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llvm-project/llvm/lib/Transforms/Scalar/CodeGenPrepare.cpp

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//===- CodeGenPrepare.cpp - Prepare a function for code generation --------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This pass munges the code in the input function to better prepare it for
// SelectionDAG-based code generation. This works around limitations in it's
// basic-block-at-a-time approach. It should eventually be removed.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "codegenprepare"
#include "llvm/Transforms/Scalar.h"
#include "llvm/Constants.h"
#include "llvm/DerivedTypes.h"
#include "llvm/Function.h"
#include "llvm/InlineAsm.h"
#include "llvm/Instructions.h"
#include "llvm/Pass.h"
#include "llvm/Target/TargetAsmInfo.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Target/TargetLowering.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/Local.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/SmallSet.h"
#include "llvm/Support/CallSite.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/GetElementPtrTypeIterator.h"
#include "llvm/Support/PatternMatch.h"
using namespace llvm;
using namespace llvm::PatternMatch;
static cl::opt<bool> FactorCommonPreds("split-critical-paths-tweak",
cl::init(false), cl::Hidden);
namespace {
class VISIBILITY_HIDDEN CodeGenPrepare : public FunctionPass {
/// TLI - Keep a pointer of a TargetLowering to consult for determining
/// transformation profitability.
const TargetLowering *TLI;
/// BackEdges - Keep a set of all the loop back edges.
///
SmallSet<std::pair<BasicBlock*,BasicBlock*>, 8> BackEdges;
public:
static char ID; // Pass identification, replacement for typeid
explicit CodeGenPrepare(const TargetLowering *tli = 0)
: FunctionPass(&ID), TLI(tli) {}
bool runOnFunction(Function &F);
private:
bool EliminateMostlyEmptyBlocks(Function &F);
bool CanMergeBlocks(const BasicBlock *BB, const BasicBlock *DestBB) const;
void EliminateMostlyEmptyBlock(BasicBlock *BB);
bool OptimizeBlock(BasicBlock &BB);
bool OptimizeMemoryInst(Instruction *I, Value *Addr, const Type *AccessTy,
DenseMap<Value*,Value*> &SunkAddrs);
bool OptimizeInlineAsmInst(Instruction *I, CallSite CS,
DenseMap<Value*,Value*> &SunkAddrs);
bool OptimizeExtUses(Instruction *I);
void findLoopBackEdges(Function &F);
};
}
char CodeGenPrepare::ID = 0;
static RegisterPass<CodeGenPrepare> X("codegenprepare",
"Optimize for code generation");
FunctionPass *llvm::createCodeGenPreparePass(const TargetLowering *TLI) {
return new CodeGenPrepare(TLI);
}
/// findLoopBackEdges - Do a DFS walk to find loop back edges.
///
void CodeGenPrepare::findLoopBackEdges(Function &F) {
SmallPtrSet<BasicBlock*, 8> Visited;
SmallVector<std::pair<BasicBlock*, succ_iterator>, 8> VisitStack;
SmallPtrSet<BasicBlock*, 8> InStack;
BasicBlock *BB = &F.getEntryBlock();
if (succ_begin(BB) == succ_end(BB))
return;
Visited.insert(BB);
VisitStack.push_back(std::make_pair(BB, succ_begin(BB)));
InStack.insert(BB);
do {
std::pair<BasicBlock*, succ_iterator> &Top = VisitStack.back();
BasicBlock *ParentBB = Top.first;
succ_iterator &I = Top.second;
bool FoundNew = false;
while (I != succ_end(ParentBB)) {
BB = *I++;
if (Visited.insert(BB)) {
FoundNew = true;
break;
}
// Successor is in VisitStack, it's a back edge.
if (InStack.count(BB))
BackEdges.insert(std::make_pair(ParentBB, BB));
}
if (FoundNew) {
// Go down one level if there is a unvisited successor.
InStack.insert(BB);
VisitStack.push_back(std::make_pair(BB, succ_begin(BB)));
} else {
// Go up one level.
std::pair<BasicBlock*, succ_iterator> &Pop = VisitStack.back();
InStack.erase(Pop.first);
VisitStack.pop_back();
}
} while (!VisitStack.empty());
}
bool CodeGenPrepare::runOnFunction(Function &F) {
bool EverMadeChange = false;
// First pass, eliminate blocks that contain only PHI nodes and an
// unconditional branch.
EverMadeChange |= EliminateMostlyEmptyBlocks(F);
// Now find loop back edges.
findLoopBackEdges(F);
bool MadeChange = true;
while (MadeChange) {
MadeChange = false;
for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
MadeChange |= OptimizeBlock(*BB);
EverMadeChange |= MadeChange;
}
return EverMadeChange;
}
/// EliminateMostlyEmptyBlocks - eliminate blocks that contain only PHI nodes
/// and an unconditional branch. Passes before isel (e.g. LSR/loopsimplify)
/// often split edges in ways that are non-optimal for isel. Start by
/// eliminating these blocks so we can split them the way we want them.
bool CodeGenPrepare::EliminateMostlyEmptyBlocks(Function &F) {
bool MadeChange = false;
// Note that this intentionally skips the entry block.
for (Function::iterator I = ++F.begin(), E = F.end(); I != E; ) {
BasicBlock *BB = I++;
// If this block doesn't end with an uncond branch, ignore it.
BranchInst *BI = dyn_cast<BranchInst>(BB->getTerminator());
if (!BI || !BI->isUnconditional())
continue;
// If the instruction before the branch isn't a phi node, then other stuff
// is happening here.
BasicBlock::iterator BBI = BI;
if (BBI != BB->begin()) {
--BBI;
if (!isa<PHINode>(BBI)) continue;
}
// Do not break infinite loops.
BasicBlock *DestBB = BI->getSuccessor(0);
if (DestBB == BB)
continue;
if (!CanMergeBlocks(BB, DestBB))
continue;
EliminateMostlyEmptyBlock(BB);
MadeChange = true;
}
return MadeChange;
}
/// CanMergeBlocks - Return true if we can merge BB into DestBB if there is a
/// single uncond branch between them, and BB contains no other non-phi
/// instructions.
bool CodeGenPrepare::CanMergeBlocks(const BasicBlock *BB,
const BasicBlock *DestBB) const {
// We only want to eliminate blocks whose phi nodes are used by phi nodes in
// the successor. If there are more complex condition (e.g. preheaders),
// don't mess around with them.
BasicBlock::const_iterator BBI = BB->begin();
while (const PHINode *PN = dyn_cast<PHINode>(BBI++)) {
for (Value::use_const_iterator UI = PN->use_begin(), E = PN->use_end();
UI != E; ++UI) {
const Instruction *User = cast<Instruction>(*UI);
if (User->getParent() != DestBB || !isa<PHINode>(User))
return false;
// If User is inside DestBB block and it is a PHINode then check
// incoming value. If incoming value is not from BB then this is
// a complex condition (e.g. preheaders) we want to avoid here.
if (User->getParent() == DestBB) {
if (const PHINode *UPN = dyn_cast<PHINode>(User))
for (unsigned I = 0, E = UPN->getNumIncomingValues(); I != E; ++I) {
Instruction *Insn = dyn_cast<Instruction>(UPN->getIncomingValue(I));
if (Insn && Insn->getParent() == BB &&
Insn->getParent() != UPN->getIncomingBlock(I))
return false;
}
}
}
}
// If BB and DestBB contain any common predecessors, then the phi nodes in BB
// and DestBB may have conflicting incoming values for the block. If so, we
// can't merge the block.
const PHINode *DestBBPN = dyn_cast<PHINode>(DestBB->begin());
if (!DestBBPN) return true; // no conflict.
