->getType()))
return CI->getOperand(0);
if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V))
if ((CE->getOpcode() == Instruction::PtrToInt ||
CE->getOpcode() == Instruction::IntToPtr) &&
SE.getTypeSizeInBits(CE->getType()) ==
SE.getTypeSizeInBits(CE->getOperand(0)->getType()))
return CE->getOperand(0);
}
// FIXME: keep track of the cast instruction.
if (Constant *C = dyn_cast<Constant>(V))
return ConstantExpr::getCast(opcode, C, Ty);
if (Argument *A = dyn_cast<Argument>(V)) {
// Check to see if there is already a cast!
for (Value::use_iterator UI = A->use_begin(), E = A->use_end();
UI != E; ++UI) {
if ((*UI)->getType() == Ty)
if (CastInst *CI = dyn_cast<CastInst>(cast<Instruction>(*UI)))
if (CI->getOpcode() == opcode) {
// If the cast isn't the first instruction of the function, move it.
if (BasicBlock::iterator(CI) !=
A->getParent()->getEntryBlock().begin()) {
// If the CastInst is the insert point, change the insert point.
if (CI == InsertPt) ++InsertPt;
// Splice the cast at the beginning of the entry block.
CI->moveBefore(A->getParent()->getEntryBlock().begin());
}
return CI;
}
}
Instruction *I = CastInst::Create(opcode, V, Ty, V->getName(),
A->getParent()->getEntryBlock().begin());
InsertedValues.insert(I);
return I;
}
Instruction *I = cast<Instruction>(V);
// Check to see if there is already a cast. If there is, use it.
for (Value::use_iterator UI = I->use_begin(), E = I->use_end();
UI != E; ++UI) {
if ((*UI)->getType() == Ty)
if (CastInst *CI = dyn_cast<CastInst>(cast<Instruction>(*UI)))
if (CI->getOpcode() == opcode) {
BasicBlock::iterator It = I; ++It;
if (isa<InvokeInst>(I))
It = cast<InvokeInst>(I)->getNormalDest()->begin();
while (isa<PHINode>(It)) ++It;
if (It != BasicBlock::iterator(CI)) {
// If the CastInst is the insert point, change the insert point.
if (CI == InsertPt) ++InsertPt;
// Splice the cast immediately after the operand in question.
CI->moveBefore(It);
}
return CI;
}
}
BasicBlock::iterator IP = I; ++IP;
if (InvokeInst *II = dyn_cast<InvokeInst>(I))
IP = II->getNormalDest()->begin();
while (isa<PHINode>(IP)) ++IP;
Instruction *CI = CastInst::Create(opcode, V, Ty, V->getName(), IP);
InsertedValues.insert(CI);
return CI;
}
/// InsertNoopCastOfTo - Insert a cast of V to the specified type,
/// which must be possible with a noop cast.
Value *SCEVExpander::InsertNoopCastOfTo(Value *V, const Type *Ty) {
Instruction::CastOps Op = CastInst::getCastOpcode(V, false, Ty, false);
assert((Op == Instruction::BitCast ||
Op == Instruction::PtrToInt ||
Op == Instruction::IntToPtr) &&
"InsertNoopCastOfTo cannot perform non-noop casts!");
assert(SE.getTypeSizeInBits(V->getType()) == SE.getTypeSizeInBits(Ty) &&
"InsertNoopCastOfTo cannot change sizes!");
return InsertCastOfTo(Op, V, Ty);
}
/// InsertBinop - Insert the specified binary operator, doing a small amount
/// of work to avoid inserting an obviously redundant operation.
Value *SCEVExpander::InsertBinop(Instruction::BinaryOps Opcode, Value *LHS,
Value *RHS, BasicBlock::iterator InsertPt) {
// Fold a binop with constant operands.
if (Constant *CLHS = dyn_cast<Constant>(LHS))
if (Constant *CRHS = dyn_cast<Constant>(RHS))
return ConstantExpr::get(Opcode, CLHS, CRHS);
// Do a quick scan to see if we have this binop nearby. If so, reuse it.
unsigned ScanLimit = 6;
BasicBlock::iterator BlockBegin = InsertPt->getParent()->begin();
if (InsertPt != BlockBegin) {
// Scanning starts from the last instruction before InsertPt.
