// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
+//
+// This file defines a MachineFunction pass which runs after register
+// allocation that turns subreg insert/extract instructions into register
+// copies, as needed. This ensures correct codegen even if the coalescer
+// isn't able to remove all subreg instructions.
+//
+//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "lowersubregs"
#include "llvm/CodeGen/Passes.h"
#include "llvm/Function.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstr.h"
+#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/Target/TargetRegisterInfo.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Support/Debug.h"
-#include "llvm/Support/Compiler.h"
+#include "llvm/Support/raw_ostream.h"
using namespace llvm;
namespace {
- struct VISIBILITY_HIDDEN LowerSubregsInstructionPass
- : public MachineFunctionPass {
+ struct LowerSubregsInstructionPass : public MachineFunctionPass {
+ private:
+ const TargetRegisterInfo *TRI;
+ const TargetInstrInfo *TII;
+
+ public:
static char ID; // Pass identification, replacement for typeid
- LowerSubregsInstructionPass() : MachineFunctionPass((intptr_t)&ID) {}
-
+ LowerSubregsInstructionPass() : MachineFunctionPass(ID) {}
+
const char *getPassName() const {
return "Subregister lowering instruction pass";
}
+ virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+ AU.setPreservesCFG();
+ AU.addPreservedID(MachineLoopInfoID);
+ AU.addPreservedID(MachineDominatorsID);
+ MachineFunctionPass::getAnalysisUsage(AU);
+ }
+
/// runOnMachineFunction - pass entry point
bool runOnMachineFunction(MachineFunction&);
-
- bool LowerExtract(MachineInstr *MI);
- bool LowerInsert(MachineInstr *MI);
+
+ private:
bool LowerSubregToReg(MachineInstr *MI);
+ bool LowerCopy(MachineInstr *MI);
+
+ void TransferDeadFlag(MachineInstr *MI, unsigned DstReg,
+ const TargetRegisterInfo *TRI);
+ void TransferImplicitDefs(MachineInstr *MI);
};
char LowerSubregsInstructionPass::ID = 0;
}
-FunctionPass *llvm::createLowerSubregsPass() {
- return new LowerSubregsInstructionPass();
+FunctionPass *llvm::createLowerSubregsPass() {
+ return new LowerSubregsInstructionPass();
}
-bool LowerSubregsInstructionPass::LowerExtract(MachineInstr *MI) {
- MachineBasicBlock *MBB = MI->getParent();
- MachineFunction &MF = *MBB->getParent();
- const TargetRegisterInfo &TRI = *MF.getTarget().getRegisterInfo();
- const TargetInstrInfo &TII = *MF.getTarget().getInstrInfo();
-
- assert(MI->getOperand(0).isRegister() && MI->getOperand(0).isDef() &&
- MI->getOperand(1).isRegister() && MI->getOperand(1).isUse() &&
- MI->getOperand(2).isImmediate() && "Malformed extract_subreg");
-
- unsigned DstReg = MI->getOperand(0).getReg();
- unsigned SuperReg = MI->getOperand(1).getReg();
- unsigned SubIdx = MI->getOperand(2).getImm();
- unsigned SrcReg = TRI.getSubReg(SuperReg, SubIdx);
-
- assert(TargetRegisterInfo::isPhysicalRegister(SuperReg) &&
- "Extract supperg source must be a physical register");
- assert(TargetRegisterInfo::isPhysicalRegister(DstReg) &&
- "Insert destination must be in a physical register");
-
- DOUT << "subreg: CONVERTING: " << *MI;
-
- if (SrcReg != DstReg) {
- const TargetRegisterClass *TRC = TRI.getPhysicalRegisterRegClass(DstReg);
- assert(TRC == TRI.getPhysicalRegisterRegClass(SrcReg) &&
- "Extract subreg and Dst must be of same register class");
- TII.copyRegToReg(*MBB, MI, DstReg, SrcReg, TRC, TRC);
-
-#ifndef NDEBUG
- MachineBasicBlock::iterator dMI = MI;
- DOUT << "subreg: " << *(--dMI);
-#endif
- }
-
- DOUT << "\n";
- MBB->remove(MI);
- return true;
+/// TransferDeadFlag - MI is a pseudo-instruction with DstReg dead,
+/// and the lowered replacement instructions immediately precede it.
+/// Mark the replacement instructions with the dead flag.
+void
+LowerSubregsInstructionPass::TransferDeadFlag(MachineInstr *MI,
+ unsigned DstReg,
+ const TargetRegisterInfo *TRI) {
+ for (MachineBasicBlock::iterator MII =
+ prior(MachineBasicBlock::iterator(MI)); ; --MII) {
+ if (MII->addRegisterDead(DstReg, TRI))
+ break;
+ assert(MII != MI->getParent()->begin() &&
+ "copyPhysReg output doesn't reference destination register!");
+ }
+}
+
+/// TransferImplicitDefs - MI is a pseudo-instruction, and the lowered
+/// replacement instructions immediately precede it. Copy any implicit-def
+/// operands from MI to the replacement instruction.
