// 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/MRegisterInfo.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&);
-
+
+ private:
bool LowerExtract(MachineInstr *MI);
bool LowerInsert(MachineInstr *MI);
+ bool LowerSubregToReg(MachineInstr *MI);
+
+ void TransferDeadFlag(MachineInstr *MI, unsigned DstReg,
+ const TargetRegisterInfo *TRI);
+ void TransferKillFlag(MachineInstr *MI, unsigned SrcReg,
+ const TargetRegisterInfo *TRI,
+ bool AddIfNotFound = false);
};
char LowerSubregsInstructionPass::ID = 0;
return new LowerSubregsInstructionPass();
}
-// Returns the Register Class of a physical register.
-static const TargetRegisterClass *getPhysicalRegisterRegClass(
- const MRegisterInfo &MRI,
- unsigned reg) {
- assert(MRegisterInfo::isPhysicalRegister(reg) &&
- "reg must be a physical register");
- // Pick the register class of the right type that contains this physreg.
- for (MRegisterInfo::regclass_iterator I = MRI.regclass_begin(),
- E = MRI.regclass_end(); I != E; ++I)
- if ((*I)->contains(reg))
- return *I;
- assert(false && "Couldn't find the register class");
- return 0;
+/// 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() &&
+ "copyRegToReg output doesn't reference destination register!");
+ }
}
-bool LowerSubregsInstructionPass::LowerExtract(MachineInstr *MI) {
- MachineBasicBlock *MBB = MI->getParent();
- MachineFunction &MF = *MBB->getParent();
- const MRegisterInfo &MRI = *MF.getTarget().getRegisterInfo();
-
- 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 SuperReg = MI->getOperand(1).getReg();
- unsigned SubIdx = MI->getOperand(2).getImm();
-
- assert(MRegisterInfo::isPhysicalRegister(SuperReg) &&
- "Extract supperg source must be a physical register");
- unsigned SrcReg = MRI.getSubReg(SuperReg, SubIdx);
- unsigned DstReg = MI->getOperand(0).getReg();
-
- DOUT << "subreg: CONVERTING: " << *MI;
-
- if (SrcReg != DstReg) {
- const TargetRegisterClass *TRC = 0;
- if (MRegisterInfo::isPhysicalRegister(DstReg)) {
- TRC = getPhysicalRegisterRegClass(MRI, DstReg);
- } else {
- TRC = MF.getRegInfo().getRegClass(DstReg);
- }
- assert(TRC == getPhysicalRegisterRegClass(MRI, SrcReg) &&
- "Extract subreg and Dst must be of same register class");
-
- MRI.copyRegToReg(*MBB, MI, DstReg, SrcReg, TRC, TRC);
- MachineBasicBlock::iterator dMI = MI;
- DOUT << "subreg: " << *(--dMI);
- }
-
- DOUT << "\n";
- MBB->remove(MI);
- return true;
+/// TransferKillFlag - MI is a pseudo-instruction with SrcReg killed,
+/// and the lowered replacement instructions immediately precede it.
+/// Mark the replacement instructions with the kill flag.
+void
+LowerSubregsInstructionPass::TransferKillFlag(MachineInstr *MI,
+ unsigned SrcReg,
+ const TargetRegisterInfo *TRI,
+ bool AddIfNotFound) {
+ for (MachineBasicBlock::iterator MII =
+ prior(MachineBasicBlock::iterator(MI)); ; --MII) {
+ if (MII->addRegisterKilled(SrcReg, TRI, AddIfNotFound))
+ break;
+ assert(MII != MI->getParent()->begin() &&
+ "copyRegToReg output doesn't reference source register!");
+ }
}
+bool LowerSubregsInstructionPass::LowerExtract(MachineInstr *MI) {
+ MachineBasicBlock *MBB = MI->getParent();
+
+ assert(MI->getOperand(0).isReg() && MI->getOperand(0).isDef() &&
+ MI->getOperand(1).isReg() && MI->getOperand(1).isUse() &&
+ MI->getOperand(2).isImm() && "Malformed extract_subreg");
-bool LowerSubregsInstructionPass::LowerInsert(MachineInstr *MI) {
+ 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) &&
+ "Extract destination must be in a physical register");
+ assert(SrcReg && "invalid subregister index for register");
+
+ DEBUG(dbgs() << "subreg: CONVERTING: " << *MI);
+
+ if (SrcReg == DstReg) {
+ // No need to insert an identity copy instruction.