// Collect the preds of BB.
SmallPtrSet<const BasicBlock*, 16> BBPreds;
if (const PHINode *BBPN = dyn_cast<PHINode>(BB->begin())) {
// It is faster to get preds from a PHI than with pred_iterator.
for (unsigned i = 0, e = BBPN->getNumIncomingValues(); i != e; ++i)
BBPreds.insert(BBPN->getIncomingBlock(i));
} else {
BBPreds.insert(pred_begin(BB), pred_end(BB));
}
// Walk the preds of DestBB.
for (unsigned i = 0, e = DestBBPN->getNumIncomingValues(); i != e; ++i) {
BasicBlock *Pred = DestBBPN->getIncomingBlock(i);
if (BBPreds.count(Pred)) { // Common predecessor?
BBI = DestBB->begin();
while (const PHINode *PN = dyn_cast<PHINode>(BBI++)) {
const Value *V1 = PN->getIncomingValueForBlock(Pred);
const Value *V2 = PN->getIncomingValueForBlock(BB);
// If V2 is a phi node in BB, look up what the mapped value will be.
if (const PHINode *V2PN = dyn_cast<PHINode>(V2))
if (V2PN->getParent() == BB)
V2 = V2PN->getIncomingValueForBlock(Pred);
// If there is a conflict, bail out.
if (V1 != V2) return false;
}
}
}
return true;
}
/// EliminateMostlyEmptyBlock - Eliminate a basic block that have only phi's and
/// an unconditional branch in it.
void CodeGenPrepare::EliminateMostlyEmptyBlock(BasicBlock *BB) {
BranchInst *BI = cast<BranchInst>(BB->getTerminator());
BasicBlock *DestBB = BI->getSuccessor(0);
DOUT << "MERGING MOSTLY EMPTY BLOCKS - BEFORE:\n" << *BB << *DestBB;
// If the destination block has a single pred, then this is a trivial edge,
// just collapse it.
if (BasicBlock *SinglePred = DestBB->getSinglePredecessor()) {
if (SinglePred != DestBB) {
// Remember if SinglePred was the entry block of the function. If so, we
// will need to move BB back to the entry position.
bool isEntry = SinglePred == &SinglePred->getParent()->getEntryBlock();
MergeBasicBlockIntoOnlyPred(DestBB);
if (isEntry && BB != &BB->getParent()->getEntryBlock())
BB->moveBefore(&BB->getParent()->getEntryBlock());
DOUT << "AFTER:\n" << *DestBB << "\n\n\n";
return;
}
}
// Otherwise, we have multiple predecessors of BB. Update the PHIs in DestBB
// to handle the new incoming edges it is about to have.
PHINode *PN;
for (BasicBlock::iterator BBI = DestBB->begin();
(PN = dyn_cast<PHINode>(BBI)); ++BBI) {
// Remove the incoming value for BB, and remember it.
Value *InVal = PN->removeIncomingValue(BB, false);
// Two options: either the InVal is a phi node defined in BB or it is some
// value that dominates BB.
PHINode *InValPhi = dyn_cast<PHINode>(InVal);
if (InValPhi && InValPhi->getParent() == BB) {
// Add all of the input values of the input PHI as inputs of this phi.
for (unsigned i = 0, e = InValPhi->getNumIncomingValues(); i != e; ++i)
PN->addIncoming(InValPhi->getIncomingValue(i),
InValPhi->getIncomingBlock(i));
} else {
// Otherwise, add one instance of the dominating value for each edge that
// we will be adding.
if (PHINode *BBPN = dyn_cast<PHINode>(BB->begin())) {
for (unsigned i = 0, e = BBPN->getNumIncomingValues(); i != e; ++i)
PN->addIncoming(InVal, BBPN->getIncomingBlock(i));
} else {
for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI)
PN->addIncoming(InVal, *PI);
}
}
}
// The PHIs are now updated, change everything that refers to BB to use
// DestBB and remove BB.
BB->replaceAllUsesWith(DestBB);
BB->eraseFromParent();
DOUT << "AFTER:\n" << *DestBB << "\n\n\n";
}
/// SplitEdgeNicely - Split the critical edge from TI to its specified
/// successor if it will improve codegen. We only do this if the successor has
/// phi nodes (otherwise critical edges are ok). If there is already another
/// predecessor of the succ that is empty (and thus has no phi nodes), use it
/// instead of introducing a new block.
static void SplitEdgeNicely(TerminatorInst *TI, unsigned SuccNum,
SmallSet<std::pair<BasicBlock*,BasicBlock*>, 8> &BackEdges,
Pass *P) {
BasicBlock *TIBB = TI->getParent();
BasicBlock *Dest = TI->getSuccessor(SuccNum);
assert(isa<PHINode>(Dest->begin()) &&
"This should only be called if Dest has a PHI!");
// As a hack, never split backedges of loops. Even though the copy for any
// PHIs inserted on the backedge would be dead for exits from the loop, we
// assume that the cost of *splitting* the backedge would be too high.
if (BackEdges.count(std::make_pair(TIBB, Dest)))
return;
if (!FactorCommonPreds) {
/// TIPHIValues - This array is lazily computed to determine the values of
/// PHIs in Dest that TI would provide.
SmallVector<Value*, 32> TIPHIValues;
// Check to see if Dest has any blocks that can be used as a split edge for
// this terminator.
for (pred_iterator PI = pred_begin(Dest), E = pred_end(Dest); PI != E; ++PI) {
BasicBlock *Pred = *PI;
// To be usable, the pred has to end with an uncond branch to the dest.
BranchInst *PredBr = dyn_cast<BranchInst>(Pred->getTerminator());
if (!PredBr || !PredBr->isUnconditional() ||
// Must be empty other than the branch.
&Pred->front() != PredBr ||
// Cannot be the entry block; its label does not get emitted.
Pred == &(Dest->getParent()->getEntryBlock()))
continue;
// Finally, since we know that Dest has phi nodes in it, we have to make
// sure that jumping to Pred will have the same affect as going to Dest in
// terms of PHI values.
