mirror of
https://github.com/c64scene-ar/llvm-6502.git
synced 2024-08-27 15:29:51 +00:00
This code is no longer usefull, because we only compute and use the IDom once. There is no benefit in caching it anymore. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@205498 91177308-0d34-0410-b5e6-96231b3b80d8
591 lines
22 KiB
C++
591 lines
22 KiB
C++
//===- ConstantHoisting.cpp - Prepare code for expensive constants --------===//
|
|
//
|
|
// The LLVM Compiler Infrastructure
|
|
//
|
|
// This file is distributed under the University of Illinois Open Source
|
|
// License. See LICENSE.TXT for details.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
//
|
|
// This pass identifies expensive constants to hoist and coalesces them to
|
|
// better prepare it for SelectionDAG-based code generation. This works around
|
|
// the limitations of the basic-block-at-a-time approach.
|
|
//
|
|
// First it scans all instructions for integer constants and calculates its
|
|
// cost. If the constant can be folded into the instruction (the cost is
|
|
// TCC_Free) or the cost is just a simple operation (TCC_BASIC), then we don't
|
|
// consider it expensive and leave it alone. This is the default behavior and
|
|
// the default implementation of getIntImmCost will always return TCC_Free.
|
|
//
|
|
// If the cost is more than TCC_BASIC, then the integer constant can't be folded
|
|
// into the instruction and it might be beneficial to hoist the constant.
|
|
// Similar constants are coalesced to reduce register pressure and
|
|
// materialization code.
|
|
//
|
|
// When a constant is hoisted, it is also hidden behind a bitcast to force it to
|
|
// be live-out of the basic block. Otherwise the constant would be just
|
|
// duplicated and each basic block would have its own copy in the SelectionDAG.
|
|
// The SelectionDAG recognizes such constants as opaque and doesn't perform
|
|
// certain transformations on them, which would create a new expensive constant.
|
|
//
|
|
// This optimization is only applied to integer constants in instructions and
|
|
// simple (this means not nested) constant cast expressions. For example:
|
|
// %0 = load i64* inttoptr (i64 big_constant to i64*)
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
#define DEBUG_TYPE "consthoist"
|
|
#include "llvm/Transforms/Scalar.h"
|
|
#include "llvm/ADT/SmallSet.h"
|
|
#include "llvm/ADT/SmallVector.h"
|
|
#include "llvm/ADT/Statistic.h"
|
|
#include "llvm/Analysis/TargetTransformInfo.h"
|
|
#include "llvm/IR/Constants.h"
|
|
#include "llvm/IR/Dominators.h"
|
|
#include "llvm/IR/IntrinsicInst.h"
|
|
#include "llvm/Pass.h"
|
|
#include "llvm/Support/Debug.h"
|
|
|
|
using namespace llvm;
|
|
|
|
STATISTIC(NumConstantsHoisted, "Number of constants hoisted");
|
|
STATISTIC(NumConstantsRebased, "Number of constants rebased");
|
|
|
|
namespace {
|
|
struct ConstantUser;
|
|
struct RebasedConstantInfo;
|
|
|
|
typedef SmallVector<ConstantUser, 8> ConstantUseListType;
|
|
typedef SmallVector<RebasedConstantInfo, 4> RebasedConstantListType;
|
|
|
|
/// \brief Keeps track of the user of a constant and the operand index where the
|
|
/// constant is used.
|
|
struct ConstantUser {
|
|
Instruction *Inst;
|
|
unsigned OpndIdx;
|
|
|
|
ConstantUser(Instruction *Inst, unsigned Idx) : Inst(Inst), OpndIdx(Idx) { }
|
|
};
|
|
|
|
/// \brief Keeps track of a constant candidate and its uses.
|
|
struct ConstantCandidate {
|
|
ConstantUseListType Uses;
|
|
ConstantInt *ConstInt;
|
|
unsigned CumulativeCost;
|
|
|
|
ConstantCandidate(ConstantInt *ConstInt)
|
|
: ConstInt(ConstInt), CumulativeCost(0) { }
|
|
|
|
/// \brief Add the user to the use list and update the cost.
