// to:
//
// A = B
-// A = A op C
+// A op= C
//
-// Note that if a register allocator chooses to use this pass, that it has to
-// be capable of handling the non-SSA nature of these rewritten virtual
-// registers.
+// Note that if a register allocator chooses to use this pass, that it
+// has to be capable of handling the non-SSA nature of these rewritten
+// virtual registers.
+//
+// It is also worth noting that the duplicate operand of the two
+// address instruction is removed.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "twoaddrinstr"
#include "llvm/CodeGen/Passes.h"
+#include "llvm/Function.h"
#include "llvm/CodeGen/LiveVariables.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/Target/MRegisterInfo.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetMachine.h"
-#include "Support/Debug.h"
-#include "Support/Statistic.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/ADT/STLExtras.h"
+#include <iostream>
using namespace llvm;
namespace {
- Statistic<> numTwoAddressInstrs("twoaddressinstruction",
- "Number of two-address instructions");
- Statistic<> numInstrsAdded("twoaddressinstruction",
- "Number of instructions added");
-
- struct TwoAddressInstructionPass : public MachineFunctionPass
- {
- virtual void getAnalysisUsage(AnalysisUsage &AU) const;
-
- /// runOnMachineFunction - pass entry point
- bool runOnMachineFunction(MachineFunction&);
- };
-
- RegisterPass<TwoAddressInstructionPass> X(
- "twoaddressinstruction", "Two-Address instruction pass");
-};
+ Statistic<> NumTwoAddressInstrs("twoaddressinstruction",
+ "Number of two-address instructions");
+ Statistic<> NumCommuted("twoaddressinstruction",
+ "Number of instructions commuted to coalesce");
+ Statistic<> NumConvertedTo3Addr("twoaddressinstruction",
+ "Number of instructions promoted to 3-address");
+
+ struct TwoAddressInstructionPass : public MachineFunctionPass {
+ virtual void getAnalysisUsage(AnalysisUsage &AU) const;
+
+ /// runOnMachineFunction - pass entry point
+ bool runOnMachineFunction(MachineFunction&);
+ };
+
+ RegisterPass<TwoAddressInstructionPass>
+ X("twoaddressinstruction", "Two-Address instruction pass");
+}
const PassInfo *llvm::TwoAddressInstructionPassID = X.getPassInfo();
-void TwoAddressInstructionPass::getAnalysisUsage(AnalysisUsage &AU) const
-{
- AU.addPreserved<LiveVariables>();
- AU.addRequired<LiveVariables>();
- AU.addPreservedID(PHIEliminationID);
- AU.addRequiredID(PHIEliminationID);
- MachineFunctionPass::getAnalysisUsage(AU);
+void TwoAddressInstructionPass::getAnalysisUsage(AnalysisUsage &AU) const {
+ AU.addRequired<LiveVariables>();
+ AU.addPreserved<LiveVariables>();
+ AU.addPreservedID(PHIEliminationID);
+ MachineFunctionPass::getAnalysisUsage(AU);
}
/// runOnMachineFunction - Reduce two-address instructions to two
/// operands.
///
bool TwoAddressInstructionPass::runOnMachineFunction(MachineFunction &MF) {
- DEBUG(std::cerr << "Machine Function\n");
- const TargetMachine &TM = MF.getTarget();
- const MRegisterInfo &MRI = *TM.getRegisterInfo();
- LiveVariables &LV = getAnalysis<LiveVariables>();
- const TargetInstrInfo &TII = TM.getInstrInfo();
-
- bool MadeChange = false;
-
- for (MachineFunction::iterator mbbi = MF.begin(), mbbe = MF.end();
- mbbi != mbbe; ++mbbi) {
- for (MachineBasicBlock::iterator mii = mbbi->begin();
- mii != mbbi->end(); ++mii) {
- MachineInstr* mi = *mii;
- unsigned opcode = mi->getOpcode();
-
- // ignore if it is not a two-address instruction
- if (!TII.isTwoAddrInstr(opcode))
- continue;
-
- ++numTwoAddressInstrs;
- MadeChange = true;
-
- DEBUG(std::cerr << "\tinstruction: "; mi->print(std::cerr, TM));
-
- // we have nothing to do if the two operands are the same
- if (mi->getOperand(0).getAllocatedRegNum() ==
- mi->getOperand(1).getAllocatedRegNum())
- continue;
-
- assert(mi->getOperand(1).isRegister() &&
- mi->getOperand(1).getAllocatedRegNum() &&
- mi->getOperand(1).isUse() &&
- "two address instruction invalid");
-
- // rewrite:
- // a = b op c
- // to:
- // a = b
- // a = a op c
- unsigned regA = mi->getOperand(0).getAllocatedRegNum();
- unsigned regB = mi->getOperand(1).getAllocatedRegNum();
-
- assert(regA >= MRegisterInfo::FirstVirtualRegister &&
- regB >= MRegisterInfo::FirstVirtualRegister &&
- "cannot update physical register live information");
-
- // first make sure we do not have a use of a in the
- // instruction (a = b + a for example) because our
- // transofrmation will not work. This should never occur
- // because of SSA.
