mirror of
https://github.com/c64scene-ar/llvm-6502.git
synced 2024-12-13 20:32:21 +00:00
eef4a339b5
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@232993 91177308-0d34-0410-b5e6-96231b3b80d8
603 lines
21 KiB
C++
603 lines
21 KiB
C++
//===- MergedLoadStoreMotion.cpp - merge and hoist/sink load/stores -------===//
|
|
//
|
|
// The LLVM Compiler Infrastructure
|
|
//
|
|
// This file is distributed under the University of Illinois Open Source
|
|
// License. See LICENSE.TXT for details.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
//
|
|
//! \file
|
|
//! \brief This pass performs merges of loads and stores on both sides of a
|
|
// diamond (hammock). It hoists the loads and sinks the stores.
|
|
//
|
|
// The algorithm iteratively hoists two loads to the same address out of a
|
|
// diamond (hammock) and merges them into a single load in the header. Similar
|
|
// it sinks and merges two stores to the tail block (footer). The algorithm
|
|
// iterates over the instructions of one side of the diamond and attempts to
|
|
// find a matching load/store on the other side. It hoists / sinks when it
|
|
// thinks it safe to do so. This optimization helps with eg. hiding load
|
|
// latencies, triggering if-conversion, and reducing static code size.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
//
|
|
//
|
|
// Example:
|
|
// Diamond shaped code before merge:
|
|
//
|
|
// header:
|
|
// br %cond, label %if.then, label %if.else
|
|
// + +
|
|
// + +
|
|
// + +
|
|
// if.then: if.else:
|
|
// %lt = load %addr_l %le = load %addr_l
|
|
// <use %lt> <use %le>
|
|
// <...> <...>
|
|
// store %st, %addr_s store %se, %addr_s
|
|
// br label %if.end br label %if.end
|
|
// + +
|
|
// + +
|
|
// + +
|
|
// if.end ("footer"):
|
|
// <...>
|
|
//
|
|
// Diamond shaped code after merge:
|
|
//
|
|
// header:
|
|
// %l = load %addr_l
|
|
// br %cond, label %if.then, label %if.else
|
|
// + +
|
|
// + +
|
|
// + +
|
|
// if.then: if.else:
|
|
// <use %l> <use %l>
|
|
// <...> <...>
|
|
// br label %if.end br label %if.end
|
|
// + +
|
|
// + +
|
|
// + +
|
|
// if.end ("footer"):
|
|
// %s.sink = phi [%st, if.then], [%se, if.else]
|
|
// <...>
|
|
// store %s.sink, %addr_s
|
|
// <...>
|
|
//
|
|
//
|
|
//===----------------------- TODO -----------------------------------------===//
|
|
//
|
|
// 1) Generalize to regions other than diamonds
|
|
// 2) Be more aggressive merging memory operations
|
|
// Note that both changes require register pressure control
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
#include "llvm/Transforms/Scalar.h"
|
|
#include "llvm/ADT/SetVector.h"
|
|
#include "llvm/ADT/SmallPtrSet.h"
|
|
#include "llvm/ADT/Statistic.h"
|
|
#include "llvm/Analysis/AliasAnalysis.h"
|
|
#include "llvm/Analysis/CFG.h"
|
|
#include "llvm/Analysis/Loads.h"
|
|
#include "llvm/Analysis/MemoryBuiltins.h"
|
|
#include "llvm/Analysis/MemoryDependenceAnalysis.h"
|
|
#include "llvm/Analysis/TargetLibraryInfo.h"
|
|
#include "llvm/IR/Metadata.h"
|
|
#include "llvm/IR/PatternMatch.h"
|
|
#include "llvm/Support/Allocator.h"
|
|
#include "llvm/Support/CommandLine.h"
|
|
#include "llvm/Support/Debug.h"
|
|
#include "llvm/Support/raw_ostream.h"
|
|
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
|
|
#include "llvm/Transforms/Utils/SSAUpdater.h"
