2247 lines
88 KiB
C++
2247 lines
88 KiB
C++
//===- ScalarEvolutionExpander.cpp - Scalar Evolution Analysis ------------===//
|
|
//
|
|
// 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/ADT/STLExtras.h"
|
|
#include "llvm/ADT/SmallSet.h"
|
|
#include "llvm/Analysis/InstructionSimplify.h"
|
|
#include "llvm/Analysis/LoopInfo.h"
|
|
#include "llvm/Analysis/TargetTransformInfo.h"
|
|
#include "llvm/IR/DataLayout.h"
|
|
#include "llvm/IR/Dominators.h"
|
|
#include "llvm/IR/IntrinsicInst.h"
|
|
#include "llvm/IR/LLVMContext.h"
|
|
#include "llvm/IR/Module.h"
|
|
#include "llvm/IR/PatternMatch.h"
|
|
#include "llvm/Support/Debug.h"
|
|
#include "llvm/Support/raw_ostream.h"
|
|
|
|
using namespace llvm;
|
|
using namespace PatternMatch;
|
|
|
|
/// ReuseOrCreateCast - Arrange 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
|
|
/// creating a new one.
|
|
Value *SCEVExpander::ReuseOrCreateCast(Value *V, Type *Ty,
|
|
Instruction::CastOps Op,
|
|
BasicBlock::iterator IP) {
|
|
// This function must be called with the builder having a valid insertion
|
|
// point. It doesn't need to be the actual IP where the uses of the returned
|
|
// cast will be added, but it must dominate such IP.
|
|
// We use this precondition to produce a cast that will dominate all its
|
|
// uses. In particular, this is crucial for the case where the builder's
|
|
// insertion point *is* the point where we were asked to put the cast.
|
|
// Since we don't know the builder's insertion point is actually
|
|
// where the uses will be added (only that it dominates it), we are
|
|
// not allowed to move it.
|
|
BasicBlock::iterator BIP = Builder.GetInsertPoint();
|
|
|
|
Instruction *Ret = nullptr;
|
|
|
|
// Check to see if there is already a cast!
|
|
for (User *U : V->users())
|
|
if (U->getType() == Ty)
|
|
if (CastInst *CI = dyn_cast<CastInst>(U))
|
|
if (CI->getOpcode() == Op) {
|
|
// If the cast isn't where we want it, create a new cast at IP.
|
|
// Likewise, do not reuse a cast at BIP because it must dominate
|
|
// instructions that might be inserted before BIP.
|
|
if (BasicBlock::iterator(CI) != IP || BIP == IP) {
|
|
// Create a new cast, and leave the old cast in place in case
|
|
// it is being used as an insert point. Clear its operand
|
|
// so that it doesn't hold anything live.
|
|
Ret = CastInst::Create(Op, V, Ty, "", &*IP);
|
|
Ret->takeName(CI);
|
|
CI->replaceAllUsesWith(Ret);
|
|
CI->setOperand(0, UndefValue::get(V->getType()));
|
|
break;
|
|
}
|
|
Ret = CI;
|
|
break;
|
|
}
|
|
|
|
// Create a new cast.
|
|
if (!Ret)
|
|
Ret = CastInst::Create(Op, V, Ty, V->getName(), &*IP);
|
|
|
|
// We assert at the end of the function since IP might point to an
|
|
// instruction with different dominance properties than a cast
|
|
// (an invoke for example) and not dominate BIP (but the cast does).
|
|
assert(SE.DT.dominates(Ret, &*BIP));
|
|
|
|
rememberInstruction(Ret);
|
|
return Ret;
|
|
}
|
|
|
|
static BasicBlock::iterator findInsertPointAfter(Instruction *I,
|
|
BasicBlock *MustDominate) {
|
|
BasicBlock::iterator IP = ++I->getIterator();
|
|
if (auto *II = dyn_cast<InvokeInst>(I))
|
|
IP = II->getNormalDest()->begin();
|
|
|
|
while (isa<PHINode>(IP))
|
|
++IP;
|
|
|
|
if (isa<FuncletPadInst>(IP) || isa<LandingPadInst>(IP)) {
|
|
++IP;
|
|
} else if (isa<CatchSwitchInst>(IP)) {
|
|
IP = MustDominate->getFirstInsertionPt();
|
|
} else {
|
|
assert(!IP->isEHPad() && "unexpected eh pad!");
|
|
}
|
|
|
|
return 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 *SCEVExpander::InsertNoopCastOfTo(Value *V, 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!");
|
|
|
|
// Short-circuit unnecessary bitcasts.
|
|
if (Op == Instruction::BitCast) {
|
|
if (V->getType() == Ty)
|
|
return V;
|
|
if (CastInst *CI = dyn_cast<CastInst>(V)) {
|
|
if (CI->getOperand(0)->getType() == Ty)
|
|
return CI->getOperand(0);
|
|
}
|
|
}
|
|
// Short-circuit unnecessary inttoptr<->ptrtoint casts.
|
|
if ((Op == Instruction::PtrToInt || Op == 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);
|
|
}
|
|
|
|
// Fold a cast of a constant.
|
|
if (Constant *C = dyn_cast<Constant>(V))
|
|
return ConstantExpr::getCast(Op, C, Ty);
|
|
|
|
// Cast the argument at the beginning of the entry block, after
|
|
// any bitcasts of other arguments.
|
|
if (Argument *A = dyn_cast<Argument>(V)) {
|
|
BasicBlock::iterator IP = A->getParent()->getEntryBlock().begin();
|
|
while ((isa<BitCastInst>(IP) &&
|
|
isa<Argument>(cast<BitCastInst>(IP)->getOperand(0)) &&
|
|
cast<BitCastInst>(IP)->getOperand(0) != A) ||
|
|
isa<DbgInfoIntrinsic>(IP))
|
|
++IP;
|
|
return ReuseOrCreateCast(A, Ty, Op, IP);
|
|
}
|
|
|
|
// Cast the instruction immediately after the instruction.
|
|
Instruction *I = cast<Instruction>(V);
|
|
BasicBlock::iterator IP = findInsertPointAfter(I, Builder.GetInsertBlock());
|
|
return ReuseOrCreateCast(I, Ty, Op, IP);
|
|
}
|
|
|
|
/// 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) {
|
|
// 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 = Builder.GetInsertBlock()->begin();
|
|
// Scanning starts from the last instruction before the insertion point.
|
|
BasicBlock::iterator IP = Builder.GetInsertPoint();
|
|
if (IP != BlockBegin) {
|
|
--IP;
|
|
for (; ScanLimit; --IP, --ScanLimit) {
|
|
// Don't count dbg.value against the ScanLimit, to avoid perturbing the
|
|
// generated code.
|
|
if (isa<DbgInfoIntrinsic>(IP))
|
|
ScanLimit++;
|
|
if (IP->getOpcode() == (unsigned)Opcode && IP->getOperand(0) == LHS &&
|
|
IP->getOperand(1) == RHS)
|
|
return &*IP;
|
|
if (IP == BlockBegin) break;
|
|
}
|
|
}
|
|
|
|
// Save the original insertion point so we can restore it when we're done.
|
|
DebugLoc Loc = Builder.GetInsertPoint()->getDebugLoc();
|
|
SCEVInsertPointGuard Guard(Builder, this);
|
|
|
|
// Move the insertion point out of as many loops as we can.
|
|
while (const Loop *L = SE.LI.getLoopFor(Builder.GetInsertBlock())) {
|
|
if (!L->isLoopInvariant(LHS) || !L->isLoopInvariant(RHS)) break;
|
|
BasicBlock *Preheader = L->getLoopPreheader();
|
|
if (!Preheader) break;
|
|
|
|
// Ok, move up a level.
|
|
Builder.SetInsertPoint(Preheader->getTerminator());
|
|
}
|
|
|
|
// If we haven't found this binop, insert it.
|
|
Instruction *BO = cast<Instruction>(Builder.CreateBinOp(Opcode, LHS, RHS));
|
|
BO->setDebugLoc(Loc);
|
|
rememberInstruction(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 divisible 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(const SCEV *&S, const SCEV *&Remainder,
|
|
const SCEV *Factor, ScalarEvolution &SE,
|
|
const DataLayout &DL) {
|
|
// Everything is divisible by one.
|
|
if (Factor->isOne())
|
|
return true;
|
|
|
|
// x/x == 1.
|
|
if (S == Factor) {
|
|
S = SE.getConstant(S->getType(), 1);
|
|
return true;
|
|
}
|
|
|
|
// For a Constant, check for a multiple of the given factor.
|
|
if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S)) {
|
|
// 0/x == 0.
|
|
if (C->isZero())
|
|
return true;
|
|
// Check for divisibility.
|
|
if (const SCEVConstant *FC = dyn_cast<SCEVConstant>(Factor)) {
|
|
ConstantInt *CI =
|
|
ConstantInt::get(SE.getContext(), C->getAPInt().sdiv(FC->getAPInt()));
|
|
// 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 (!CI->isZero()) {
|
|
const SCEV *Div = SE.getConstant(CI);
|
|
S = Div;
|
|
Remainder = SE.getAddExpr(
|
|
Remainder, SE.getConstant(C->getAPInt().srem(FC->getAPInt())));
|
|
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)) {
|
|
// Size is known, check if there is a constant operand which is a multiple
|
|
// of the given factor. If so, we can factor it.
|
|
const SCEVConstant *FC = cast<SCEVConstant>(Factor);
|
|
if (const SCEVConstant *C = dyn_cast<SCEVConstant>(M->getOperand(0)))
|
|
if (!C->getAPInt().srem(FC->getAPInt())) {
|
|
SmallVector<const SCEV *, 4> NewMulOps(M->op_begin(), M->op_end());
|
|
NewMulOps[0] = SE.getConstant(C->getAPInt().sdiv(FC->getAPInt()));
|
|
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)) {
|
|
const SCEV *Step = A->getStepRecurrence(SE);
|
|
const SCEV *StepRem = SE.getConstant(Step->getType(), 0);
|
|
if (!FactorOutConstant(Step, StepRem, Factor, SE, DL))
|
|
return false;
|
|
if (!StepRem->isZero())
|
|
return false;
|
|
const SCEV *Start = A->getStart();
|
|
if (!FactorOutConstant(Start, Remainder, Factor, SE, DL))
|
|
return false;
|
|
S = SE.getAddRecExpr(Start, Step, A->getLoop(),
|
|
A->getNoWrapFlags(SCEV::FlagNW));
|
|
return true;
|
|
}
|
|
|
|
return false;
|
|
}
|
|
|
|
/// SimplifyAddOperands - Sort and simplify a list of add operands. NumAddRecs
|
|
/// is the number of SCEVAddRecExprs present, which are kept at the end of
|
|
/// the list.
|
|
///
|
|
static void SimplifyAddOperands(SmallVectorImpl<const SCEV *> &Ops,
|
|
Type *Ty,
|
|
ScalarEvolution &SE) {
|
|
unsigned NumAddRecs = 0;
|
|
for (unsigned i = Ops.size(); i > 0 && isa<SCEVAddRecExpr>(Ops[i-1]); --i)
|
|
++NumAddRecs;
|
|
// Group Ops into non-addrecs and addrecs.
|
|
SmallVector<const SCEV *, 8> NoAddRecs(Ops.begin(), Ops.end() - NumAddRecs);
|
|
SmallVector<const SCEV *, 8> AddRecs(Ops.end() - NumAddRecs, Ops.end());
|
|
// Let ScalarEvolution sort and simplify the non-addrecs list.
|
|
const SCEV *Sum = NoAddRecs.empty() ?
|
|
SE.getConstant(Ty, 0) :
|
|
SE.getAddExpr(NoAddRecs);
|
|
// If it returned an add, use the operands. Otherwise it simplified
|
|
// the sum into a single value, so just use that.
|
|
Ops.clear();
|
|
if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(Sum))
|
|
Ops.append(Add->op_begin(), Add->op_end());
|
|
else if (!Sum->isZero())
|
|
Ops.push_back(Sum);
|
|
// Then append the addrecs.
|
|
Ops.append(AddRecs.begin(), AddRecs.end());
|
|
}
|
|
|
|
/// SplitAddRecs - Flatten a list of add operands, moving addrec start values
|
|
/// out to the top level. For example, convert {a + b,+,c} to a, b, {0,+,d}.
|
|
/// This helps expose more opportunities for folding parts of the expressions
|
|
/// into GEP indices.
|
|
///
|
|
static void SplitAddRecs(SmallVectorImpl<const SCEV *> &Ops,
|
|
Type *Ty,
|
|
ScalarEvolution &SE) {
|
|
// Find the addrecs.
|
|
SmallVector<const SCEV *, 8> AddRecs;
|
|
for (unsigned i = 0, e = Ops.size(); i != e; ++i)
|
|
while (const SCEVAddRecExpr *A = dyn_cast<SCEVAddRecExpr>(Ops[i])) {
|
|
const SCEV *Start = A->getStart();
|
|
if (Start->isZero()) break;
|
|
const SCEV *Zero = SE.getConstant(Ty, 0);
|
|
AddRecs.push_back(SE.getAddRecExpr(Zero,
|
|
A->getStepRecurrence(SE),
|
|
A->getLoop(),
|
|
A->getNoWrapFlags(SCEV::FlagNW)));
|
|
if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(Start)) {
|
|
Ops[i] = Zero;
|
|
Ops.append(Add->op_begin(), Add->op_end());
|
|
e += Add->getNumOperands();
|
|
} else {
|
|
Ops[i] = Start;
|
|
}
|
|
}
|
|
if (!AddRecs.empty()) {
|
|
// Add the addrecs onto the end of the list.
