HexagonCFGOptimizer.cpp [plain text]
#include "Hexagon.h"
#include "HexagonMachineFunctionInfo.h"
#include "HexagonSubtarget.h"
#include "HexagonTargetMachine.h"
#include "llvm/CodeGen/MachineDominators.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineLoopInfo.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/Passes.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetRegisterInfo.h"
using namespace llvm;
#define DEBUG_TYPE "hexagon_cfg"
namespace llvm {
void initializeHexagonCFGOptimizerPass(PassRegistry&);
}
namespace {
class HexagonCFGOptimizer : public MachineFunctionPass {
private:
void InvertAndChangeJumpTarget(MachineInstr*, MachineBasicBlock*);
public:
static char ID;
HexagonCFGOptimizer() : MachineFunctionPass(ID) {
initializeHexagonCFGOptimizerPass(*PassRegistry::getPassRegistry());
}
const char *getPassName() const override {
return "Hexagon CFG Optimizer";
}
bool runOnMachineFunction(MachineFunction &Fn) override;
};
char HexagonCFGOptimizer::ID = 0;
static bool IsConditionalBranch(int Opc) {
return (Opc == Hexagon::J2_jumpt) || (Opc == Hexagon::J2_jumpf)
|| (Opc == Hexagon::J2_jumptnewpt) || (Opc == Hexagon::J2_jumpfnewpt);
}
static bool IsUnconditionalJump(int Opc) {
return (Opc == Hexagon::J2_jump);
}
void
HexagonCFGOptimizer::InvertAndChangeJumpTarget(MachineInstr* MI,
MachineBasicBlock* NewTarget) {
const TargetInstrInfo *TII =
MI->getParent()->getParent()->getSubtarget().getInstrInfo();
int NewOpcode = 0;
switch(MI->getOpcode()) {
case Hexagon::J2_jumpt:
NewOpcode = Hexagon::J2_jumpf;
break;
case Hexagon::J2_jumpf:
NewOpcode = Hexagon::J2_jumpt;
break;
case Hexagon::J2_jumptnewpt:
NewOpcode = Hexagon::J2_jumpfnewpt;
break;
case Hexagon::J2_jumpfnewpt:
NewOpcode = Hexagon::J2_jumptnewpt;
break;
default:
llvm_unreachable("Cannot handle this case");
}
MI->setDesc(TII->get(NewOpcode));
MI->getOperand(1).setMBB(NewTarget);
}
bool HexagonCFGOptimizer::runOnMachineFunction(MachineFunction &Fn) {
for (MachineFunction::iterator MBBb = Fn.begin(), MBBe = Fn.end();
MBBb != MBBe; ++MBBb) {
MachineBasicBlock* MBB = MBBb;
MachineBasicBlock::iterator MII = MBB->getFirstTerminator();
if (MII != MBB->end()) {
MachineInstr *MI = MII;
int Opc = MI->getOpcode();
if (IsConditionalBranch(Opc)) {
unsigned NumSuccs = MBB->succ_size();
MachineBasicBlock::succ_iterator SI = MBB->succ_begin();
MachineBasicBlock* FirstSucc = *SI;
MachineBasicBlock* SecondSucc = *(++SI);
MachineBasicBlock* LayoutSucc = nullptr;
MachineBasicBlock* JumpAroundTarget = nullptr;
if (MBB->isLayoutSuccessor(FirstSucc)) {
LayoutSucc = FirstSucc;
JumpAroundTarget = SecondSucc;
} else if (MBB->isLayoutSuccessor(SecondSucc)) {
LayoutSucc = SecondSucc;
JumpAroundTarget = FirstSucc;
} else {
}
MachineBasicBlock* CondBranchTarget = nullptr;
if ((MI->getOpcode() == Hexagon::J2_jumpt) ||
(MI->getOpcode() == Hexagon::J2_jumpf)) {
CondBranchTarget = MI->getOperand(1).getMBB();
}
if (!LayoutSucc || (CondBranchTarget != JumpAroundTarget)) {
continue;
}
if ((NumSuccs == 2) && LayoutSucc && (LayoutSucc->pred_size() == 1)) {
if ((LayoutSucc->size() == 1) &&
IsUnconditionalJump(LayoutSucc->front().getOpcode())) {
MachineBasicBlock* UncondTarget =
LayoutSucc->front().getOperand(0).getMBB();
bool case1 = LayoutSucc->isLayoutSuccessor(JumpAroundTarget);
bool case2 = JumpAroundTarget->isSuccessor(UncondTarget) &&
JumpAroundTarget->size() >= 1 &&
IsUnconditionalJump(JumpAroundTarget->back().getOpcode()) &&
JumpAroundTarget->pred_size() == 1 &&
JumpAroundTarget->succ_size() == 1;
if (case1 || case2) {
InvertAndChangeJumpTarget(MI, UncondTarget);
MBB->removeSuccessor(JumpAroundTarget);
MBB->addSuccessor(UncondTarget);
LayoutSucc->erase(LayoutSucc->begin());
LayoutSucc->removeSuccessor(UncondTarget);
LayoutSucc->addSuccessor(JumpAroundTarget);
if (case2 && !case1) {
JumpAroundTarget->moveAfter(LayoutSucc);
if (!UncondTarget->canFallThrough()) {
UncondTarget->moveAfter(JumpAroundTarget);
}
}
std::vector<unsigned> OrigLiveIn(LayoutSucc->livein_begin(),
LayoutSucc->livein_end());
std::vector<unsigned> NewLiveIn(JumpAroundTarget->livein_begin(),
JumpAroundTarget->livein_end());
for (unsigned i = 0; i < OrigLiveIn.size(); ++i) {
LayoutSucc->removeLiveIn(OrigLiveIn[i]);
}
for (unsigned i = 0; i < NewLiveIn.size(); ++i) {
LayoutSucc->addLiveIn(NewLiveIn[i]);
}
}
}
}
}
}
}
return true;
}
}
static void initializePassOnce(PassRegistry &Registry) {
PassInfo *PI = new PassInfo("Hexagon CFG Optimizer", "hexagon-cfg",
&HexagonCFGOptimizer::ID, nullptr, false, false);
Registry.registerPass(*PI, true);
}
void llvm::initializeHexagonCFGOptimizerPass(PassRegistry &Registry) {
CALL_ONCE_INITIALIZATION(initializePassOnce)
}
FunctionPass *llvm::createHexagonCFGOptimizer() {
return new HexagonCFGOptimizer();
}