BasicBlock::iterator IP = InsertPt;
--IP;
for (; ScanLimit; --IP, --ScanLimit) {
if (IP->getOpcode() == (unsigned)Opcode && IP->getOperand(0) == LHS &&
IP->getOperand(1) == RHS)
return IP;
if (IP == BlockBegin) break;
}
}
// If we haven't found this binop, insert it.
Instruction *BO = BinaryOperator::Create(Opcode, LHS, RHS, "tmp", InsertPt);
InsertedValues.insert(BO);
return BO;
}
/// FactorOutConstant - Test if S is divisible by Factor, using signed
/// division. If so, update S with Factor divided out and return true.
/// S need not be evenly divisble if a reasonable remainder can be
/// computed.
/// TODO: When ScalarEvolution gets a SCEVSDivExpr, this can be made
/// unnecessary; in its place, just signed-divide Ops[i] by the scale and
/// check to see if the divide was folded.
static bool FactorOutConstant(SCEVHandle &S,
SCEVHandle &Remainder,
const APInt &Factor,
ScalarEvolution &SE) {
// Everything is divisible by one.
if (Factor == 1)
return true;
// For a Constant, check for a multiple of the given factor.
if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S)) {
ConstantInt *CI =
ConstantInt::get(C->getValue()->getValue().sdiv(Factor));
// If the quotient is zero and the remainder is non-zero, reject
// the value at this scale. It will be considered for subsequent
// smaller scales.
if (C->isZero() || !CI->isZero()) {
SCEVHandle Div = SE.getConstant(CI);
S = Div;
Remainder =
SE.getAddExpr(Remainder,
SE.getConstant(C->getValue()->getValue().srem(Factor)));
return true;
}
}
// In a Mul, check if there is a constant operand which is a multiple
// of the given factor.
if (const SCEVMulExpr *M = dyn_cast<SCEVMulExpr>(S))
if (const SCEVConstant *C = dyn_cast<SCEVConstant>(M->getOperand(0)))
if (!C->getValue()->getValue().srem(Factor)) {
std::vector<SCEVHandle> NewMulOps(M->getOperands());
NewMulOps[0] =
SE.getConstant(C->getValue()->getValue().sdiv(Factor));
S = SE.getMulExpr(NewMulOps);
return true;
}
// In an AddRec, check if both start and step are divisible.
if (const SCEVAddRecExpr *A = dyn_cast<SCEVAddRecExpr>(S)) {
SCEVHandle Step = A->getStepRecurrence(SE);
SCEVHandle StepRem = SE.getIntegerSCEV(0, Step->getType());
if (!FactorOutConstant(Step, StepRem, Factor, SE))
return false;
if (!StepRem->isZero())
return false;
SCEVHandle Start = A->getStart();
if (!FactorOutConstant(Start, Remainder, Factor, SE))
return false;
S = SE.getAddRecExpr(Start, Step, A->getLoop());
return true;
}
return false;
}
/// expandAddToGEP - Expand a SCEVAddExpr with a pointer type into a GEP
/// instead of using ptrtoint+arithmetic+inttoptr. This helps
/// BasicAliasAnalysis analyze the result. However, it suffers from the
/// underlying bug described in PR2831. Addition in LLVM currently always
/// has two's complement wrapping guaranteed. However, the semantics for
/// getelementptr overflow are ambiguous. In the common case though, this
/// expansion gets used when a GEP in the original code has been converted
/// into integer arithmetic, in which case the resulting code will be no
/// more undefined than it was originally.
///
/// Design note: It might seem desirable for this function to be more
/// loop-aware. If some of the indices are loop-invariant while others
/// aren't, it might seem desirable to emit multiple GEPs, keeping the
/// loop-invariant portions of the overall computation outside the loop.