|
|
Ops.append(AddRecs.begin(), AddRecs.end());
|
|
// Resort the operand list, moving any constants to the front.
|
|
SimplifyAddOperands(Ops, Ty, SE);
|
|
}
|
|
}
|
|
|
|
/// expandAddToGEP - Expand an addition expression with a pointer type into
|
|
/// a GEP instead of using ptrtoint+arithmetic+inttoptr. This helps
|
|
/// BasicAliasAnalysis and other passes analyze the result. See the rules
|
|
/// for getelementptr vs. inttoptr in
|
|
/// http://llvm.org/docs/LangRef.html#pointeraliasing
|
|
/// for details.
|
|
///
|
|
/// Design note: The correctness of using getelementptr here depends on
|
|
/// ScalarEvolution not recognizing inttoptr and ptrtoint operators, as
|
|
/// they may introduce pointer arithmetic which may not be safely converted
|
|
/// into getelementptr.
|
|
///
|
|
/// 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 SCEV *const *op_begin,
|
|
const SCEV *const *op_end,
|
|
PointerType *PTy,
|
|
Type *Ty,
|
|
Value *V) {
|
|
Type *OriginalElTy = PTy->getElementType();
|
|
Type *ElTy = OriginalElTy;
|
|
SmallVector<Value *, 4> GepIndices;
|
|
SmallVector<const SCEV *, 8> Ops(op_begin, op_end);
|
|
bool AnyNonZeroIndices = false;
|
|
|
|
// Split AddRecs up into parts as either of the parts may be usable
|
|
// without the other.
|
|
SplitAddRecs(Ops, Ty, SE);
|
|
|
|
Type *IntPtrTy = DL.getIntPtrType(PTy);
|
|
|
|
// Descend 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 (;;) {
|
|
// If the scale size is not 0, attempt to factor out a scale for
|
|
// array indexing.
|
|
SmallVector<const SCEV *, 8> ScaledOps;
|
|
if (ElTy->isSized()) {
|
|
const SCEV *ElSize = SE.getSizeOfExpr(IntPtrTy, ElTy);
|
|
if (!ElSize->isZero()) {
|
|
SmallVector<const SCEV *, 8> NewOps;
|
|
for (const SCEV *Op : Ops) {
|
|
const SCEV *Remainder = SE.getConstant(Ty, 0);
|
|
if (FactorOutConstant(Op, Remainder, ElSize, SE, DL)) {
|
|
// Op now has ElSize factored out.
|
|
ScaledOps.push_back(Op);
|
|
if (!Remainder->isZero())
|
|
NewOps.push_back(Remainder);
|
|
AnyNonZeroIndices = true;
|
|
} else {
|
|
// The operand was not divisible, so add it to the list of operands
|
|
// we'll scan next iteration.
|
|
NewOps.push_back(Op);
|
|
}
|
|
}
|
|
// If we made any changes, update Ops.
|
|
if (!ScaledOps.empty()) {
|
|
Ops = NewOps;
|
|
SimplifyAddOperands(Ops, Ty, SE);
|
|
}
|
|
}
|
|
}
|
|
|
|
// Record the scaled array index for this level of the type. If
|
|
// we didn't find any operands that could be factored, tentatively
|
|
// assume that element zero was selected (since the zero offset
|
|
// would obviously be folded away).
|
|
Value *Scaled = ScaledOps.empty() ?
|
|
Constant::getNullValue(Ty) :
|
|
expandCodeFor(SE.getAddExpr(ScaledOps), Ty);
|
|
GepIndices.push_back(Scaled);
|
|
|
|
// Collect struct field index operands.
|
|
while (StructType *STy = dyn_cast<StructType>(ElTy)) {
|
|
bool FoundFieldNo = false;
|
|
// An empty struct has no fields.
|
|
if (STy->getNumElements() == 0) break;
|
|
// Field offsets are known. See if a constant offset falls within any of
|
|
// the struct fields.
|
|
if (Ops.empty())
|
|
break;
|
|
if (const SCEVConstant *C = dyn_cast<SCEVConstant>(Ops[0]))
|
|
if (SE.getTypeSizeInBits(C->getType()) <= 64) {
|
|
const StructLayout &SL = *DL.getStructLayout(STy);
|
|
uint64_t FullOffset = C->getValue()->getZExtValue();
|
|
if (FullOffset < SL.getSizeInBytes()) {
|
|
unsigned ElIdx = SL.getElementContainingOffset(FullOffset);
|
|
GepIndices.push_back(
|
|
ConstantInt::get(Type::getInt32Ty(Ty->getContext()), ElIdx));
|
|
ElTy = STy->getTypeAtIndex(ElIdx);
|
|
Ops[0] =
|
|
SE.getConstant(Ty, FullOffset - SL.getElementOffset(ElIdx));
|
|
AnyNonZeroIndices = true;
|
|
FoundFieldNo = true;
|
|
}
|
|
}
|
|
// If no struct field offsets were found, tentatively assume that
|
|
// field zero was selected (since the zero offset would obviously
|
|
// be folded away).
|
|
if (!FoundFieldNo) {
|
|
ElTy = STy->getTypeAtIndex(0u);
|
|
GepIndices.push_back(
|
|
Constant::getNullValue(Type::getInt32Ty(Ty->getContext())));
|
|
}
|
|
}
|
|
|
|
if (ArrayType *ATy = dyn_cast<ArrayType>(ElTy))
|
|
ElTy = ATy->getElementType();
|
|
else
|
|
break;
|
|
}
|
|
|
|
// If none of the operands were convertible 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) {
|
|
// Cast the base to i8*.
|
|
V = InsertNoopCastOfTo(V,
|
|
Type::getInt8PtrTy(Ty->getContext(), PTy->getAddressSpace()));
|
|
|
|
assert(!isa<Instruction>(V) ||
|
|
SE.DT.dominates(cast<Instruction>(V), &*Builder.GetInsertPoint()));
|
|
|
|
// Expand the operands for a plain byte offset.
|
|
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(Type::getInt8Ty(Ty->getContext()),
|
|
CLHS, CRHS);
|
|
|
|
// Do a quick scan to see if we have this GEP nearby. If so, reuse it.
|
|
unsigned ScanLimit = 6;
|
|
BasicBlock::iterator BlockBegin = Builder.GetInsertBlock()->begin();
|
|
// Scanning starts from the last instruction before the insertion point.
|
|
BasicBlock::iterator IP = Builder.GetInsertPoint();
|
|
if (IP != BlockBegin) {
|
|
--IP;
|
|
for (; ScanLimit; --IP, --ScanLimit) {
|
|
// Don't count dbg.value against the ScanLimit, to avoid perturbing the
|
|
// generated code.
|
|
if (isa<DbgInfoIntrinsic>(IP))
|
|
ScanLimit++;
|
|
if (IP->getOpcode() == Instruction::GetElementPtr &&
|
|
IP->getOperand(0) == V && IP->getOperand(1) == Idx)
|
|
return &*IP;
|
|
if (IP == BlockBegin) break;
|
|
}
|
|
}
|
|
|
|
// Save the original insertion point so we can restore it when we're done.
|
|
SCEVInsertPointGuard Guard(Builder, this);
|
|
|
|
// Move the insertion point out of as many loops as we can.
|
|
while (const Loop *L = SE.LI.getLoopFor(Builder.GetInsertBlock())) {
|
|
if (!L->isLoopInvariant(V) || !L->isLoopInvariant(Idx)) break;
|
|
BasicBlock *Preheader = L->getLoopPreheader();
|
|
if (!Preheader) break;
|
|
|
|
// Ok, move up a level.
|
|
Builder.SetInsertPoint(Preheader->getTerminator());
|
|
}
|
|
|
|
// Emit a GEP.
|
|
Value *GEP = Builder.CreateGEP(Builder.getInt8Ty(), V, Idx, "uglygep");
|
|
rememberInstruction(GEP);
|
|
|
|
return GEP;
|
|
}
|
|
|
|
{
|
|
SCEVInsertPointGuard Guard(Builder, this);
|
|
|
|
// Move the insertion point out of as many loops as we can.
|
|
while (const Loop *L = SE.LI.getLoopFor(Builder.GetInsertBlock())) {
|
|
if (!L->isLoopInvariant(V)) break;
|
|
|
|
bool AnyIndexNotLoopInvariant = any_of(
|
|
GepIndices, [L](Value *Op) { return !L->isLoopInvariant(Op); });
|
|
|
|
if (AnyIndexNotLoopInvariant)
|
|
break;
|
|
|
|
BasicBlock *Preheader = L->getLoopPreheader();
|
|
if (!Preheader) break;
|
|
|
|
// Ok, move up a level.
|
|
Builder.SetInsertPoint(Preheader->getTerminator());
|
|
}
|
|
|
|
// Insert a pretty getelementptr. Note that this GEP is not marked inbounds,
|
|
// because ScalarEvolution may have changed the address arithmetic to
|
|
// compute a value which is beyond the end of the allocated object.
|
|
Value *Casted = V;
|
|
if (V->getType() != PTy)
|
|
Casted = InsertNoopCastOfTo(Casted, PTy);
|
|
Value *GEP = Builder.CreateGEP(OriginalElTy, Casted, GepIndices, "scevgep");
|
|
Ops.push_back(SE.getUnknown(GEP));
|
|
rememberInstruction(GEP);
|
|
}
|
|
|
|
return expand(SE.getAddExpr(Ops));
|
|
}
|
|
|
|
/// PickMostRelevantLoop - Given two loops pick the one that's most relevant for
|
|
/// SCEV expansion. If they are nested, this is the most nested. If they are
|
|
/// neighboring, pick the later.
|
|
static const Loop *PickMostRelevantLoop(const Loop *A, const Loop *B,
|
|
DominatorTree &DT) {
|
|
if (!A) return B;
|
|
if (!B) return A;
|
|
if (A->contains(B)) return B;
|
|
if (B->contains(A)) return A;
|
|
if (DT.dominates(A->getHeader(), B->getHeader())) return B;
|
|
if (DT.dominates(B->getHeader(), A->getHeader())) return A;
|
|
return A; // Arbitrarily break the tie.
|
|
}
|
|
|
|
/// getRelevantLoop - Get the most relevant loop associated with the given
|
|
/// expression, according to PickMostRelevantLoop.
|
|
const Loop *SCEVExpander::getRelevantLoop(const SCEV *S) {
|
|
// Test whether we've already computed the most relevant loop for this SCEV.
|
|
auto Pair = RelevantLoops.insert(std::make_pair(S, nullptr));
|
|
if (!Pair.second)
|
|
return Pair.first->second;
|
|
|
|
if (isa<SCEVConstant>(S))
|
|
// A constant has no relevant loops.
|
|
return nullptr;
|
|
if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
|
|
if (const Instruction *I = dyn_cast<Instruction>(U->getValue()))
|
|
return Pair.first->second = SE.LI.getLoopFor(I->getParent());
|
|
// A non-instruction has no relevant loops.
|
|
return nullptr;
|
|
}
|
|
if (const SCEVNAryExpr *N = dyn_cast<SCEVNAryExpr>(S)) {
|
|
const Loop *L = nullptr;
|
|
if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S))
|
|
L = AR->getLoop();
|
|
for (const SCEV *Op : N->operands())
|
|
L = PickMostRelevantLoop(L, getRelevantLoop(Op), SE.DT);
|
|
return RelevantLoops[N] = L;
|
|
}
|
|
if (const SCEVCastExpr *C = dyn_cast<SCEVCastExpr>(S)) {
|
|
const Loop *Result = getRelevantLoop(C->getOperand());
|
|
return RelevantLoops[C] = Result;
|
|
}
|
|
if (const SCEVUDivExpr *D = dyn_cast<SCEVUDivExpr>(S)) {
|
|
const Loop *Result = PickMostRelevantLoop(
|
|
getRelevantLoop(D->getLHS()), getRelevantLoop(D->getRHS()), SE.DT);
|
|
return RelevantLoops[D] = Result;
|
|
}
|
|
llvm_unreachable("Unexpected SCEV type!");
|
|
}
|
|
|
|
namespace {
|
|
|
|
/// LoopCompare - Compare loops by PickMostRelevantLoop.
|
|
class LoopCompare {
|
|
DominatorTree &DT;
|
|
public:
|
|
explicit LoopCompare(DominatorTree &dt) : DT(dt) {}
|
|
|
|
bool operator()(std::pair<const Loop *, const SCEV *> LHS,
|
|
std::pair<const Loop *, const SCEV *> RHS) const {
|
|
// Keep pointer operands sorted at the end.
|
|
if (LHS.second->getType()->isPointerTy() !=
|
|
RHS.second->getType()->isPointerTy())
|
|
return LHS.second->getType()->isPointerTy();
|
|
|
|
// Compare loops with PickMostRelevantLoop.
|
|
if (LHS.first != RHS.first)
|
|
return PickMostRelevantLoop(LHS.first, RHS.first, DT) != LHS.first;
|
|
|
|
// If one operand is a non-constant negative and the other is not,
|
|
// put the non-constant negative on the right so that a sub can
|
|
// be used instead of a negate and add.