PHINode *PN;
unsigned PHINo = 0;
bool FoundMatch = true;
for (BasicBlock::iterator I = Dest->begin();
(PN = dyn_cast<PHINode>(I)); ++I, ++PHINo) {
if (PHINo == TIPHIValues.size())
TIPHIValues.push_back(PN->getIncomingValueForBlock(TIBB));
// If the PHI entry doesn't work, we can't use this pred.
if (TIPHIValues[PHINo] != PN->getIncomingValueForBlock(Pred)) {
FoundMatch = false;
break;
}
}
// If we found a workable predecessor, change TI to branch to Succ.
if (FoundMatch) {
Dest->removePredecessor(TIBB);
TI->setSuccessor(SuccNum, Pred);
return;
}
}
SplitCriticalEdge(TI, SuccNum, P, true);
return;
}
PHINode *PN;
SmallVector<Value*, 8> TIPHIValues;
for (BasicBlock::iterator I = Dest->begin();
(PN = dyn_cast<PHINode>(I)); ++I)
TIPHIValues.push_back(PN->getIncomingValueForBlock(TIBB));
SmallVector<BasicBlock*, 8> IdenticalPreds;
for (pred_iterator PI = pred_begin(Dest), E = pred_end(Dest); PI != E; ++PI) {
BasicBlock *Pred = *PI;
if (BackEdges.count(std::make_pair(Pred, Dest)))
continue;
if (PI == TIBB)
IdenticalPreds.push_back(Pred);
else {
bool Identical = true;
unsigned PHINo = 0;
for (BasicBlock::iterator I = Dest->begin();
(PN = dyn_cast<PHINode>(I)); ++I, ++PHINo)
if (TIPHIValues[PHINo] != PN->getIncomingValueForBlock(Pred)) {
Identical = false;
break;
}
if (Identical)
IdenticalPreds.push_back(Pred);
}
}
assert(!IdenticalPreds.empty());
SplitBlockPredecessors(Dest, &IdenticalPreds[0], IdenticalPreds.size(),
".critedge", P);
}
/// OptimizeNoopCopyExpression - If the specified cast instruction is a noop
/// copy (e.g. it's casting from one pointer type to another, int->uint, or
/// int->sbyte on PPC), sink it into user blocks to reduce the number of virtual
/// registers that must be created and coalesced.
///
/// Return true if any changes are made.
///
static bool OptimizeNoopCopyExpression(CastInst *CI, const TargetLowering &TLI){
// If this is a noop copy,
MVT SrcVT = TLI.getValueType(CI->getOperand(0)->getType());
MVT DstVT = TLI.getValueType(CI->getType());
// This is an fp<->int conversion?
if (SrcVT.isInteger() != DstVT.isInteger())
return false;
// If this is an extension, it will be a zero or sign extension, which
// isn't a noop.
if (SrcVT.bitsLT(DstVT)) return false;
// If these values will be promoted, find out what they will be promoted
// to. This helps us consider truncates on PPC as noop copies when they
// are.
if (TLI.getTypeAction(SrcVT) == TargetLowering::Promote)
SrcVT = TLI.getTypeToTransformTo(SrcVT);
if (TLI.getTypeAction(DstVT) == TargetLowering::Promote)
DstVT = TLI.getTypeToTransformTo(DstVT);
// If, after promotion, these are the same types, this is a noop copy.
if (SrcVT != DstVT)
return false;
BasicBlock *DefBB = CI->getParent();
/// InsertedCasts - Only insert a cast in each block once.
DenseMap<BasicBlock*, CastInst*> InsertedCasts;
bool MadeChange = false;
for (Value::use_iterator UI = CI->use_begin(), E = CI->use_end();
UI != E; ) {
Use &TheUse = UI.getUse();
Instruction *User = cast<Instruction>(*UI);
// Figure out which BB this cast is used in. For PHI's this is the
// appropriate predecessor block.
BasicBlock *UserBB = User->getParent();
if (PHINode *PN = dyn_cast<PHINode>(User)) {
UserBB = PN->getIncomingBlock(UI);
}
// Preincrement use iterator so we don't invalidate it.
++UI;
// If this user is in the same block as the cast, don't change the cast.
if (UserBB == DefBB) continue;
// If we have already inserted a cast into this block, use it.
CastInst *&InsertedCast = InsertedCasts[UserBB];
if (!InsertedCast) {
BasicBlock::iterator InsertPt = UserBB->getFirstNonPHI();
InsertedCast =
CastInst::Create(CI->getOpcode(), CI->getOperand(0), CI->getType(), "",
InsertPt);
MadeChange = true;
}
// Replace a use of the cast with a use of the new cast.
TheUse = InsertedCast;
}
// If we removed all uses, nuke the cast.
if (CI->use_empty()) {
CI->eraseFromParent();
MadeChange = true;
}
return MadeChange;
}
/// OptimizeCmpExpression - sink the given CmpInst into user blocks to reduce
/// the number of virtual registers that must be created and coalesced. This is
/// a clear win except on targets with multiple condition code registers
/// (PowerPC), where it might lose; some adjustment may be wanted there.
///
/// Return true if any changes are made.
static bool OptimizeCmpExpression(CmpInst *CI) {
BasicBlock *DefBB = CI->getParent();
/// InsertedCmp - Only insert a cmp in each block once.
DenseMap<BasicBlock*, CmpInst*> InsertedCmps;
bool MadeChange = false;
for (Value::use_iterator UI = CI->use_begin(), E = CI->use_end();
UI != E; ) {
Use &TheUse = UI.getUse();
Instruction *User = cast<Instruction>(*UI);
// Preincrement use iterator so we don't invalidate it.
++UI;
// Don't bother for PHI nodes.
if (isa<PHINode>(User))
continue;
// Figure out which BB this cmp is used in.
BasicBlock *UserBB = User->getParent();
// If this user is in the same block as the cmp, don't change the cmp.
if (UserBB == DefBB) continue;
// If we have already inserted a cmp into this block, use it.
CmpInst *&InsertedCmp = InsertedCmps[UserBB];
if (!InsertedCmp) {
BasicBlock::iterator InsertPt = UserBB->getFirstNonPHI();
InsertedCmp =
CmpInst::Create(CI->getOpcode(), CI->getPredicate(), CI->getOperand(0),
CI->getOperand(1), "", InsertPt);
MadeChange = true;
}
// Replace a use of the cmp with a use of the new cmp.
TheUse = InsertedCmp;
}
// If we removed all uses, nuke the cmp.
if (CI->use_empty())
CI->eraseFromParent();
return MadeChange;
}
//===----------------------------------------------------------------------===//
// Addressing Mode Analysis and Optimization
//===----------------------------------------------------------------------===//
namespace {
/// ExtAddrMode - This is an extended version of TargetLowering::AddrMode
/// which holds actual Value*'s for register values.
struct ExtAddrMode : public TargetLowering::AddrMode {
Value *BaseReg;
Value *ScaledReg;
ExtAddrMode() : BaseReg(0), ScaledReg(0) {}
void print(OStream &OS) const;
void dump() const {
print(cerr);
cerr << '\n';
}
};
} // end anonymous namespace
static inline OStream &operator<<(OStream &OS, const ExtAddrMode &AM) {
AM.print(OS);
return OS;
}
void ExtAddrMode::print(OStream &OS) const {
bool NeedPlus = false;
OS << "[";
if (BaseGV)
OS << (NeedPlus ? " + " : "")
<< "GV:%" << BaseGV->getName(), NeedPlus = true;
if (BaseOffs)
OS << (NeedPlus ? " + " : "") << BaseOffs, NeedPlus = true;
if (BaseReg)
OS << (NeedPlus ? " + " : "")
<< "Base:%" << BaseReg->getName(), NeedPlus = true;
if (Scale)
OS << (NeedPlus ? " + " : "")
<< Scale << "*%" << ScaledReg->getName(), NeedPlus = true;
OS << ']';
}
namespace {
/// AddressingModeMatcher - This class exposes a single public method, which is
/// used to construct a "maximal munch" of the addressing mode for the target
/// specified by TLI for an access to "V" with an access type of AccessTy. This
/// returns the addressing mode that is actually matched by value, but also
/// returns the list of instructions involved in that addressing computation in
/// AddrModeInsts.
class AddressingModeMatcher {
SmallVectorImpl<Instruction*> &AddrModeInsts;
const TargetLowering &TLI;
/// AccessTy/MemoryInst - This is the type for the access (e.g. double) and
/// the memory instruction that we're computing this address for.
const Type *AccessTy;
Instruction *MemoryInst;
/// AddrMode - This is the addressing mode that we're building up. This is
/// part of the return value of this addressing mode matching stuff.