/// However, there are a few reasons this is not done here. Hoisting simple
/// arithmetic is a low-level optimization that often isn't very
/// important until late in the optimization process. In fact, passes
/// like InstructionCombining will combine GEPs, even if it means
/// pushing loop-invariant computation down into loops, so even if the
/// GEPs were split here, the work would quickly be undone. The
/// LoopStrengthReduction pass, which is usually run quite late (and
/// after the last InstructionCombining pass), takes care of hoisting
/// loop-invariant portions of expressions, after considering what
/// can be folded using target addressing modes.
///
Value *SCEVExpander::expandAddToGEP(const SCEVHandle *op_begin,
const SCEVHandle *op_end,
const PointerType *PTy,
const Type *Ty,
Value *V) {
const Type *ElTy = PTy->getElementType();
SmallVector<Value *, 4> GepIndices;
std::vector<SCEVHandle> Ops(op_begin, op_end);
bool AnyNonZeroIndices = false;
// Decend down the pointer's type and attempt to convert the other
// operands into GEP indices, at each level. The first index in a GEP
// indexes into the array implied by the pointer operand; the rest of
// the indices index into the element or field type selected by the
// preceding index.
for (;;) {
APInt ElSize = APInt(SE.getTypeSizeInBits(Ty),
ElTy->isSized() ? SE.TD->getTypeAllocSize(ElTy) : 0);
std::vector<SCEVHandle> NewOps;
std::vector<SCEVHandle> ScaledOps;
for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
// Split AddRecs up into parts as either of the parts may be usable
// without the other.
if (const SCEVAddRecExpr *A = dyn_cast<SCEVAddRecExpr>(Ops[i]))
if (!A->getStart()->isZero()) {
SCEVHandle Start = A->getStart();
Ops.push_back(SE.getAddRecExpr(SE.getIntegerSCEV(0, A->getType()),
A->getStepRecurrence(SE),
A->getLoop()));
Ops[i] = Start;
++e;
}
// If the scale size is not 0, attempt to factor out a scale.
if (ElSize != 0) {
SCEVHandle Op = Ops[i];
SCEVHandle Remainder = SE.getIntegerSCEV(0, Op->getType());
if (FactorOutConstant(Op, Remainder, ElSize, SE)) {
ScaledOps.push_back(Op); // Op now has ElSize factored out.
NewOps.push_back(Remainder);
continue;
}
}
// If the operand was not divisible, add it to the list of operands
// we'll scan next iteration.
NewOps.push_back(Ops[i]);
}
Ops = NewOps;
AnyNonZeroIndices |= !ScaledOps.empty();
Value *Scaled = ScaledOps.empty() ?
Constant::getNullValue(Ty) :
expandCodeFor(SE.getAddExpr(ScaledOps), Ty);
GepIndices.push_back(Scaled);
// Collect struct field index operands.
if (!Ops.empty())
while (const StructType *STy = dyn_cast<StructType>(ElTy)) {
if (const SCEVConstant *C = dyn_cast<SCEVConstant>(Ops[0]))
if (SE.getTypeSizeInBits(C->getType()) <= 64) {
const StructLayout &SL = *SE.TD->getStructLayout(STy);
uint64_t FullOffset = C->getValue()->getZExtValue();
if (FullOffset < SL.getSizeInBytes()) {
unsigned ElIdx = SL.getElementContainingOffset(FullOffset);
GepIndices.push_back(ConstantInt::get(Type::Int32Ty, ElIdx));
ElTy = STy->getTypeAtIndex(ElIdx);
Ops[0] =
SE.getConstant(ConstantInt::get(Ty,
FullOffset -
SL.getElementOffset(ElIdx)));
AnyNonZeroIndices = true;
continue;
}
}
break;
}
if (const ArrayType *ATy = dyn_cast<ArrayType>(ElTy)) {
ElTy = ATy->getElementType();
continue;
}
break;
}
// If none of the operands were convertable to proper GEP indices, cast
// the base to i8* and do an ugly getelementptr with that. It's still
// better than ptrtoint+arithmetic+inttoptr at least.