- for (unsigned i = 1; i < mi->getNumOperands(); ++i) {
- assert(!mi->getOperand(i).isRegister() ||
- mi->getOperand(i).getAllocatedRegNum() != (int)regA);
+ DEBUG(std::cerr << "Machine Function\n");
+ const TargetMachine &TM = MF.getTarget();
+ const MRegisterInfo &MRI = *TM.getRegisterInfo();
+ const TargetInstrInfo &TII = *TM.getInstrInfo();
+ LiveVariables &LV = getAnalysis<LiveVariables>();
+
+ bool MadeChange = false;
+
+ DEBUG(std::cerr << "********** REWRITING TWO-ADDR INSTRS **********\n");
+ DEBUG(std::cerr << "********** Function: "
+ << MF.getFunction()->getName() << '\n');
+
+ for (MachineFunction::iterator mbbi = MF.begin(), mbbe = MF.end();
+ mbbi != mbbe; ++mbbi) {
+ for (MachineBasicBlock::iterator mi = mbbi->begin(), me = mbbi->end();
+ mi != me; ++mi) {
+ unsigned opcode = mi->getOpcode();
+
+ // ignore if it is not a two-address instruction
+ if (!TII.isTwoAddrInstr(opcode))
+ continue;
+
+ ++NumTwoAddressInstrs;
+ DEBUG(std::cerr << '\t'; mi->print(std::cerr, &TM));
+ assert(mi->getOperand(1).isRegister() && mi->getOperand(1).getReg() &&
+ mi->getOperand(1).isUse() && "two address instruction invalid");
+
+ // if the two operands are the same we just remove the use
+ // and mark the def as def&use, otherwise we have to insert a copy.
+ if (mi->getOperand(0).getReg() != mi->getOperand(1).getReg()) {
+ // rewrite:
+ // a = b op c
+ // to:
+ // a = b
+ // a = a op c
+ unsigned regA = mi->getOperand(0).getReg();
+ unsigned regB = mi->getOperand(1).getReg();
+
+ assert(MRegisterInfo::isVirtualRegister(regA) &&
+ MRegisterInfo::isVirtualRegister(regB) &&
+ "cannot update physical register live information");
+
+#ifndef NDEBUG
+ // First, verify that we do not have a use of a in the instruction (a =
+ // b + a for example) because our transformation will not work. This
+ // should never occur because we are in SSA form.
+ for (unsigned i = 1; i != mi->getNumOperands(); ++i)
+ assert(!mi->getOperand(i).isRegister() ||
+ mi->getOperand(i).getReg() != regA);
+#endif
+
+ // If this instruction is not the killing user of B, see if we can
+ // rearrange the code to make it so. Making it the killing user will
+ // allow us to coalesce A and B together, eliminating the copy we are
+ // about to insert.
+ if (!LV.KillsRegister(mi, regB)) {
+ const TargetInstrDescriptor &TID = TII.get(opcode);
+
+ // If this instruction is commutative, check to see if C dies. If so,
+ // swap the B and C operands. This makes the live ranges of A and C
+ // joinable.
+ if (TID.Flags & M_COMMUTABLE) {
+ assert(mi->getOperand(2).isRegister() &&
+ "Not a proper commutative instruction!");
+ unsigned regC = mi->getOperand(2).getReg();
+ if (LV.KillsRegister(mi, regC)) {
+ DEBUG(std::cerr << "2addr: COMMUTING : " << *mi);
+ MachineInstr *NewMI = TII.commuteInstruction(mi);
+ if (NewMI == 0) {
+ DEBUG(std::cerr << "2addr: COMMUTING FAILED!\n");
+ } else {
+ DEBUG(std::cerr << "2addr: COMMUTED TO: " << *NewMI);
+ // If the instruction changed to commute it, update livevar.