ExtAddrMode &AddrMode;
/// IgnoreProfitability - This is set to true when we should not do
/// profitability checks. When true, IsProfitableToFoldIntoAddressingMode
/// always returns true.
bool IgnoreProfitability;
AddressingModeMatcher(SmallVectorImpl<Instruction*> &AMI,
const TargetLowering &T, const Type *AT,
Instruction *MI, ExtAddrMode &AM)
: AddrModeInsts(AMI), TLI(T), AccessTy(AT), MemoryInst(MI), AddrMode(AM) {
IgnoreProfitability = false;
}
public:
/// Match - Find the maximal addressing mode that a load/store of V can fold,
/// give an access type of AccessTy. This returns a list of involved
/// instructions in AddrModeInsts.
static ExtAddrMode Match(Value *V, const Type *AccessTy,
Instruction *MemoryInst,
SmallVectorImpl<Instruction*> &AddrModeInsts,
const TargetLowering &TLI) {
ExtAddrMode Result;
bool Success =
AddressingModeMatcher(AddrModeInsts, TLI, AccessTy,
MemoryInst, Result).MatchAddr(V, 0);
Success = Success; assert(Success && "Couldn't select *anything*?");
return Result;
}
private:
bool MatchScaledValue(Value *ScaleReg, int64_t Scale, unsigned Depth);
bool MatchAddr(Value *V, unsigned Depth);
bool MatchOperationAddr(User *Operation, unsigned Opcode, unsigned Depth);
bool IsProfitableToFoldIntoAddressingMode(Instruction *I,
ExtAddrMode &AMBefore,
ExtAddrMode &AMAfter);
bool ValueAlreadyLiveAtInst(Value *Val, Value *KnownLive1, Value *KnownLive2);
};
} // end anonymous namespace
/// MatchScaledValue - Try adding ScaleReg*Scale to the current addressing mode.
/// Return true and update AddrMode if this addr mode is legal for the target,
/// false if not.
bool AddressingModeMatcher::MatchScaledValue(Value *ScaleReg, int64_t Scale,
unsigned Depth) {
// If Scale is 1, then this is the same as adding ScaleReg to the addressing
// mode. Just process that directly.
if (Scale == 1)
return MatchAddr(ScaleReg, Depth);
// If the scale is 0, it takes nothing to add this.
if (Scale == 0)
return true;
// If we already have a scale of this value, we can add to it, otherwise, we
// need an available scale field.
if (AddrMode.Scale != 0 && AddrMode.ScaledReg != ScaleReg)
return false;
ExtAddrMode TestAddrMode = AddrMode;
// Add scale to turn X*4+X*3 -> X*7. This could also do things like
// [A+B + A*7] -> [B+A*8].
TestAddrMode.Scale += Scale;
TestAddrMode.ScaledReg = ScaleReg;
// If the new address isn't legal, bail out.
if (!TLI.isLegalAddressingMode(TestAddrMode, AccessTy))
return false;
// It was legal, so commit it.
AddrMode = TestAddrMode;
// Okay, we decided that we can add ScaleReg+Scale to AddrMode. Check now
// to see if ScaleReg is actually X+C. If so, we can turn this into adding
// X*Scale + C*Scale to addr mode.
ConstantInt *CI; Value *AddLHS;
if (isa<Instruction>(ScaleReg) && // not a constant expr.
match(ScaleReg, m_Add(m_Value(AddLHS), m_ConstantInt(CI)))) {
TestAddrMode.ScaledReg = AddLHS;
TestAddrMode.BaseOffs += CI->getSExtValue()*TestAddrMode.Scale;
// If this addressing mode is legal, commit it and remember that we folded
// this instruction.
if (TLI.isLegalAddressingMode(TestAddrMode, AccessTy)) {
AddrModeInsts.push_back(cast<Instruction>(ScaleReg));
AddrMode = TestAddrMode;
return true;
}
}
// Otherwise, not (x+c)*scale, just return what we have.
return true;
}
/// MightBeFoldableInst - This is a little filter, which returns true if an
/// addressing computation involving I might be folded into a load/store
/// accessing it. This doesn't need to be perfect, but needs to accept at least
/// the set of instructions that MatchOperationAddr can.
static bool MightBeFoldableInst(Instruction *I) {
switch (I->getOpcode()) {
case Instruction::BitCast:
// Don't touch identity bitcasts.
if (I->getType() == I->getOperand(0)->getType())
return false;
return isa<PointerType>(I->getType()) || isa<IntegerType>(I->getType());
case Instruction::PtrToInt:
// PtrToInt is always a noop, as we know that the int type is pointer sized.
return true;
case Instruction::IntToPtr:
// We know the input is intptr_t, so this is foldable.
return true;
case Instruction::Add:
return true;
case Instruction::Mul:
case Instruction::Shl:
// Can only handle X*C and X << C.
return isa<ConstantInt>(I->getOperand(1));
case Instruction::GetElementPtr:
return true;
default:
return false;
}
}
/// MatchOperationAddr - Given an instruction or constant expr, see if we can
/// fold the operation into the addressing mode. If so, update the addressing
/// mode and return true, otherwise return false without modifying AddrMode.
bool AddressingModeMatcher::MatchOperationAddr(User *AddrInst, unsigned Opcode,
unsigned Depth) {
// Avoid exponential behavior on extremely deep expression trees.
if (Depth >= 5) return false;
switch (Opcode) {
case Instruction::PtrToInt:
// PtrToInt is always a noop, as we know that the int type is pointer sized.
return MatchAddr(AddrInst->getOperand(0), Depth);
case Instruction::IntToPtr:
// This inttoptr is a no-op if the integer type is pointer sized.
if (TLI.getValueType(AddrInst->getOperand(0)->getType()) ==
TLI.getPointerTy())
return MatchAddr(AddrInst->getOperand(0), Depth);
return false;
case Instruction::BitCast:
// BitCast is always a noop, and we can handle it as long as it is
// int->int or pointer->pointer (we don't want int<->fp or something).
if ((isa<PointerType>(AddrInst->getOperand(0)->getType()) ||
isa<IntegerType>(AddrInst->getOperand(0)->getType())) &&
// Don't touch identity bitcasts. These were probably put here by LSR,
// and we don't want to mess around with them. Assume it knows what it
// is doing.
AddrInst->getOperand(0)->getType() != AddrInst->getType())
return MatchAddr(AddrInst->getOperand(0), Depth);
return false;
case Instruction::Add: {
// Check to see if we can merge in the RHS then the LHS. If so, we win.
ExtAddrMode BackupAddrMode = AddrMode;
unsigned OldSize = AddrModeInsts.size();
if (MatchAddr(AddrInst->getOperand(1), Depth+1) &&
MatchAddr(AddrInst->getOperand(0), Depth+1))
return true;
// Restore the old addr mode info.