|
|
void addUser(Instruction *Inst, unsigned Idx, unsigned Cost) {
|
|
CumulativeCost += Cost;
|
|
Uses.push_back(ConstantUser(Inst, Idx));
|
|
}
|
|
};
|
|
|
|
/// \brief This represents a constant that has been rebased with respect to a
|
|
/// base constant. The difference to the base constant is recorded in Offset.
|
|
struct RebasedConstantInfo {
|
|
ConstantUseListType Uses;
|
|
Constant *Offset;
|
|
|
|
RebasedConstantInfo(ConstantUseListType &&Uses, Constant *Offset)
|
|
: Uses(Uses), Offset(Offset) { }
|
|
};
|
|
|
|
/// \brief A base constant and all its rebased constants.
|
|
struct ConstantInfo {
|
|
ConstantInt *BaseConstant;
|
|
RebasedConstantListType RebasedConstants;
|
|
};
|
|
|
|
/// \brief The constant hoisting pass.
|
|
class ConstantHoisting : public FunctionPass {
|
|
typedef DenseMap<ConstantInt *, unsigned> ConstCandMapType;
|
|
typedef std::vector<ConstantCandidate> ConstCandVecType;
|
|
|
|
const TargetTransformInfo *TTI;
|
|
DominatorTree *DT;
|
|
BasicBlock *Entry;
|
|
|
|
/// Keeps track of constant candidates found in the function.
|
|
ConstCandVecType ConstCandVec;
|
|
|
|
/// Keep track of cast instructions we already cloned.
|
|
SmallDenseMap<Instruction *, Instruction *> ClonedCastMap;
|
|
|
|
/// These are the final constants we decided to hoist.
|
|
SmallVector<ConstantInfo, 8> ConstantVec;
|
|
public:
|
|
static char ID; // Pass identification, replacement for typeid
|
|
ConstantHoisting() : FunctionPass(ID), TTI(0), DT(0), Entry(0) {
|
|
initializeConstantHoistingPass(*PassRegistry::getPassRegistry());
|
|
}
|
|
|
|
bool runOnFunction(Function &Fn) override;
|
|
|
|
const char *getPassName() const override { return "Constant Hoisting"; }
|
|
|
|
void getAnalysisUsage(AnalysisUsage &AU) const override {
|
|
AU.setPreservesCFG();
|
|
AU.addRequired<DominatorTreeWrapperPass>();
|
|
AU.addRequired<TargetTransformInfo>();
|
|
}
|
|
|
|
private:
|
|
/// \brief Initialize the pass.
|
|
void setup(Function &Fn) {
|
|
DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
|
|
TTI = &getAnalysis<TargetTransformInfo>();
|
|
Entry = &Fn.getEntryBlock();
|
|
}
|
|
|
|
/// \brief Cleanup.
|
|
void cleanup() {
|
|
ConstantVec.clear();
|
|
ClonedCastMap.clear();
|
|
ConstCandVec.clear();
|
|
|
|
TTI = nullptr;
|
|
DT = nullptr;
|
|
Entry = nullptr;
|
|
}
|
|
|
|
Instruction *findMatInsertPt(Instruction *Inst, unsigned Idx = ~0U) const;
|
|
Instruction *findConstantInsertionPoint(const ConstantInfo &ConstInfo) const;
|
|
void collectConstantCandidates(ConstCandMapType &ConstCandMap,
|
|
Instruction *Inst, unsigned Idx,
|
|
ConstantInt *ConstInt);
|
|
void collectConstantCandidates(ConstCandMapType &ConstCandMap,
|
|
Instruction *Inst);
|
|
void collectConstantCandidates(Function &Fn);
|
|
void findAndMakeBaseConstant(ConstCandVecType::iterator S,
|
|
ConstCandVecType::iterator E);
|
|
void findBaseConstants();
|
|
void emitBaseConstants(Instruction *Base, Constant *Offset,
|
|
const ConstantUser &ConstUser);
|
|
bool emitBaseConstants();
|
|
void deleteDeadCastInst() const;
|
|
bool optimizeConstants(Function &Fn);
|
|
};
|
|
}
|
|
|
|
char ConstantHoisting::ID = 0;
|
|
INITIALIZE_PASS_BEGIN(ConstantHoisting, "consthoist", "Constant Hoisting",
|
|
false, false)
|
|
INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
|
|
INITIALIZE_AG_DEPENDENCY(TargetTransformInfo)
|
|
INITIALIZE_PASS_END(ConstantHoisting, "consthoist", "Constant Hoisting",
|
|
false, false)
|
|
|
|
FunctionPass *llvm::createConstantHoistingPass() {
|
|
return new ConstantHoisting();
|
|
}
|
|
|
|
/// \brief Perform the constant hoisting optimization for the given function.