+ if (NewMI != mi) {
+ LV.instructionChanged(mi, NewMI); // Update live variables
+ mbbi->insert(mi, NewMI); // Insert the new inst
+ mbbi->erase(mi); // Nuke the old inst.
+ mi = NewMI;
+ }
+
+ ++NumCommuted;
+ regB = regC;
+ goto InstructionRearranged;
+ }
}
+ }
+ // If this instruction is potentially convertible to a true
+ // three-address instruction,
+ if (TID.Flags & M_CONVERTIBLE_TO_3_ADDR)
+ if (MachineInstr *New = TII.convertToThreeAddress(mi)) {
+ DEBUG(std::cerr << "2addr: CONVERTING 2-ADDR: " << *mi);
+ DEBUG(std::cerr << "2addr: TO 3-ADDR: " << *New);
+ LV.instructionChanged(mi, New); // Update live variables
+ mbbi->insert(mi, New); // Insert the new inst
+ mbbi->erase(mi); // Nuke the old inst.
+ mi = New;
+ ++NumConvertedTo3Addr;
+ assert(!TII.isTwoAddrInstr(New->getOpcode()) &&
+ "convertToThreeAddress returned a 2-addr instruction??");
+ // Done with this instruction.
+ continue;
+ }
+ }
+ InstructionRearranged:
+ const TargetRegisterClass* rc = MF.getSSARegMap()->getRegClass(regA);
+ MRI.copyRegToReg(*mbbi, mi, regA, regB, rc);
- const TargetRegisterClass* rc =
- MF.getSSARegMap()->getRegClass(regA);
- numInstrsAdded += MRI.copyRegToReg(*mbbi, mii, regA, regB, rc);
-
- MachineInstr* prevMi = *(mii - 1);
- DEBUG(std::cerr << "\t\tadded instruction: ";
- prevMi->print(std::cerr, TM));
+ MachineBasicBlock::iterator prevMi = prior(mi);
+ DEBUG(std::cerr << "\t\tprepend:\t"; prevMi->print(std::cerr, &TM));
- // update live variables for regA
- LiveVariables::VarInfo& varInfo = LV.getVarInfo(regA);
- varInfo.DefInst = prevMi;
+ // Update live variables for regA
+ LiveVariables::VarInfo& varInfo = LV.getVarInfo(regA);
+ varInfo.DefInst = prevMi;
- // update live variables for regB
- if (LV.removeVirtualRegisterKilled(regB, &*mbbi, mi))
- LV.addVirtualRegisterKilled(regB, &*mbbi, prevMi);
+ // update live variables for regB
+ if (LV.removeVirtualRegisterKilled(regB, mbbi, mi))
+ LV.addVirtualRegisterKilled(regB, prevMi);
- if (LV.removeVirtualRegisterDead(regB, &*mbbi, mi))
- LV.addVirtualRegisterDead(regB, &*mbbi, prevMi);
+ if (LV.removeVirtualRegisterDead(regB, mbbi, mi))
+ LV.addVirtualRegisterDead(regB, prevMi);
- // replace all occurences of regB with regA
- for (unsigned i = 1; i < mi->getNumOperands(); ++i) {
- if (mi->getOperand(i).isRegister() &&
- mi->getOperand(i).getReg() == regB)
- mi->SetMachineOperandReg(i, regA);
- }
- DEBUG(std::cerr << "\t\tmodified original to: ";
- mi->print(std::cerr, TM));
- assert(mi->getOperand(0).getAllocatedRegNum() ==
- mi->getOperand(1).getAllocatedRegNum());
+ // replace all occurences of regB with regA
+ for (unsigned i = 1, e = mi->getNumOperands(); i != e; ++i) {
+ if (mi->getOperand(i).isRegister() &&
+ mi->getOperand(i).getReg() == regB)
+ mi->getOperand(i).setReg(regA);
}
+ }
+
+ assert(mi->getOperand(0).isDef());
+ mi->getOperand(0).setUse();
+ mi->RemoveOperand(1);
+ MadeChange = true;
+
+ DEBUG(std::cerr << "\t\trewrite to:\t"; mi->print(std::cerr, &TM));
}
+ }
- return MadeChange;
+ return MadeChange;
}
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