440 lines
16 KiB
C++
440 lines
16 KiB
C++
//===- PHITransAddr.cpp - PHI Translation for Addresses -------------------===//
|
|
//
|
|
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
|
|
// See https://llvm.org/LICENSE.txt for license information.
|
|
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
//
|
|
// This file implements the PHITransAddr class.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
#include "llvm/Analysis/PHITransAddr.h"
|
|
#include "llvm/Analysis/InstructionSimplify.h"
|
|
#include "llvm/Analysis/ValueTracking.h"
|
|
#include "llvm/Config/llvm-config.h"
|
|
#include "llvm/IR/Constants.h"
|
|
#include "llvm/IR/Dominators.h"
|
|
#include "llvm/IR/Instructions.h"
|
|
#include "llvm/Support/Debug.h"
|
|
#include "llvm/Support/ErrorHandling.h"
|
|
#include "llvm/Support/raw_ostream.h"
|
|
using namespace llvm;
|
|
|
|
static bool CanPHITrans(Instruction *Inst) {
|
|
if (isa<PHINode>(Inst) ||
|
|
isa<GetElementPtrInst>(Inst))
|
|
return true;
|
|
|
|
if (isa<CastInst>(Inst) &&
|
|
isSafeToSpeculativelyExecute(Inst))
|
|
return true;
|
|
|
|
if (Inst->getOpcode() == Instruction::Add &&
|
|
isa<ConstantInt>(Inst->getOperand(1)))
|
|
return true;
|
|
|
|
// cerr << "MEMDEP: Could not PHI translate: " << *Pointer;
|
|
// if (isa<BitCastInst>(PtrInst) || isa<GetElementPtrInst>(PtrInst))
|
|
// cerr << "OP:\t\t\t\t" << *PtrInst->getOperand(0);
|
|
return false;
|
|
}
|
|
|
|
#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
|
|
LLVM_DUMP_METHOD void PHITransAddr::dump() const {
|
|
if (!Addr) {
|
|
dbgs() << "PHITransAddr: null\n";
|
|
return;
|
|
}
|
|
dbgs() << "PHITransAddr: " << *Addr << "\n";
|
|
for (unsigned i = 0, e = InstInputs.size(); i != e; ++i)
|
|
dbgs() << " Input #" << i << " is " << *InstInputs[i] << "\n";
|
|
}
|
|
#endif
|
|
|
|
|
|
static bool VerifySubExpr(Value *Expr,
|
|
SmallVectorImpl<Instruction*> &InstInputs) {
|
|
// If this is a non-instruction value, there is nothing to do.
|
|
Instruction *I = dyn_cast<Instruction>(Expr);
|
|
if (!I) return true;
|
|
|
|
// If it's an instruction, it is either in Tmp or its operands recursively
|
|
// are.
|
|
SmallVectorImpl<Instruction *>::iterator Entry = find(InstInputs, I);
|
|
if (Entry != InstInputs.end()) {
|
|
InstInputs.erase(Entry);
|
|
return true;
|
|
}
|
|
|
|
// If it isn't in the InstInputs list it is a subexpr incorporated into the
|
|
// address. Sanity check that it is phi translatable.
|
|
if (!CanPHITrans(I)) {
|
|
errs() << "Instruction in PHITransAddr is not phi-translatable:\n";
|
|
errs() << *I << '\n';
|
|
llvm_unreachable("Either something is missing from InstInputs or "
|
|
"CanPHITrans is wrong.");
|
|
}
|
|
|
|
// Validate the operands of the instruction.
|
|
for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
|
|
if (!VerifySubExpr(I->getOperand(i), InstInputs))
|
|
return false;
|
|
|
|
return true;
|
|
}
|
|
|
|
/// Verify - Check internal consistency of this data structure. If the
|
|
/// structure is valid, it returns true. If invalid, it prints errors and
|
|
/// returns false.
|
|
bool PHITransAddr::Verify() const {
|
|
if (!Addr) return true;
|
|
|
|
SmallVector<Instruction*, 8> Tmp(InstInputs.begin(), InstInputs.end());
|
|
|
|
if (!VerifySubExpr(Addr, Tmp))
|
|
return false;
|
|
|
|
if (!Tmp.empty()) {
|
|
errs() << "PHITransAddr contains extra instructions:\n";
|
|
for (unsigned i = 0, e = InstInputs.size(); i != e; ++i)
|
|
errs() << " InstInput #" << i << " is " << *InstInputs[i] << "\n";
|
|
llvm_unreachable("This is unexpected.");
|
|
}
|
|
|
|
// a-ok.