AddrMode = BackupAddrMode;
AddrModeInsts.resize(OldSize);
// Otherwise this was over-aggressive. Try merging in the LHS then the RHS.
if (MatchAddr(AddrInst->getOperand(0), Depth+1) &&
MatchAddr(AddrInst->getOperand(1), Depth+1))
return true;
// Otherwise we definitely can't merge the ADD in.
AddrMode = BackupAddrMode;
AddrModeInsts.resize(OldSize);
break;
}
//case Instruction::Or:
// TODO: We can handle "Or Val, Imm" iff this OR is equivalent to an ADD.
//break;
case Instruction::Mul:
case Instruction::Shl: {
// Can only handle X*C and X << C.
ConstantInt *RHS = dyn_cast<ConstantInt>(AddrInst->getOperand(1));
if (!RHS) return false;
int64_t Scale = RHS->getSExtValue();
if (Opcode == Instruction::Shl)
Scale = 1 << Scale;
return MatchScaledValue(AddrInst->getOperand(0), Scale, Depth);
}
case Instruction::GetElementPtr: {
// Scan the GEP. We check it if it contains constant offsets and at most
// one variable offset.
int VariableOperand = -1;
unsigned VariableScale = 0;
int64_t ConstantOffset = 0;
const TargetData *TD = TLI.getTargetData();
gep_type_iterator GTI = gep_type_begin(AddrInst);
for (unsigned i = 1, e = AddrInst->getNumOperands(); i != e; ++i, ++GTI) {
if (const StructType *STy = dyn_cast<StructType>(*GTI)) {
const StructLayout *SL = TD->getStructLayout(STy);
unsigned Idx =
cast<ConstantInt>(AddrInst->getOperand(i))->getZExtValue();
ConstantOffset += SL->getElementOffset(Idx);
} else {
uint64_t TypeSize = TD->getTypePaddedSize(GTI.getIndexedType());
if (ConstantInt *CI = dyn_cast<ConstantInt>(AddrInst->getOperand(i))) {
ConstantOffset += CI->getSExtValue()*TypeSize;
} else if (TypeSize) { // Scales of zero don't do anything.
// We only allow one variable index at the moment.
if (VariableOperand != -1)
return false;
// Remember the variable index.
VariableOperand = i;
VariableScale = TypeSize;
}
}
}
// A common case is for the GEP to only do a constant offset. In this case,
// just add it to the disp field and check validity.
if (VariableOperand == -1) {
AddrMode.BaseOffs += ConstantOffset;
if (ConstantOffset == 0 || TLI.isLegalAddressingMode(AddrMode, AccessTy)){
// Check to see if we can fold the base pointer in too.
if (MatchAddr(AddrInst->getOperand(0), Depth+1))
return true;
}
AddrMode.BaseOffs -= ConstantOffset;
return false;
}
// Save the valid addressing mode in case we can't match.
ExtAddrMode BackupAddrMode = AddrMode;
// Check that this has no base reg yet. If so, we won't have a place to
// put the base of the GEP (assuming it is not a null ptr).
bool SetBaseReg = true;
if (isa<ConstantPointerNull>(AddrInst->getOperand(0)))
SetBaseReg = false; // null pointer base doesn't need representation.
else if (AddrMode.HasBaseReg)
return false; // Base register already specified, can't match GEP.
else {
// Otherwise, we'll use the GEP base as the BaseReg.
AddrMode.HasBaseReg = true;
AddrMode.BaseReg = AddrInst->getOperand(0);
}
// See if the scale and offset amount is valid for this target.
AddrMode.BaseOffs += ConstantOffset;
if (!MatchScaledValue(AddrInst->getOperand(VariableOperand), VariableScale,
Depth)) {
AddrMode = BackupAddrMode;
return false;
}
// If we have a null as the base of the GEP, folding in the constant offset
// plus variable scale is all we can do.
if (!SetBaseReg) return true;
// If this match succeeded, we know that we can form an address with the
// GepBase as the basereg. Match the base pointer of the GEP more
// aggressively by zeroing out BaseReg and rematching. If the base is
// (for example) another GEP, this allows merging in that other GEP into
// the addressing mode we're forming.
AddrMode.HasBaseReg = false;
AddrMode.BaseReg = 0;
bool Success = MatchAddr(AddrInst->getOperand(0), Depth+1);
assert(Success && "MatchAddr should be able to fill in BaseReg!");
Success=Success;
return true;
}
}
return false;
}
/// MatchAddr - If we can, try to add the value of 'Addr' into the current
/// addressing mode. If Addr can't be added to AddrMode this returns false and
/// leaves AddrMode unmodified. This assumes that Addr is either a pointer type
/// or intptr_t for the target.
///
bool AddressingModeMatcher::MatchAddr(Value *Addr, unsigned Depth) {
if (ConstantInt *CI = dyn_cast<ConstantInt>(Addr)) {
// Fold in immediates if legal for the target.
AddrMode.BaseOffs += CI->getSExtValue();
if (TLI.isLegalAddressingMode(AddrMode, AccessTy))
return true;
AddrMode.BaseOffs -= CI->getSExtValue();
} else if (GlobalValue *GV = dyn_cast<GlobalValue>(Addr)) {
// If this is a global variable, try to fold it into the addressing mode.
if (AddrMode.BaseGV == 0) {
AddrMode.BaseGV = GV;
if (TLI.isLegalAddressingMode(AddrMode, AccessTy))
return true;
AddrMode.BaseGV = 0;
}
} else if (Instruction *I = dyn_cast<Instruction>(Addr)) {
ExtAddrMode BackupAddrMode = AddrMode;
unsigned OldSize = AddrModeInsts.size();
// Check to see if it is possible to fold this operation.
if (MatchOperationAddr(I, I->getOpcode(), Depth)) {
// Okay, it's possible to fold this. Check to see if it is actually
// *profitable* to do so. We use a simple cost model to avoid increasing
// register pressure too much.
if (I->hasOneUse() ||
IsProfitableToFoldIntoAddressingMode(I, BackupAddrMode, AddrMode)) {
AddrModeInsts.push_back(I);
return true;
}
// It isn't profitable to do this, roll back.
//cerr << "NOT FOLDING: " << *I;
AddrMode = BackupAddrMode;
AddrModeInsts.resize(OldSize);
}
} else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Addr)) {
if (MatchOperationAddr(CE, CE->getOpcode(), Depth))
return true;
} else if (isa<ConstantPointerNull>(Addr)) {
// Null pointer gets folded without affecting the addressing mode.
return true;
}
// Worse case, the target should support [reg] addressing modes. :)
if (!AddrMode.HasBaseReg) {
AddrMode.HasBaseReg = true;
AddrMode.BaseReg = Addr;
// Still check for legality in case the target supports [imm] but not [i+r].
if (TLI.isLegalAddressingMode(AddrMode, AccessTy))
return true;
AddrMode.HasBaseReg = false;
AddrMode.BaseReg = 0;
}
// If the base register is already taken, see if we can do [r+r].
if (AddrMode.Scale == 0) {
AddrMode.Scale = 1;
AddrMode.ScaledReg = Addr;
if (TLI.isLegalAddressingMode(AddrMode, AccessTy))
return true;
AddrMode.Scale = 0;
AddrMode.ScaledReg = 0;
}
// Couldn't match.