if (!AnyNonZeroIndices) {
V = InsertNoopCastOfTo(V,
Type::Int8Ty->getPointerTo(PTy->getAddressSpace()));
Value *Idx = expandCodeFor(SE.getAddExpr(Ops), Ty);
// Fold a GEP with constant operands.
if (Constant *CLHS = dyn_cast<Constant>(V))
if (Constant *CRHS = dyn_cast<Constant>(Idx))
return ConstantExpr::getGetElementPtr(CLHS, &CRHS, 1);
// Do a quick scan to see if we have this GEP nearby. If so, reuse it.
unsigned ScanLimit = 6;
BasicBlock::iterator BlockBegin = InsertPt->getParent()->begin();
if (InsertPt != BlockBegin) {
// Scanning starts from the last instruction before InsertPt.
BasicBlock::iterator IP = InsertPt;
--IP;
for (; ScanLimit; --IP, --ScanLimit) {
if (IP->getOpcode() == Instruction::GetElementPtr &&
IP->getOperand(0) == V && IP->getOperand(1) == Idx)
return IP;
if (IP == BlockBegin) break;
}
}
Value *GEP = GetElementPtrInst::Create(V, Idx, "scevgep", InsertPt);
InsertedValues.insert(GEP);
return GEP;
}
// Insert a pretty getelementptr.
Value *GEP = GetElementPtrInst::Create(V,
GepIndices.begin(),
GepIndices.end(),
"scevgep", InsertPt);
Ops.push_back(SE.getUnknown(GEP));
InsertedValues.insert(GEP);
return expand(SE.getAddExpr(Ops));
}
Value *SCEVExpander::visitAddExpr(const SCEVAddExpr *S) {
const Type *Ty = SE.getEffectiveSCEVType(S->getType());
Value *V = expand(S->getOperand(S->getNumOperands()-1));
// Turn things like ptrtoint+arithmetic+inttoptr into GEP. See the
// comments on expandAddToGEP for details.
if (SE.TD)
if (const PointerType *PTy = dyn_cast<PointerType>(V->getType())) {
const std::vector<SCEVHandle> &Ops = S->getOperands();
return expandAddToGEP(&Ops[0], &Ops[Ops.size() - 1],
PTy, Ty, V);
}
V = InsertNoopCastOfTo(V, Ty);
// Emit a bunch of add instructions
for (int i = S->getNumOperands()-2; i >= 0; --i) {
Value *W = expandCodeFor(S->getOperand(i), Ty);
V = InsertBinop(Instruction::Add, V, W, InsertPt);
}
return V;
}
Value *SCEVExpander::visitMulExpr(const SCEVMulExpr *S) {
const Type *Ty = SE.getEffectiveSCEVType(S->getType());
int FirstOp = 0; // Set if we should emit a subtract.
if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(S->getOperand(0)))
if (SC->getValue()->isAllOnesValue())
FirstOp = 1;
int i = S->getNumOperands()-2;
Value *V = expandCodeFor(S->getOperand(i+1), Ty);
// Emit a bunch of multiply instructions
for (; i >= FirstOp; --i) {
Value *W = expandCodeFor(S->getOperand(i), Ty);
V = InsertBinop(Instruction::Mul, V, W, InsertPt);
}
// -1 * ... ---> 0 - ...
if (FirstOp == 1)
V = InsertBinop(Instruction::Sub, Constant::getNullValue(Ty), V, InsertPt);
return V;
}
Value *SCEVExpander::visitUDivExpr(const SCEVUDivExpr *S) {
const Type *Ty = SE.getEffectiveSCEVType(S->getType());
Value *LHS = expandCodeFor(S->getLHS(), Ty);
if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(S->getRHS())) {
const APInt &RHS = SC->getValue()->getValue();
if (RHS.isPowerOf2())
return InsertBinop(Instruction::LShr, LHS,
ConstantInt::get(Ty, RHS.logBase2()),
InsertPt);
}
Value *RHS = expandCodeFor(S->getRHS(), Ty);
return InsertBinop(Instruction::UDiv, LHS, RHS, InsertPt);
}
/// Move parts of Base into Rest to leave Base with the minimal
/// expression that provides a pointer operand suitable for a
/// GEP expansion.