+void
+LowerSubregsInstructionPass::TransferImplicitDefs(MachineInstr *MI) {
+ MachineBasicBlock::iterator CopyMI = MI;
+ --CopyMI;
+
+ for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
+ MachineOperand &MO = MI->getOperand(i);
+ if (!MO.isReg() || !MO.isImplicit() || MO.isUse())
+ continue;
+ CopyMI->addOperand(MachineOperand::CreateReg(MO.getReg(), true, true));
+ }
}
bool LowerSubregsInstructionPass::LowerSubregToReg(MachineInstr *MI) {
MachineBasicBlock *MBB = MI->getParent();
- MachineFunction &MF = *MBB->getParent();
- const TargetRegisterInfo &TRI = *MF.getTarget().getRegisterInfo();
- const TargetInstrInfo &TII = *MF.getTarget().getInstrInfo();
- assert((MI->getOperand(0).isRegister() && MI->getOperand(0).isDef()) &&
- MI->getOperand(1).isImmediate() &&
- (MI->getOperand(2).isRegister() && MI->getOperand(2).isUse()) &&
- MI->getOperand(3).isImmediate() && "Invalid subreg_to_reg");
-
+ assert((MI->getOperand(0).isReg() && MI->getOperand(0).isDef()) &&
+ MI->getOperand(1).isImm() &&
+ (MI->getOperand(2).isReg() && MI->getOperand(2).isUse()) &&
+ MI->getOperand(3).isImm() && "Invalid subreg_to_reg");
+
unsigned DstReg = MI->getOperand(0).getReg();
unsigned InsReg = MI->getOperand(2).getReg();
- unsigned SubIdx = MI->getOperand(3).getImm();
+ assert(!MI->getOperand(2).getSubReg() && "SubIdx on physreg?");
+ unsigned SubIdx = MI->getOperand(3).getImm();
assert(SubIdx != 0 && "Invalid index for insert_subreg");
- unsigned DstSubReg = TRI.getSubReg(DstReg, SubIdx);
-
+ unsigned DstSubReg = TRI->getSubReg(DstReg, SubIdx);
+
assert(TargetRegisterInfo::isPhysicalRegister(DstReg) &&
"Insert destination must be in a physical register");
assert(TargetRegisterInfo::isPhysicalRegister(InsReg) &&
"Inserted value must be in a physical register");
- DOUT << "subreg: CONVERTING: " << *MI;
+ DEBUG(dbgs() << "subreg: CONVERTING: " << *MI);
- // Insert sub-register copy
- const TargetRegisterClass *TRC0= TRI.getPhysicalRegisterRegClass(DstSubReg);
- const TargetRegisterClass *TRC1= TRI.getPhysicalRegisterRegClass(InsReg);
- TII.copyRegToReg(*MBB, MI, DstSubReg, InsReg, TRC0, TRC1);
-
-#ifndef NDEBUG
- MachineBasicBlock::iterator dMI = MI;
- DOUT << "subreg: " << *(--dMI);
-#endif
+ if (DstSubReg == InsReg) {
+ // No need to insert an identify copy instruction.
+ // Watch out for case like this:
+ // %RAX<def> = SUBREG_TO_REG 0, %EAX<kill>, 3
+ // We must leave %RAX live.
+ if (DstReg != InsReg) {
+ MI->setDesc(TII->get(TargetOpcode::KILL));
+ MI->RemoveOperand(3); // SubIdx
+ MI->RemoveOperand(1); // Imm
+ DEBUG(dbgs() << "subreg: replace by: " << *MI);
+ return true;
+ }
+ DEBUG(dbgs() << "subreg: eliminated!");
+ } else {
+ TII->copyPhysReg(*MBB, MI, MI->getDebugLoc(), DstSubReg, InsReg,
+ MI->getOperand(2).isKill());
+ // Transfer the kill/dead flags, if needed.
+ if (MI->getOperand(0).isDead())
+ TransferDeadFlag(MI, DstSubReg, TRI);
+ DEBUG({
+ MachineBasicBlock::iterator dMI = MI;
+ dbgs() << "subreg: " << *(--dMI);
+ });
+ }
- DOUT << "\n";
- MBB->remove(MI);
- return true;
+ DEBUG(dbgs() << '\n');
+ MBB->erase(MI);
+ return true;
}
-bool LowerSubregsInstructionPass::LowerInsert(MachineInstr *MI) {
- MachineBasicBlock *MBB = MI->getParent();
- MachineFunction &MF = *MBB->getParent();
- const TargetRegisterInfo &TRI = *MF.getTarget().getRegisterInfo();
- const TargetInstrInfo &TII = *MF.getTarget().getInstrInfo();
- assert((MI->getOperand(0).isRegister() && MI->getOperand(0).isDef()) &&
- (MI->getOperand(1).isRegister() && MI->getOperand(1).isUse()) &&
- (MI->getOperand(2).isRegister() && MI->getOperand(2).isUse()) &&
- MI->getOperand(3).isImmediate() && "Invalid insert_subreg");
-
- unsigned DstReg = MI->getOperand(0).getReg();
- unsigned SrcReg = MI->getOperand(1).getReg();
- unsigned InsReg = MI->getOperand(2).getReg();
- unsigned SubIdx = MI->getOperand(3).getImm();
-
- assert(DstReg == SrcReg && "insert_subreg not a two-address instruction?");
- assert(SubIdx != 0 && "Invalid index for insert_subreg");
- unsigned DstSubReg = TRI.getSubReg(DstReg, SubIdx);
-
- assert(TargetRegisterInfo::isPhysicalRegister(SrcReg) &&
- "Insert superreg source must be in a physical register");
- assert(TargetRegisterInfo::isPhysicalRegister(InsReg) &&
- "Inserted value must be in a physical register");
+bool LowerSubregsInstructionPass::LowerCopy(MachineInstr *MI) {
+ MachineOperand &DstMO = MI->getOperand(0);
+ MachineOperand &SrcMO = MI->getOperand(1);
+
+ if (SrcMO.getReg() == DstMO.getReg()) {
+ DEBUG(dbgs() << "identity copy: " << *MI);
+ // No need to insert an identity copy instruction, but replace with a KILL
+ // if liveness is changed.