return false;
}
/// IsOperandAMemoryOperand - Check to see if all uses of OpVal by the specified
/// inline asm call are due to memory operands. If so, return true, otherwise
/// return false.
static bool IsOperandAMemoryOperand(CallInst *CI, InlineAsm *IA, Value *OpVal,
const TargetLowering &TLI) {
std::vector<InlineAsm::ConstraintInfo>
Constraints = IA->ParseConstraints();
unsigned ArgNo = 1; // ArgNo - The operand of the CallInst.
for (unsigned i = 0, e = Constraints.size(); i != e; ++i) {
TargetLowering::AsmOperandInfo OpInfo(Constraints[i]);
// Compute the value type for each operand.
switch (OpInfo.Type) {
case InlineAsm::isOutput:
if (OpInfo.isIndirect)
OpInfo.CallOperandVal = CI->getOperand(ArgNo++);
break;
case InlineAsm::isInput:
OpInfo.CallOperandVal = CI->getOperand(ArgNo++);
break;
case InlineAsm::isClobber:
// Nothing to do.
break;
}
// Compute the constraint code and ConstraintType to use.
TLI.ComputeConstraintToUse(OpInfo, SDValue(),
OpInfo.ConstraintType == TargetLowering::C_Memory);
// If this asm operand is our Value*, and if it isn't an indirect memory
// operand, we can't fold it!
if (OpInfo.CallOperandVal == OpVal &&
(OpInfo.ConstraintType != TargetLowering::C_Memory ||
!OpInfo.isIndirect))
return false;
}
return true;
}
/// FindAllMemoryUses - Recursively walk all the uses of I until we find a
/// memory use. If we find an obviously non-foldable instruction, return true.
/// Add the ultimately found memory instructions to MemoryUses.
static bool FindAllMemoryUses(Instruction *I,
SmallVectorImpl<std::pair<Instruction*,unsigned> > &MemoryUses,
SmallPtrSet<Instruction*, 16> &ConsideredInsts,
const TargetLowering &TLI) {
// If we already considered this instruction, we're done.
if (!ConsideredInsts.insert(I))
return false;
// If this is an obviously unfoldable instruction, bail out.
if (!MightBeFoldableInst(I))
return true;
// Loop over all the uses, recursively processing them.
for (Value::use_iterator UI = I->use_begin(), E = I->use_end();
UI != E; ++UI) {
if (LoadInst *LI = dyn_cast<LoadInst>(*UI)) {
MemoryUses.push_back(std::make_pair(LI, UI.getOperandNo()));
continue;
}
if (StoreInst *SI = dyn_cast<StoreInst>(*UI)) {
if (UI.getOperandNo() == 0) return true; // Storing addr, not into addr.
MemoryUses.push_back(std::make_pair(SI, UI.getOperandNo()));
continue;
}
if (CallInst *CI = dyn_cast<CallInst>(*UI)) {
InlineAsm *IA = dyn_cast<InlineAsm>(CI->getCalledValue());
if (IA == 0) return true;
// If this is a memory operand, we're cool, otherwise bail out.
if (!IsOperandAMemoryOperand(CI, IA, I, TLI))
return true;
continue;
}
if (FindAllMemoryUses(cast<Instruction>(*UI), MemoryUses, ConsideredInsts,
TLI))
return true;
}
return false;
}
/// ValueAlreadyLiveAtInst - Retrn true if Val is already known to be live at
/// the use site that we're folding it into. If so, there is no cost to
/// include it in the addressing mode. KnownLive1 and KnownLive2 are two values
/// that we know are live at the instruction already.
bool AddressingModeMatcher::ValueAlreadyLiveAtInst(Value *Val,Value *KnownLive1,
Value *KnownLive2) {
// If Val is either of the known-live values, we know it is live!
if (Val == 0 || Val == KnownLive1 || Val == KnownLive2)
return true;
// All values other than instructions and arguments (e.g. constants) are live.
if (!isa<Instruction>(Val) && !isa<Argument>(Val)) return true;
// If Val is a constant sized alloca in the entry block, it is live, this is
// true because it is just a reference to the stack/frame pointer, which is
// live for the whole function.
if (AllocaInst *AI = dyn_cast<AllocaInst>(Val))
if (AI->isStaticAlloca())
return true;
// Check to see if this value is already used in the memory instruction's
// block. If so, it's already live into the block at the very least, so we
// can reasonably fold it.
BasicBlock *MemBB = MemoryInst->getParent();
for (Value::use_iterator UI = Val->use_begin(), E = Val->use_end();
UI != E; ++UI)
// We know that uses of arguments and instructions have to be instructions.
if (cast<Instruction>(*UI)->getParent() == MemBB)
return true;
return false;
}
/// IsProfitableToFoldIntoAddressingMode - It is possible for the addressing
/// mode of the machine to fold the specified instruction into a load or store
/// that ultimately uses it. However, the specified instruction has multiple
/// uses. Given this, it may actually increase register pressure to fold it
/// into the load. For example, consider this code:
///
/// X = ...
/// Y = X+1
/// use(Y) -> nonload/store
/// Z = Y+1
/// load Z
///
/// In this case, Y has multiple uses, and can be folded into the load of Z
/// (yielding load [X+2]). However, doing this will cause both "X" and "X+1" to
/// be live at the use(Y) line. If we don't fold Y into load Z, we use one
/// fewer register. Since Y can't be folded into "use(Y)" we don't increase the
/// number of computations either.
///
/// Note that this (like most of CodeGenPrepare) is just a rough heuristic. If
/// X was live across 'load Z' for other reasons, we actually *would* want to
/// fold the addressing mode in the Z case. This would make Y die earlier.
bool AddressingModeMatcher::
IsProfitableToFoldIntoAddressingMode(Instruction *I, ExtAddrMode &AMBefore,
ExtAddrMode &AMAfter) {
if (IgnoreProfitability) return true;
// AMBefore is the addressing mode before this instruction was folded into it,
// and AMAfter is the addressing mode after the instruction was folded. Get
// the set of registers referenced by AMAfter and subtract out those
// referenced by AMBefore: this is the set of values which folding in this
// address extends the lifetime of.
//
// Note that there are only two potential values being referenced here,
// BaseReg and ScaleReg (global addresses are always available, as are any
// folded immediates).
Value *BaseReg = AMAfter.BaseReg, *ScaledReg = AMAfter.ScaledReg;
// If the BaseReg or ScaledReg was referenced by the previous addrmode, their
// lifetime wasn't extended by adding this instruction.
if (ValueAlreadyLiveAtInst(BaseReg, AMBefore.BaseReg, AMBefore.ScaledReg))
BaseReg = 0;
if (ValueAlreadyLiveAtInst(ScaledReg, AMBefore.BaseReg, AMBefore.ScaledReg))
ScaledReg = 0;
// If folding this instruction (and it's subexprs) didn't extend any live
// ranges, we're ok with it.
if (BaseReg == 0 && ScaledReg == 0)
return true;
// If all uses of this instruction are ultimately load/store/inlineasm's,
// check to see if their addressing modes will include this instruction. If
// so, we can fold it into all uses, so it doesn't matter if it has multiple
// uses.
