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//===-- lib/CodeGen/GlobalISel/Combiner.cpp -------------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file constains common code to combine machine functions at generic
// level.
//===----------------------------------------------------------------------===//
#include "llvm/CodeGen/GlobalISel/Combiner.h"
#include "llvm/ADT/PostOrderIterator.h"
#include "llvm/CodeGen/GlobalISel/CombinerInfo.h"
#include "llvm/CodeGen/GlobalISel/GISelChangeObserver.h"
#include "llvm/CodeGen/GlobalISel/GISelWorkList.h"
#include "llvm/CodeGen/GlobalISel/MachineIRBuilder.h"
#include "llvm/CodeGen/GlobalISel/Utils.h"
#include "llvm/CodeGen/MachineOptimizationRemarkEmitter.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/Support/Debug.h"
#define DEBUG_TYPE "gi-combiner"
using namespace llvm;
namespace {
/// This class acts as the glue the joins the CombinerHelper to the overall
/// Combine algorithm. The CombinerHelper is intended to report the
/// modifications it makes to the MIR to the GISelChangeObserver and the
/// observer subclass will act on these events. In this case, instruction
/// erasure will cancel any future visits to the erased instruction and
/// instruction creation will schedule that instruction for a future visit.
/// Other Combiner implementations may require more complex behaviour from
/// their GISelChangeObserver subclass.
class WorkListMaintainer : public GISelChangeObserver,
public MachineFunction::Delegate {
using WorkListTy = GISelWorkList<512>;
MachineFunction &MF;
WorkListTy &WorkList;
/// The instructions that have been created but we want to report once they
/// have their operands. This is only maintained if debug output is requested.
SmallPtrSet<const MachineInstr *, 4> CreatedInstrs;
public:
WorkListMaintainer(MachineFunction &MF, WorkListTy &WorkList)
: GISelChangeObserver(), MF(MF), WorkList(WorkList) {
MF.setDelegate(this);
}
virtual ~WorkListMaintainer() {
MF.resetDelegate(this);
}
void erasingInstr(const MachineInstr &MI) override {
LLVM_DEBUG(dbgs() << "Erased: " << MI << "\n");
WorkList.remove(&MI);
}
void createdInstr(const MachineInstr &MI) override {
LLVM_DEBUG(dbgs() << "Creating: " << MI << "\n");
WorkList.insert(&MI);
LLVM_DEBUG(CreatedInstrs.insert(&MI));
}
void changingInstr(const MachineInstr &MI) override {
LLVM_DEBUG(dbgs() << "Changing: " << MI << "\n");
WorkList.insert(&MI);
}
void changedInstr(const MachineInstr &MI) override {
LLVM_DEBUG(dbgs() << "Changed: " << MI << "\n");
WorkList.insert(&MI);
}
void reportFullyCreatedInstrs() {
LLVM_DEBUG(for (const auto *MI
: CreatedInstrs) {
dbgs() << "Created: ";
MI->print(dbgs());
});
LLVM_DEBUG(CreatedInstrs.clear());
}
void MF_HandleInsertion(const MachineInstr &MI) override {
createdInstr(MI);
}
void MF_HandleRemoval(const MachineInstr &MI) override {
erasingInstr(MI);
}
};
}
Combiner::Combiner(CombinerInfo &Info, const TargetPassConfig *TPC)
: CInfo(Info), TPC(TPC) {
(void)this->TPC; // FIXME: Remove when used.
}
bool Combiner::combineMachineInstrs(MachineFunction &MF) {
// If the ISel pipeline failed, do not bother running this pass.
// FIXME: Should this be here or in individual combiner passes.
if (MF.getProperties().hasProperty(
MachineFunctionProperties::Property::FailedISel))
return false;
MRI = &MF.getRegInfo();
Builder.setMF(MF);
LLVM_DEBUG(dbgs() << "Generic MI Combiner for: " << MF.getName() << '\n');
MachineOptimizationRemarkEmitter MORE(MF, /*MBFI=*/nullptr);
bool MFChanged = false;
bool Changed;
do {
// Collect all instructions. Do a post order traversal for basic blocks and
// insert with list bottom up, so while we pop_back_val, we'll traverse top
// down RPOT.
Changed = false;
GISelWorkList<512> WorkList(&MF);
WorkListMaintainer Observer(MF, WorkList);
for (MachineBasicBlock *MBB : post_order(&MF)) {
if (MBB->empty())
continue;
for (auto MII = MBB->rbegin(), MIE = MBB->rend(); MII != MIE;) {
MachineInstr *CurMI = &*MII;
++MII;
// Erase dead insts before even adding to the list.
if (isTriviallyDead(*CurMI, *MRI)) {
LLVM_DEBUG(dbgs() << *CurMI << "Is dead; erasing.\n");
CurMI->eraseFromParentAndMarkDBGValuesForRemoval();
continue;
}
WorkList.insert(CurMI);
}
}
// Main Loop. Process the instructions here.
while (!WorkList.empty()) {
MachineInstr *CurrInst = WorkList.pop_back_val();
LLVM_DEBUG(dbgs() << "\nTry combining " << *CurrInst;);
Changed |= CInfo.combine(Observer, *CurrInst, Builder);
Observer.reportFullyCreatedInstrs();
}
MFChanged |= Changed;
} while (Changed);
return MFChanged;
}
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