static void ExposePointerBase(SCEVHandle &Base, SCEVHandle &Rest,
ScalarEvolution &SE) {
while (const SCEVAddRecExpr *A = dyn_cast<SCEVAddRecExpr>(Base)) {
Base = A->getStart();
Rest = SE.getAddExpr(Rest,
SE.getAddRecExpr(SE.getIntegerSCEV(0, A->getType()),
A->getStepRecurrence(SE),
A->getLoop()));
}
if (const SCEVAddExpr *A = dyn_cast<SCEVAddExpr>(Base)) {
Base = A->getOperand(A->getNumOperands()-1);
std::vector<SCEVHandle> NewAddOps(A->op_begin(), A->op_end());
NewAddOps.back() = Rest;
Rest = SE.getAddExpr(NewAddOps);
ExposePointerBase(Base, Rest, SE);
}
}
Value *SCEVExpander::visitAddRecExpr(const SCEVAddRecExpr *S) {
const Type *Ty = SE.getEffectiveSCEVType(S->getType());
const Loop *L = S->getLoop();
// First check for an existing canonical IV in a suitable type.
PHINode *CanonicalIV = 0;
if (PHINode *PN = L->getCanonicalInductionVariable())
if (SE.isSCEVable(PN->getType()) &&
isa<IntegerType>(SE.getEffectiveSCEVType(PN->getType())) &&
SE.getTypeSizeInBits(PN->getType()) >= SE.getTypeSizeInBits(Ty))
CanonicalIV = PN;
// Rewrite an AddRec in terms of the canonical induction variable, if
// its type is more narrow.
if (CanonicalIV &&
SE.getTypeSizeInBits(CanonicalIV->getType()) >
SE.getTypeSizeInBits(Ty)) {
SCEVHandle Start = SE.getAnyExtendExpr(S->getStart(),
CanonicalIV->getType());
SCEVHandle Step = SE.getAnyExtendExpr(S->getStepRecurrence(SE),
CanonicalIV->getType());
Value *V = expand(SE.getAddRecExpr(Start, Step, S->getLoop()));
BasicBlock::iterator SaveInsertPt = getInsertionPoint();
BasicBlock::iterator NewInsertPt =
next(BasicBlock::iterator(cast<Instruction>(V)));
while (isa<PHINode>(NewInsertPt)) ++NewInsertPt;
V = expandCodeFor(SE.getTruncateExpr(SE.getUnknown(V), Ty), 0,
NewInsertPt);
setInsertionPoint(SaveInsertPt);
return V;
}
// {X,+,F} --> X + {0,+,F}
if (!S->getStart()->isZero()) {
std::vector<SCEVHandle> NewOps(S->getOperands());
NewOps[0] = SE.getIntegerSCEV(0, Ty);
SCEVHandle Rest = SE.getAddRecExpr(NewOps, L);
// Turn things like ptrtoint+arithmetic+inttoptr into GEP. See the
// comments on expandAddToGEP for details.
if (SE.TD) {
SCEVHandle Base = S->getStart();
SCEVHandle RestArray[1] = { Rest };
// Dig into the expression to find the pointer base for a GEP.
ExposePointerBase(Base, RestArray[0], SE);
// If we found a pointer, expand the AddRec with a GEP.
if (const PointerType *PTy = dyn_cast<PointerType>(Base->getType())) {
// Make sure the Base isn't something exotic, such as a multiplied
// or divided pointer value. In those cases, the result type isn't
// actually a pointer type.
if (!isa<SCEVMulExpr>(Base) && !isa<SCEVUDivExpr>(Base)) {
Value *StartV = expand(Base);
assert(StartV->getType() == PTy && "Pointer type mismatch for GEP!");
return expandAddToGEP(RestArray, RestArray+1, PTy, Ty, StartV);
}
}
}
Value *RestV = expand(Rest);
return expand(SE.getAddExpr(S->getStart(), SE.getUnknown(RestV)));
}
// {0,+,1} --> Insert a canonical induction variable into the loop!