SmallVector<std::pair<Instruction*,unsigned>, 16> MemoryUses;
SmallPtrSet<Instruction*, 16> ConsideredInsts;
if (FindAllMemoryUses(I, MemoryUses, ConsideredInsts, TLI))
return false; // Has a non-memory, non-foldable use!
// Now that we know that all uses of this instruction are part of a chain of
// computation involving only operations that could theoretically be folded
// into a memory use, loop over each of these uses and see if they could
// *actually* fold the instruction.
SmallVector<Instruction*, 32> MatchedAddrModeInsts;
for (unsigned i = 0, e = MemoryUses.size(); i != e; ++i) {
Instruction *User = MemoryUses[i].first;
unsigned OpNo = MemoryUses[i].second;
// Get the access type of this use. If the use isn't a pointer, we don't
// know what it accesses.
Value *Address = User->getOperand(OpNo);
if (!isa<PointerType>(Address->getType()))
return false;
const Type *AddressAccessTy =
cast<PointerType>(Address->getType())->getElementType();
// Do a match against the root of this address, ignoring profitability. This
// will tell us if the addressing mode for the memory operation will
// *actually* cover the shared instruction.
ExtAddrMode Result;
AddressingModeMatcher Matcher(MatchedAddrModeInsts, TLI, AddressAccessTy,
MemoryInst, Result);
Matcher.IgnoreProfitability = true;
bool Success = Matcher.MatchAddr(Address, 0);
Success = Success; assert(Success && "Couldn't select *anything*?");
// If the match didn't cover I, then it won't be shared by it.
if (std::find(MatchedAddrModeInsts.begin(), MatchedAddrModeInsts.end(),
I) == MatchedAddrModeInsts.end())
return false;
MatchedAddrModeInsts.clear();
}
return true;
}
//===----------------------------------------------------------------------===//
// Memory Optimization
//===----------------------------------------------------------------------===//
/// IsNonLocalValue - Return true if the specified values are defined in a
/// different basic block than BB.
static bool IsNonLocalValue(Value *V, BasicBlock *BB) {
if (Instruction *I = dyn_cast<Instruction>(V))
return I->getParent() != BB;
return false;
}
/// OptimizeMemoryInst - Load and Store Instructions have often have
/// addressing modes that can do significant amounts of computation. As such,
/// instruction selection will try to get the load or store to do as much
/// computation as possible for the program. The problem is that isel can only
/// see within a single block. As such, we sink as much legal addressing mode
/// stuff into the block as possible.
///
/// This method is used to optimize both load/store and inline asms with memory
/// operands.
bool CodeGenPrepare::OptimizeMemoryInst(Instruction *MemoryInst, Value *Addr,
const Type *AccessTy,
DenseMap<Value*,Value*> &SunkAddrs) {
// Figure out what addressing mode will be built up for this operation.
SmallVector<Instruction*, 16> AddrModeInsts;
ExtAddrMode AddrMode = AddressingModeMatcher::Match(Addr, AccessTy,MemoryInst,
AddrModeInsts, *TLI);
// Check to see if any of the instructions supersumed by this addr mode are
// non-local to I's BB.
bool AnyNonLocal = false;
for (unsigned i = 0, e = AddrModeInsts.size(); i != e; ++i) {
if (IsNonLocalValue(AddrModeInsts[i], MemoryInst->getParent())) {
AnyNonLocal = true;
break;
}
}
// If all the instructions matched are already in this BB, don't do anything.
if (!AnyNonLocal) {
DEBUG(cerr << "CGP: Found local addrmode: " << AddrMode << "\n");
return false;
}
// Insert this computation right after this user. Since our caller is
// scanning from the top of the BB to the bottom, reuse of the expr are
// guaranteed to happen later.
BasicBlock::iterator InsertPt = MemoryInst;
// Now that we determined the addressing expression we want to use and know
// that we have to sink it into this block. Check to see if we have already
// done this for some other load/store instr in this block. If so, reuse the
// computation.
Value *&SunkAddr = SunkAddrs[Addr];
if (SunkAddr) {
DEBUG(cerr << "CGP: Reusing nonlocal addrmode: " << AddrMode << " for "
<< *MemoryInst);
if (SunkAddr->getType() != Addr->getType())
SunkAddr = new BitCastInst(SunkAddr, Addr->getType(), "tmp", InsertPt);
} else {
DEBUG(cerr << "CGP: SINKING nonlocal addrmode: " << AddrMode << " for "
<< *MemoryInst);
const Type *IntPtrTy = TLI->getTargetData()->getIntPtrType();
Value *Result = 0;
// Start with the scale value.
if (AddrMode.Scale) {
Value *V = AddrMode.ScaledReg;
if (V->getType() == IntPtrTy) {
// done.
} else if (isa<PointerType>(V->getType())) {
V = new PtrToIntInst(V, IntPtrTy, "sunkaddr", InsertPt);
} else if (cast<IntegerType>(IntPtrTy)->getBitWidth() <
cast<IntegerType>(V->getType())->getBitWidth()) {
V = new TruncInst(V, IntPtrTy, "sunkaddr", InsertPt);
} else {
V = new SExtInst(V, IntPtrTy, "sunkaddr", InsertPt);
}
if (AddrMode.Scale != 1)
V = BinaryOperator::CreateMul(V, ConstantInt::get(IntPtrTy,
AddrMode.Scale),
"sunkaddr", InsertPt);
Result = V;
}
// Add in the base register.
if (AddrMode.BaseReg) {
Value *V = AddrMode.BaseReg;
if (V->getType() != IntPtrTy)
V = new PtrToIntInst(V, IntPtrTy, "sunkaddr", InsertPt);
if (Result)
Result = BinaryOperator::CreateAdd(Result, V, "sunkaddr", InsertPt);
else
Result = V;
}
// Add in the BaseGV if present.
if (AddrMode.BaseGV) {
Value *V = new PtrToIntInst(AddrMode.BaseGV, IntPtrTy, "sunkaddr",
InsertPt);
if (Result)
Result = BinaryOperator::CreateAdd(Result, V, "sunkaddr", InsertPt);
else
Result = V;
}
// Add in the Base Offset if present.
if (AddrMode.BaseOffs) {
Value *V = ConstantInt::get(IntPtrTy, AddrMode.BaseOffs);
if (Result)
Result = BinaryOperator::CreateAdd(Result, V, "sunkaddr", InsertPt);
else
Result = V;
}
if (Result == 0)
SunkAddr = Constant::getNullValue(Addr->getType());
else
SunkAddr = new IntToPtrInst(Result, Addr->getType(), "sunkaddr",InsertPt);
}
MemoryInst->replaceUsesOfWith(Addr, SunkAddr);
if (Addr->use_empty())
RecursivelyDeleteTriviallyDeadInstructions(Addr);
return true;
}
/// OptimizeInlineAsmInst - If there are any memory operands, use
/// OptimizeMemoryInst to sink their address computing into the block when
/// possible / profitable.
bool CodeGenPrepare::OptimizeInlineAsmInst(Instruction *I, CallSite CS,
DenseMap<Value*,Value*> &SunkAddrs) {
bool MadeChange = false;
InlineAsm *IA = cast<InlineAsm>(CS.getCalledValue());
// Do a prepass over the constraints, canonicalizing them, and building up the
// ConstraintOperands list.
std::vector<InlineAsm::ConstraintInfo>
ConstraintInfos = IA->ParseConstraints();
/// ConstraintOperands - Information about all of the constraints.
std::vector<TargetLowering::AsmOperandInfo> ConstraintOperands;
unsigned ArgNo = 0; // ArgNo - The argument of the CallInst.
for (unsigned i = 0, e = ConstraintInfos.size(); i != e; ++i) {
ConstraintOperands.
push_back(TargetLowering::AsmOperandInfo(ConstraintInfos[i]));
TargetLowering::AsmOperandInfo &OpInfo = ConstraintOperands.back();
// Compute the value type for each operand.
switch (OpInfo.Type) {
case InlineAsm::isOutput:
if (OpInfo.isIndirect)
OpInfo.CallOperandVal = CS.getArgument(ArgNo++);
break;
case InlineAsm::isInput:
OpInfo.CallOperandVal = CS.getArgument(ArgNo++);
break;
case InlineAsm::isClobber:
// Nothing to do.
break;
}
// Compute the constraint code and ConstraintType to use.