|
|
if (LHS.second->isNonConstantNegative()) {
|
|
if (!RHS.second->isNonConstantNegative())
|
|
return false;
|
|
} else if (RHS.second->isNonConstantNegative())
|
|
return true;
|
|
|
|
// Otherwise they are equivalent according to this comparison.
|
|
return false;
|
|
}
|
|
};
|
|
|
|
}
|
|
|
|
Value *SCEVExpander::visitAddExpr(const SCEVAddExpr *S) {
|
|
Type *Ty = SE.getEffectiveSCEVType(S->getType());
|
|
|
|
// Collect all the add operands in a loop, along with their associated loops.
|
|
// Iterate in reverse so that constants are emitted last, all else equal, and
|
|
// so that pointer operands are inserted first, which the code below relies on
|
|
// to form more involved GEPs.
|
|
SmallVector<std::pair<const Loop *, const SCEV *>, 8> OpsAndLoops;
|
|
for (std::reverse_iterator<SCEVAddExpr::op_iterator> I(S->op_end()),
|
|
E(S->op_begin()); I != E; ++I)
|
|
OpsAndLoops.push_back(std::make_pair(getRelevantLoop(*I), *I));
|
|
|
|
// Sort by loop. Use a stable sort so that constants follow non-constants and
|
|
// pointer operands precede non-pointer operands.
|
|
std::stable_sort(OpsAndLoops.begin(), OpsAndLoops.end(), LoopCompare(SE.DT));
|
|
|
|
// Emit instructions to add all the operands. Hoist as much as possible
|
|
// out of loops, and form meaningful getelementptrs where possible.
|
|
Value *Sum = nullptr;
|
|
for (auto I = OpsAndLoops.begin(), E = OpsAndLoops.end(); I != E;) {
|
|
const Loop *CurLoop = I->first;
|
|
const SCEV *Op = I->second;
|
|
if (!Sum) {
|
|
// This is the first operand. Just expand it.
|
|
Sum = expand(Op);
|
|
++I;
|
|
} else if (PointerType *PTy = dyn_cast<PointerType>(Sum->getType())) {
|
|
// The running sum expression is a pointer. Try to form a getelementptr
|
|
// at this level with that as the base.
|
|
SmallVector<const SCEV *, 4> NewOps;
|
|
for (; I != E && I->first == CurLoop; ++I) {
|
|
// If the operand is SCEVUnknown and not instructions, peek through
|
|
// it, to enable more of it to be folded into the GEP.
|
|
const SCEV *X = I->second;
|
|
if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(X))
|
|
if (!isa<Instruction>(U->getValue()))
|
|
X = SE.getSCEV(U->getValue());
|
|
NewOps.push_back(X);
|
|
}
|
|
Sum = expandAddToGEP(NewOps.begin(), NewOps.end(), PTy, Ty, Sum);
|
|
} else if (PointerType *PTy = dyn_cast<PointerType>(Op->getType())) {
|
|
// The running sum is an integer, and there's a pointer at this level.
|
|
// Try to form a getelementptr. If the running sum is instructions,
|
|
// use a SCEVUnknown to avoid re-analyzing them.
|
|
SmallVector<const SCEV *, 4> NewOps;
|
|
NewOps.push_back(isa<Instruction>(Sum) ? SE.getUnknown(Sum) :
|
|
SE.getSCEV(Sum));
|
|
for (++I; I != E && I->first == CurLoop; ++I)
|
|
NewOps.push_back(I->second);
|
|
Sum = expandAddToGEP(NewOps.begin(), NewOps.end(), PTy, Ty, expand(Op));
|
|
} else if (Op->isNonConstantNegative()) {
|
|
// Instead of doing a negate and add, just do a subtract.
|
|
Value *W = expandCodeFor(SE.getNegativeSCEV(Op), Ty);
|
|
Sum = InsertNoopCastOfTo(Sum, Ty);
|
|
Sum = InsertBinop(Instruction::Sub, Sum, W);
|
|
++I;
|
|
} else {
|
|
// A simple add.
|
|
Value *W = expandCodeFor(Op, Ty);
|
|
Sum = InsertNoopCastOfTo(Sum, Ty);
|
|
// Canonicalize a constant to the RHS.
|
|
if (isa<Constant>(Sum)) std::swap(Sum, W);
|
|
Sum = InsertBinop(Instruction::Add, Sum, W);
|
|
++I;
|
|
}
|
|
}
|
|
|
|
return Sum;
|
|
}
|
|
|
|
Value *SCEVExpander::visitMulExpr(const SCEVMulExpr *S) {
|
|
Type *Ty = SE.getEffectiveSCEVType(S->getType());
|
|
|
|
// Collect all the mul operands in a loop, along with their associated loops.
|
|
// Iterate in reverse so that constants are emitted last, all else equal.
|
|
SmallVector<std::pair<const Loop *, const SCEV *>, 8> OpsAndLoops;
|
|
for (std::reverse_iterator<SCEVMulExpr::op_iterator> I(S->op_end()),
|
|
E(S->op_begin()); I != E; ++I)
|
|
OpsAndLoops.push_back(std::make_pair(getRelevantLoop(*I), *I));
|
|
|
|
// Sort by loop. Use a stable sort so that constants follow non-constants.
|
|
std::stable_sort(OpsAndLoops.begin(), OpsAndLoops.end(), LoopCompare(SE.DT));
|
|
|
|
// Emit instructions to mul all the operands. Hoist as much as possible
|
|
// out of loops.
|
|
Value *Prod = nullptr;
|
|
for (const auto &I : OpsAndLoops) {
|
|
const SCEV *Op = I.second;
|
|
if (!Prod) {
|
|
// This is the first operand. Just expand it.
|
|
Prod = expand(Op);
|
|
} else if (Op->isAllOnesValue()) {
|
|
// Instead of doing a multiply by negative one, just do a negate.
|
|
Prod = InsertNoopCastOfTo(Prod, Ty);
|
|
Prod = InsertBinop(Instruction::Sub, Constant::getNullValue(Ty), Prod);
|
|
} else {
|
|
// A simple mul.
|
|
Value *W = expandCodeFor(Op, Ty);
|
|
Prod = InsertNoopCastOfTo(Prod, Ty);
|
|
// Canonicalize a constant to the RHS.
|
|
if (isa<Constant>(Prod)) std::swap(Prod, W);
|
|
const APInt *RHS;
|
|
if (match(W, m_Power2(RHS))) {
|
|
// Canonicalize Prod*(1<<C) to Prod<<C.
|
|
assert(!Ty->isVectorTy() && "vector types are not SCEVable");
|
|
Prod = InsertBinop(Instruction::Shl, Prod,
|
|
ConstantInt::get(Ty, RHS->logBase2()));
|
|
} else {
|
|
Prod = InsertBinop(Instruction::Mul, Prod, W);
|
|
}
|
|
}
|
|
}
|
|
|
|
return Prod;
|
|
}
|
|
|
|
Value *SCEVExpander::visitUDivExpr(const SCEVUDivExpr *S) {
|
|
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->getAPInt();
|
|
if (RHS.isPowerOf2())
|
|
return InsertBinop(Instruction::LShr, LHS,
|
|
ConstantInt::get(Ty, RHS.logBase2()));
|
|
}
|
|
|
|
Value *RHS = expandCodeFor(S->getRHS(), Ty);
|
|
return InsertBinop(Instruction::UDiv, LHS, RHS);
|
|
}
|
|
|
|
/// 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(const SCEV *&Base, const SCEV *&Rest,
|
|
ScalarEvolution &SE) {
|
|
while (const SCEVAddRecExpr *A = dyn_cast<SCEVAddRecExpr>(Base)) {
|
|
Base = A->getStart();
|
|
Rest = SE.getAddExpr(Rest,
|
|
SE.getAddRecExpr(SE.getConstant(A->getType(), 0),
|
|
A->getStepRecurrence(SE),
|
|
A->getLoop(),
|
|
A->getNoWrapFlags(SCEV::FlagNW)));
|
|
}
|
|
if (const SCEVAddExpr *A = dyn_cast<SCEVAddExpr>(Base)) {
|
|
Base = A->getOperand(A->getNumOperands()-1);
|
|
SmallVector<const SCEV *, 8> NewAddOps(A->op_begin(), A->op_end());
|
|
NewAddOps.back() = Rest;
|
|
Rest = SE.getAddExpr(NewAddOps);
|
|
ExposePointerBase(Base, Rest, SE);
|
|
}
|
|
}
|
|
|
|
/// Determine if this is a well-behaved chain of instructions leading back to
|
|
/// the PHI. If so, it may be reused by expanded expressions.
|
|
bool SCEVExpander::isNormalAddRecExprPHI(PHINode *PN, Instruction *IncV,
|
|
const Loop *L) {
|
|
if (IncV->getNumOperands() == 0 || isa<PHINode>(IncV) ||
|
|
(isa<CastInst>(IncV) && !isa<BitCastInst>(IncV)))
|
|
return false;
|
|
// If any of the operands don't dominate the insert position, bail.
|
|
// Addrec operands are always loop-invariant, so this can only happen
|
|
// if there are instructions which haven't been hoisted.
|
|
if (L == IVIncInsertLoop) {
|
|
for (User::op_iterator OI = IncV->op_begin()+1,
|
|
OE = IncV->op_end(); OI != OE; ++OI)
|
|
if (Instruction *OInst = dyn_cast<Instruction>(OI))
|
|
if (!SE.DT.dominates(OInst, IVIncInsertPos))
|
|
return false;
|
|
}
|
|
// Advance to the next instruction.
|
|
IncV = dyn_cast<Instruction>(IncV->getOperand(0));
|
|
if (!IncV)
|
|
return false;
|
|
|
|
if (IncV->mayHaveSideEffects())
|
|
return false;
|
|
|
|
if (IncV != PN)
|
|
return true;
|
|
|
|
return isNormalAddRecExprPHI(PN, IncV, L);
|
|
}
|
|
|
|
/// getIVIncOperand returns an induction variable increment's induction
|
|
/// variable operand.
|
|
///
|
|
/// If allowScale is set, any type of GEP is allowed as long as the nonIV
|
|
/// operands dominate InsertPos.
|
|
///
|
|
/// If allowScale is not set, ensure that a GEP increment conforms to one of the
|
|
/// simple patterns generated by getAddRecExprPHILiterally and
|
|
/// expandAddtoGEP. If the pattern isn't recognized, return NULL.
|
|
Instruction *SCEVExpander::getIVIncOperand(Instruction *IncV,
|
|
Instruction *InsertPos,
|
|
bool allowScale) {
|
|
if (IncV == InsertPos)
|
|
return nullptr;
|
|
|
|
switch (IncV->getOpcode()) {
|
|
default:
|
|
return nullptr;
|
|
// Check for a simple Add/Sub or GEP of a loop invariant step.
|
|
case Instruction::Add:
|
|
case Instruction::Sub: {
|
|
Instruction *OInst = dyn_cast<Instruction>(IncV->getOperand(1));
|
|
if (!OInst || SE.DT.dominates(OInst, InsertPos))
|
|
return dyn_cast<Instruction>(IncV->getOperand(0));
|
|
return nullptr;
|
|
}
|
|
case Instruction::BitCast:
|
|
return dyn_cast<Instruction>(IncV->getOperand(0));
|
|
case Instruction::GetElementPtr:
|
|
for (auto I = IncV->op_begin() + 1, E = IncV->op_end(); I != E; ++I) {
|
|
if (isa<Constant>(*I))
|
|
continue;
|
|
if (Instruction *OInst = dyn_cast<Instruction>(*I)) {
|
|
if (!SE.DT.dominates(OInst, InsertPos))
|
|
return nullptr;
|
|
}
|
|
if (allowScale) {
|
|
// allow any kind of GEP as long as it can be hoisted.
|
|
continue;
|
|
}
|
|
// This must be a pointer addition of constants (pretty), which is already
|
|
// handled, or some number of address-size elements (ugly). Ugly geps
|
|
// have 2 operands. i1* is used by the expander to represent an
|
|
// address-size element.
|
|
if (IncV->getNumOperands() != 2)
|
|
return nullptr;
|
|
unsigned AS = cast<PointerType>(IncV->getType())->getAddressSpace();
|
|
if (IncV->getType() != Type::getInt1PtrTy(SE.getContext(), AS)
|
|
&& IncV->getType() != Type::getInt8PtrTy(SE.getContext(), AS))
|
|
return nullptr;
|
|
break;
|
|
}
|
|
return dyn_cast<Instruction>(IncV->getOperand(0));
|
|
}
|
|
}
|
|
|
|
/// If the insert point of the current builder or any of the builders on the
|
|
/// stack of saved builders has 'I' as its insert point, update it to point to
|
|
/// the instruction after 'I'. This is intended to be used when the instruction
|
|
/// 'I' is being moved. If this fixup is not done and 'I' is moved to a
|
|
/// different block, the inconsistent insert point (with a mismatched
|
|
/// Instruction and Block) can lead to an instruction being inserted in a block
|
|
/// other than its parent.