|
|
#include <vector>
|
|
using namespace llvm;
|
|
|
|
#define DEBUG_TYPE "mldst-motion"
|
|
|
|
//===----------------------------------------------------------------------===//
|
|
// MergedLoadStoreMotion Pass
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
namespace {
|
|
class MergedLoadStoreMotion : public FunctionPass {
|
|
AliasAnalysis *AA;
|
|
MemoryDependenceAnalysis *MD;
|
|
|
|
public:
|
|
static char ID; // Pass identification, replacement for typeid
|
|
explicit MergedLoadStoreMotion(void)
|
|
: FunctionPass(ID), MD(nullptr), MagicCompileTimeControl(250) {
|
|
initializeMergedLoadStoreMotionPass(*PassRegistry::getPassRegistry());
|
|
}
|
|
|
|
bool runOnFunction(Function &F) override;
|
|
|
|
private:
|
|
// This transformation requires dominator postdominator info
|
|
void getAnalysisUsage(AnalysisUsage &AU) const override {
|
|
AU.addRequired<TargetLibraryInfoWrapperPass>();
|
|
AU.addRequired<MemoryDependenceAnalysis>();
|
|
AU.addRequired<AliasAnalysis>();
|
|
AU.addPreserved<AliasAnalysis>();
|
|
}
|
|
|
|
// Helper routines
|
|
|
|
///
|
|
/// \brief Remove instruction from parent and update memory dependence
|
|
/// analysis.
|
|
///
|
|
void removeInstruction(Instruction *Inst);
|
|
BasicBlock *getDiamondTail(BasicBlock *BB);
|
|
bool isDiamondHead(BasicBlock *BB);
|
|
// Routines for hoisting loads
|
|
bool isLoadHoistBarrierInRange(const Instruction& Start,
|
|
const Instruction& End,
|
|
LoadInst* LI);
|
|
LoadInst *canHoistFromBlock(BasicBlock *BB, LoadInst *LI);
|
|
void hoistInstruction(BasicBlock *BB, Instruction *HoistCand,
|
|
Instruction *ElseInst);
|
|
bool isSafeToHoist(Instruction *I) const;
|
|
bool hoistLoad(BasicBlock *BB, LoadInst *HoistCand, LoadInst *ElseInst);
|
|
bool mergeLoads(BasicBlock *BB);
|
|
// Routines for sinking stores
|
|
StoreInst *canSinkFromBlock(BasicBlock *BB, StoreInst *SI);
|
|
PHINode *getPHIOperand(BasicBlock *BB, StoreInst *S0, StoreInst *S1);
|
|
bool isStoreSinkBarrierInRange(const Instruction& Start,
|
|
const Instruction& End,
|
|
AliasAnalysis::Location Loc);
|
|
bool sinkStore(BasicBlock *BB, StoreInst *SinkCand, StoreInst *ElseInst);
|
|
bool mergeStores(BasicBlock *BB);
|
|
// The mergeLoad/Store algorithms could have Size0 * Size1 complexity,
|
|
// where Size0 and Size1 are the #instructions on the two sides of
|
|
// the diamond. The constant chosen here is arbitrary. Compiler Time
|
|
// Control is enforced by the check Size0 * Size1 < MagicCompileTimeControl.
|
|
const int MagicCompileTimeControl;
|
|
};
|
|
|
|
char MergedLoadStoreMotion::ID = 0;
|
|
}
|
|
|
|
///
|
|
/// \brief createMergedLoadStoreMotionPass - The public interface to this file.
|
|
///
|
|
FunctionPass *llvm::createMergedLoadStoreMotionPass() {
|
|
return new MergedLoadStoreMotion();
|
|
}
|
|
|
|
INITIALIZE_PASS_BEGIN(MergedLoadStoreMotion, "mldst-motion",
|
|
"MergedLoadStoreMotion", false, false)
|
|
INITIALIZE_PASS_DEPENDENCY(MemoryDependenceAnalysis)
|
|
INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)
|
|
INITIALIZE_AG_DEPENDENCY(AliasAnalysis)
|
|
INITIALIZE_PASS_END(MergedLoadStoreMotion, "mldst-motion",
|
|
"MergedLoadStoreMotion", false, false)
|
|
|
|
///
|
|
/// \brief Remove instruction from parent and update memory dependence analysis.
