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