|
|
bool ConstantHoisting::runOnFunction(Function &Fn) {
|
|
DEBUG(dbgs() << "********** Begin Constant Hoisting **********\n");
|
|
DEBUG(dbgs() << "********** Function: " << Fn.getName() << '\n');
|
|
|
|
setup(Fn);
|
|
|
|
bool MadeChange = optimizeConstants(Fn);
|
|
|
|
if (MadeChange) {
|
|
DEBUG(dbgs() << "********** Function after Constant Hoisting: "
|
|
<< Fn.getName() << '\n');
|
|
DEBUG(dbgs() << Fn);
|
|
}
|
|
DEBUG(dbgs() << "********** End Constant Hoisting **********\n");
|
|
|
|
cleanup();
|
|
|
|
return MadeChange;
|
|
}
|
|
|
|
|
|
/// \brief Find the constant materialization insertion point.
|
|
Instruction *ConstantHoisting::findMatInsertPt(Instruction *Inst,
|
|
unsigned Idx) const {
|
|
// The simple and common case.
|
|
if (!isa<PHINode>(Inst) && !isa<LandingPadInst>(Inst))
|
|
return Inst;
|
|
|
|
// We can't insert directly before a phi node or landing pad. Insert before
|
|
// the terminator of the incoming or dominating block.
|
|
assert(Entry != Inst->getParent() && "PHI or landing pad in entry block!");
|
|
if (Idx != ~0U && isa<PHINode>(Inst))
|
|
return cast<PHINode>(Inst)->getIncomingBlock(Idx)->getTerminator();
|
|
|
|
BasicBlock *IDom = DT->getNode(Inst->getParent())->getIDom()->getBlock();
|
|
return IDom->getTerminator();
|
|
}
|
|
|
|
/// \brief Find an insertion point that dominates all uses.
|
|
Instruction *ConstantHoisting::
|
|
findConstantInsertionPoint(const ConstantInfo &ConstInfo) const {
|
|
assert(!ConstInfo.RebasedConstants.empty() && "Invalid constant info entry.");
|
|
// Collect all basic blocks.
|
|
SmallPtrSet<BasicBlock *, 8> BBs;
|
|
for (auto const &RCI : ConstInfo.RebasedConstants)
|
|
for (auto const &U : RCI.Uses)
|
|
BBs.insert(U.Inst->getParent());
|
|
|
|
if (BBs.count(Entry))
|
|
return &Entry->front();
|
|
|
|
while (BBs.size() >= 2) {
|
|
BasicBlock *BB, *BB1, *BB2;
|
|
BB1 = *BBs.begin();
|
|
BB2 = *std::next(BBs.begin());
|
|
BB = DT->findNearestCommonDominator(BB1, BB2);
|
|
if (BB == Entry)
|
|
return &Entry->front();
|
|
BBs.erase(BB1);
|
|
BBs.erase(BB2);
|
|
BBs.insert(BB);
|
|
}
|
|
assert((BBs.size() == 1) && "Expected only one element.");
|
|
Instruction &FirstInst = (*BBs.begin())->front();
|
|
return findMatInsertPt(&FirstInst);
|
|
}
|
|
|
|
|
|
/// \brief Record constant integer ConstInt for instruction Inst at operand
|
|
/// index Idx.
|
|
///
|
|
/// The operand at index Idx is not necessarily the constant integer itself. It
|
|
/// could also be a cast instruction or a constant expression that uses the
|
|
// constant integer.
|
|
void ConstantHoisting::collectConstantCandidates(ConstCandMapType &ConstCandMap,
|
|
Instruction *Inst,
|
|
unsigned Idx,
|
|
ConstantInt *ConstInt) {
|
|
unsigned Cost;
|
|
// Ask the target about the cost of materializing the constant for the given
|
|
// instruction and operand index.