|
|
void SCEVExpander::fixupInsertPoints(Instruction *I) {
|
|
BasicBlock::iterator It(*I);
|
|
BasicBlock::iterator NewInsertPt = std::next(It);
|
|
if (Builder.GetInsertPoint() == It)
|
|
Builder.SetInsertPoint(&*NewInsertPt);
|
|
for (auto *InsertPtGuard : InsertPointGuards)
|
|
if (InsertPtGuard->GetInsertPoint() == It)
|
|
InsertPtGuard->SetInsertPoint(NewInsertPt);
|
|
}
|
|
|
|
/// hoistStep - Attempt to hoist a simple IV increment above InsertPos to make
|
|
/// it available to other uses in this loop. Recursively hoist any operands,
|
|
/// until we reach a value that dominates InsertPos.
|
|
bool SCEVExpander::hoistIVInc(Instruction *IncV, Instruction *InsertPos) {
|
|
if (SE.DT.dominates(IncV, InsertPos))
|
|
return true;
|
|
|
|
// InsertPos must itself dominate IncV so that IncV's new position satisfies
|
|
// its existing users.
|
|
if (isa<PHINode>(InsertPos) ||
|
|
!SE.DT.dominates(InsertPos->getParent(), IncV->getParent()))
|
|
return false;
|
|
|
|
if (!SE.LI.movementPreservesLCSSAForm(IncV, InsertPos))
|
|
return false;
|
|
|
|
// Check that the chain of IV operands leading back to Phi can be hoisted.
|
|
SmallVector<Instruction*, 4> IVIncs;
|
|
for(;;) {
|
|
Instruction *Oper = getIVIncOperand(IncV, InsertPos, /*allowScale*/true);
|
|
if (!Oper)
|
|
return false;
|
|
// IncV is safe to hoist.
|
|
IVIncs.push_back(IncV);
|
|
IncV = Oper;
|
|
if (SE.DT.dominates(IncV, InsertPos))
|
|
break;
|
|
}
|
|
for (auto I = IVIncs.rbegin(), E = IVIncs.rend(); I != E; ++I) {
|
|
fixupInsertPoints(*I);
|
|
(*I)->moveBefore(InsertPos);
|
|
}
|
|
return true;
|
|
}
|
|
|
|
/// Determine if this cyclic phi is in a form that would have been generated by
|
|
/// LSR. We don't care if the phi was actually expanded in this pass, as long
|
|
/// as it is in a low-cost form, for example, no implied multiplication. This
|
|
/// should match any patterns generated by getAddRecExprPHILiterally and
|
|
/// expandAddtoGEP.
|
|
bool SCEVExpander::isExpandedAddRecExprPHI(PHINode *PN, Instruction *IncV,
|
|
const Loop *L) {
|
|
for(Instruction *IVOper = IncV;
|
|
(IVOper = getIVIncOperand(IVOper, L->getLoopPreheader()->getTerminator(),
|
|
/*allowScale=*/false));) {
|
|
if (IVOper == PN)
|
|
return true;
|
|
}
|
|
return false;
|
|
}
|
|
|
|
/// expandIVInc - Expand an IV increment at Builder's current InsertPos.
|
|
/// Typically this is the LatchBlock terminator or IVIncInsertPos, but we may
|
|
/// need to materialize IV increments elsewhere to handle difficult situations.
|
|
Value *SCEVExpander::expandIVInc(PHINode *PN, Value *StepV, const Loop *L,
|
|
Type *ExpandTy, Type *IntTy,
|
|
bool useSubtract) {
|
|
Value *IncV;
|
|
// If the PHI is a pointer, use a GEP, otherwise use an add or sub.
|
|
if (ExpandTy->isPointerTy()) {
|
|
PointerType *GEPPtrTy = cast<PointerType>(ExpandTy);
|
|
// If the step isn't constant, don't use an implicitly scaled GEP, because
|
|
// that would require a multiply inside the loop.
|
|
if (!isa<ConstantInt>(StepV))
|
|
GEPPtrTy = PointerType::get(Type::getInt1Ty(SE.getContext()),
|
|
GEPPtrTy->getAddressSpace());
|
|
const SCEV *const StepArray[1] = { SE.getSCEV(StepV) };
|
|
IncV = expandAddToGEP(StepArray, StepArray+1, GEPPtrTy, IntTy, PN);
|
|
if (IncV->getType() != PN->getType()) {
|
|
IncV = Builder.CreateBitCast(IncV, PN->getType());
|
|
rememberInstruction(IncV);
|
|
}
|
|
} else {
|
|
IncV = useSubtract ?
|
|
Builder.CreateSub(PN, StepV, Twine(IVName) + ".iv.next") :
|
|
Builder.CreateAdd(PN, StepV, Twine(IVName) + ".iv.next");
|
|
rememberInstruction(IncV);
|
|
}
|
|
return IncV;
|
|
}
|
|
|
|
/// \brief Hoist the addrec instruction chain rooted in the loop phi above the
|
|
/// position. This routine assumes that this is possible (has been checked).
|
|
void SCEVExpander::hoistBeforePos(DominatorTree *DT, Instruction *InstToHoist,
|
|
Instruction *Pos, PHINode *LoopPhi) {
|
|
do {
|
|
if (DT->dominates(InstToHoist, Pos))
|
|
break;
|
|
// Make sure the increment is where we want it. But don't move it
|
|
// down past a potential existing post-inc user.
|
|
fixupInsertPoints(InstToHoist);
|
|
InstToHoist->moveBefore(Pos);
|
|
Pos = InstToHoist;
|
|
InstToHoist = cast<Instruction>(InstToHoist->getOperand(0));
|
|
} while (InstToHoist != LoopPhi);
|
|
}
|
|
|
|
/// \brief Check whether we can cheaply express the requested SCEV in terms of
|
|
/// the available PHI SCEV by truncation and/or inversion of the step.
|
|
static bool canBeCheaplyTransformed(ScalarEvolution &SE,
|
|
const SCEVAddRecExpr *Phi,
|
|
const SCEVAddRecExpr *Requested,
|
|
bool &InvertStep) {
|
|
Type *PhiTy = SE.getEffectiveSCEVType(Phi->getType());
|
|
Type *RequestedTy = SE.getEffectiveSCEVType(Requested->getType());
|
|
|
|
if (RequestedTy->getIntegerBitWidth() > PhiTy->getIntegerBitWidth())
|
|
return false;
|
|
|
|
// Try truncate it if necessary.
|
|
Phi = dyn_cast<SCEVAddRecExpr>(SE.getTruncateOrNoop(Phi, RequestedTy));
|
|
if (!Phi)
|
|
return false;
|
|
|
|
// Check whether truncation will help.
|
|
if (Phi == Requested) {
|
|
InvertStep = false;
|
|
return true;
|
|
}
|
|
|
|
// Check whether inverting will help: {R,+,-1} == R - {0,+,1}.
|
|
if (SE.getAddExpr(Requested->getStart(),
|
|
SE.getNegativeSCEV(Requested)) == Phi) {
|
|
InvertStep = true;
|
|
return true;
|
|
}
|
|
|
|
return false;
|
|
}
|
|
|
|
static bool IsIncrementNSW(ScalarEvolution &SE, const SCEVAddRecExpr *AR) {
|
|
if (!isa<IntegerType>(AR->getType()))
|
|
return false;
|
|
|
|
unsigned BitWidth = cast<IntegerType>(AR->getType())->getBitWidth();
|
|
Type *WideTy = IntegerType::get(AR->getType()->getContext(), BitWidth * 2);
|
|
const SCEV *Step = AR->getStepRecurrence(SE);
|
|
const SCEV *OpAfterExtend = SE.getAddExpr(SE.getSignExtendExpr(Step, WideTy),
|
|
SE.getSignExtendExpr(AR, WideTy));
|
|
const SCEV *ExtendAfterOp =
|
|
SE.getSignExtendExpr(SE.getAddExpr(AR, Step), WideTy);
|
|
return ExtendAfterOp == OpAfterExtend;
|
|
}
|
|
|
|
static bool IsIncrementNUW(ScalarEvolution &SE, const SCEVAddRecExpr *AR) {
|
|
if (!isa<IntegerType>(AR->getType()))
|
|
return false;
|
|
|
|
unsigned BitWidth = cast<IntegerType>(AR->getType())->getBitWidth();
|
|
Type *WideTy = IntegerType::get(AR->getType()->getContext(), BitWidth * 2);
|
|
const SCEV *Step = AR->getStepRecurrence(SE);
|
|
const SCEV *OpAfterExtend = SE.getAddExpr(SE.getZeroExtendExpr(Step, WideTy),
|
|
SE.getZeroExtendExpr(AR, WideTy));
|
|
const SCEV *ExtendAfterOp =
|
|
SE.getZeroExtendExpr(SE.getAddExpr(AR, Step), WideTy);
|
|
return ExtendAfterOp == OpAfterExtend;
|
|
}
|
|
|
|
/// getAddRecExprPHILiterally - Helper for expandAddRecExprLiterally. Expand
|
|
/// the base addrec, which is the addrec without any non-loop-dominating
|
|
/// values, and return the PHI.
|
|
PHINode *
|
|
SCEVExpander::getAddRecExprPHILiterally(const SCEVAddRecExpr *Normalized,
|
|
const Loop *L,
|
|
Type *ExpandTy,
|
|
Type *IntTy,
|
|
Type *&TruncTy,
|
|
bool &InvertStep) {
|
|
assert((!IVIncInsertLoop||IVIncInsertPos) && "Uninitialized insert position");
|
|
|
|
// Reuse a previously-inserted PHI, if present.
|
|
BasicBlock *LatchBlock = L->getLoopLatch();
|
|
if (LatchBlock) {
|
|
PHINode *AddRecPhiMatch = nullptr;
|
|
Instruction *IncV = nullptr;
|
|
TruncTy = nullptr;
|
|
InvertStep = false;
|
|
|
|
// Only try partially matching scevs that need truncation and/or
|
|
// step-inversion if we know this loop is outside the current loop.
|
|
bool TryNonMatchingSCEV =
|
|
IVIncInsertLoop &&
|
|
SE.DT.properlyDominates(LatchBlock, IVIncInsertLoop->getHeader());
|
|
|
|
for (auto &I : *L->getHeader()) {
|
|
auto *PN = dyn_cast<PHINode>(&I);
|
|
if (!PN || !SE.isSCEVable(PN->getType()))
|
|
continue;
|
|
|
|
const SCEVAddRecExpr *PhiSCEV = dyn_cast<SCEVAddRecExpr>(SE.getSCEV(PN));
|
|
if (!PhiSCEV)
|
|
continue;
|
|
|
|
bool IsMatchingSCEV = PhiSCEV == Normalized;
|
|
// We only handle truncation and inversion of phi recurrences for the
|
|
// expanded expression if the expanded expression's loop dominates the
|
|
// loop we insert to. Check now, so we can bail out early.
|
|
if (!IsMatchingSCEV && !TryNonMatchingSCEV)
|
|
continue;
|
|
|
|
Instruction *TempIncV =
|
|
cast<Instruction>(PN->getIncomingValueForBlock(LatchBlock));
|
|
|
|
// Check whether we can reuse this PHI node.
|
|
if (LSRMode) {
|
|
if (!isExpandedAddRecExprPHI(PN, TempIncV, L))
|
|
continue;
|
|
if (L == IVIncInsertLoop && !hoistIVInc(TempIncV, IVIncInsertPos))
|
|
continue;
|
|
} else {
|
|
if (!isNormalAddRecExprPHI(PN, TempIncV, L))
|
|
continue;
|
|
}
|
|
|
|
// Stop if we have found an exact match SCEV.
|
|
if (IsMatchingSCEV) {
|
|
IncV = TempIncV;
|
|
TruncTy = nullptr;
|
|
InvertStep = false;
|
|
AddRecPhiMatch = PN;
|
|
break;
|
|
}
|
|
|
|
// Try whether the phi can be translated into the requested form
|
|
// (truncated and/or offset by a constant).
|
|
if ((!TruncTy || InvertStep) &&
|
|
canBeCheaplyTransformed(SE, PhiSCEV, Normalized, InvertStep)) {
|
|
// Record the phi node. But don't stop we might find an exact match
|
|
// later.
|
|
AddRecPhiMatch = PN;
|
|
IncV = TempIncV;
|
|
TruncTy = SE.getEffectiveSCEVType(Normalized->getType());
|
|
}
|
|
}
|
|
|
|
if (AddRecPhiMatch) {
|
|
// Potentially, move the increment. We have made sure in
|
|
// isExpandedAddRecExprPHI or hoistIVInc that this is possible.
|
|
if (L == IVIncInsertLoop)
|
|
hoistBeforePos(&SE.DT, IncV, IVIncInsertPos, AddRecPhiMatch);
|
|
|
|
// Ok, the add recurrence looks usable.
|
|
// Remember this PHI, even in post-inc mode.
|
|
InsertedValues.insert(AddRecPhiMatch);
|
|
// Remember the increment.
|
|
rememberInstruction(IncV);
|
|
return AddRecPhiMatch;
|
|
}
|
|
}
|
|
|
|
// Save the original insertion point so we can restore it when we're done.
|
|
SCEVInsertPointGuard Guard(Builder, this);
|
|
|
|
// Another AddRec may need to be recursively expanded below. For example, if
|
|
// this AddRec is quadratic, the StepV may itself be an AddRec in this
|
|
// loop. Remove this loop from the PostIncLoops set before expanding such
|
|
// AddRecs. Otherwise, we cannot find a valid position for the step
|
|
// (i.e. StepV can never dominate its loop header). Ideally, we could do
|
|
// SavedIncLoops.swap(PostIncLoops), but we generally have a single element,
|
|
// so it's not worth implementing SmallPtrSet::swap.