|
|
return true;
|
|
}
|
|
|
|
|
|
/// IsPotentiallyPHITranslatable - If this needs PHI translation, return true
|
|
/// if we have some hope of doing it. This should be used as a filter to
|
|
/// avoid calling PHITranslateValue in hopeless situations.
|
|
bool PHITransAddr::IsPotentiallyPHITranslatable() const {
|
|
// If the input value is not an instruction, or if it is not defined in CurBB,
|
|
// then we don't need to phi translate it.
|
|
Instruction *Inst = dyn_cast<Instruction>(Addr);
|
|
return !Inst || CanPHITrans(Inst);
|
|
}
|
|
|
|
|
|
static void RemoveInstInputs(Value *V,
|
|
SmallVectorImpl<Instruction*> &InstInputs) {
|
|
Instruction *I = dyn_cast<Instruction>(V);
|
|
if (!I) return;
|
|
|
|
// If the instruction is in the InstInputs list, remove it.
|
|
SmallVectorImpl<Instruction *>::iterator Entry = find(InstInputs, I);
|
|
if (Entry != InstInputs.end()) {
|
|
InstInputs.erase(Entry);
|
|
return;
|
|
}
|
|
|
|
assert(!isa<PHINode>(I) && "Error, removing something that isn't an input");
|
|
|
|
// Otherwise, it must have instruction inputs itself. Zap them recursively.
|
|
for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) {
|
|
if (Instruction *Op = dyn_cast<Instruction>(I->getOperand(i)))
|
|
RemoveInstInputs(Op, InstInputs);
|
|
}
|
|
}
|
|
|
|
Value *PHITransAddr::PHITranslateSubExpr(Value *V, BasicBlock *CurBB,
|
|
BasicBlock *PredBB,
|
|
const DominatorTree *DT) {
|
|
// If this is a non-instruction value, it can't require PHI translation.
|
|
Instruction *Inst = dyn_cast<Instruction>(V);
|
|
if (!Inst) return V;
|
|
|
|
// Determine whether 'Inst' is an input to our PHI translatable expression.
|
|
bool isInput = is_contained(InstInputs, Inst);
|
|
|
|
// Handle inputs instructions if needed.
|
|
if (isInput) {
|
|
if (Inst->getParent() != CurBB) {
|
|
// If it is an input defined in a different block, then it remains an
|
|
// input.
|
|
return Inst;
|
|
}
|
|
|
|
// If 'Inst' is defined in this block and is an input that needs to be phi
|
|
// translated, we need to incorporate the value into the expression or fail.
|
|
|
|
// In either case, the instruction itself isn't an input any longer.
|
|
InstInputs.erase(find(InstInputs, Inst));
|
|
|
|
// If this is a PHI, go ahead and translate it.
|
|
if (PHINode *PN = dyn_cast<PHINode>(Inst))
|
|
return AddAsInput(PN->getIncomingValueForBlock(PredBB));
|
|
|
|
// If this is a non-phi value, and it is analyzable, we can incorporate it
|
|
// into the expression by making all instruction operands be inputs.
|
|
if (!CanPHITrans(Inst))
|
|
return nullptr;
|
|
|
|
// All instruction operands are now inputs (and of course, they may also be
|
|
// defined in this block, so they may need to be phi translated themselves.
|
|
for (unsigned i = 0, e = Inst->getNumOperands(); i != e; ++i)
|
|
if (Instruction *Op = dyn_cast<Instruction>(Inst->getOperand(i)))
|
|
InstInputs.push_back(Op);
|
|
}
|
|
|
|
// Ok, it must be an intermediate result (either because it started that way
|
|
// or because we just incorporated it into the expression). See if its
|
|
// operands need to be phi translated, and if so, reconstruct it.