|
|
if (auto IntrInst = dyn_cast<IntrinsicInst>(Inst))
|
|
Cost = TTI->getIntImmCost(IntrInst->getIntrinsicID(), Idx,
|
|
ConstInt->getValue(), ConstInt->getType());
|
|
else
|
|
Cost = TTI->getIntImmCost(Inst->getOpcode(), Idx, ConstInt->getValue(),
|
|
ConstInt->getType());
|
|
|
|
// Ignore cheap integer constants.
|
|
if (Cost > TargetTransformInfo::TCC_Basic) {
|
|
ConstCandMapType::iterator Itr;
|
|
bool Inserted;
|
|
std::tie(Itr, Inserted) = ConstCandMap.insert(std::make_pair(ConstInt, 0));
|
|
if (Inserted) {
|
|
ConstCandVec.push_back(ConstantCandidate(ConstInt));
|
|
Itr->second = ConstCandVec.size() - 1;
|
|
}
|
|
ConstCandVec[Itr->second].addUser(Inst, Idx, Cost);
|
|
DEBUG(if (isa<ConstantInt>(Inst->getOperand(Idx)))
|
|
dbgs() << "Collect constant " << *ConstInt << " from " << *Inst
|
|
<< " with cost " << Cost << '\n';
|
|
else
|
|
dbgs() << "Collect constant " << *ConstInt << " indirectly from "
|
|
<< *Inst << " via " << *Inst->getOperand(Idx) << " with cost "
|
|
<< Cost << '\n';
|
|
);
|
|
}
|
|
}
|
|
|
|
/// \brief Scan the instruction for expensive integer constants and record them
|
|
/// in the constant candidate vector.
|
|
void ConstantHoisting::collectConstantCandidates(ConstCandMapType &ConstCandMap,
|
|
Instruction *Inst) {
|
|
// Skip all cast instructions. They are visited indirectly later on.
|
|
if (Inst->isCast())
|
|
return;
|
|
|
|
// Can't handle inline asm. Skip it.
|
|
if (auto Call = dyn_cast<CallInst>(Inst))
|
|
if (isa<InlineAsm>(Call->getCalledValue()))
|
|
return;
|
|
|
|
// Scan all operands.
|
|
for (unsigned Idx = 0, E = Inst->getNumOperands(); Idx != E; ++Idx) {
|
|
Value *Opnd = Inst->getOperand(Idx);
|
|
|
|
// Visit constant integers.
|
|
if (auto ConstInt = dyn_cast<ConstantInt>(Opnd)) {
|
|
collectConstantCandidates(ConstCandMap, Inst, Idx, ConstInt);
|
|
continue;
|
|
}
|
|
|
|
// Visit cast instructions that have constant integers.
|
|
if (auto CastInst = dyn_cast<Instruction>(Opnd)) {
|
|
// Only visit cast instructions, which have been skipped. All other
|
|
// instructions should have already been visited.
|
|
if (!CastInst->isCast())
|
|
continue;
|
|
|
|
if (auto *ConstInt = dyn_cast<ConstantInt>(CastInst->getOperand(0))) {
|
|
// Pretend the constant is directly used by the instruction and ignore
|
|
// the cast instruction.
|
|
collectConstantCandidates(ConstCandMap, Inst, Idx, ConstInt);
|
|
continue;
|
|
}
|
|
}
|
|
|
|
// Visit constant expressions that have constant integers.
|
|
if (auto ConstExpr = dyn_cast<ConstantExpr>(Opnd)) {
|
|
// Only visit constant cast expressions.
|
|
if (!ConstExpr->isCast())
|
|
continue;
|
|
|
|
if (auto ConstInt = dyn_cast<ConstantInt>(ConstExpr->getOperand(0))) {
|
|
// Pretend the constant is directly used by the instruction and ignore
|
|
// the constant expression.
|
|
collectConstantCandidates(ConstCandMap, Inst, Idx, ConstInt);
|
|
continue;
|
|
}
|
|
}
|
|
} // end of for all operands
|
|
}
|
|
|
|
/// \brief Collect all integer constants in the function that cannot be folded
|
|
/// into an instruction itself.