|
|
PostIncLoopSet SavedPostIncLoops = PostIncLoops;
|
|
PostIncLoops.clear();
|
|
|
|
// Expand code for the start value into the loop preheader.
|
|
assert(L->getLoopPreheader() &&
|
|
"Can't expand add recurrences without a loop preheader!");
|
|
Value *StartV = expandCodeFor(Normalized->getStart(), ExpandTy,
|
|
L->getLoopPreheader()->getTerminator());
|
|
|
|
// StartV must have been be inserted into L's preheader to dominate the new
|
|
// phi.
|
|
assert(!isa<Instruction>(StartV) ||
|
|
SE.DT.properlyDominates(cast<Instruction>(StartV)->getParent(),
|
|
L->getHeader()));
|
|
|
|
// Expand code for the step value. Do this before creating the PHI so that PHI
|
|
// reuse code doesn't see an incomplete PHI.
|
|
const SCEV *Step = Normalized->getStepRecurrence(SE);
|
|
// If the stride is negative, insert a sub instead of an add for the increment
|
|
// (unless it's a constant, because subtracts of constants are canonicalized
|
|
// to adds).
|
|
bool useSubtract = !ExpandTy->isPointerTy() && Step->isNonConstantNegative();
|
|
if (useSubtract)
|
|
Step = SE.getNegativeSCEV(Step);
|
|
// Expand the step somewhere that dominates the loop header.
|
|
Value *StepV = expandCodeFor(Step, IntTy, &L->getHeader()->front());
|
|
|
|
// The no-wrap behavior proved by IsIncrement(NUW|NSW) is only applicable if
|
|
// we actually do emit an addition. It does not apply if we emit a
|
|
// subtraction.
|
|
bool IncrementIsNUW = !useSubtract && IsIncrementNUW(SE, Normalized);
|
|
bool IncrementIsNSW = !useSubtract && IsIncrementNSW(SE, Normalized);
|
|
|
|
// Create the PHI.
|
|
BasicBlock *Header = L->getHeader();
|
|
Builder.SetInsertPoint(Header, Header->begin());
|
|
pred_iterator HPB = pred_begin(Header), HPE = pred_end(Header);
|
|
PHINode *PN = Builder.CreatePHI(ExpandTy, std::distance(HPB, HPE),
|
|
Twine(IVName) + ".iv");
|
|
rememberInstruction(PN);
|
|
|
|
// Create the step instructions and populate the PHI.
|
|
for (pred_iterator HPI = HPB; HPI != HPE; ++HPI) {
|
|
BasicBlock *Pred = *HPI;
|
|
|
|
// Add a start value.
|
|
if (!L->contains(Pred)) {
|
|
PN->addIncoming(StartV, Pred);
|
|
continue;
|
|
}
|
|
|
|
// Create a step value and add it to the PHI.
|
|
// If IVIncInsertLoop is non-null and equal to the addrec's loop, insert the
|
|
// instructions at IVIncInsertPos.
|
|
Instruction *InsertPos = L == IVIncInsertLoop ?
|
|
IVIncInsertPos : Pred->getTerminator();
|
|
Builder.SetInsertPoint(InsertPos);
|
|
Value *IncV = expandIVInc(PN, StepV, L, ExpandTy, IntTy, useSubtract);
|
|
|
|
if (isa<OverflowingBinaryOperator>(IncV)) {
|
|
if (IncrementIsNUW)
|
|
cast<BinaryOperator>(IncV)->setHasNoUnsignedWrap();
|
|
if (IncrementIsNSW)
|
|
cast<BinaryOperator>(IncV)->setHasNoSignedWrap();
|
|
}
|
|
PN->addIncoming(IncV, Pred);
|
|
}
|
|
|
|
// After expanding subexpressions, restore the PostIncLoops set so the caller
|
|
// can ensure that IVIncrement dominates the current uses.
|
|
PostIncLoops = SavedPostIncLoops;
|
|
|
|
// Remember this PHI, even in post-inc mode.
|
|
InsertedValues.insert(PN);
|
|
|
|
return PN;
|
|
}
|
|
|
|
Value *SCEVExpander::expandAddRecExprLiterally(const SCEVAddRecExpr *S) {
|
|
Type *STy = S->getType();
|
|
Type *IntTy = SE.getEffectiveSCEVType(STy);
|
|
const Loop *L = S->getLoop();
|
|
|
|
// Determine a normalized form of this expression, which is the expression
|
|
// before any post-inc adjustment is made.
|
|
const SCEVAddRecExpr *Normalized = S;
|
|
if (PostIncLoops.count(L)) {
|
|
PostIncLoopSet Loops;
|
|
Loops.insert(L);
|
|
Normalized = cast<SCEVAddRecExpr>(normalizeForPostIncUse(S, Loops, SE));
|
|
}
|
|
|
|
// Strip off any non-loop-dominating component from the addrec start.
|
|
const SCEV *Start = Normalized->getStart();
|
|
const SCEV *PostLoopOffset = nullptr;
|
|
if (!SE.properlyDominates(Start, L->getHeader())) {
|
|
PostLoopOffset = Start;
|
|
Start = SE.getConstant(Normalized->getType(), 0);
|
|
Normalized = cast<SCEVAddRecExpr>(
|
|
SE.getAddRecExpr(Start, Normalized->getStepRecurrence(SE),
|
|
Normalized->getLoop(),
|
|
Normalized->getNoWrapFlags(SCEV::FlagNW)));
|
|
}
|
|
|
|
// Strip off any non-loop-dominating component from the addrec step.
|
|
const SCEV *Step = Normalized->getStepRecurrence(SE);
|
|
const SCEV *PostLoopScale = nullptr;
|
|
if (!SE.dominates(Step, L->getHeader())) {
|
|
PostLoopScale = Step;
|
|
Step = SE.getConstant(Normalized->getType(), 1);
|
|
if (!Start->isZero()) {
|
|
// The normalization below assumes that Start is constant zero, so if
|
|
// it isn't re-associate Start to PostLoopOffset.
|
|
assert(!PostLoopOffset && "Start not-null but PostLoopOffset set?");
|
|
PostLoopOffset = Start;
|
|
Start = SE.getConstant(Normalized->getType(), 0);
|
|
}
|
|
Normalized =
|
|
cast<SCEVAddRecExpr>(SE.getAddRecExpr(
|
|
Start, Step, Normalized->getLoop(),
|
|
Normalized->getNoWrapFlags(SCEV::FlagNW)));
|
|
}
|
|
|
|
// Expand the core addrec. If we need post-loop scaling, force it to
|
|
// expand to an integer type to avoid the need for additional casting.
|
|
Type *ExpandTy = PostLoopScale ? IntTy : STy;
|
|
// In some cases, we decide to reuse an existing phi node but need to truncate
|
|
// it and/or invert the step.
|
|
Type *TruncTy = nullptr;
|
|
bool InvertStep = false;
|
|
PHINode *PN = getAddRecExprPHILiterally(Normalized, L, ExpandTy, IntTy,
|
|
TruncTy, InvertStep);
|
|
|
|
// Accommodate post-inc mode, if necessary.
|
|
Value *Result;
|
|
if (!PostIncLoops.count(L))
|
|
Result = PN;
|
|
else {
|
|
// In PostInc mode, use the post-incremented value.
|
|
BasicBlock *LatchBlock = L->getLoopLatch();
|
|
assert(LatchBlock && "PostInc mode requires a unique loop latch!");
|
|
Result = PN->getIncomingValueForBlock(LatchBlock);
|
|
|
|
// For an expansion to use the postinc form, the client must call
|
|
// expandCodeFor with an InsertPoint that is either outside the PostIncLoop
|
|
// or dominated by IVIncInsertPos.
|
|
if (isa<Instruction>(Result) &&
|
|
!SE.DT.dominates(cast<Instruction>(Result),
|
|
&*Builder.GetInsertPoint())) {
|
|
// The induction variable's postinc expansion does not dominate this use.
|
|
// IVUsers tries to prevent this case, so it is rare. However, it can
|
|
// happen when an IVUser outside the loop is not dominated by the latch
|
|
// block. Adjusting IVIncInsertPos before expansion begins cannot handle
|
|
// all cases. Consider a phi outide whose operand is replaced during
|
|
// expansion with the value of the postinc user. Without fundamentally
|
|
// changing the way postinc users are tracked, the only remedy is
|
|
// inserting an extra IV increment. StepV might fold into PostLoopOffset,
|
|
// but hopefully expandCodeFor handles that.
|
|
bool useSubtract =
|
|
!ExpandTy->isPointerTy() && Step->isNonConstantNegative();
|
|
if (useSubtract)
|
|
Step = SE.getNegativeSCEV(Step);
|
|
Value *StepV;
|
|
{
|
|
// Expand the step somewhere that dominates the loop header.
|
|
SCEVInsertPointGuard Guard(Builder, this);
|
|
StepV = expandCodeFor(Step, IntTy, &L->getHeader()->front());
|
|
}
|
|
Result = expandIVInc(PN, StepV, L, ExpandTy, IntTy, useSubtract);
|
|
}
|
|
}
|
|
|
|
// We have decided to reuse an induction variable of a dominating loop. Apply
|
|
// truncation and/or invertion of the step.
|
|
if (TruncTy) {
|
|
Type *ResTy = Result->getType();
|
|
// Normalize the result type.
|
|
if (ResTy != SE.getEffectiveSCEVType(ResTy))
|
|
Result = InsertNoopCastOfTo(Result, SE.getEffectiveSCEVType(ResTy));
|
|
// Truncate the result.
|
|
if (TruncTy != Result->getType()) {
|
|
Result = Builder.CreateTrunc(Result, TruncTy);
|
|
rememberInstruction(Result);
|
|
}
|
|
// Invert the result.
|
|
if (InvertStep) {
|
|
Result = Builder.CreateSub(expandCodeFor(Normalized->getStart(), TruncTy),
|
|
Result);
|
|
rememberInstruction(Result);
|
|
}
|
|
}
|
|
|
|
// Re-apply any non-loop-dominating scale.
|
|
if (PostLoopScale) {
|
|
assert(S->isAffine() && "Can't linearly scale non-affine recurrences.");
|
|
Result = InsertNoopCastOfTo(Result, IntTy);
|
|
Result = Builder.CreateMul(Result,
|
|
expandCodeFor(PostLoopScale, IntTy));
|
|
rememberInstruction(Result);
|
|
}
|
|
|
|
// Re-apply any non-loop-dominating offset.
|
|
if (PostLoopOffset) {
|
|
if (PointerType *PTy = dyn_cast<PointerType>(ExpandTy)) {
|
|
const SCEV *const OffsetArray[1] = { PostLoopOffset };
|
|
Result = expandAddToGEP(OffsetArray, OffsetArray+1, PTy, IntTy, Result);
|
|
} else {
|
|
Result = InsertNoopCastOfTo(Result, IntTy);
|
|
Result = Builder.CreateAdd(Result,
|
|
expandCodeFor(PostLoopOffset, IntTy));
|
|
rememberInstruction(Result);
|
|
}
|
|
}
|
|
|
|
return Result;
|
|
}
|
|
|
|
Value *SCEVExpander::visitAddRecExpr(const SCEVAddRecExpr *S) {
|
|
if (!CanonicalMode) return expandAddRecExprLiterally(S);
|
|
|
|
Type *Ty = SE.getEffectiveSCEVType(S->getType());
|
|
const Loop *L = S->getLoop();
|
|
|
|
// First check for an existing canonical IV in a suitable type.
|
|
PHINode *CanonicalIV = nullptr;
|
|
if (PHINode *PN = L->getCanonicalInductionVariable())
|
|
if (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)) {
|
|
SmallVector<const SCEV *, 4> NewOps(S->getNumOperands());
|
|
for (unsigned i = 0, e = S->getNumOperands(); i != e; ++i)
|
|
NewOps[i] = SE.getAnyExtendExpr(S->op_begin()[i], CanonicalIV->getType());
|
|
Value *V = expand(SE.getAddRecExpr(NewOps, S->getLoop(),
|
|
S->getNoWrapFlags(SCEV::FlagNW)));
|
|
BasicBlock::iterator NewInsertPt =
|
|
findInsertPointAfter(cast<Instruction>(V), Builder.GetInsertBlock());
|
|
V = expandCodeFor(SE.getTruncateExpr(SE.getUnknown(V), Ty), nullptr,
|
|
&*NewInsertPt);
|
|
return V;
|
|
}
|
|
|
|
// {X,+,F} --> X + {0,+,F}
|
|
if (!S->getStart()->isZero()) {
|
|
SmallVector<const SCEV *, 4> NewOps(S->op_begin(), S->op_end());
|
|
NewOps[0] = SE.getConstant(Ty, 0);
|
|
const SCEV *Rest = SE.getAddRecExpr(NewOps, L,
|
|
S->getNoWrapFlags(SCEV::FlagNW));
|
|
|
|
// Turn things like ptrtoint+arithmetic+inttoptr into GEP. See the
|
|
// comments on expandAddToGEP for details.