|
|
|
|
if (CastInst *Cast = dyn_cast<CastInst>(Inst)) {
|
|
if (!isSafeToSpeculativelyExecute(Cast)) return nullptr;
|
|
Value *PHIIn = PHITranslateSubExpr(Cast->getOperand(0), CurBB, PredBB, DT);
|
|
if (!PHIIn) return nullptr;
|
|
if (PHIIn == Cast->getOperand(0))
|
|
return Cast;
|
|
|
|
// Find an available version of this cast.
|
|
|
|
// Constants are trivial to find.
|
|
if (Constant *C = dyn_cast<Constant>(PHIIn))
|
|
return AddAsInput(ConstantExpr::getCast(Cast->getOpcode(),
|
|
C, Cast->getType()));
|
|
|
|
// Otherwise we have to see if a casted version of the incoming pointer
|
|
// is available. If so, we can use it, otherwise we have to fail.
|
|
for (User *U : PHIIn->users()) {
|
|
if (CastInst *CastI = dyn_cast<CastInst>(U))
|
|
if (CastI->getOpcode() == Cast->getOpcode() &&
|
|
CastI->getType() == Cast->getType() &&
|
|
(!DT || DT->dominates(CastI->getParent(), PredBB)))
|
|
return CastI;
|
|
}
|
|
return nullptr;
|
|
}
|
|
|
|
// Handle getelementptr with at least one PHI translatable operand.
|
|
if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Inst)) {
|
|
SmallVector<Value*, 8> GEPOps;
|
|
bool AnyChanged = false;
|
|
for (unsigned i = 0, e = GEP->getNumOperands(); i != e; ++i) {
|
|
Value *GEPOp = PHITranslateSubExpr(GEP->getOperand(i), CurBB, PredBB, DT);
|
|
if (!GEPOp) return nullptr;
|
|
|
|
AnyChanged |= GEPOp != GEP->getOperand(i);
|
|
GEPOps.push_back(GEPOp);
|
|
}
|
|
|
|
if (!AnyChanged)
|
|
return GEP;
|
|
|
|
// Simplify the GEP to handle 'gep x, 0' -> x etc.
|
|
if (Value *V = SimplifyGEPInst(GEP->getSourceElementType(),
|
|
GEPOps, {DL, TLI, DT, AC})) {
|
|
for (unsigned i = 0, e = GEPOps.size(); i != e; ++i)
|
|
RemoveInstInputs(GEPOps[i], InstInputs);
|
|
|
|
return AddAsInput(V);
|
|
}
|
|
|
|
// Scan to see if we have this GEP available.
|
|
Value *APHIOp = GEPOps[0];
|
|
for (User *U : APHIOp->users()) {
|
|
if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(U))
|
|
if (GEPI->getType() == GEP->getType() &&
|
|
GEPI->getNumOperands() == GEPOps.size() &&
|
|
GEPI->getParent()->getParent() == CurBB->getParent() &&
|
|
(!DT || DT->dominates(GEPI->getParent(), PredBB))) {
|
|
if (std::equal(GEPOps.begin(), GEPOps.end(), GEPI->op_begin()))
|
|
return GEPI;
|
|
}
|
|
}
|
|
return nullptr;
|
|
}
|
|
|
|
// Handle add with a constant RHS.
|
|
if (Inst->getOpcode() == Instruction::Add &&
|
|
isa<ConstantInt>(Inst->getOperand(1))) {
|
|
// PHI translate the LHS.
|
|
Constant *RHS = cast<ConstantInt>(Inst->getOperand(1));
|
|
bool isNSW = cast<BinaryOperator>(Inst)->hasNoSignedWrap();
|
|
bool isNUW = cast<BinaryOperator>(Inst)->hasNoUnsignedWrap();
|
|
|
|
Value *LHS = PHITranslateSubExpr(Inst->getOperand(0), CurBB, PredBB, DT);
|
|
if (!LHS) return nullptr;
|
|
|
|
// If the PHI translated LHS is an add of a constant, fold the immediates.
|
|
if (BinaryOperator *BOp = dyn_cast<BinaryOperator>(LHS))
|
|
if (BOp->getOpcode() == Instruction::Add)
|
|
if (ConstantInt *CI = dyn_cast<ConstantInt>(BOp->getOperand(1))) {
|
|
LHS = BOp->getOperand(0);
|
|
RHS = ConstantExpr::getAdd(RHS, CI);
|
|
isNSW = isNUW = false;
|
|
|
|
// If the old 'LHS' was an input, add the new 'LHS' as an input.
