llvm-6502/lib/Analysis/PHITransAddr.cpp
Chris Lattner 34f849098b fix a typo (and -> add) and fix GetAvailablePHITranslatedSubExpr to not
side-effect the current object.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@90837 91177308-0d34-0410-b5e6-96231b3b80d8
2009-12-08 06:06:26 +00:00

326 lines
12 KiB
C++

//===- PHITransAddr.cpp - PHI Translation for Addresses -------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements the PHITransAddr class.
//
//===----------------------------------------------------------------------===//
#include "llvm/Analysis/PHITransAddr.h"
#include "llvm/Analysis/Dominators.h"
#include "llvm/Analysis/InstructionSimplify.h"
using namespace llvm;
static bool CanPHITrans(Instruction *Inst) {
if (isa<PHINode>(Inst) ||
isa<BitCastInst>(Inst) ||
isa<GetElementPtrInst>(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;
}
/// 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 == 0 || CanPHITrans(Inst);
}
Value *PHITransAddr::PHITranslateSubExpr(Value *V, BasicBlock *CurBB,
BasicBlock *PredBB) {
// If this is a non-instruction value, it can't require PHI translation.
Instruction *Inst = dyn_cast<Instruction>(V);
if (Inst == 0) return V;
// If 'Inst' is defined in this block, it must be an input that needs to be
// phi translated or an intermediate expression that needs to be incorporated
// into the expression.
if (Inst->getParent() == CurBB) {
assert(std::count(InstInputs.begin(), InstInputs.end(), Inst) &&
"Not an input?");
// If this is a PHI, go ahead and translate it.
if (PHINode *PN = dyn_cast<PHINode>(Inst))
return 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 0;
// Okay, we can incorporate it, this instruction is no longer an input.
InstInputs.erase(std::find(InstInputs.begin(), InstInputs.end(), Inst));
// 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);
} else {
// Determine whether 'Inst' is an input to our PHI translatable expression.
bool isInput = std::count(InstInputs.begin(), InstInputs.end(), Inst);
// If it is an input defined in a different block, then it remains an input.
if (isInput)
return Inst;
}
// 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 (BitCastInst *BC = dyn_cast<BitCastInst>(Inst)) {
Value *PHIIn = PHITranslateSubExpr(BC->getOperand(0), CurBB, PredBB);
if (PHIIn == 0) return 0;
if (PHIIn == BC->getOperand(0))
return BC;
// Find an available version of this cast.
// Constants are trivial to find.
if (Constant *C = dyn_cast<Constant>(PHIIn))
return ConstantExpr::getBitCast(C, BC->getType());
// Otherwise we have to see if a bitcasted version of the incoming pointer
// is available. If so, we can use it, otherwise we have to fail.
for (Value::use_iterator UI = PHIIn->use_begin(), E = PHIIn->use_end();
UI != E; ++UI) {
if (BitCastInst *BCI = dyn_cast<BitCastInst>(*UI))
if (BCI->getType() == BC->getType())
return BCI;
}
return 0;
}
// Handle getelementptr with at least one PHI translatable operand.
if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Inst)) {
SmallVector<Value*, 8> GEPOps;
BasicBlock *CurBB = GEP->getParent();
bool AnyChanged = false;
for (unsigned i = 0, e = GEP->getNumOperands(); i != e; ++i) {
Value *GEPOp = PHITranslateSubExpr(GEP->getOperand(i), CurBB, PredBB);
if (GEPOp == 0) return 0;
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(&GEPOps[0], GEPOps.size(), TD))
return V;
// Scan to see if we have this GEP available.
Value *APHIOp = GEPOps[0];
for (Value::use_iterator UI = APHIOp->use_begin(), E = APHIOp->use_end();
UI != E; ++UI) {
if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(*UI))
if (GEPI->getType() == GEP->getType() &&
GEPI->getNumOperands() == GEPOps.size() &&
GEPI->getParent()->getParent() == CurBB->getParent()) {
bool Mismatch = false;
for (unsigned i = 0, e = GEPOps.size(); i != e; ++i)
if (GEPI->getOperand(i) != GEPOps[i]) {
Mismatch = true;
break;
}
if (!Mismatch)
return GEPI;
}
}
return 0;
}
// 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);
if (LHS == 0) return 0;
// 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;
}
// See if the add simplifies away.
if (Value *Res = SimplifyAddInst(LHS, RHS, isNSW, isNUW, TD))
return Res;
// Otherwise, see if we have this add available somewhere.
for (Value::use_iterator UI = LHS->use_begin(), E = LHS->use_end();
UI != E; ++UI) {
if (BinaryOperator *BO = dyn_cast<BinaryOperator>(*UI))
if (BO->getOperand(0) == LHS && BO->getOperand(1) == RHS &&
BO->getParent()->getParent() == CurBB->getParent())
return BO;
}
return 0;
}
// Otherwise, we failed.
return 0;
}
/// PHITranslateValue - PHI translate the current address up the CFG from
/// CurBB to Pred, updating our state the reflect any needed changes. This
/// returns true on failure and sets Addr to null.
bool PHITransAddr::PHITranslateValue(BasicBlock *CurBB, BasicBlock *PredBB) {
Addr = PHITranslateSubExpr(Addr, CurBB, PredBB);
return Addr == 0;
}
/// GetAvailablePHITranslatedSubExpr - Return the value computed by
/// PHITranslateSubExpr if it dominates PredBB, otherwise return null.
Value *PHITransAddr::
GetAvailablePHITranslatedSubExpr(Value *V, BasicBlock *CurBB,BasicBlock *PredBB,
const DominatorTree &DT) const {
PHITransAddr Tmp(V, TD);
Tmp.PHITranslateValue(CurBB, PredBB);
// See if PHI translation succeeds.
V = Tmp.getAddr();
// Make sure the value is live in the predecessor.
if (Instruction *Inst = dyn_cast_or_null<Instruction>(V))
if (!DT.dominates(Inst->getParent(), PredBB))
return 0;
return V;
}
/// 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 0;
}
/// 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.
if (Value *Res = GetAvailablePHITranslatedSubExpr(InVal, CurBB, PredBB, DT))
return Res;
// If we don't have an available version of this value, it must be an
// instruction.
Instruction *Inst = cast<Instruction>(InVal);
// Handle bitcast of PHI translatable value.
if (BitCastInst *BC = dyn_cast<BitCastInst>(Inst)) {
Value *OpVal = InsertPHITranslatedSubExpr(BC->getOperand(0),
CurBB, PredBB, DT, NewInsts);
if (OpVal == 0) return 0;
// Otherwise insert a bitcast at the end of PredBB.
BitCastInst *New = new BitCastInst(OpVal, InVal->getType(),
InVal->getName()+".phi.trans.insert",
PredBB->getTerminator());
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 == 0) return 0;
GEPOps.push_back(OpVal);
}
GetElementPtrInst *Result =
GetElementPtrInst::Create(GEPOps[0], GEPOps.begin()+1, GEPOps.end(),
InVal->getName()+".phi.trans.insert",
PredBB->getTerminator());
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 0;
}