|
|
void ConstantHoisting::collectConstantCandidates(Function &Fn) {
|
|
ConstCandMapType ConstCandMap;
|
|
for (Function::iterator BB : Fn)
|
|
for (BasicBlock::iterator Inst : *BB)
|
|
collectConstantCandidates(ConstCandMap, Inst);
|
|
}
|
|
|
|
/// \brief Find the base constant within the given range and rebase all other
|
|
/// constants with respect to the base constant.
|
|
void ConstantHoisting::findAndMakeBaseConstant(ConstCandVecType::iterator S,
|
|
ConstCandVecType::iterator E) {
|
|
auto MaxCostItr = S;
|
|
unsigned NumUses = 0;
|
|
// Use the constant that has the maximum cost as base constant.
|
|
for (auto ConstCand = S; ConstCand != E; ++ConstCand) {
|
|
NumUses += ConstCand->Uses.size();
|
|
if (ConstCand->CumulativeCost > MaxCostItr->CumulativeCost)
|
|
MaxCostItr = ConstCand;
|
|
}
|
|
|
|
// Don't hoist constants that have only one use.
|
|
if (NumUses <= 1)
|
|
return;
|
|
|
|
ConstantInfo ConstInfo;
|
|
ConstInfo.BaseConstant = MaxCostItr->ConstInt;
|
|
Type *Ty = ConstInfo.BaseConstant->getType();
|
|
|
|
// Rebase the constants with respect to the base constant.
|
|
for (auto ConstCand = S; ConstCand != E; ++ConstCand) {
|
|
APInt Diff = ConstCand->ConstInt->getValue() -
|
|
ConstInfo.BaseConstant->getValue();
|
|
Constant *Offset = Diff == 0 ? nullptr : ConstantInt::get(Ty, Diff);
|
|
ConstInfo.RebasedConstants.push_back(
|
|
RebasedConstantInfo(std::move(ConstCand->Uses), Offset));
|
|
}
|
|
ConstantVec.push_back(ConstInfo);
|
|
}
|
|
|
|
/// \brief Finds and combines constant candidates that can be easily
|
|
/// rematerialized with an add from a common base constant.
|
|
void ConstantHoisting::findBaseConstants() {
|
|
// Sort the constants by value and type. This invalidates the mapping!
|
|
std::sort(ConstCandVec.begin(), ConstCandVec.end(),
|
|
[](const ConstantCandidate &LHS, const ConstantCandidate &RHS) {
|
|
if (LHS.ConstInt->getType() != RHS.ConstInt->getType())
|
|
return LHS.ConstInt->getType()->getBitWidth() <
|
|
RHS.ConstInt->getType()->getBitWidth();
|
|
return LHS.ConstInt->getValue().ult(RHS.ConstInt->getValue());
|
|
});
|
|
|
|
// Simple linear scan through the sorted constant candidate vector for viable
|
|
// merge candidates.
|
|
auto MinValItr = ConstCandVec.begin();
|
|
for (auto CC = std::next(ConstCandVec.begin()), E = ConstCandVec.end();
|
|
CC != E; ++CC) {
|
|
if (MinValItr->ConstInt->getType() == CC->ConstInt->getType()) {
|
|
// Check if the constant is in range of an add with immediate.
|
|
APInt Diff = CC->ConstInt->getValue() - MinValItr->ConstInt->getValue();
|
|
if ((Diff.getBitWidth() <= 64) &&
|
|
TTI->isLegalAddImmediate(Diff.getSExtValue()))
|
|
continue;
|
|
}
|
|
// We either have now a different constant type or the constant is not in
|
|
// range of an add with immediate anymore.
|
|
findAndMakeBaseConstant(MinValItr, CC);
|
|
// Start a new base constant search.
|
|
MinValItr = CC;
|
|
}
|
|
// Finalize the last base constant search.
|
|
findAndMakeBaseConstant(MinValItr, ConstCandVec.end());
|
|
}
|
|
|
|
/// \brief Updates the operand at Idx in instruction Inst with the result of
|
|
/// instruction Mat. If the instruction is a PHI node then special
|
|
/// handling for duplicate values form the same incomming basic block is
|
|
/// required.