|
|
if (is_contained(InstInputs, BOp)) {
|
|
RemoveInstInputs(BOp, InstInputs);
|
|
AddAsInput(LHS);
|
|
}
|
|
}
|
|
|
|
// See if the add simplifies away.
|
|
if (Value *Res = SimplifyAddInst(LHS, RHS, isNSW, isNUW, {DL, TLI, DT, AC})) {
|
|
// If we simplified the operands, the LHS is no longer an input, but Res
|
|
// is.
|
|
RemoveInstInputs(LHS, InstInputs);
|
|
return AddAsInput(Res);
|
|
}
|
|
|
|
// If we didn't modify the add, just return it.
|
|
if (LHS == Inst->getOperand(0) && RHS == Inst->getOperand(1))
|
|
return Inst;
|
|
|
|
// Otherwise, see if we have this add available somewhere.
|
|
for (User *U : LHS->users()) {
|
|
if (BinaryOperator *BO = dyn_cast<BinaryOperator>(U))
|
|
if (BO->getOpcode() == Instruction::Add &&
|
|
BO->getOperand(0) == LHS && BO->getOperand(1) == RHS &&
|
|
BO->getParent()->getParent() == CurBB->getParent() &&
|
|
(!DT || DT->dominates(BO->getParent(), PredBB)))
|
|
return BO;
|
|
}
|
|
|
|
return nullptr;
|
|
}
|
|
|
|
// Otherwise, we failed.
|
|
return nullptr;
|
|
}
|
|
|
|
|
|
/// PHITranslateValue - PHI translate the current address up the CFG from
|
|
/// CurBB to Pred, updating our state to reflect any needed changes. If
|
|
/// 'MustDominate' is true, the translated value must dominate
|
|
/// PredBB. This returns true on failure and sets Addr to null.
|
|
bool PHITransAddr::PHITranslateValue(BasicBlock *CurBB, BasicBlock *PredBB,
|
|
const DominatorTree *DT,
|
|
bool MustDominate) {
|
|
assert(DT || !MustDominate);
|
|
assert(Verify() && "Invalid PHITransAddr!");
|
|
if (DT && DT->isReachableFromEntry(PredBB))
|
|
Addr =
|
|
PHITranslateSubExpr(Addr, CurBB, PredBB, MustDominate ? DT : nullptr);
|
|
else
|
|
Addr = nullptr;
|
|
assert(Verify() && "Invalid PHITransAddr!");
|
|
|
|
if (MustDominate)
|
|
// Make sure the value is live in the predecessor.
|
|
if (Instruction *Inst = dyn_cast_or_null<Instruction>(Addr))
|
|
if (!DT->dominates(Inst->getParent(), PredBB))
|
|
Addr = nullptr;
|
|
|
|
return Addr == nullptr;
|
|
}
|
|
|
|
/// PHITranslateWithInsertion - PHI translate this value into the specified
|
|
/// predecessor block, inserting a computation of the value if it is
|
|
/// unavailable.
|
|
///
|
|
/// All newly created instructions are added to the NewInsts list. This
|
|
/// returns null on failure.
|
|
///
|
|
Value *PHITransAddr::
|
|
PHITranslateWithInsertion(BasicBlock *CurBB, BasicBlock *PredBB,
|
|
const DominatorTree &DT,
|
|
SmallVectorImpl<Instruction*> &NewInsts) {
|
|
unsigned NISize = NewInsts.size();
|
|
|
|
// Attempt to PHI translate with insertion.
|
|
Addr = InsertPHITranslatedSubExpr(Addr, CurBB, PredBB, DT, NewInsts);
|
|
|
|
// If successful, return the new value.
|
|
if (Addr) return Addr;
|
|
|
|
// If not, destroy any intermediate instructions inserted.
|
|
while (NewInsts.size() != NISize)
|
|
NewInsts.pop_back_val()->eraseFromParent();
|
|
return nullptr;
|
|
}
|
|
|
|
|
|
/// InsertPHITranslatedPointer - Insert a computation of the PHI translated
|
|
/// version of 'V' for the edge PredBB->CurBB into the end of the PredBB
|
|
/// block. All newly created instructions are added to the NewInsts list.