TLI->ComputeConstraintToUse(OpInfo, SDValue(),
OpInfo.ConstraintType == TargetLowering::C_Memory);
if (OpInfo.ConstraintType == TargetLowering::C_Memory &&
OpInfo.isIndirect) {
Value *OpVal = OpInfo.CallOperandVal;
MadeChange |= OptimizeMemoryInst(I, OpVal, OpVal->getType(), SunkAddrs);
}
}
return MadeChange;
}
bool CodeGenPrepare::OptimizeExtUses(Instruction *I) {
BasicBlock *DefBB = I->getParent();
// If both result of the {s|z}xt and its source are live out, rewrite all
// other uses of the source with result of extension.
Value *Src = I->getOperand(0);
if (Src->hasOneUse())
return false;
// Only do this xform if truncating is free.
if (TLI && !TLI->isTruncateFree(I->getType(), Src->getType()))
return false;
// Only safe to perform the optimization if the source is also defined in
// this block.
if (!isa<Instruction>(Src) || DefBB != cast<Instruction>(Src)->getParent())
return false;
bool DefIsLiveOut = false;
for (Value::use_iterator UI = I->use_begin(), E = I->use_end();
UI != E; ++UI) {
Instruction *User = cast<Instruction>(*UI);
// Figure out which BB this ext is used in.
BasicBlock *UserBB = User->getParent();
if (UserBB == DefBB) continue;
DefIsLiveOut = true;
break;
}
if (!DefIsLiveOut)
return false;
// Make sure non of the uses are PHI nodes.
for (Value::use_iterator UI = Src->use_begin(), E = Src->use_end();
UI != E; ++UI) {
Instruction *User = cast<Instruction>(*UI);
BasicBlock *UserBB = User->getParent();
if (UserBB == DefBB) continue;
// Be conservative. We don't want this xform to end up introducing
// reloads just before load / store instructions.
if (isa<PHINode>(User) || isa<LoadInst>(User) || isa<StoreInst>(User))
return false;
}
// InsertedTruncs - Only insert one trunc in each block once.
DenseMap<BasicBlock*, Instruction*> InsertedTruncs;
bool MadeChange = false;
for (Value::use_iterator UI = Src->use_begin(), E = Src->use_end();
UI != E; ++UI) {
Use &TheUse = UI.getUse();
Instruction *User = cast<Instruction>(*UI);
// Figure out which BB this ext is used in.
BasicBlock *UserBB = User->getParent();
if (UserBB == DefBB) continue;
// Both src and def are live in this block. Rewrite the use.
Instruction *&InsertedTrunc = InsertedTruncs[UserBB];
if (!InsertedTrunc) {
BasicBlock::iterator InsertPt = UserBB->getFirstNonPHI();
InsertedTrunc = new TruncInst(I, Src->getType(), "", InsertPt);
}
// Replace a use of the {s|z}ext source with a use of the result.
TheUse = InsertedTrunc;
MadeChange = true;
}
return MadeChange;
}
// In this pass we look for GEP and cast instructions that are used
// across basic blocks and rewrite them to improve basic-block-at-a-time
// selection.
bool CodeGenPrepare::OptimizeBlock(BasicBlock &BB) {
bool MadeChange = false;
// Split all critical edges where the dest block has a PHI.
TerminatorInst *BBTI = BB.getTerminator();
if (BBTI->getNumSuccessors() > 1) {
for (unsigned i = 0, e = BBTI->getNumSuccessors(); i != e; ++i) {
BasicBlock *SuccBB = BBTI->getSuccessor(i);
if (isa<PHINode>(SuccBB->begin()) && isCriticalEdge(BBTI, i, true))
SplitEdgeNicely(BBTI, i, BackEdges, this);
}
}
// Keep track of non-local addresses that have been sunk into this block.
// This allows us to avoid inserting duplicate code for blocks with multiple
// load/stores of the same address.
DenseMap<Value*, Value*> SunkAddrs;
for (BasicBlock::iterator BBI = BB.begin(), E = BB.end(); BBI != E; ) {
Instruction *I = BBI++;
if (CastInst *CI = dyn_cast<CastInst>(I)) {
// If the source of the cast is a constant, then this should have
// already been constant folded. The only reason NOT to constant fold
// it is if something (e.g. LSR) was careful to place the constant
// evaluation in a block other than then one that uses it (e.g. to hoist
// the address of globals out of a loop). If this is the case, we don't
// want to forward-subst the cast.
if (isa<Constant>(CI->getOperand(0)))
continue;
bool Change = false;
if (TLI) {
Change = OptimizeNoopCopyExpression(CI, *TLI);
MadeChange |= Change;
}
if (!Change && (isa<ZExtInst>(I) || isa<SExtInst>(I)))
MadeChange |= OptimizeExtUses(I);
} else if (CmpInst *CI = dyn_cast<CmpInst>(I)) {
MadeChange |= OptimizeCmpExpression(CI);
} else if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
if (TLI)
MadeChange |= OptimizeMemoryInst(I, I->getOperand(0), LI->getType(),
SunkAddrs);
} else if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
if (TLI)
MadeChange |= OptimizeMemoryInst(I, SI->getOperand(1),
SI->getOperand(0)->getType(),
SunkAddrs);
} else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(I)) {
if (GEPI->hasAllZeroIndices()) {
/// The GEP operand must be a pointer, so must its result -> BitCast
Instruction *NC = new BitCastInst(GEPI->getOperand(0), GEPI->getType(),
GEPI->getName(), GEPI);
GEPI->replaceAllUsesWith(NC);
GEPI->eraseFromParent();
MadeChange = true;
BBI = NC;
}
} else if (CallInst *CI = dyn_cast<CallInst>(I)) {
// If we found an inline asm expession, and if the target knows how to
// lower it to normal LLVM code, do so now.
if (TLI && isa<InlineAsm>(CI->getCalledValue()))
if (const TargetAsmInfo *TAI =
TLI->getTargetMachine().getTargetAsmInfo()) {
if (TAI->ExpandInlineAsm(CI)) {
BBI = BB.begin();
// Avoid processing instructions out of order, which could cause
// reuse before a value is defined.
SunkAddrs.clear();
} else
// Sink address computing for memory operands into the block.
MadeChange |= OptimizeInlineAsmInst(I, &(*CI), SunkAddrs);
}
}
}
return MadeChange;
}
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