|
|
///
|
|
void MergedLoadStoreMotion::removeInstruction(Instruction *Inst) {
|
|
// Notify the memory dependence analysis.
|
|
if (MD) {
|
|
MD->removeInstruction(Inst);
|
|
if (LoadInst *LI = dyn_cast<LoadInst>(Inst))
|
|
MD->invalidateCachedPointerInfo(LI->getPointerOperand());
|
|
if (Inst->getType()->getScalarType()->isPointerTy()) {
|
|
MD->invalidateCachedPointerInfo(Inst);
|
|
}
|
|
}
|
|
Inst->eraseFromParent();
|
|
}
|
|
|
|
///
|
|
/// \brief Return tail block of a diamond.
|
|
///
|
|
BasicBlock *MergedLoadStoreMotion::getDiamondTail(BasicBlock *BB) {
|
|
assert(isDiamondHead(BB) && "Basic block is not head of a diamond");
|
|
BranchInst *BI = (BranchInst *)(BB->getTerminator());
|
|
BasicBlock *Succ0 = BI->getSuccessor(0);
|
|
BasicBlock *Tail = Succ0->getTerminator()->getSuccessor(0);
|
|
return Tail;
|
|
}
|
|
|
|
///
|
|
/// \brief True when BB is the head of a diamond (hammock)
|
|
///
|
|
bool MergedLoadStoreMotion::isDiamondHead(BasicBlock *BB) {
|
|
if (!BB)
|
|
return false;
|
|
if (!isa<BranchInst>(BB->getTerminator()))
|
|
return false;
|
|
if (BB->getTerminator()->getNumSuccessors() != 2)
|
|
return false;
|
|
|
|
BranchInst *BI = (BranchInst *)(BB->getTerminator());
|
|
BasicBlock *Succ0 = BI->getSuccessor(0);
|
|
BasicBlock *Succ1 = BI->getSuccessor(1);
|
|
|
|
if (!Succ0->getSinglePredecessor() ||
|
|
Succ0->getTerminator()->getNumSuccessors() != 1)
|
|
return false;
|
|
if (!Succ1->getSinglePredecessor() ||
|
|
Succ1->getTerminator()->getNumSuccessors() != 1)
|
|
return false;
|
|
|
|
BasicBlock *Tail = Succ0->getTerminator()->getSuccessor(0);
|
|
// Ignore triangles.
|
|
if (Succ1->getTerminator()->getSuccessor(0) != Tail)
|
|
return false;
|
|
return true;
|
|
}
|
|
|
|
///
|
|
/// \brief True when instruction is a hoist barrier for a load
|
|
///
|
|
/// Whenever an instruction could possibly modify the value
|
|
/// being loaded or protect against the load from happening
|
|
/// it is considered a hoist barrier.
|
|
///
|
|
|
|
bool MergedLoadStoreMotion::isLoadHoistBarrierInRange(const Instruction& Start,
|
|
const Instruction& End,
|
|
LoadInst* LI) {
|
|
AliasAnalysis::Location Loc = AA->getLocation(LI);
|
|
return AA->canInstructionRangeModRef(Start, End, Loc, AliasAnalysis::Mod);
|
|
}
|
|
|
|
///
|
|
/// \brief Decide if a load can be hoisted
|
|
///
|
|
/// When there is a load in \p BB to the same address as \p LI
|
|
/// and it can be hoisted from \p BB, return that load.
|
|
/// Otherwise return Null.