+ if (MI->getOperand(1).isKill()) {
+ // We must make sure the super-register gets killed. Replace the
+ // instruction with KILL.
+ MI->setDesc(TII->get(TargetOpcode::KILL));
+ MI->RemoveOperand(2); // SubIdx
+ DEBUG(dbgs() << "subreg: replace by: " << *MI);
+ return true;
+ }
+
+ DEBUG(dbgs() << "subreg: eliminated!");
+ } else {
+ // Insert copy
+ const TargetRegisterClass *TRCS = TRI->getPhysicalRegisterRegClass(DstReg);
+ const TargetRegisterClass *TRCD = TRI->getPhysicalRegisterRegClass(SrcReg);
+ bool Emitted = TII->copyRegToReg(*MBB, MI, DstReg, SrcReg, TRCD, TRCS);
+ (void)Emitted;
+ assert(Emitted && "Subreg and Dst must be of compatible register class");
+ // Transfer the kill/dead flags, if needed.
+ if (MI->getOperand(0).isDead())
+ TransferDeadFlag(MI, DstReg, TRI);
+ if (MI->getOperand(1).isKill())
+ TransferKillFlag(MI, SuperReg, TRI, true);
+ DEBUG({
+ MachineBasicBlock::iterator dMI = MI;
+ dbgs() << "subreg: " << *(--dMI);
+ });
+ }
+
+ DEBUG(dbgs() << '\n');
+ MBB->erase(MI);
+ return true;
+}
+
+bool LowerSubregsInstructionPass::LowerSubregToReg(MachineInstr *MI) {
MachineBasicBlock *MBB = MI->getParent();
- MachineFunction &MF = *MBB->getParent();
- const MRegisterInfo &MRI = *MF.getTarget().getRegisterInfo();
- unsigned DstReg = 0;
- unsigned SrcReg = 0;
- unsigned InsReg = 0;
- unsigned SubIdx = 0;
-
- // If only have 3 operands, then the source superreg is undef
- // and we can supress the copy from the undef value
- if (MI->getNumOperands() == 3) {
- assert((MI->getOperand(0).isRegister() && MI->getOperand(0).isDef()) &&
- (MI->getOperand(1).isRegister() && MI->getOperand(1).isUse()) &&
- MI->getOperand(2).isImmediate() && "Invalid extract_subreg");
- DstReg = MI->getOperand(0).getReg();
- SrcReg = DstReg;
- InsReg = MI->getOperand(1).getReg();
- SubIdx = MI->getOperand(2).getImm();
- } else if (MI->getNumOperands() == 4) {
- 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 extract_subreg");
- DstReg = MI->getOperand(0).getReg();
- SrcReg = MI->getOperand(1).getReg();
- InsReg = MI->getOperand(2).getReg();
- SubIdx = MI->getOperand(3).getImm();
- } else
- assert(0 && "Malformed extract_subreg");
-
- assert(SubIdx != 0 && "Invalid index for extract_subreg");
- unsigned DstSubReg = MRI.getSubReg(DstReg, SubIdx);
-
- assert(MRegisterInfo::isPhysicalRegister(SrcReg) &&
- "Insert superreg source must be in a physical register");
- assert(MRegisterInfo::isPhysicalRegister(DstReg) &&
+ 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 InsSIdx = MI->getOperand(2).getSubReg();
+ unsigned SubIdx = MI->getOperand(3).getImm();
+
+ assert(SubIdx != 0 && "Invalid index for insert_subreg");
+ unsigned DstSubReg = TRI->getSubReg(DstReg, SubIdx);
+
+ assert(TargetRegisterInfo::isPhysicalRegister(DstReg) &&
"Insert destination must be in a physical register");
- assert(MRegisterInfo::isPhysicalRegister(InsReg) &&
+ assert(TargetRegisterInfo::isPhysicalRegister(InsReg) &&
"Inserted value must be in a physical register");
- DOUT << "subreg: CONVERTING: " << *MI;
-
- // If the inserted register is already allocated into a subregister
- // of the destination, we copy the subreg into the source
- // However, this is only safe if the insert instruction is the kill
- // of the source register
- bool revCopyOrder = MRI.isSubRegister(DstReg, InsReg);
- if (revCopyOrder && InsReg != DstSubReg) {
- if (MI->getOperand(1).isKill()) {
- DstSubReg = MRI.getSubReg(SrcReg, SubIdx);
- // Insert sub-register copy
- const TargetRegisterClass *TRC1 = 0;
- if (MRegisterInfo::isPhysicalRegister(InsReg)) {