if (S->isAffine() &&
S->getOperand(1) == SE.getIntegerSCEV(1, Ty)) {
// If there's a canonical IV, just use it.
if (CanonicalIV) {
assert(Ty == SE.getEffectiveSCEVType(CanonicalIV->getType()) &&
"IVs with types different from the canonical IV should "
"already have been handled!");
return CanonicalIV;
}
// Create and insert the PHI node for the induction variable in the
// specified loop.
BasicBlock *Header = L->getHeader();
PHINode *PN = PHINode::Create(Ty, "indvar", Header->begin());
InsertedValues.insert(PN);
PN->addIncoming(Constant::getNullValue(Ty), L->getLoopPreheader());
pred_iterator HPI = pred_begin(Header);
assert(HPI != pred_end(Header) && "Loop with zero preds???");
if (!L->contains(*HPI)) ++HPI;
assert(HPI != pred_end(Header) && L->contains(*HPI) &&
"No backedge in loop?");
// Insert a unit add instruction right before the terminator corresponding
// to the back-edge.
Constant *One = ConstantInt::get(Ty, 1);
Instruction *Add = BinaryOperator::CreateAdd(PN, One, "indvar.next",
(*HPI)->getTerminator());
InsertedValues.insert(Add);
pred_iterator PI = pred_begin(Header);
if (*PI == L->getLoopPreheader())
++PI;
PN->addIncoming(Add, *PI);
return PN;
}
// {0,+,F} --> {0,+,1} * F
// Get the canonical induction variable I for this loop.
Value *I = CanonicalIV ?
CanonicalIV :
getOrInsertCanonicalInductionVariable(L, Ty);
// If this is a simple linear addrec, emit it now as a special case.
if (S->isAffine()) { // {0,+,F} --> i*F
Value *F = expandCodeFor(S->getOperand(1), Ty);
// If the insert point is directly inside of the loop, emit the multiply at
// the insert point. Otherwise, L is a loop that is a parent of the insert
// point loop. If we can, move the multiply to the outer most loop that it
// is safe to be in.
BasicBlock::iterator MulInsertPt = getInsertionPoint();
Loop *InsertPtLoop = SE.LI->getLoopFor(MulInsertPt->getParent());
if (InsertPtLoop != L && InsertPtLoop &&
L->contains(InsertPtLoop->getHeader())) {
do {
// If we cannot hoist the multiply out of this loop, don't.
if (!InsertPtLoop->isLoopInvariant(F)) break;
BasicBlock *InsertPtLoopPH = InsertPtLoop->getLoopPreheader();
// If this loop hasn't got a preheader, we aren't able to hoist the
// multiply.
if (!InsertPtLoopPH)
break;
// Otherwise, move the insert point to the preheader.
MulInsertPt = InsertPtLoopPH->getTerminator();
InsertPtLoop = InsertPtLoop->getParentLoop();
} while (InsertPtLoop != L);
}
return InsertBinop(Instruction::Mul, I, F, MulInsertPt);
}
// If this is a chain of recurrences, turn it into a closed form, using the
// folders, then expandCodeFor the closed form. This allows the folders to
// simplify the expression without having to build a bunch of special code
// into this folder.
SCEVHandle IH = SE.getUnknown(I); // Get I as a "symbolic" SCEV.
// Promote S up to the canonical IV type, if the cast is foldable.
SCEVHandle NewS = S;
SCEVHandle Ext = SE.getNoopOrAnyExtend(S, I->getType());
if (isa<SCEVAddRecExpr>(Ext))
NewS = Ext;
SCEVHandle V = cast<SCEVAddRecExpr>(NewS)->evaluateAtIteration(IH, SE);
//cerr << "Evaluated: " << *this << "\n to: " << *V << "\n";
// Truncate the result down to the original type, if needed.
