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330 lines
12 KiB
C++
330 lines
12 KiB
C++
//===-- LowerSubregs.cpp - Subregister Lowering instruction pass ----------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file defines a MachineFunction pass which runs after register
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// allocation that turns subreg insert/extract instructions into register
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// copies, as needed. This ensures correct codegen even if the coalescer
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// isn't able to remove all subreg instructions.
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//
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//===----------------------------------------------------------------------===//
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#define DEBUG_TYPE "lowersubregs"
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#include "llvm/CodeGen/Passes.h"
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#include "llvm/Function.h"
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#include "llvm/CodeGen/MachineFunctionPass.h"
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#include "llvm/CodeGen/MachineInstr.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/Target/TargetRegisterInfo.h"
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#include "llvm/Target/TargetInstrInfo.h"
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#include "llvm/Target/TargetMachine.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/raw_ostream.h"
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using namespace llvm;
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namespace {
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struct LowerSubregsInstructionPass : public MachineFunctionPass {
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private:
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const TargetRegisterInfo *TRI;
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const TargetInstrInfo *TII;
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public:
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static char ID; // Pass identification, replacement for typeid
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LowerSubregsInstructionPass() : MachineFunctionPass(&ID) {}
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const char *getPassName() const {
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return "Subregister lowering instruction pass";
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}
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virtual void getAnalysisUsage(AnalysisUsage &AU) const {
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AU.setPreservesCFG();
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AU.addPreservedID(MachineLoopInfoID);
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AU.addPreservedID(MachineDominatorsID);
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MachineFunctionPass::getAnalysisUsage(AU);
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}
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/// runOnMachineFunction - pass entry point
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bool runOnMachineFunction(MachineFunction&);
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private:
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bool LowerExtract(MachineInstr *MI);
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bool LowerInsert(MachineInstr *MI);
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bool LowerSubregToReg(MachineInstr *MI);
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void TransferDeadFlag(MachineInstr *MI, unsigned DstReg,
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const TargetRegisterInfo *TRI);
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void TransferKillFlag(MachineInstr *MI, unsigned SrcReg,
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const TargetRegisterInfo *TRI,
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bool AddIfNotFound = false);
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};
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char LowerSubregsInstructionPass::ID = 0;
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}
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FunctionPass *llvm::createLowerSubregsPass() {
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return new LowerSubregsInstructionPass();
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}
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/// TransferDeadFlag - MI is a pseudo-instruction with DstReg dead,
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/// and the lowered replacement instructions immediately precede it.
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/// Mark the replacement instructions with the dead flag.
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void
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LowerSubregsInstructionPass::TransferDeadFlag(MachineInstr *MI,
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unsigned DstReg,
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const TargetRegisterInfo *TRI) {
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for (MachineBasicBlock::iterator MII =
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prior(MachineBasicBlock::iterator(MI)); ; --MII) {
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if (MII->addRegisterDead(DstReg, TRI))
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break;
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assert(MII != MI->getParent()->begin() &&
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"copyRegToReg output doesn't reference destination register!");
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}
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}
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/// TransferKillFlag - MI is a pseudo-instruction with SrcReg killed,
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/// and the lowered replacement instructions immediately precede it.
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/// Mark the replacement instructions with the kill flag.
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void
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LowerSubregsInstructionPass::TransferKillFlag(MachineInstr *MI,
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unsigned SrcReg,
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const TargetRegisterInfo *TRI,
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bool AddIfNotFound) {
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for (MachineBasicBlock::iterator MII =
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prior(MachineBasicBlock::iterator(MI)); ; --MII) {
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if (MII->addRegisterKilled(SrcReg, TRI, AddIfNotFound))
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break;
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assert(MII != MI->getParent()->begin() &&
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"copyRegToReg output doesn't reference source register!");
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}
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}
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bool LowerSubregsInstructionPass::LowerExtract(MachineInstr *MI) {
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MachineBasicBlock *MBB = MI->getParent();
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assert(MI->getOperand(0).isReg() && MI->getOperand(0).isDef() &&
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MI->getOperand(1).isReg() && MI->getOperand(1).isUse() &&
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MI->getOperand(2).isImm() && "Malformed extract_subreg");
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unsigned DstReg = MI->getOperand(0).getReg();
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unsigned SuperReg = MI->getOperand(1).getReg();
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unsigned SubIdx = MI->getOperand(2).getImm();
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unsigned SrcReg = TRI->getSubReg(SuperReg, SubIdx);
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assert(TargetRegisterInfo::isPhysicalRegister(SuperReg) &&
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"Extract supperg source must be a physical register");
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assert(TargetRegisterInfo::isPhysicalRegister(DstReg) &&
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"Extract destination must be in a physical register");
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assert(SrcReg && "invalid subregister index for register");
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DEBUG(errs() << "subreg: CONVERTING: " << *MI);
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if (SrcReg == DstReg) {
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// No need to insert an identity copy instruction.