|
|
///
|
|
LoadInst *MergedLoadStoreMotion::canHoistFromBlock(BasicBlock *BB1,
|
|
LoadInst *Load0) {
|
|
|
|
for (BasicBlock::iterator BBI = BB1->begin(), BBE = BB1->end(); BBI != BBE;
|
|
++BBI) {
|
|
Instruction *Inst = BBI;
|
|
|
|
// Only merge and hoist loads when their result in used only in BB
|
|
if (!isa<LoadInst>(Inst) || Inst->isUsedOutsideOfBlock(BB1))
|
|
continue;
|
|
|
|
LoadInst *Load1 = dyn_cast<LoadInst>(Inst);
|
|
BasicBlock *BB0 = Load0->getParent();
|
|
|
|
AliasAnalysis::Location Loc0 = AA->getLocation(Load0);
|
|
AliasAnalysis::Location Loc1 = AA->getLocation(Load1);
|
|
if (AA->isMustAlias(Loc0, Loc1) && Load0->isSameOperationAs(Load1) &&
|
|
!isLoadHoistBarrierInRange(BB1->front(), *Load1, Load1) &&
|
|
!isLoadHoistBarrierInRange(BB0->front(), *Load0, Load0)) {
|
|
return Load1;
|
|
}
|
|
}
|
|
return nullptr;
|
|
}
|
|
|
|
///
|
|
/// \brief Merge two equivalent instructions \p HoistCand and \p ElseInst into
|
|
/// \p BB
|
|
///
|
|
/// BB is the head of a diamond
|
|
///
|
|
void MergedLoadStoreMotion::hoistInstruction(BasicBlock *BB,
|
|
Instruction *HoistCand,
|
|
Instruction *ElseInst) {
|
|
DEBUG(dbgs() << " Hoist Instruction into BB \n"; BB->dump();
|
|
dbgs() << "Instruction Left\n"; HoistCand->dump(); dbgs() << "\n";
|
|
dbgs() << "Instruction Right\n"; ElseInst->dump(); dbgs() << "\n");
|
|
// Hoist the instruction.
|
|
assert(HoistCand->getParent() != BB);
|
|
|
|
// Intersect optional metadata.
|
|
HoistCand->intersectOptionalDataWith(ElseInst);
|
|
HoistCand->dropUnknownMetadata();
|
|
|
|
// Prepend point for instruction insert
|
|
Instruction *HoistPt = BB->getTerminator();
|
|
|
|
// Merged instruction
|
|
Instruction *HoistedInst = HoistCand->clone();
|
|
|
|
// Notify AA of the new value.
|
|
if (isa<LoadInst>(HoistCand))
|
|
AA->copyValue(HoistCand, HoistedInst);
|
|
|
|
// Hoist instruction.
|
|
HoistedInst->insertBefore(HoistPt);
|
|
|
|
HoistCand->replaceAllUsesWith(HoistedInst);
|
|
removeInstruction(HoistCand);
|
|
// Replace the else block instruction.
|
|
ElseInst->replaceAllUsesWith(HoistedInst);
|
|
removeInstruction(ElseInst);
|
|
}
|
|
|
|
///
|
|
/// \brief Return true if no operand of \p I is defined in I's parent block
|
|
///
|
|
bool MergedLoadStoreMotion::isSafeToHoist(Instruction *I) const {
|
|
BasicBlock *Parent = I->getParent();
|
|
for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) {
|
|
Instruction *Instr = dyn_cast<Instruction>(I->getOperand(i));
|
|
if (Instr && Instr->getParent() == Parent)
|
|
return false;
|
|
}
|
|
return true;
|
|
}
|
|
|
|
///
|
|
/// \brief Merge two equivalent loads and GEPs and hoist into diamond head
|
|
///
|
|
bool MergedLoadStoreMotion::hoistLoad(BasicBlock *BB, LoadInst *L0,
|
|
LoadInst *L1) {
|
|
// Only one definition?