- TRC1 = getPhysicalRegisterRegClass(MRI, InsReg);
- } else {
- TRC1 = MF.getRegInfo().getRegClass(InsReg);
- }
- MRI.copyRegToReg(*MBB, MI, DstSubReg, InsReg, TRC1, TRC1);
+ DEBUG(dbgs() << "subreg: CONVERTING: " << *MI);
-#ifndef NDEBUG
- MachineBasicBlock::iterator dMI = MI;
- DOUT << "subreg: " << *(--dMI);
-#endif
- } else {
- assert(0 && "Don't know how to convert this insert");
- }
+ if (DstSubReg == InsReg && InsSIdx == 0) {
+ // No need to insert an identify copy instruction.
+ // Watch out for case like this:
+ // %RAX<def> = ...
+ // %RAX<def> = SUBREG_TO_REG 0, %EAX:3<kill>, 3
+ // The first def is defining RAX, not EAX so the top bits were not
+ // zero extended.
+ DEBUG(dbgs() << "subreg: eliminated!");
+ } else {
+ // Insert sub-register copy
+ const TargetRegisterClass *TRC0= TRI->getPhysicalRegisterRegClass(DstSubReg);
+ const TargetRegisterClass *TRC1= TRI->getPhysicalRegisterRegClass(InsReg);
+ bool Emitted = TII->copyRegToReg(*MBB, MI, DstSubReg, InsReg, TRC0, TRC1);
+ (void)Emitted;
+ assert(Emitted && "Subreg and Dst must be of compatible register class");
+ // Transfer the kill/dead flags, if needed.
+ if (MI->getOperand(0).isDead())
+ TransferDeadFlag(MI, DstSubReg, TRI);
+ if (MI->getOperand(2).isKill())
+ TransferKillFlag(MI, InsReg, TRI);
+ DEBUG({
+ MachineBasicBlock::iterator dMI = MI;
+ dbgs() << "subreg: " << *(--dMI);
+ });
}
+
+ DEBUG(dbgs() << '\n');
+ MBB->erase(MI);
+ return true;
+}
+
+bool LowerSubregsInstructionPass::LowerInsert(MachineInstr *MI) {
+ MachineBasicBlock *MBB = MI->getParent();
+ assert((MI->getOperand(0).isReg() && MI->getOperand(0).isDef()) &&
+ (MI->getOperand(1).isReg() && MI->getOperand(1).isUse()) &&
+ (MI->getOperand(2).isReg() && MI->getOperand(2).isUse()) &&
+ MI->getOperand(3).isImm() && "Invalid insert_subreg");
+
+ unsigned DstReg = MI->getOperand(0).getReg();
#ifndef NDEBUG
- if (InsReg == DstSubReg) {
- DOUT << "subreg: Eliminated subreg copy\n";
- }
+ unsigned SrcReg = MI->getOperand(1).getReg();
#endif
+ 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(DstSubReg && "invalid subregister index for register");
+ 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");
- if (SrcReg != DstReg) {
- // Insert super-register copy
- const TargetRegisterClass *TRC0 = 0;
- if (MRegisterInfo::isPhysicalRegister(DstReg)) {
- TRC0 = getPhysicalRegisterRegClass(MRI, DstReg);
+ DEBUG(dbgs() << "subreg: CONVERTING: " << *MI);
+
+ if (DstSubReg == InsReg) {
+ // No need to insert an identity copy instruction. If the SrcReg was
+ // <undef>, we need to make sure it is alive by inserting a KILL
+ if (MI->getOperand(1).isUndef() && !MI->getOperand(0).isDead()) {
+ MachineInstrBuilder MIB = BuildMI(*MBB, MI, MI->getDebugLoc(),
+ TII->get(TargetOpcode::KILL), DstReg);
+ if (MI->getOperand(2).isUndef())
+ MIB.addReg(InsReg, RegState::Undef);
+ else
+ MIB.addReg(InsReg, RegState::Kill);
} else {
- TRC0 = MF.getRegInfo().getRegClass(DstReg);
+ DEBUG(dbgs() << "subreg: eliminated!\n");
+ MBB->erase(MI);
+ return true;
}
- assert(TRC0 == getPhysicalRegisterRegClass(MRI, SrcReg) &&
- "Insert superreg and Dst must be of same register class");
-
- MRI.copyRegToReg(*MBB, MI, DstReg, SrcReg, TRC0, TRC0);
+ } else {
+ // Insert sub-register copy
+ const TargetRegisterClass *TRC0= TRI->getPhysicalRegisterRegClass(DstSubReg);
+ const TargetRegisterClass *TRC1= TRI->getPhysicalRegisterRegClass(InsReg);
+ if (MI->getOperand(2).isUndef())
+ // If the source register being inserted is undef, then this becomes a
+ // KILL.