|
|
const SCEV *Base = S->getStart();
|
|
const SCEV *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 (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);
|
|
}
|
|
}
|
|
|
|
// Just do a normal add. Pre-expand the operands to suppress folding.
|
|
//
|
|
// The LHS and RHS values are factored out of the expand call to make the
|
|
// output independent of the argument evaluation order.
|
|
const SCEV *AddExprLHS = SE.getUnknown(expand(S->getStart()));
|
|
const SCEV *AddExprRHS = SE.getUnknown(expand(Rest));
|
|
return expand(SE.getAddExpr(AddExprLHS, AddExprRHS));
|
|
}
|
|
|
|
// If we don't yet have a canonical IV, create one.
|
|
if (!CanonicalIV) {
|
|
// Create and insert the PHI node for the induction variable in the
|
|
// specified loop.
|
|
BasicBlock *Header = L->getHeader();
|
|
pred_iterator HPB = pred_begin(Header), HPE = pred_end(Header);
|
|
CanonicalIV = PHINode::Create(Ty, std::distance(HPB, HPE), "indvar",
|
|
&Header->front());
|
|
rememberInstruction(CanonicalIV);
|
|
|
|
SmallSet<BasicBlock *, 4> PredSeen;
|
|
Constant *One = ConstantInt::get(Ty, 1);
|
|
for (pred_iterator HPI = HPB; HPI != HPE; ++HPI) {
|
|
BasicBlock *HP = *HPI;
|
|
if (!PredSeen.insert(HP).second) {
|
|
// There must be an incoming value for each predecessor, even the
|
|
// duplicates!
|
|
CanonicalIV->addIncoming(CanonicalIV->getIncomingValueForBlock(HP), HP);
|
|
continue;
|
|
}
|
|
|
|
if (L->contains(HP)) {
|
|
// Insert a unit add instruction right before the terminator
|
|
// corresponding to the back-edge.
|
|
Instruction *Add = BinaryOperator::CreateAdd(CanonicalIV, One,
|
|
"indvar.next",
|
|
HP->getTerminator());
|
|
Add->setDebugLoc(HP->getTerminator()->getDebugLoc());
|
|
rememberInstruction(Add);
|
|
CanonicalIV->addIncoming(Add, HP);
|
|
} else {
|
|
CanonicalIV->addIncoming(Constant::getNullValue(Ty), HP);
|
|
}
|
|
}
|
|
}
|
|
|
|
// {0,+,1} --> Insert a canonical induction variable into the loop!
|
|
if (S->isAffine() && S->getOperand(1)->isOne()) {
|
|
assert(Ty == SE.getEffectiveSCEVType(CanonicalIV->getType()) &&
|
|
"IVs with types different from the canonical IV should "
|
|
"already have been handled!");
|
|
return CanonicalIV;
|
|
}
|
|
|
|
// {0,+,F} --> {0,+,1} * F
|
|
|
|
// If this is a simple linear addrec, emit it now as a special case.
|
|
if (S->isAffine()) // {0,+,F} --> i*F
|
|
return
|
|
expand(SE.getTruncateOrNoop(
|
|
SE.getMulExpr(SE.getUnknown(CanonicalIV),
|
|
SE.getNoopOrAnyExtend(S->getOperand(1),
|
|
CanonicalIV->getType())),
|
|
Ty));
|
|
|
|
// 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.
|
|
const SCEV *IH = SE.getUnknown(CanonicalIV); // Get I as a "symbolic" SCEV.
|
|
|
|
// Promote S up to the canonical IV type, if the cast is foldable.
|
|
const SCEV *NewS = S;
|
|
const SCEV *Ext = SE.getNoopOrAnyExtend(S, CanonicalIV->getType());
|
|
if (isa<SCEVAddRecExpr>(Ext))
|
|
NewS = Ext;
|
|
|
|
const SCEV *V = cast<SCEVAddRecExpr>(NewS)->evaluateAtIteration(IH, SE);
|
|
//cerr << "Evaluated: " << *this << "\n to: " << *V << "\n";
|
|
|
|
// Truncate the result down to the original type, if needed.
|
|
const SCEV *T = SE.getTruncateOrNoop(V, Ty);
|
|
return expand(T);
|
|
}
|
|
|
|
Value *SCEVExpander::visitTruncateExpr(const SCEVTruncateExpr *S) {
|
|
Type *Ty = SE.getEffectiveSCEVType(S->getType());
|
|
Value *V = expandCodeFor(S->getOperand(),
|
|
SE.getEffectiveSCEVType(S->getOperand()->getType()));
|
|
Value *I = Builder.CreateTrunc(V, Ty);
|
|
rememberInstruction(I);
|
|
return I;
|
|
}
|
|
|
|
Value *SCEVExpander::visitZeroExtendExpr(const SCEVZeroExtendExpr *S) {
|
|
Type *Ty = SE.getEffectiveSCEVType(S->getType());
|
|
Value *V = expandCodeFor(S->getOperand(),
|
|
SE.getEffectiveSCEVType(S->getOperand()->getType()));
|
|
Value *I = Builder.CreateZExt(V, Ty);
|
|
rememberInstruction(I);
|
|
return I;
|
|
}
|
|
|
|
Value *SCEVExpander::visitSignExtendExpr(const SCEVSignExtendExpr *S) {
|
|
Type *Ty = SE.getEffectiveSCEVType(S->getType());
|
|
Value *V = expandCodeFor(S->getOperand(),
|
|
SE.getEffectiveSCEVType(S->getOperand()->getType()));
|
|
Value *I = Builder.CreateSExt(V, Ty);
|
|
rememberInstruction(I);
|
|
return I;
|
|
}
|
|
|
|
Value *SCEVExpander::visitSMaxExpr(const SCEVSMaxExpr *S) {
|
|
Value *LHS = expand(S->getOperand(S->getNumOperands()-1));
|
|
Type *Ty = LHS->getType();
|
|
for (int i = S->getNumOperands()-2; i >= 0; --i) {
|
|
// In the case of mixed integer and pointer types, do the
|
|
// rest of the comparisons as integer.
|
|
if (S->getOperand(i)->getType() != Ty) {
|
|
Ty = SE.getEffectiveSCEVType(Ty);
|
|
LHS = InsertNoopCastOfTo(LHS, Ty);
|
|
}
|
|
Value *RHS = expandCodeFor(S->getOperand(i), Ty);
|
|
Value *ICmp = Builder.CreateICmpSGT(LHS, RHS);
|
|
rememberInstruction(ICmp);
|
|
Value *Sel = Builder.CreateSelect(ICmp, LHS, RHS, "smax");
|
|
rememberInstruction(Sel);
|
|
LHS = Sel;
|
|
}
|
|
// In the case of mixed integer and pointer types, cast the
|
|
// final result back to the pointer type.
|
|
if (LHS->getType() != S->getType())
|
|
LHS = InsertNoopCastOfTo(LHS, S->getType());
|
|
return LHS;
|
|
}
|
|
|
|
Value *SCEVExpander::visitUMaxExpr(const SCEVUMaxExpr *S) {
|
|
Value *LHS = expand(S->getOperand(S->getNumOperands()-1));
|
|
Type *Ty = LHS->getType();
|
|
for (int i = S->getNumOperands()-2; i >= 0; --i) {
|
|
// In the case of mixed integer and pointer types, do the
|
|
// rest of the comparisons as integer.
|
|
if (S->getOperand(i)->getType() != Ty) {
|
|
Ty = SE.getEffectiveSCEVType(Ty);
|
|
LHS = InsertNoopCastOfTo(LHS, Ty);
|
|
}
|
|
Value *RHS = expandCodeFor(S->getOperand(i), Ty);
|
|
Value *ICmp = Builder.CreateICmpUGT(LHS, RHS);
|
|
rememberInstruction(ICmp);
|
|
Value *Sel = Builder.CreateSelect(ICmp, LHS, RHS, "umax");
|
|
rememberInstruction(Sel);
|
|
LHS = Sel;
|
|
}
|
|
// In the case of mixed integer and pointer types, cast the
|
|
// final result back to the pointer type.
|
|
if (LHS->getType() != S->getType())
|
|
LHS = InsertNoopCastOfTo(LHS, S->getType());
|
|
return LHS;
|
|
}
|
|
|
|
Value *SCEVExpander::expandCodeFor(const SCEV *SH, Type *Ty,
|
|
Instruction *IP) {
|
|
setInsertPoint(IP);
|
|
return expandCodeFor(SH, Ty);
|
|
}
|
|
|
|
Value *SCEVExpander::expandCodeFor(const SCEV *SH, 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;
|
|
}
|
|
|
|
ScalarEvolution::ValueOffsetPair
|
|
SCEVExpander::FindValueInExprValueMap(const SCEV *S,
|
|
const Instruction *InsertPt) {
|
|
SetVector<ScalarEvolution::ValueOffsetPair> *Set = SE.getSCEVValues(S);
|
|
// If the expansion is not in CanonicalMode, and the SCEV contains any
|
|
// sub scAddRecExpr type SCEV, it is required to expand the SCEV literally.
|
|
if (CanonicalMode || !SE.containsAddRecurrence(S)) {
|
|
// If S is scConstant, it may be worse to reuse an existing Value.
|
|
if (S->getSCEVType() != scConstant && Set) {
|
|
// Choose a Value from the set which dominates the insertPt.
|
|
// insertPt should be inside the Value's parent loop so as not to break
|
|
// the LCSSA form.
|
|
for (auto const &VOPair : *Set) {
|
|
Value *V = VOPair.first;
|
|
ConstantInt *Offset = VOPair.second;
|
|
Instruction *EntInst = nullptr;
|
|
if (V && isa<Instruction>(V) && (EntInst = cast<Instruction>(V)) &&
|
|
S->getType() == V->getType() &&
|
|
EntInst->getFunction() == InsertPt->getFunction() &&
|
|
SE.DT.dominates(EntInst, InsertPt) &&
|
|
(SE.LI.getLoopFor(EntInst->getParent()) == nullptr ||
|
|
SE.LI.getLoopFor(EntInst->getParent())->contains(InsertPt)))
|
|
return {V, Offset};
|
|
}
|
|
}
|
|
}
|
|
return {nullptr, nullptr};
|
|
}
|
|
|
|
// The expansion of SCEV will either reuse a previous Value in ExprValueMap,
|
|
// or expand the SCEV literally. Specifically, if the expansion is in LSRMode,
|
|
// and the SCEV contains any sub scAddRecExpr type SCEV, it will be expanded
|
|
// literally, to prevent LSR's transformed SCEV from being reverted. Otherwise,
|
|
// the expansion will try to reuse Value from ExprValueMap, and only when it
|
|
// fails, expand the SCEV literally.
|
|
Value *SCEVExpander::expand(const SCEV *S) {
|
|
// Compute an insertion point for this SCEV object. Hoist the instructions
|
|
// as far out in the loop nest as possible.
|
|
Instruction *InsertPt = &*Builder.GetInsertPoint();
|
|
for (Loop *L = SE.LI.getLoopFor(Builder.GetInsertBlock());;
|
|
L = L->getParentLoop())
|
|
if (SE.isLoopInvariant(S, L)) {
|
|
if (!L) break;
|
|
if (BasicBlock *Preheader = L->getLoopPreheader())
|
|
InsertPt = Preheader->getTerminator();
|
|
else {
|
|
// LSR sets the insertion point for AddRec start/step values to the
|
|
// block start to simplify value reuse, even though it's an invalid
|
|
// position. SCEVExpander must correct for this in all cases.
|
|
InsertPt = &*L->getHeader()->getFirstInsertionPt();
|
|
}
|
|
} else {
|
|
// If the SCEV is computable at this level, insert it into the header
|
|
// after the PHIs (and after any other instructions that we've inserted
|
|
// there) so that it is guaranteed to dominate any user inside the loop.
|
|
if (L && SE.hasComputableLoopEvolution(S, L) && !PostIncLoops.count(L))
|
|
InsertPt = &*L->getHeader()->getFirstInsertionPt();
|
|
while (InsertPt->getIterator() != Builder.GetInsertPoint() &&
|
|
(isInsertedInstruction(InsertPt) ||
|
|
isa<DbgInfoIntrinsic>(InsertPt))) {
|
|
InsertPt = &*std::next(InsertPt->getIterator());
|
|
}
|
|
break;
|
|
}
|
|
|
|
// Check to see if we already expanded this here.
|
|
auto I = InsertedExpressions.find(std::make_pair(S, InsertPt));
|
|
if (I != InsertedExpressions.end())
|
|
return I->second;
|
|
|
|
SCEVInsertPointGuard Guard(Builder, this);
|
|
Builder.SetInsertPoint(InsertPt);
|
|
|
|
// Expand the expression into instructions.