|
|
Instruction *A0 = dyn_cast<Instruction>(L0->getPointerOperand());
|
|
Instruction *A1 = dyn_cast<Instruction>(L1->getPointerOperand());
|
|
if (A0 && A1 && A0->isIdenticalTo(A1) && isSafeToHoist(A0) &&
|
|
A0->hasOneUse() && (A0->getParent() == L0->getParent()) &&
|
|
A1->hasOneUse() && (A1->getParent() == L1->getParent()) &&
|
|
isa<GetElementPtrInst>(A0)) {
|
|
DEBUG(dbgs() << "Hoist Instruction into BB \n"; BB->dump();
|
|
dbgs() << "Instruction Left\n"; L0->dump(); dbgs() << "\n";
|
|
dbgs() << "Instruction Right\n"; L1->dump(); dbgs() << "\n");
|
|
hoistInstruction(BB, A0, A1);
|
|
hoistInstruction(BB, L0, L1);
|
|
return true;
|
|
} else
|
|
return false;
|
|
}
|
|
|
|
///
|
|
/// \brief Try to hoist two loads to same address into diamond header
|
|
///
|
|
/// Starting from a diamond head block, iterate over the instructions in one
|
|
/// successor block and try to match a load in the second successor.
|
|
///
|
|
bool MergedLoadStoreMotion::mergeLoads(BasicBlock *BB) {
|
|
bool MergedLoads = false;
|
|
assert(isDiamondHead(BB));
|
|
BranchInst *BI = dyn_cast<BranchInst>(BB->getTerminator());
|
|
BasicBlock *Succ0 = BI->getSuccessor(0);
|
|
BasicBlock *Succ1 = BI->getSuccessor(1);
|
|
// #Instructions in Succ1 for Compile Time Control
|
|
int Size1 = Succ1->size();
|
|
int NLoads = 0;
|
|
for (BasicBlock::iterator BBI = Succ0->begin(), BBE = Succ0->end();
|
|
BBI != BBE;) {
|
|
|
|
Instruction *I = BBI;
|
|
++BBI;
|
|
|
|
// Only move non-simple (atomic, volatile) loads.
|
|
LoadInst *L0 = dyn_cast<LoadInst>(I);
|
|
if (!L0 || !L0->isSimple() || L0->isUsedOutsideOfBlock(Succ0))
|
|
continue;
|
|
|
|
++NLoads;
|
|
if (NLoads * Size1 >= MagicCompileTimeControl)
|
|
break;
|
|
if (LoadInst *L1 = canHoistFromBlock(Succ1, L0)) {
|
|
bool Res = hoistLoad(BB, L0, L1);
|
|
MergedLoads |= Res;
|
|
// Don't attempt to hoist above loads that had not been hoisted.
|
|
if (!Res)
|
|
break;
|
|
}
|
|
}
|
|
return MergedLoads;
|
|
}
|
|
|
|
///
|
|
/// \brief True when instruction is a sink barrier for a store
|
|
/// located in Loc
|
|
///
|
|
/// Whenever an instruction could possibly read or modify the
|
|
/// value being stored or protect against the store from
|
|
/// happening it is considered a sink barrier.
|
|
///
|
|
|
|
bool MergedLoadStoreMotion::isStoreSinkBarrierInRange(const Instruction& Start,
|
|
const Instruction& End,
|
|
AliasAnalysis::Location
|
|
Loc) {
|
|
return AA->canInstructionRangeModRef(Start, End, Loc, AliasAnalysis::ModRef);
|
|
}
|
|
|
|
///
|
|
/// \brief Check if \p BB contains a store to the same address as \p SI
|
|
///
|
|
/// \return The store in \p when it is safe to sink. Otherwise return Null.
