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llvm-project/llvm/lib/Target/Hexagon/HexagonPeephole.cpp

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//===-- HexagonPeephole.cpp - Hexagon Peephole Optimiztions ---------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
// This peephole pass optimizes in the following cases.
// 1. Optimizes redundant sign extends for the following case
// Transform the following pattern
// %170 = SXTW %166
// ...
// %176 = COPY %170:isub_lo
//
// Into
// %176 = COPY %166
//
// 2. Optimizes redundant negation of predicates.
// %15 = CMPGTrr %6, %2
// ...
// %16 = NOT_p killed %15
// ...
// JMP_c killed %16, <%bb.1>, implicit dead %pc
//
// Into
// %15 = CMPGTrr %6, %2;
// ...
// JMP_cNot killed %15, <%bb.1>, implicit dead %pc;
//
// Note: The peephole pass makes the instrucstions like
// %170 = SXTW %166 or %16 = NOT_p killed %15
// redundant and relies on some form of dead removal instructions, like
// DCE or DIE to actually eliminate them.
//===----------------------------------------------------------------------===//
#include "Hexagon.h"
#include "HexagonTargetMachine.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/Passes.h"
#include "llvm/CodeGen/TargetInstrInfo.h"
#include "llvm/CodeGen/TargetRegisterInfo.h"
#include "llvm/IR/Constants.h"
#include "llvm/Pass.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetMachine.h"
#include <algorithm>
using namespace llvm;
#define DEBUG_TYPE "hexagon-peephole"
static cl::opt<bool> DisableHexagonPeephole("disable-hexagon-peephole",
cl::Hidden, cl::ZeroOrMore, cl::init(false),
cl::desc("Disable Peephole Optimization"));
static cl::opt<bool> DisablePNotP("disable-hexagon-pnotp",
cl::Hidden, cl::ZeroOrMore, cl::init(false),
cl::desc("Disable Optimization of PNotP"));
static cl::opt<bool> DisableOptSZExt("disable-hexagon-optszext",
cl::Hidden, cl::ZeroOrMore, cl::init(true),
cl::desc("Disable Optimization of Sign/Zero Extends"));
static cl::opt<bool> DisableOptExtTo64("disable-hexagon-opt-ext-to-64",
cl::Hidden, cl::ZeroOrMore, cl::init(true),
cl::desc("Disable Optimization of extensions to i64."));
namespace llvm {
FunctionPass *createHexagonPeephole();
void initializeHexagonPeepholePass(PassRegistry&);
}
namespace {
struct HexagonPeephole : public MachineFunctionPass {
const HexagonInstrInfo *QII;
const HexagonRegisterInfo *QRI;
const MachineRegisterInfo *MRI;
public:
static char ID;
HexagonPeephole() : MachineFunctionPass(ID) {
initializeHexagonPeepholePass(*PassRegistry::getPassRegistry());
}
bool runOnMachineFunction(MachineFunction &MF) override;
StringRef getPassName() const override {
return "Hexagon optimize redundant zero and size extends";
}
void getAnalysisUsage(AnalysisUsage &AU) const override {
MachineFunctionPass::getAnalysisUsage(AU);
}
};
}
char HexagonPeephole::ID = 0;
INITIALIZE_PASS(HexagonPeephole, "hexagon-peephole", "Hexagon Peephole",
false, false)
bool HexagonPeephole::runOnMachineFunction(MachineFunction &MF) {
if (skipFunction(MF.getFunction()))
return false;
QII = static_cast<const HexagonInstrInfo *>(MF.getSubtarget().getInstrInfo());
QRI = MF.getSubtarget<HexagonSubtarget>().getRegisterInfo();
MRI = &MF.getRegInfo();
DenseMap<unsigned, unsigned> PeepholeMap;
DenseMap<unsigned, std::pair<unsigned, unsigned> > PeepholeDoubleRegsMap;
if (DisableHexagonPeephole) return false;
// Loop over all of the basic blocks.
for (MachineFunction::iterator MBBb = MF.begin(), MBBe = MF.end();
MBBb != MBBe; ++MBBb) {
MachineBasicBlock *MBB = &*MBBb;
PeepholeMap.clear();
PeepholeDoubleRegsMap.clear();
// Traverse the basic block.
for (auto I = MBB->begin(), E = MBB->end(), NextI = I; I != E; I = NextI) {
NextI = std::next(I);
MachineInstr &MI = *I;
// Look for sign extends:
// %170 = SXTW %166
if (!DisableOptSZExt && MI.getOpcode() == Hexagon::A2_sxtw) {
assert(MI.getNumOperands() == 2);
MachineOperand &Dst = MI.getOperand(0);
MachineOperand &Src = MI.getOperand(1);
Register DstReg = Dst.getReg();
Register SrcReg = Src.getReg();
// Just handle virtual registers.
if (Register::isVirtualRegister(DstReg) &&
Register::isVirtualRegister(SrcReg)) {
// Map the following:
// %170 = SXTW %166
// PeepholeMap[170] = %166
PeepholeMap[DstReg] = SrcReg;
}
}
// Look for %170 = COMBINE_ir_V4 (0, %169)
// %170:DoublRegs, %169:IntRegs
if (!DisableOptExtTo64 && MI.getOpcode() == Hexagon::A4_combineir) {
assert(MI.getNumOperands() == 3);
MachineOperand &Dst = MI.getOperand(0);
MachineOperand &Src1 = MI.getOperand(1);
MachineOperand &Src2 = MI.getOperand(2);
if (Src1.getImm() != 0)
continue;
Register DstReg = Dst.getReg();
Register SrcReg = Src2.getReg();
PeepholeMap[DstReg] = SrcReg;
}
// Look for this sequence below
// %DoubleReg1 = LSRd_ri %DoubleReg0, 32
// %IntReg = COPY %DoubleReg1:isub_lo.