+ BuildMI(*MBB, MI, MI->getDebugLoc(),
+ TII->get(TargetOpcode::KILL), DstSubReg);
+ else {
+ bool Emitted = TII->copyRegToReg(*MBB, MI, DstSubReg, InsReg, TRC0, TRC1);
+ (void)Emitted;
+ assert(Emitted && "Subreg and Dst must be of compatible register class");
+ }
+ MachineBasicBlock::iterator CopyMI = MI;
+ --CopyMI;
-#ifndef NDEBUG
- MachineBasicBlock::iterator dMI = MI;
- DOUT << "subreg: " << *(--dMI);
-#endif
- }
-
-#ifndef NDEBUG
- if (SrcReg == DstReg) {
- DOUT << "subreg: Eliminated superreg copy\n";
- }
-#endif
+ // INSERT_SUBREG is a two-address instruction so it implicitly kills SrcReg.
+ if (!MI->getOperand(1).isUndef())
+ CopyMI->addOperand(MachineOperand::CreateReg(DstReg, false, true, true));
- if (!revCopyOrder && InsReg != DstSubReg) {
- // Insert sub-register copy
- const TargetRegisterClass *TRC1 = 0;
- if (MRegisterInfo::isPhysicalRegister(InsReg)) {
- TRC1 = getPhysicalRegisterRegClass(MRI, InsReg);
+ // Transfer the kill/dead flags, if needed.
+ if (MI->getOperand(0).isDead()) {
+ TransferDeadFlag(MI, DstSubReg, TRI);
} else {
- TRC1 = MF.getRegInfo().getRegClass(InsReg);
+ // Make sure the full DstReg is live after this replacement.
+ CopyMI->addOperand(MachineOperand::CreateReg(DstReg, true, true));
}
- MRI.copyRegToReg(*MBB, MI, DstSubReg, InsReg, TRC1, TRC1);
-#ifndef NDEBUG
- MachineBasicBlock::iterator dMI = MI;
- DOUT << "subreg: " << *(--dMI);
-#endif
+ // Make sure the inserted register gets killed
+ if (MI->getOperand(2).isKill() && !MI->getOperand(2).isUndef())
+ TransferKillFlag(MI, InsReg, TRI);
}
- DOUT << "\n";
- MBB->remove(MI);
- return true;
+ DEBUG({
+ MachineBasicBlock::iterator dMI = MI;
+ dbgs() << "subreg: " << *(--dMI) << "\n";
+ });
+
+ MBB->erase(MI);
+ 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) {
+ MachineBasicBlock::iterator nmi = llvm::next(mi);
+ MachineInstr *MI = mi;
+ if (MI->isExtractSubreg()) {
MadeChange |= LowerExtract(MI);
- } else if (MI->getOpcode() == TargetInstrInfo::INSERT_SUBREG) {
+ } else if (MI->isInsertSubreg()) {
MadeChange |= LowerInsert(MI);
+ } else if (MI->isSubregToReg()) {
+ MadeChange |= LowerSubregToReg(MI);
}
+ mi = nmi;
}
}