|
|
///
|
|
StoreInst *MergedLoadStoreMotion::canSinkFromBlock(BasicBlock *BB1,
|
|
StoreInst *Store0) {
|
|
DEBUG(dbgs() << "can Sink? : "; Store0->dump(); dbgs() << "\n");
|
|
BasicBlock *BB0 = Store0->getParent();
|
|
for (BasicBlock::reverse_iterator RBI = BB1->rbegin(), RBE = BB1->rend();
|
|
RBI != RBE; ++RBI) {
|
|
Instruction *Inst = &*RBI;
|
|
|
|
if (!isa<StoreInst>(Inst))
|
|
continue;
|
|
|
|
StoreInst *Store1 = cast<StoreInst>(Inst);
|
|
|
|
AliasAnalysis::Location Loc0 = AA->getLocation(Store0);
|
|
AliasAnalysis::Location Loc1 = AA->getLocation(Store1);
|
|
if (AA->isMustAlias(Loc0, Loc1) && Store0->isSameOperationAs(Store1) &&
|
|
!isStoreSinkBarrierInRange(*(std::next(BasicBlock::iterator(Store1))),
|
|
BB1->back(), Loc1) &&
|
|
!isStoreSinkBarrierInRange(*(std::next(BasicBlock::iterator(Store0))),
|
|
BB0->back(), Loc0)) {
|
|
return Store1;
|
|
}
|
|
}
|
|
return nullptr;
|
|
}
|
|
|
|
///
|
|
/// \brief Create a PHI node in BB for the operands of S0 and S1
|
|
///
|
|
PHINode *MergedLoadStoreMotion::getPHIOperand(BasicBlock *BB, StoreInst *S0,
|
|
StoreInst *S1) {
|
|
// Create a phi if the values mismatch.
|
|
PHINode *NewPN = 0;
|
|
Value *Opd1 = S0->getValueOperand();
|
|
Value *Opd2 = S1->getValueOperand();
|
|
if (Opd1 != Opd2) {
|
|
NewPN = PHINode::Create(Opd1->getType(), 2, Opd2->getName() + ".sink",
|
|
BB->begin());
|
|
NewPN->addIncoming(Opd1, S0->getParent());
|
|
NewPN->addIncoming(Opd2, S1->getParent());
|
|
if (NewPN->getType()->getScalarType()->isPointerTy()) {
|
|
// Notify AA of the new value.
|
|
AA->copyValue(Opd1, NewPN);
|
|
AA->copyValue(Opd2, NewPN);
|
|
// AA needs to be informed when a PHI-use of the pointer value is added
|
|
for (unsigned I = 0, E = NewPN->getNumIncomingValues(); I != E; ++I) {
|
|
unsigned J = PHINode::getOperandNumForIncomingValue(I);
|
|
AA->addEscapingUse(NewPN->getOperandUse(J));
|
|
}
|
|
if (MD)
|
|
MD->invalidateCachedPointerInfo(NewPN);
|
|
}
|
|
}
|
|
return NewPN;
|
|
}
|
|
|
|
///
|
|
/// \brief Merge two stores to same address and sink into \p BB
|
|
///
|
|
/// Also sinks GEP instruction computing the store address
|
|
///
|
|
bool MergedLoadStoreMotion::sinkStore(BasicBlock *BB, StoreInst *S0,
|
|
StoreInst *S1) {
|
|
// Only one definition?
|
|
Instruction *A0 = dyn_cast<Instruction>(S0->getPointerOperand());
|
|
Instruction *A1 = dyn_cast<Instruction>(S1->getPointerOperand());
|
|
if (A0 && A1 && A0->isIdenticalTo(A1) && A0->hasOneUse() &&
|
|
(A0->getParent() == S0->getParent()) && A1->hasOneUse() &&
|
|
(A1->getParent() == S1->getParent()) && isa<GetElementPtrInst>(A0)) {
|
|
DEBUG(dbgs() << "Sink Instruction into BB \n"; BB->dump();
|
|
dbgs() << "Instruction Left\n"; S0->dump(); dbgs() << "\n";
|
|
dbgs() << "Instruction Right\n"; S1->dump(); dbgs() << "\n");
|
|
// Hoist the instruction.
|
|
BasicBlock::iterator InsertPt = BB->getFirstInsertionPt();
|
|
// Intersect optional metadata.
|
|
S0->intersectOptionalDataWith(S1);
|
|
S0->dropUnknownMetadata();
|
|
|
|
// Create the new store to be inserted at the join point.
|
|
StoreInst *SNew = (StoreInst *)(S0->clone());
|
|
Instruction *ANew = A0->clone();
|
|
AA->copyValue(S0, SNew);
|
|
SNew->insertBefore(InsertPt);
|
|
ANew->insertBefore(SNew);
|
|
|
|
assert(S0->getParent() == A0->getParent());
|
|
assert(S1->getParent() == A1->getParent());
|
|
|
|
PHINode *NewPN = getPHIOperand(BB, S0, S1);
|
|
// New PHI operand? Use it.