|
|
/// \return The update will always succeed, but the return value indicated if
|
|
/// Mat was used for the update or not.
|
|
static bool updateOperand(Instruction *Inst, unsigned Idx, Instruction *Mat) {
|
|
if (auto PHI = dyn_cast<PHINode>(Inst)) {
|
|
// Check if any previous operand of the PHI node has the same incoming basic
|
|
// block. This is a very odd case that happens when the incoming basic block
|
|
// has a switch statement. In this case use the same value as the previous
|
|
// operand(s), otherwise we will fail verification due to different values.
|
|
// The values are actually the same, but the variable names are different
|
|
// and the verifier doesn't like that.
|
|
BasicBlock *IncomingBB = PHI->getIncomingBlock(Idx);
|
|
for (unsigned i = 0; i < Idx; ++i) {
|
|
if (PHI->getIncomingBlock(i) == IncomingBB) {
|
|
Value *IncomingVal = PHI->getIncomingValue(i);
|
|
Inst->setOperand(Idx, IncomingVal);
|
|
return false;
|
|
}
|
|
}
|
|
}
|
|
|
|
Inst->setOperand(Idx, Mat);
|
|
return true;
|
|
}
|
|
|
|
/// \brief Emit materialization code for all rebased constants and update their
|
|
/// users.
|
|
void ConstantHoisting::emitBaseConstants(Instruction *Base, Constant *Offset,
|
|
const ConstantUser &ConstUser) {
|
|
Instruction *Mat = Base;
|
|
if (Offset) {
|
|
Instruction *InsertionPt = findMatInsertPt(ConstUser.Inst,
|
|
ConstUser.OpndIdx);
|
|
Mat = BinaryOperator::Create(Instruction::Add, Base, Offset,
|
|
"const_mat", InsertionPt);
|
|
|
|
DEBUG(dbgs() << "Materialize constant (" << *Base->getOperand(0)
|
|
<< " + " << *Offset << ") in BB "
|
|
<< Mat->getParent()->getName() << '\n' << *Mat << '\n');
|
|
Mat->setDebugLoc(ConstUser.Inst->getDebugLoc());
|
|
}
|
|
Value *Opnd = ConstUser.Inst->getOperand(ConstUser.OpndIdx);
|
|
|
|
// Visit constant integer.
|
|
if (isa<ConstantInt>(Opnd)) {
|
|
DEBUG(dbgs() << "Update: " << *ConstUser.Inst << '\n');
|
|
if (!updateOperand(ConstUser.Inst, ConstUser.OpndIdx, Mat) && Offset)
|
|
Mat->eraseFromParent();
|
|
DEBUG(dbgs() << "To : " << *ConstUser.Inst << '\n');
|
|
return;
|
|
}
|
|
|
|
// Visit cast instruction.
|
|
if (auto CastInst = dyn_cast<Instruction>(Opnd)) {
|
|
assert(CastInst->isCast() && "Expected an cast instruction!");
|
|
// Check if we already have visited this cast instruction before to avoid
|
|
// unnecessary cloning.
|
|
Instruction *&ClonedCastInst = ClonedCastMap[CastInst];
|
|
if (!ClonedCastInst) {
|
|
ClonedCastInst = CastInst->clone();
|
|
ClonedCastInst->setOperand(0, Mat);
|
|
ClonedCastInst->insertAfter(CastInst);
|
|
// Use the same debug location as the original cast instruction.
|
|
ClonedCastInst->setDebugLoc(CastInst->getDebugLoc());
|
|
DEBUG(dbgs() << "Clone instruction: " << *ClonedCastInst << '\n'
|
|
<< "To : " << *CastInst << '\n');
|
|
}
|
|
|
|
DEBUG(dbgs() << "Update: " << *ConstUser.Inst << '\n');
|
|
updateOperand(ConstUser.Inst, ConstUser.OpndIdx, ClonedCastInst);
|
|
DEBUG(dbgs() << "To : " << *ConstUser.Inst << '\n');
|
|
return;
|
|
}
|
|
|
|
// Visit constant expression.