// and convert into
// %IntReg = COPY %DoubleReg0:isub_hi.
if (MI.getOpcode() == Hexagon::S2_lsr_i_p) {
assert(MI.getNumOperands() == 3);
MachineOperand &Dst = MI.getOperand(0);
MachineOperand &Src1 = MI.getOperand(1);
MachineOperand &Src2 = MI.getOperand(2);
if (Src2.getImm() != 32)
continue;
Register DstReg = Dst.getReg();
Register SrcReg = Src1.getReg();
PeepholeDoubleRegsMap[DstReg] =
std::make_pair(*&SrcReg, Hexagon::isub_hi);
}
// Look for P=NOT(P).
if (!DisablePNotP && MI.getOpcode() == Hexagon::C2_not) {
assert(MI.getNumOperands() == 2);
MachineOperand &Dst = MI.getOperand(0);
MachineOperand &Src = MI.getOperand(1);
Register DstReg = Dst.getReg();
Register SrcReg = Src.getReg();
// Just handle virtual registers.
if (Register::isVirtualRegister(DstReg) &&
Register::isVirtualRegister(SrcReg)) {
// Map the following:
// %170 = NOT_xx %166
// PeepholeMap[170] = %166
PeepholeMap[DstReg] = SrcReg;
}
}
// Look for copy:
// %176 = COPY %170:isub_lo
if (!DisableOptSZExt && MI.isCopy()) {
assert(MI.getNumOperands() == 2);
MachineOperand &Dst = MI.getOperand(0);
MachineOperand &Src = MI.getOperand(1);
// Make sure we are copying the lower 32 bits.
if (Src.getSubReg() != Hexagon::isub_lo)
continue;
Register DstReg = Dst.getReg();
Register SrcReg = Src.getReg();
if (Register::isVirtualRegister(DstReg) &&
Register::isVirtualRegister(SrcReg)) {
// Try to find in the map.
if (unsigned PeepholeSrc = PeepholeMap.lookup(SrcReg)) {
// Change the 1st operand.
MI.RemoveOperand(1);
MI.addOperand(MachineOperand::CreateReg(PeepholeSrc, false));
} else {
DenseMap<unsigned, std::pair<unsigned, unsigned> >::iterator DI =
PeepholeDoubleRegsMap.find(SrcReg);
if (DI != PeepholeDoubleRegsMap.end()) {
std::pair<unsigned,unsigned> PeepholeSrc = DI->second;
MI.RemoveOperand(1);
MI.addOperand(MachineOperand::CreateReg(
PeepholeSrc.first, false /*isDef*/, false /*isImp*/,
false /*isKill*/, false /*isDead*/, false /*isUndef*/,
false /*isEarlyClobber*/, PeepholeSrc.second));
}
}
}
}
// Look for Predicated instructions.
if (!DisablePNotP) {
bool Done = false;
if (QII->isPredicated(MI)) {
MachineOperand &Op0 = MI.getOperand(0);
Register Reg0 = Op0.getReg();
const TargetRegisterClass *RC0 = MRI->getRegClass(Reg0);
if (RC0->getID() == Hexagon::PredRegsRegClassID) {
// Handle instructions that have a prediate register in op0
// (most cases of predicable instructions).
if (Register::isVirtualRegister(Reg0)) {
// Try to find in the map.
if (unsigned PeepholeSrc = PeepholeMap.lookup(Reg0)) {
// Change the 1st operand and, flip the opcode.
MI.getOperand(0).setReg(PeepholeSrc);
MRI->clearKillFlags(PeepholeSrc);
int NewOp = QII->getInvertedPredicatedOpcode(MI.getOpcode());
MI.setDesc(QII->get(NewOp));
Done = true;
}
}
}
}
if (!Done) {
// Handle special instructions.
unsigned Op = MI.getOpcode();
unsigned NewOp = 0;
unsigned PR = 1, S1 = 2, S2 = 3; // Operand indices.
switch (Op) {
case Hexagon::C2_mux:
case Hexagon::C2_muxii:
NewOp = Op;
break;
case Hexagon::C2_muxri:
NewOp = Hexagon::C2_muxir;
break;
case Hexagon::C2_muxir:
NewOp = Hexagon::C2_muxri;
break;
}
if (NewOp) {
Register PSrc = MI.getOperand(PR).getReg();
if (unsigned POrig = PeepholeMap.lookup(PSrc)) {
BuildMI(*MBB, MI.getIterator(), MI.getDebugLoc(),
QII->get(NewOp), MI.getOperand(0).getReg())
.addReg(POrig)
.add(MI.getOperand(S2))
.add(MI.getOperand(S1));
MRI->clearKillFlags(POrig);
MI.eraseFromParent();
}
} // if (NewOp)
} // if (!Done)
} // if (!DisablePNotP)
} // Instruction
} // Basic Block
return true;
}
FunctionPass *llvm::createHexagonPeephole() {
return new HexagonPeephole();
}
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