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if (MI->getOperand(1).isKill()) {
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// We must make sure the super-register gets killed. Replace the
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// instruction with KILL.
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MI->setDesc(TII->get(TargetInstrInfo::KILL));
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MI->RemoveOperand(2); // SubIdx
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DEBUG(errs() << "subreg: replace by: " << *MI);
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return true;
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}
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DEBUG(errs() << "subreg: eliminated!");
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} else {
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// Insert copy
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const TargetRegisterClass *TRCS = TRI->getPhysicalRegisterRegClass(DstReg);
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const TargetRegisterClass *TRCD = TRI->getPhysicalRegisterRegClass(SrcReg);
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bool Emitted = TII->copyRegToReg(*MBB, MI, DstReg, SrcReg, TRCD, TRCS);
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(void)Emitted;
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assert(Emitted && "Subreg and Dst must be of compatible register class");
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// Transfer the kill/dead flags, if needed.
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if (MI->getOperand(0).isDead())
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TransferDeadFlag(MI, DstReg, TRI);
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if (MI->getOperand(1).isKill())
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TransferKillFlag(MI, SuperReg, TRI, true);
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DEBUG({
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MachineBasicBlock::iterator dMI = MI;
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errs() << "subreg: " << *(--dMI);
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});
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}
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DEBUG(errs() << '\n');
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MBB->erase(MI);
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return true;
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}
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bool LowerSubregsInstructionPass::LowerSubregToReg(MachineInstr *MI) {
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MachineBasicBlock *MBB = MI->getParent();
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assert((MI->getOperand(0).isReg() && MI->getOperand(0).isDef()) &&
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MI->getOperand(1).isImm() &&
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(MI->getOperand(2).isReg() && MI->getOperand(2).isUse()) &&
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MI->getOperand(3).isImm() && "Invalid subreg_to_reg");
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unsigned DstReg = MI->getOperand(0).getReg();
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unsigned InsReg = MI->getOperand(2).getReg();
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unsigned InsSIdx = MI->getOperand(2).getSubReg();
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unsigned SubIdx = MI->getOperand(3).getImm();
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assert(SubIdx != 0 && "Invalid index for insert_subreg");
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unsigned DstSubReg = TRI->getSubReg(DstReg, SubIdx);
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assert(TargetRegisterInfo::isPhysicalRegister(DstReg) &&
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"Insert destination must be in a physical register");
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assert(TargetRegisterInfo::isPhysicalRegister(InsReg) &&
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"Inserted value must be in a physical register");
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DEBUG(errs() << "subreg: CONVERTING: " << *MI);
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if (DstSubReg == InsReg && InsSIdx == 0) {
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// No need to insert an identify copy instruction.
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// Watch out for case like this:
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// %RAX<def> = ...
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// %RAX<def> = SUBREG_TO_REG 0, %EAX:3<kill>, 3
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// The first def is defining RAX, not EAX so the top bits were not
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// zero extended.
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DEBUG(errs() << "subreg: eliminated!");
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} else {
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// Insert sub-register copy
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const TargetRegisterClass *TRC0= TRI->getPhysicalRegisterRegClass(DstSubReg);
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const TargetRegisterClass *TRC1= TRI->getPhysicalRegisterRegClass(InsReg);
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bool Emitted = TII->copyRegToReg(*MBB, MI, DstSubReg, InsReg, TRC0, TRC1);
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(void)Emitted;
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assert(Emitted && "Subreg and Dst must be of compatible register class");
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// Transfer the kill/dead flags, if needed.