|
|
if (auto ConstExpr = dyn_cast<ConstantExpr>(Opnd)) {
|
|
Instruction *ConstExprInst = ConstExpr->getAsInstruction();
|
|
ConstExprInst->setOperand(0, Mat);
|
|
ConstExprInst->insertBefore(findMatInsertPt(ConstUser.Inst,
|
|
ConstUser.OpndIdx));
|
|
|
|
// Use the same debug location as the instruction we are about to update.
|
|
ConstExprInst->setDebugLoc(ConstUser.Inst->getDebugLoc());
|
|
|
|
DEBUG(dbgs() << "Create instruction: " << *ConstExprInst << '\n'
|
|
<< "From : " << *ConstExpr << '\n');
|
|
DEBUG(dbgs() << "Update: " << *ConstUser.Inst << '\n');
|
|
if (!updateOperand(ConstUser.Inst, ConstUser.OpndIdx, ConstExprInst)) {
|
|
ConstExprInst->eraseFromParent();
|
|
if (Offset)
|
|
Mat->eraseFromParent();
|
|
}
|
|
DEBUG(dbgs() << "To : " << *ConstUser.Inst << '\n');
|
|
return;
|
|
}
|
|
}
|
|
|
|
/// \brief Hoist and hide the base constant behind a bitcast and emit
|
|
/// materialization code for derived constants.
|
|
bool ConstantHoisting::emitBaseConstants() {
|
|
bool MadeChange = false;
|
|
for (auto const &ConstInfo : ConstantVec) {
|
|
// Hoist and hide the base constant behind a bitcast.
|
|
Instruction *IP = findConstantInsertionPoint(ConstInfo);
|
|
IntegerType *Ty = ConstInfo.BaseConstant->getType();
|
|
Instruction *Base =
|
|
new BitCastInst(ConstInfo.BaseConstant, Ty, "const", IP);
|
|
DEBUG(dbgs() << "Hoist constant (" << *ConstInfo.BaseConstant << ") to BB "
|
|
<< IP->getParent()->getName() << '\n' << *Base << '\n');
|
|
NumConstantsHoisted++;
|
|
|
|
// Emit materialization code for all rebased constants.
|
|
for (auto const &RCI : ConstInfo.RebasedConstants) {
|
|
NumConstantsRebased++;
|
|
for (auto const &U : RCI.Uses)
|
|
emitBaseConstants(Base, RCI.Offset, U);
|
|
}
|
|
|
|
// Use the same debug location as the last user of the constant.
|
|
assert(!Base->use_empty() && "The use list is empty!?");
|
|
assert(isa<Instruction>(Base->user_back()) &&
|
|
"All uses should be instructions.");
|
|
Base->setDebugLoc(cast<Instruction>(Base->user_back())->getDebugLoc());
|
|
|
|
// Correct for base constant, which we counted above too.
|
|
NumConstantsRebased--;
|
|
MadeChange = true;
|
|
}
|
|
return MadeChange;
|
|
}
|
|
|
|
/// \brief Check all cast instructions we made a copy of and remove them if they
|
|
/// have no more users.
|
|
void ConstantHoisting::deleteDeadCastInst() const {
|
|
for (auto const &I : ClonedCastMap)
|
|
if (I.first->use_empty())
|
|
I.first->eraseFromParent();
|
|
}
|
|
|
|
/// \brief Optimize expensive integer constants in the given function.
|
|
bool ConstantHoisting::optimizeConstants(Function &Fn) {
|
|
// Collect all constant candidates.
|
|
collectConstantCandidates(Fn);
|
|
|
|
// There are no constant candidates to worry about.
|
|
if (ConstCandVec.empty())
|
|
return false;
|
|
|
|
// Combine constants that can be easily materialized with an add from a common
|
|
// base constant.
|
|
findBaseConstants();
|
|
|
|
// There are no constants to emit.
|
|
if (ConstantVec.empty())
|
|
return false;
|
|
|
|
// Finally hoist the base constant and emit materialization code for dependent
|
|
// constants.
|
|
bool MadeChange = emitBaseConstants();
|
|
|
|
// Cleanup dead instructions.
|
|
deleteDeadCastInst();
|
|
|
|
return MadeChange;
|
|
}
|