|
|
/// This returns null on failure.
|
|
///
|
|
Value *PHITransAddr::
|
|
InsertPHITranslatedSubExpr(Value *InVal, BasicBlock *CurBB,
|
|
BasicBlock *PredBB, const DominatorTree &DT,
|
|
SmallVectorImpl<Instruction*> &NewInsts) {
|
|
// See if we have a version of this value already available and dominating
|
|
// PredBB. If so, there is no need to insert a new instance of it.
|
|
PHITransAddr Tmp(InVal, DL, AC);
|
|
if (!Tmp.PHITranslateValue(CurBB, PredBB, &DT, /*MustDominate=*/true))
|
|
return Tmp.getAddr();
|
|
|
|
// We don't need to PHI translate values which aren't instructions.
|
|
auto *Inst = dyn_cast<Instruction>(InVal);
|
|
if (!Inst)
|
|
return nullptr;
|
|
|
|
// Handle cast of PHI translatable value.
|
|
if (CastInst *Cast = dyn_cast<CastInst>(Inst)) {
|
|
if (!isSafeToSpeculativelyExecute(Cast)) return nullptr;
|
|
Value *OpVal = InsertPHITranslatedSubExpr(Cast->getOperand(0),
|
|
CurBB, PredBB, DT, NewInsts);
|
|
if (!OpVal) return nullptr;
|
|
|
|
// Otherwise insert a cast at the end of PredBB.
|
|
CastInst *New = CastInst::Create(Cast->getOpcode(), OpVal, InVal->getType(),
|
|
InVal->getName() + ".phi.trans.insert",
|
|
PredBB->getTerminator());
|
|
New->setDebugLoc(Inst->getDebugLoc());
|
|
NewInsts.push_back(New);
|
|
return New;
|
|
}
|
|
|
|
// Handle getelementptr with at least one PHI operand.
|
|
if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Inst)) {
|
|
SmallVector<Value*, 8> GEPOps;
|
|
BasicBlock *CurBB = GEP->getParent();
|
|
for (unsigned i = 0, e = GEP->getNumOperands(); i != e; ++i) {
|
|
Value *OpVal = InsertPHITranslatedSubExpr(GEP->getOperand(i),
|
|
CurBB, PredBB, DT, NewInsts);
|
|
if (!OpVal) return nullptr;
|
|
GEPOps.push_back(OpVal);
|
|
}
|
|
|
|
GetElementPtrInst *Result = GetElementPtrInst::Create(
|
|
GEP->getSourceElementType(), GEPOps[0], makeArrayRef(GEPOps).slice(1),
|
|
InVal->getName() + ".phi.trans.insert", PredBB->getTerminator());
|
|
Result->setDebugLoc(Inst->getDebugLoc());
|
|
Result->setIsInBounds(GEP->isInBounds());
|
|
NewInsts.push_back(Result);
|
|
return Result;
|
|
}
|
|
|
|
#if 0
|
|
// FIXME: This code works, but it is unclear that we actually want to insert
|
|
// a big chain of computation in order to make a value available in a block.
|
|
// This needs to be evaluated carefully to consider its cost trade offs.
|
|
|
|
// Handle add with a constant RHS.
|
|
if (Inst->getOpcode() == Instruction::Add &&
|
|
isa<ConstantInt>(Inst->getOperand(1))) {
|
|
// PHI translate the LHS.
|
|
Value *OpVal = InsertPHITranslatedSubExpr(Inst->getOperand(0),
|
|
CurBB, PredBB, DT, NewInsts);
|
|
if (OpVal == 0) return 0;
|
|
|
|
BinaryOperator *Res = BinaryOperator::CreateAdd(OpVal, Inst->getOperand(1),
|
|
InVal->getName()+".phi.trans.insert",
|
|
PredBB->getTerminator());
|
|
Res->setHasNoSignedWrap(cast<BinaryOperator>(Inst)->hasNoSignedWrap());
|
|
Res->setHasNoUnsignedWrap(cast<BinaryOperator>(Inst)->hasNoUnsignedWrap());
|
|
NewInsts.push_back(Res);
|
|
return Res;
|
|
}
|
|
#endif
|
|
|
|
return nullptr;
|
|
}
|