|
|
ScalarEvolution::ValueOffsetPair VO = FindValueInExprValueMap(S, InsertPt);
|
|
Value *V = VO.first;
|
|
|
|
if (!V)
|
|
V = visit(S);
|
|
else if (VO.second) {
|
|
if (PointerType *Vty = dyn_cast<PointerType>(V->getType())) {
|
|
Type *Ety = Vty->getPointerElementType();
|
|
int64_t Offset = VO.second->getSExtValue();
|
|
int64_t ESize = SE.getTypeSizeInBits(Ety);
|
|
if ((Offset * 8) % ESize == 0) {
|
|
ConstantInt *Idx =
|
|
ConstantInt::getSigned(VO.second->getType(), -(Offset * 8) / ESize);
|
|
V = Builder.CreateGEP(Ety, V, Idx, "scevgep");
|
|
} else {
|
|
ConstantInt *Idx =
|
|
ConstantInt::getSigned(VO.second->getType(), -Offset);
|
|
unsigned AS = Vty->getAddressSpace();
|
|
V = Builder.CreateBitCast(V, Type::getInt8PtrTy(SE.getContext(), AS));
|
|
V = Builder.CreateGEP(Type::getInt8Ty(SE.getContext()), V, Idx,
|
|
"uglygep");
|
|
V = Builder.CreateBitCast(V, Vty);
|
|
}
|
|
} else {
|
|
V = Builder.CreateSub(V, VO.second);
|
|
}
|
|
}
|
|
// Remember the expanded value for this SCEV at this location.
|
|
//
|
|
// This is independent of PostIncLoops. The mapped value simply materializes
|
|
// the expression at this insertion point. If the mapped value happened to be
|
|
// a postinc expansion, it could be reused by a non-postinc user, but only if
|
|
// its insertion point was already at the head of the loop.
|
|
InsertedExpressions[std::make_pair(S, InsertPt)] = V;
|
|
return V;
|
|
}
|
|
|
|
void SCEVExpander::rememberInstruction(Value *I) {
|
|
if (!PostIncLoops.empty())
|
|
InsertedPostIncValues.insert(I);
|
|
else
|
|
InsertedValues.insert(I);
|
|
}
|
|
|
|
/// 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 *
|
|
SCEVExpander::getOrInsertCanonicalInductionVariable(const Loop *L,
|
|
Type *Ty) {
|
|
assert(Ty->isIntegerTy() && "Can only insert integer induction variables!");
|
|
|
|
// Build a SCEV for {0,+,1}<L>.
|
|
// Conservatively use FlagAnyWrap for now.
|
|
const SCEV *H = SE.getAddRecExpr(SE.getConstant(Ty, 0),
|
|
SE.getConstant(Ty, 1), L, SCEV::FlagAnyWrap);
|
|
|
|
// Emit code for it.
|
|
SCEVInsertPointGuard Guard(Builder, this);
|
|
PHINode *V =
|
|
cast<PHINode>(expandCodeFor(H, nullptr, &L->getHeader()->front()));
|
|
|
|
return V;
|
|
}
|
|
|
|
/// replaceCongruentIVs - Check for congruent phis in this loop header and
|
|
/// replace them with their most canonical representative. Return the number of
|
|
/// phis eliminated.
|
|
///
|
|
/// This does not depend on any SCEVExpander state but should be used in
|
|
/// the same context that SCEVExpander is used.
|
|
unsigned
|
|
SCEVExpander::replaceCongruentIVs(Loop *L, const DominatorTree *DT,
|
|
SmallVectorImpl<WeakTrackingVH> &DeadInsts,
|
|
const TargetTransformInfo *TTI) {
|
|
// Find integer phis in order of increasing width.
|
|
SmallVector<PHINode*, 8> Phis;
|
|
for (auto &I : *L->getHeader()) {
|
|
if (auto *PN = dyn_cast<PHINode>(&I))
|
|
Phis.push_back(PN);
|
|
else
|
|
break;
|
|
}
|
|
|
|
if (TTI)
|
|
std::sort(Phis.begin(), Phis.end(), [](Value *LHS, Value *RHS) {
|
|
// Put pointers at the back and make sure pointer < pointer = false.
|
|
if (!LHS->getType()->isIntegerTy() || !RHS->getType()->isIntegerTy())
|
|
return RHS->getType()->isIntegerTy() && !LHS->getType()->isIntegerTy();
|
|
return RHS->getType()->getPrimitiveSizeInBits() <
|
|
LHS->getType()->getPrimitiveSizeInBits();
|
|
});
|
|
|
|
unsigned NumElim = 0;
|
|
DenseMap<const SCEV *, PHINode *> ExprToIVMap;
|
|
// Process phis from wide to narrow. Map wide phis to their truncation
|
|
// so narrow phis can reuse them.
|
|
for (PHINode *Phi : Phis) {
|
|
auto SimplifyPHINode = [&](PHINode *PN) -> Value * {
|
|
if (Value *V = SimplifyInstruction(PN, {DL, &SE.TLI, &SE.DT, &SE.AC}))
|
|
return V;
|
|
if (!SE.isSCEVable(PN->getType()))
|
|
return nullptr;
|
|
auto *Const = dyn_cast<SCEVConstant>(SE.getSCEV(PN));
|
|
if (!Const)
|
|
return nullptr;
|
|
return Const->getValue();
|
|
};
|
|
|
|
// Fold constant phis. They may be congruent to other constant phis and
|
|
// would confuse the logic below that expects proper IVs.
|
|
if (Value *V = SimplifyPHINode(Phi)) {
|
|
if (V->getType() != Phi->getType())
|
|
continue;
|
|
Phi->replaceAllUsesWith(V);
|
|
DeadInsts.emplace_back(Phi);
|
|
++NumElim;
|
|
DEBUG_WITH_TYPE(DebugType, dbgs()
|
|
<< "INDVARS: Eliminated constant iv: " << *Phi << '\n');
|
|
continue;
|
|
}
|
|
|
|
if (!SE.isSCEVable(Phi->getType()))
|
|
continue;
|
|
|
|
PHINode *&OrigPhiRef = ExprToIVMap[SE.getSCEV(Phi)];
|
|
if (!OrigPhiRef) {
|
|
OrigPhiRef = Phi;
|
|
if (Phi->getType()->isIntegerTy() && TTI &&
|
|
TTI->isTruncateFree(Phi->getType(), Phis.back()->getType())) {
|
|
// This phi can be freely truncated to the narrowest phi type. Map the
|
|
// truncated expression to it so it will be reused for narrow types.
|
|
const SCEV *TruncExpr =
|
|
SE.getTruncateExpr(SE.getSCEV(Phi), Phis.back()->getType());
|
|
ExprToIVMap[TruncExpr] = Phi;
|
|
}
|
|
continue;
|
|
}
|
|
|
|
// Replacing a pointer phi with an integer phi or vice-versa doesn't make
|
|
// sense.
|
|
if (OrigPhiRef->getType()->isPointerTy() != Phi->getType()->isPointerTy())
|
|
continue;
|
|
|
|
if (BasicBlock *LatchBlock = L->getLoopLatch()) {
|
|
Instruction *OrigInc = dyn_cast<Instruction>(
|
|
OrigPhiRef->getIncomingValueForBlock(LatchBlock));
|
|
Instruction *IsomorphicInc =
|
|
dyn_cast<Instruction>(Phi->getIncomingValueForBlock(LatchBlock));
|
|
|
|
if (OrigInc && IsomorphicInc) {
|
|
// If this phi has the same width but is more canonical, replace the
|
|
// original with it. As part of the "more canonical" determination,
|
|
// respect a prior decision to use an IV chain.
|
|
if (OrigPhiRef->getType() == Phi->getType() &&
|
|
!(ChainedPhis.count(Phi) ||
|
|
isExpandedAddRecExprPHI(OrigPhiRef, OrigInc, L)) &&
|
|
(ChainedPhis.count(Phi) ||
|
|
isExpandedAddRecExprPHI(Phi, IsomorphicInc, L))) {
|
|
std::swap(OrigPhiRef, Phi);
|
|
std::swap(OrigInc, IsomorphicInc);
|
|
}
|
|
// Replacing the congruent phi is sufficient because acyclic
|
|
// redundancy elimination, CSE/GVN, should handle the
|
|
// rest. However, once SCEV proves that a phi is congruent,
|
|
// it's often the head of an IV user cycle that is isomorphic
|
|
// with the original phi. It's worth eagerly cleaning up the
|
|
// common case of a single IV increment so that DeleteDeadPHIs
|
|
// can remove cycles that had postinc uses.
|
|
const SCEV *TruncExpr =
|
|
SE.getTruncateOrNoop(SE.getSCEV(OrigInc), IsomorphicInc->getType());
|
|
if (OrigInc != IsomorphicInc &&
|
|
TruncExpr == SE.getSCEV(IsomorphicInc) &&
|
|
SE.LI.replacementPreservesLCSSAForm(IsomorphicInc, OrigInc) &&
|
|
hoistIVInc(OrigInc, IsomorphicInc)) {
|
|
DEBUG_WITH_TYPE(DebugType,
|
|
dbgs() << "INDVARS: Eliminated congruent iv.inc: "
|
|
<< *IsomorphicInc << '\n');
|
|
Value *NewInc = OrigInc;
|
|
if (OrigInc->getType() != IsomorphicInc->getType()) {
|
|
Instruction *IP = nullptr;
|
|
if (PHINode *PN = dyn_cast<PHINode>(OrigInc))
|
|
IP = &*PN->getParent()->getFirstInsertionPt();
|
|
else
|
|
IP = OrigInc->getNextNode();
|
|
|
|
IRBuilder<> Builder(IP);
|
|
Builder.SetCurrentDebugLocation(IsomorphicInc->getDebugLoc());
|
|
NewInc = Builder.CreateTruncOrBitCast(
|
|
OrigInc, IsomorphicInc->getType(), IVName);
|
|
}
|
|
IsomorphicInc->replaceAllUsesWith(NewInc);
|
|
DeadInsts.emplace_back(IsomorphicInc);
|
|
}
|
|
}
|
|
}
|
|
DEBUG_WITH_TYPE(DebugType, dbgs() << "INDVARS: Eliminated congruent iv: "
|
|
<< *Phi << '\n');
|
|
++NumElim;
|
|
Value *NewIV = OrigPhiRef;
|
|
if (OrigPhiRef->getType() != Phi->getType()) {
|
|
IRBuilder<> Builder(&*L->getHeader()->getFirstInsertionPt());
|
|
Builder.SetCurrentDebugLocation(Phi->getDebugLoc());
|
|
NewIV = Builder.CreateTruncOrBitCast(OrigPhiRef, Phi->getType(), IVName);
|
|
}
|
|
Phi->replaceAllUsesWith(NewIV);
|
|
DeadInsts.emplace_back(Phi);
|
|
}
|
|
return NumElim;
|
|
}
|
|
|
|
Value *SCEVExpander::getExactExistingExpansion(const SCEV *S,
|
|
const Instruction *At, Loop *L) {
|
|
Optional<ScalarEvolution::ValueOffsetPair> VO =
|
|
getRelatedExistingExpansion(S, At, L);
|
|
if (VO && VO.getValue().second == nullptr)
|
|
return VO.getValue().first;
|
|
return nullptr;
|
|
}
|
|
|
|
Optional<ScalarEvolution::ValueOffsetPair>
|
|
SCEVExpander::getRelatedExistingExpansion(const SCEV *S, const Instruction *At,
|
|
Loop *L) {
|
|
using namespace llvm::PatternMatch;
|
|
|
|
SmallVector<BasicBlock *, 4> ExitingBlocks;
|
|
L->getExitingBlocks(ExitingBlocks);
|
|
|
|
// Look for suitable value in simple conditions at the loop exits.
|
|
for (BasicBlock *BB : ExitingBlocks) {
|
|
ICmpInst::Predicate Pred;
|
|
Instruction *LHS, *RHS;
|
|
BasicBlock *TrueBB, *FalseBB;
|
|
|
|
if (!match(BB->getTerminator(),
|
|
m_Br(m_ICmp(Pred, m_Instruction(LHS), m_Instruction(RHS)),
|
|
TrueBB, FalseBB)))
|
|
continue;
|
|
|
|
if (SE.getSCEV(LHS) == S && SE.DT.dominates(LHS, At))
|
|
return ScalarEvolution::ValueOffsetPair(LHS, nullptr);
|
|
|
|
if (SE.getSCEV(RHS) == S && SE.DT.dominates(RHS, At))
|
|
return ScalarEvolution::ValueOffsetPair(RHS, nullptr);
|
|
}
|
|
|
|
// Use expand's logic which is used for reusing a previous Value in
|
|
// ExprValueMap.
|
|
ScalarEvolution::ValueOffsetPair VO = FindValueInExprValueMap(S, At);
|
|
if (VO.first)
|
|
return VO;
|
|
|
|
// There is potential to make this significantly smarter, but this simple
|
|
// heuristic already gets some interesting cases.
|
|
|
|
// Can not find suitable value.
|
|
return None;
|
|
}
|
|
|
|
bool SCEVExpander::isHighCostExpansionHelper(
|
|
const SCEV *S, Loop *L, const Instruction *At,
|
|
SmallPtrSetImpl<const SCEV *> &Processed) {
|
|
|
|
// If we can find an existing value for this scev available at the point "At"
|
|
// then consider the expression cheap.
|
|
if (At && getRelatedExistingExpansion(S, At, L))
|
|
return false;
|
|
|
|
// Zero/One operand expressions
|
|
switch (S->getSCEVType()) {
|
|
case scUnknown:
|
|
case scConstant:
|
|
return false;
|
|
case scTruncate:
|
|
return isHighCostExpansionHelper(cast<SCEVTruncateExpr>(S)->getOperand(),
|
|
L, At, Processed);
|
|
case scZeroExtend:
|
|
return isHighCostExpansionHelper(cast<SCEVZeroExtendExpr>(S)->getOperand(),
|
|
L, At, Processed);
|
|
case scSignExtend:
|
|
return isHighCostExpansionHelper(cast<SCEVSignExtendExpr>(S)->getOperand(),
|
|
L, At, Processed);
|
|
}
|
|
|
|
if (!Processed.insert(S).second)
|
|
return false;
|
|
|
|
if (auto *UDivExpr = dyn_cast<SCEVUDivExpr>(S)) {
|
|
// If the divisor is a power of two and the SCEV type fits in a native
|
|
// integer, consider the division cheap irrespective of whether it occurs in
|
|
// the user code since it can be lowered into a right shift.