+ if (DstMO.isDead() || SrcMO.isUndef() || MI->getNumOperands() > 2) {
+ // We must make sure the super-register gets killed. Replace the
+ // instruction with KILL.
+ MI->setDesc(TII->get(TargetOpcode::KILL));
+ DEBUG(dbgs() << "replaced by: " << *MI);
+ return true;
+ }
+ // Vanilla identity copy.
+ MI->eraseFromParent();
+ return true;
+ }
- DOUT << "subreg: CONVERTING: " << *MI;
+ DEBUG(dbgs() << "real copy: " << *MI);
+ TII->copyPhysReg(*MI->getParent(), MI, MI->getDebugLoc(),
+ DstMO.getReg(), SrcMO.getReg(), SrcMO.isKill());
- if (DstSubReg == InsReg) {
- // No need to insert an identify copy instruction.
- DOUT << "subreg: eliminated!";
- } else {
- // Insert sub-register copy
- const TargetRegisterClass *TRC0= TRI.getPhysicalRegisterRegClass(DstSubReg);
- const TargetRegisterClass *TRC1= TRI.getPhysicalRegisterRegClass(InsReg);
- TII.copyRegToReg(*MBB, MI, DstSubReg, InsReg, TRC0, TRC1);
-#ifndef NDEBUG
+ if (DstMO.isDead())
+ TransferDeadFlag(MI, DstMO.getReg(), TRI);
+ if (MI->getNumOperands() > 2)
+ TransferImplicitDefs(MI);
+ DEBUG({
MachineBasicBlock::iterator dMI = MI;
- DOUT << "subreg: " << *(--dMI);
-#endif
- }
-
- DOUT << "\n";
- MBB->remove(MI);
- return true;
+ dbgs() << "replaced by: " << *(--dMI);
+ });
+ MI->eraseFromParent();
+ return true;
}
/// runOnMachineFunction - Reduce subregister inserts and extracts to register
/// copies.
///
bool LowerSubregsInstructionPass::runOnMachineFunction(MachineFunction &MF) {
- DOUT << "Machine Function\n";
-
- bool MadeChange = false;
+ DEBUG(dbgs() << "Machine Function\n"
+ << "********** LOWERING SUBREG INSTRS **********\n"
+ << "********** Function: "
+ << MF.getFunction()->getName() << '\n');
+ TRI = MF.getTarget().getRegisterInfo();
+ TII = MF.getTarget().getInstrInfo();
- DOUT << "********** LOWERING SUBREG INSTRS **********\n";
- DOUT << "********** Function: " << MF.getFunction()->getName() << '\n';
+ bool MadeChange = false;
for (MachineFunction::iterator mbbi = MF.begin(), mbbe = MF.end();
mbbi != mbbe; ++mbbi) {
for (MachineBasicBlock::iterator mi = mbbi->begin(), me = mbbi->end();
mi != me;) {
- MachineInstr *MI = mi++;
-
- if (MI->getOpcode() == TargetInstrInfo::EXTRACT_SUBREG) {
- MadeChange |= LowerExtract(MI);
- } else if (MI->getOpcode() == TargetInstrInfo::INSERT_SUBREG) {
- MadeChange |= LowerInsert(MI);
- } else if (MI->getOpcode() == TargetInstrInfo::SUBREG_TO_REG) {
+ MachineBasicBlock::iterator nmi = llvm::next(mi);
+ MachineInstr *MI = mi;
+ assert(!MI->isInsertSubreg() && "INSERT_SUBREG should no longer appear");
+ assert(MI->getOpcode() != TargetOpcode::EXTRACT_SUBREG &&
+ "EXTRACT_SUBREG should no longer appear");
+ if (MI->isSubregToReg()) {
MadeChange |= LowerSubregToReg(MI);
+ } else if (MI->isCopy()) {
+ MadeChange |= LowerCopy(MI);
}
+ mi = nmi;
}
}
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