SCEVHandle T = SE.getTruncateOrNoop(V, Ty);
return expand(V);
}
Value *SCEVExpander::visitTruncateExpr(const SCEVTruncateExpr *S) {
const Type *Ty = SE.getEffectiveSCEVType(S->getType());
Value *V = expandCodeFor(S->getOperand(),
SE.getEffectiveSCEVType(S->getOperand()->getType()));
Instruction *I = new TruncInst(V, Ty, "tmp.", InsertPt);
InsertedValues.insert(I);
return I;
}
Value *SCEVExpander::visitZeroExtendExpr(const SCEVZeroExtendExpr *S) {
const Type *Ty = SE.getEffectiveSCEVType(S->getType());
Value *V = expandCodeFor(S->getOperand(),
SE.getEffectiveSCEVType(S->getOperand()->getType()));
Instruction *I = new ZExtInst(V, Ty, "tmp.", InsertPt);
InsertedValues.insert(I);
return I;
}
Value *SCEVExpander::visitSignExtendExpr(const SCEVSignExtendExpr *S) {
const Type *Ty = SE.getEffectiveSCEVType(S->getType());
Value *V = expandCodeFor(S->getOperand(),
SE.getEffectiveSCEVType(S->getOperand()->getType()));
Instruction *I = new SExtInst(V, Ty, "tmp.", InsertPt);
InsertedValues.insert(I);
return I;
}
Value *SCEVExpander::visitSMaxExpr(const SCEVSMaxExpr *S) {
const Type *Ty = SE.getEffectiveSCEVType(S->getType());
Value *LHS = expandCodeFor(S->getOperand(0), Ty);
for (unsigned i = 1; i < S->getNumOperands(); ++i) {
Value *RHS = expandCodeFor(S->getOperand(i), Ty);
Instruction *ICmp =
new ICmpInst(ICmpInst::ICMP_SGT, LHS, RHS, "tmp", InsertPt);
InsertedValues.insert(ICmp);
Instruction *Sel = SelectInst::Create(ICmp, LHS, RHS, "smax", InsertPt);
InsertedValues.insert(Sel);
LHS = Sel;
}
return LHS;
}
Value *SCEVExpander::visitUMaxExpr(const SCEVUMaxExpr *S) {
const Type *Ty = SE.getEffectiveSCEVType(S->getType());
Value *LHS = expandCodeFor(S->getOperand(0), Ty);
for (unsigned i = 1; i < S->getNumOperands(); ++i) {
Value *RHS = expandCodeFor(S->getOperand(i), Ty);
Instruction *ICmp =
new ICmpInst(ICmpInst::ICMP_UGT, LHS, RHS, "tmp", InsertPt);
InsertedValues.insert(ICmp);
Instruction *Sel = SelectInst::Create(ICmp, LHS, RHS, "umax", InsertPt);
InsertedValues.insert(Sel);
LHS = Sel;
}
return LHS;
}
Value *SCEVExpander::expandCodeFor(SCEVHandle SH, const Type *Ty) {
// Expand the code for this SCEV.
Value *V = expand(SH);
if (Ty) {
assert(SE.getTypeSizeInBits(Ty) == SE.getTypeSizeInBits(SH->getType()) &&
"non-trivial casts should be done with the SCEVs directly!");
V = InsertNoopCastOfTo(V, Ty);
}
return V;
}
Value *SCEVExpander::expand(const SCEV *S) {
// Check to see if we already expanded this.
std::map<SCEVHandle, AssertingVH<Value> >::iterator I =
InsertedExpressions.find(S);
if (I != InsertedExpressions.end())
return I->second;
Value *V = visit(S);
InsertedExpressions[S] = V;
return V;
}
/// 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.
Value *
SCEVExpander::getOrInsertCanonicalInductionVariable(const Loop *L,
const Type *Ty) {
assert(Ty->isInteger() && "Can only insert integer induction variables!");
SCEVHandle H = SE.getAddRecExpr(SE.getIntegerSCEV(0, Ty),
SE.getIntegerSCEV(1, Ty), L);
return expand(H);
}
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