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if (MI->getOperand(0).isDead())
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TransferDeadFlag(MI, DstSubReg, TRI);
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if (MI->getOperand(2).isKill())
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TransferKillFlag(MI, InsReg, TRI);
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DEBUG({
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MachineBasicBlock::iterator dMI = MI;
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errs() << "subreg: " << *(--dMI);
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});
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}
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DEBUG(errs() << '\n');
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MBB->erase(MI);
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return true;
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}
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bool LowerSubregsInstructionPass::LowerInsert(MachineInstr *MI) {
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MachineBasicBlock *MBB = MI->getParent();
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assert((MI->getOperand(0).isReg() && MI->getOperand(0).isDef()) &&
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(MI->getOperand(1).isReg() && MI->getOperand(1).isUse()) &&
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(MI->getOperand(2).isReg() && MI->getOperand(2).isUse()) &&
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MI->getOperand(3).isImm() && "Invalid insert_subreg");
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unsigned DstReg = MI->getOperand(0).getReg();
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#ifndef NDEBUG
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unsigned SrcReg = MI->getOperand(1).getReg();
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#endif
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unsigned InsReg = MI->getOperand(2).getReg();
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unsigned SubIdx = MI->getOperand(3).getImm();
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assert(DstReg == SrcReg && "insert_subreg not a two-address instruction?");
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assert(SubIdx != 0 && "Invalid index for insert_subreg");
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unsigned DstSubReg = TRI->getSubReg(DstReg, SubIdx);
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assert(DstSubReg && "invalid subregister index for register");
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assert(TargetRegisterInfo::isPhysicalRegister(SrcReg) &&
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"Insert superreg source must be in a physical register");
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assert(TargetRegisterInfo::isPhysicalRegister(InsReg) &&
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"Inserted value must be in a physical register");
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DEBUG(errs() << "subreg: CONVERTING: " << *MI);
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if (DstSubReg == InsReg) {
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// No need to insert an identity copy instruction. If the SrcReg was
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// <undef>, we need to make sure it is alive by inserting a KILL
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if (MI->getOperand(1).isUndef() && !MI->getOperand(0).isDead()) {
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MachineInstrBuilder MIB = BuildMI(*MBB, MI, MI->getDebugLoc(),
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TII->get(TargetInstrInfo::KILL), DstReg);
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if (MI->getOperand(2).isUndef())
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MIB.addReg(InsReg, RegState::Undef);
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else
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MIB.addReg(InsReg, RegState::Kill);
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} else {
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DEBUG(errs() << "subreg: eliminated!\n");
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MBB->erase(MI);
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return true;
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}
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} else {
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// Insert sub-register copy
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const TargetRegisterClass *TRC0= TRI->getPhysicalRegisterRegClass(DstSubReg);
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const TargetRegisterClass *TRC1= TRI->getPhysicalRegisterRegClass(InsReg);
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if (MI->getOperand(2).isUndef())
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// If the source register being inserted is undef, then this becomes a
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// KILL.
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BuildMI(*MBB, MI, MI->getDebugLoc(),
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TII->get(TargetInstrInfo::KILL), DstSubReg);
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else {
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bool Emitted = TII->copyRegToReg(*MBB, MI, DstSubReg, InsReg, TRC0, TRC1);
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(void)Emitted;
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assert(Emitted && "Subreg and Dst must be of compatible register class");
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}
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MachineBasicBlock::iterator CopyMI = MI;
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--CopyMI;
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// INSERT_SUBREG is a two-address instruction so it implicitly kills SrcReg.
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if (!MI->getOperand(1).isUndef())
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CopyMI->addOperand(MachineOperand::CreateReg(DstReg, false, true, true));
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// Transfer the kill/dead flags, if needed.
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if (MI->getOperand(0).isDead()) {
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TransferDeadFlag(MI, DstSubReg, TRI);
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} else {
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// Make sure the full DstReg is live after this replacement.
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CopyMI->addOperand(MachineOperand::CreateReg(DstReg, true, true));
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}
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// Make sure the inserted register gets killed
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if (MI->getOperand(2).isKill() && !MI->getOperand(2).isUndef())
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TransferKillFlag(MI, InsReg, TRI);
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}
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DEBUG({
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MachineBasicBlock::iterator dMI = MI;
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errs() << "subreg: " << *(--dMI) << "\n";
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});
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MBB->erase(MI);
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return true;
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}
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/// runOnMachineFunction - Reduce subregister inserts and extracts to register
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/// copies.
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///
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bool LowerSubregsInstructionPass::runOnMachineFunction(MachineFunction &MF) {
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DEBUG(errs() << "Machine Function\n"
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<< "********** LOWERING SUBREG INSTRS **********\n"
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<< "********** Function: "
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<< MF.getFunction()->getName() << '\n');
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TRI = MF.getTarget().getRegisterInfo();
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TII = MF.getTarget().getInstrInfo();
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bool MadeChange = false;
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for (MachineFunction::iterator mbbi = MF.begin(), mbbe = MF.end();
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mbbi != mbbe; ++mbbi) {
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for (MachineBasicBlock::iterator mi = mbbi->begin(), me = mbbi->end();
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mi != me;) {
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MachineBasicBlock::iterator nmi = llvm::next(mi);
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MachineInstr *MI = mi;
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if (MI->getOpcode() == TargetInstrInfo::EXTRACT_SUBREG) {
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MadeChange |= LowerExtract(MI);
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} else if (MI->getOpcode() == TargetInstrInfo::INSERT_SUBREG) {
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MadeChange |= LowerInsert(MI);
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} else if (MI->getOpcode() == TargetInstrInfo::SUBREG_TO_REG) {
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MadeChange |= LowerSubregToReg(MI);
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}
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mi = nmi;
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}
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}
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return MadeChange;
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}
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