|
|
if (auto *SC = dyn_cast<SCEVConstant>(UDivExpr->getRHS()))
|
|
if (SC->getAPInt().isPowerOf2()) {
|
|
const DataLayout &DL =
|
|
L->getHeader()->getParent()->getParent()->getDataLayout();
|
|
unsigned Width = cast<IntegerType>(UDivExpr->getType())->getBitWidth();
|
|
return DL.isIllegalInteger(Width);
|
|
}
|
|
|
|
// UDivExpr is very likely a UDiv that ScalarEvolution's HowFarToZero or
|
|
// HowManyLessThans produced to compute a precise expression, rather than a
|
|
// UDiv from the user's code. If we can't find a UDiv in the code with some
|
|
// simple searching, assume the former consider UDivExpr expensive to
|
|
// compute.
|
|
BasicBlock *ExitingBB = L->getExitingBlock();
|
|
if (!ExitingBB)
|
|
return true;
|
|
|
|
// At the beginning of this function we already tried to find existing value
|
|
// for plain 'S'. Now try to lookup 'S + 1' since it is common pattern
|
|
// involving division. This is just a simple search heuristic.
|
|
if (!At)
|
|
At = &ExitingBB->back();
|
|
if (!getRelatedExistingExpansion(
|
|
SE.getAddExpr(S, SE.getConstant(S->getType(), 1)), At, L))
|
|
return true;
|
|
}
|
|
|
|
// HowManyLessThans uses a Max expression whenever the loop is not guarded by
|
|
// the exit condition.
|
|
if (isa<SCEVSMaxExpr>(S) || isa<SCEVUMaxExpr>(S))
|
|
return true;
|
|
|
|
// Recurse past nary expressions, which commonly occur in the
|
|
// BackedgeTakenCount. They may already exist in program code, and if not,
|
|
// they are not too expensive rematerialize.
|
|
if (const SCEVNAryExpr *NAry = dyn_cast<SCEVNAryExpr>(S)) {
|
|
for (auto *Op : NAry->operands())
|
|
if (isHighCostExpansionHelper(Op, L, At, Processed))
|
|
return true;
|
|
}
|
|
|
|
// If we haven't recognized an expensive SCEV pattern, assume it's an
|
|
// expression produced by program code.
|
|
return false;
|
|
}
|
|
|
|
Value *SCEVExpander::expandCodeForPredicate(const SCEVPredicate *Pred,
|
|
Instruction *IP) {
|
|
assert(IP);
|
|
switch (Pred->getKind()) {
|
|
case SCEVPredicate::P_Union:
|
|
return expandUnionPredicate(cast<SCEVUnionPredicate>(Pred), IP);
|
|
case SCEVPredicate::P_Equal:
|
|
return expandEqualPredicate(cast<SCEVEqualPredicate>(Pred), IP);
|
|
case SCEVPredicate::P_Wrap: {
|
|
auto *AddRecPred = cast<SCEVWrapPredicate>(Pred);
|
|
return expandWrapPredicate(AddRecPred, IP);
|
|
}
|
|
}
|
|
llvm_unreachable("Unknown SCEV predicate type");
|
|
}
|
|
|
|
Value *SCEVExpander::expandEqualPredicate(const SCEVEqualPredicate *Pred,
|
|
Instruction *IP) {
|
|
Value *Expr0 = expandCodeFor(Pred->getLHS(), Pred->getLHS()->getType(), IP);
|
|
Value *Expr1 = expandCodeFor(Pred->getRHS(), Pred->getRHS()->getType(), IP);
|
|
|
|
Builder.SetInsertPoint(IP);
|
|
auto *I = Builder.CreateICmpNE(Expr0, Expr1, "ident.check");
|
|
return I;
|
|
}
|
|
|
|
Value *SCEVExpander::generateOverflowCheck(const SCEVAddRecExpr *AR,
|
|
Instruction *Loc, bool Signed) {
|
|
assert(AR->isAffine() && "Cannot generate RT check for "
|
|
"non-affine expression");
|
|
|
|
SCEVUnionPredicate Pred;
|
|
const SCEV *ExitCount =
|
|
SE.getPredicatedBackedgeTakenCount(AR->getLoop(), Pred);
|
|
|
|
assert(ExitCount != SE.getCouldNotCompute() && "Invalid loop count");
|
|
|
|
const SCEV *Step = AR->getStepRecurrence(SE);
|
|
const SCEV *Start = AR->getStart();
|
|
|
|
unsigned SrcBits = SE.getTypeSizeInBits(ExitCount->getType());
|
|
unsigned DstBits = SE.getTypeSizeInBits(AR->getType());
|
|
|
|
// The expression {Start,+,Step} has nusw/nssw if
|
|
// Step < 0, Start - |Step| * Backedge <= Start
|
|
// Step >= 0, Start + |Step| * Backedge > Start
|
|
// and |Step| * Backedge doesn't unsigned overflow.
|
|
|
|
IntegerType *CountTy = IntegerType::get(Loc->getContext(), SrcBits);
|
|
Builder.SetInsertPoint(Loc);
|
|
Value *TripCountVal = expandCodeFor(ExitCount, CountTy, Loc);
|
|
|
|
IntegerType *Ty =
|
|
IntegerType::get(Loc->getContext(), SE.getTypeSizeInBits(AR->getType()));
|
|
|
|
Value *StepValue = expandCodeFor(Step, Ty, Loc);
|
|
Value *NegStepValue = expandCodeFor(SE.getNegativeSCEV(Step), Ty, Loc);
|
|
Value *StartValue = expandCodeFor(Start, Ty, Loc);
|
|
|
|
ConstantInt *Zero =
|
|
ConstantInt::get(Loc->getContext(), APInt::getNullValue(DstBits));
|
|
|
|
Builder.SetInsertPoint(Loc);
|
|
// Compute |Step|
|
|
Value *StepCompare = Builder.CreateICmp(ICmpInst::ICMP_SLT, StepValue, Zero);
|
|
Value *AbsStep = Builder.CreateSelect(StepCompare, NegStepValue, StepValue);
|
|
|
|
// Get the backedge taken count and truncate or extended to the AR type.
|
|
Value *TruncTripCount = Builder.CreateZExtOrTrunc(TripCountVal, Ty);
|
|
auto *MulF = Intrinsic::getDeclaration(Loc->getModule(),
|
|
Intrinsic::umul_with_overflow, Ty);
|
|
|
|
// Compute |Step| * Backedge
|
|
CallInst *Mul = Builder.CreateCall(MulF, {AbsStep, TruncTripCount}, "mul");
|
|
Value *MulV = Builder.CreateExtractValue(Mul, 0, "mul.result");
|
|
Value *OfMul = Builder.CreateExtractValue(Mul, 1, "mul.overflow");
|
|
|
|
// Compute:
|
|
// Start + |Step| * Backedge < Start
|
|
// Start - |Step| * Backedge > Start
|
|
Value *Add = Builder.CreateAdd(StartValue, MulV);
|
|
Value *Sub = Builder.CreateSub(StartValue, MulV);
|
|
|
|
Value *EndCompareGT = Builder.CreateICmp(
|
|
Signed ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT, Sub, StartValue);
|
|
|
|
Value *EndCompareLT = Builder.CreateICmp(
|
|
Signed ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT, Add, StartValue);
|
|
|
|
// Select the answer based on the sign of Step.
|
|
Value *EndCheck =
|
|
Builder.CreateSelect(StepCompare, EndCompareGT, EndCompareLT);
|
|
|
|
// If the backedge taken count type is larger than the AR type,
|
|
// check that we don't drop any bits by truncating it. If we are
|
|
// droping bits, then we have overflow (unless the step is zero).
|
|
if (SE.getTypeSizeInBits(CountTy) > SE.getTypeSizeInBits(Ty)) {
|
|
auto MaxVal = APInt::getMaxValue(DstBits).zext(SrcBits);
|
|
auto *BackedgeCheck =
|
|
Builder.CreateICmp(ICmpInst::ICMP_UGT, TripCountVal,
|
|
ConstantInt::get(Loc->getContext(), MaxVal));
|
|
BackedgeCheck = Builder.CreateAnd(
|
|
BackedgeCheck, Builder.CreateICmp(ICmpInst::ICMP_NE, StepValue, Zero));
|
|
|
|
EndCheck = Builder.CreateOr(EndCheck, BackedgeCheck);
|
|
}
|
|
|
|
EndCheck = Builder.CreateOr(EndCheck, OfMul);
|
|
return EndCheck;
|
|
}
|
|
|
|
Value *SCEVExpander::expandWrapPredicate(const SCEVWrapPredicate *Pred,
|
|
Instruction *IP) {
|
|
const auto *A = cast<SCEVAddRecExpr>(Pred->getExpr());
|
|
Value *NSSWCheck = nullptr, *NUSWCheck = nullptr;
|
|
|
|
// Add a check for NUSW
|
|
if (Pred->getFlags() & SCEVWrapPredicate::IncrementNUSW)
|
|
NUSWCheck = generateOverflowCheck(A, IP, false);
|
|
|
|
// Add a check for NSSW
|
|
if (Pred->getFlags() & SCEVWrapPredicate::IncrementNSSW)
|
|
NSSWCheck = generateOverflowCheck(A, IP, true);
|
|
|
|
if (NUSWCheck && NSSWCheck)
|
|
return Builder.CreateOr(NUSWCheck, NSSWCheck);
|
|
|
|
if (NUSWCheck)
|
|
return NUSWCheck;
|
|
|
|
if (NSSWCheck)
|
|
return NSSWCheck;
|
|
|
|
return ConstantInt::getFalse(IP->getContext());
|
|
}
|
|
|
|
Value *SCEVExpander::expandUnionPredicate(const SCEVUnionPredicate *Union,
|
|
Instruction *IP) {
|
|
auto *BoolType = IntegerType::get(IP->getContext(), 1);
|
|
Value *Check = ConstantInt::getNullValue(BoolType);
|
|
|
|
// Loop over all checks in this set.
|
|
for (auto Pred : Union->getPredicates()) {
|
|
auto *NextCheck = expandCodeForPredicate(Pred, IP);
|
|
Builder.SetInsertPoint(IP);
|
|
Check = Builder.CreateOr(Check, NextCheck);
|
|
}
|
|
|
|
return Check;
|
|
}
|
|
|
|
namespace {
|
|
// Search for a SCEV subexpression that is not safe to expand. Any expression
|
|
// that may expand to a !isSafeToSpeculativelyExecute value is unsafe, namely
|
|
// UDiv expressions. We don't know if the UDiv is derived from an IR divide
|
|
// instruction, but the important thing is that we prove the denominator is
|
|
// nonzero before expansion.
|
|
//
|
|
// IVUsers already checks that IV-derived expressions are safe. So this check is
|
|
// only needed when the expression includes some subexpression that is not IV
|
|
// derived.
|
|
//
|
|
// Currently, we only allow division by a nonzero constant here. If this is
|
|
// inadequate, we could easily allow division by SCEVUnknown by using
|
|
// ValueTracking to check isKnownNonZero().
|
|
//
|
|
// We cannot generally expand recurrences unless the step dominates the loop
|
|
// header. The expander handles the special case of affine recurrences by
|
|
// scaling the recurrence outside the loop, but this technique isn't generally
|
|
// applicable. Expanding a nested recurrence outside a loop requires computing
|
|
// binomial coefficients. This could be done, but the recurrence has to be in a
|
|
// perfectly reduced form, which can't be guaranteed.
|
|
struct SCEVFindUnsafe {
|
|
ScalarEvolution &SE;
|
|
bool IsUnsafe;
|
|
|
|
SCEVFindUnsafe(ScalarEvolution &se): SE(se), IsUnsafe(false) {}
|
|
|
|
bool follow(const SCEV *S) {
|
|
if (const SCEVUDivExpr *D = dyn_cast<SCEVUDivExpr>(S)) {
|
|
const SCEVConstant *SC = dyn_cast<SCEVConstant>(D->getRHS());
|
|
if (!SC || SC->getValue()->isZero()) {
|
|
IsUnsafe = true;
|
|
return false;
|
|
}
|
|
}
|
|
if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
|
|
const SCEV *Step = AR->getStepRecurrence(SE);
|
|
if (!AR->isAffine() && !SE.dominates(Step, AR->getLoop()->getHeader())) {
|
|
IsUnsafe = true;
|
|
return false;
|
|
}
|
|
}
|
|
return true;
|
|
}
|
|
bool isDone() const { return IsUnsafe; }
|
|
};
|
|
}
|
|
|
|
namespace llvm {
|
|
bool isSafeToExpand(const SCEV *S, ScalarEvolution &SE) {
|
|
SCEVFindUnsafe Search(SE);
|
|
visitAll(S, Search);
|
|
return !Search.IsUnsafe;
|
|
}
|
|
}
|