|
|
if (NewPN)
|
|
SNew->setOperand(0, NewPN);
|
|
removeInstruction(S0);
|
|
removeInstruction(S1);
|
|
A0->replaceAllUsesWith(ANew);
|
|
removeInstruction(A0);
|
|
A1->replaceAllUsesWith(ANew);
|
|
removeInstruction(A1);
|
|
return true;
|
|
}
|
|
return false;
|
|
}
|
|
|
|
///
|
|
/// \brief True when two stores are equivalent and can sink into the footer
|
|
///
|
|
/// Starting from a diamond tail block, iterate over the instructions in one
|
|
/// predecessor block and try to match a store in the second predecessor.
|
|
///
|
|
bool MergedLoadStoreMotion::mergeStores(BasicBlock *T) {
|
|
|
|
bool MergedStores = false;
|
|
assert(T && "Footer of a diamond cannot be empty");
|
|
|
|
pred_iterator PI = pred_begin(T), E = pred_end(T);
|
|
assert(PI != E);
|
|
BasicBlock *Pred0 = *PI;
|
|
++PI;
|
|
BasicBlock *Pred1 = *PI;
|
|
++PI;
|
|
// tail block of a diamond/hammock?
|
|
if (Pred0 == Pred1)
|
|
return false; // No.
|
|
if (PI != E)
|
|
return false; // No. More than 2 predecessors.
|
|
|
|
// #Instructions in Succ1 for Compile Time Control
|
|
int Size1 = Pred1->size();
|
|
int NStores = 0;
|
|
|
|
for (BasicBlock::reverse_iterator RBI = Pred0->rbegin(), RBE = Pred0->rend();
|
|
RBI != RBE;) {
|
|
|
|
Instruction *I = &*RBI;
|
|
++RBI;
|
|
|
|
// Sink move non-simple (atomic, volatile) stores
|
|
if (!isa<StoreInst>(I))
|
|
continue;
|
|
StoreInst *S0 = (StoreInst *)I;
|
|
if (!S0->isSimple())
|
|
continue;
|
|
|
|
++NStores;
|
|
if (NStores * Size1 >= MagicCompileTimeControl)
|
|
break;
|
|
if (StoreInst *S1 = canSinkFromBlock(Pred1, S0)) {
|
|
bool Res = sinkStore(T, S0, S1);
|
|
MergedStores |= Res;
|
|
// Don't attempt to sink below stores that had to stick around
|
|
// But after removal of a store and some of its feeding
|
|
// instruction search again from the beginning since the iterator
|
|
// is likely stale at this point.
|
|
if (!Res)
|
|
break;
|
|
else {
|
|
RBI = Pred0->rbegin();
|
|
RBE = Pred0->rend();
|
|
DEBUG(dbgs() << "Search again\n"; Instruction *I = &*RBI; I->dump());
|
|
}
|
|
}
|
|
}
|
|
return MergedStores;
|
|
}
|
|
///
|
|
/// \brief Run the transformation for each function
|
|
///
|
|
bool MergedLoadStoreMotion::runOnFunction(Function &F) {
|
|
MD = &getAnalysis<MemoryDependenceAnalysis>();
|
|
AA = &getAnalysis<AliasAnalysis>();
|
|
|
|
bool Changed = false;
|
|
DEBUG(dbgs() << "Instruction Merger\n");
|
|
|
|
// Merge unconditional branches, allowing PRE to catch more
|
|
// optimization opportunities.
|
|
for (Function::iterator FI = F.begin(), FE = F.end(); FI != FE;) {
|
|
BasicBlock *BB = FI++;
|
|
|
|
// Hoist equivalent loads and sink stores
|
|
// outside diamonds when possible
|
|
if (isDiamondHead(BB)) {
|
|
Changed |= mergeLoads(BB);
|
|
Changed |= mergeStores(getDiamondTail(BB));
|
|
}
|
|
}
|
|
return Changed;
|
|
}
|