Add TwoAddressInstructionPass to handle instructions that have two or

more operands and the two first operands are constrained to be the
same. The pass takes an instruction of the form:

        a = b op c

and transforms it into:

        a = b
        a = a op c

and also preserves live variables.

llvm-svn: 10512

include/llvm/CodeGen/LiveVariables.h

@@ -57,15 +57,18 @@ public:
 
     VarInfo() : DefBlock(0), DefInst(0) {}
 
-    /// removeKill - Delete a kill corresponding to the specified machine instr
-    void removeKill(MachineInstr *MI) {
-      for (unsigned i = 0; ; ++i) {
-        assert(i < Kills.size() && "Machine instr is not a kill!");
-        if (Kills[i].second == MI) {
-          Kills.erase(Kills.begin()+i);
-          return;
+    /// removeKill - Delete a kill corresponding to the specified
+    /// machine instruction. Returns true if there was a kill
+    /// corresponding to this instruction, false otherwise.
+    bool removeKill(MachineInstr *MI) {
+      for (std::vector<std::pair<MachineBasicBlock*, MachineInstr*> >::iterator
+             i = Kills.begin(); i != Kills.end(); ++i) {
+        if (i->second == MI) {
+          Kills.erase(i);
+          return true;
         }
       }
+      return false;
     }
   };
 
@@ -156,30 +159,71 @@ public:
   /// specified register is killed after being used by the specified
   /// instruction.
   ///
-  void addVirtualRegisterKilled(unsigned IncomingReg, MachineBasicBlock *MBB,
+  void addVirtualRegisterKilled(unsigned IncomingReg,
+                                MachineBasicBlock *MBB,
                                 MachineInstr *MI) {
     RegistersKilled.insert(std::make_pair(MI, IncomingReg));
     getVarInfo(IncomingReg).Kills.push_back(std::make_pair(MBB, MI));
   }
 
+  /// removeVirtualRegisterKilled - Remove the specified virtual
+  /// register from the live variable information. Returns true if the
+  /// variable was marked as killed by the specified instruction,
+  /// false otherwise.
+  bool removeVirtualRegisterKilled(unsigned reg,
+                                   MachineBasicBlock *MBB,
+                                   MachineInstr *MI) {
+    if (!getVarInfo(reg).removeKill(MI))
+      return false;
+    for (killed_iterator i = killed_begin(MI), e = killed_end(MI); i != e; ) {
+      if (i->second == reg)
+        RegistersKilled.erase(i++);
+      else
+        ++i;
+    }
+    return true;
+  }
+
   /// removeVirtualRegistersKilled - Remove all of the specified killed
   /// registers from the live variable information.
   void removeVirtualRegistersKilled(killed_iterator B, killed_iterator E) {
-    for (killed_iterator I = B; I != E; ++I)  // Remove VarInfo entries...
-      getVarInfo(I->second).removeKill(I->first);
+    for (killed_iterator I = B; I != E; ++I) { // Remove VarInfo entries...
+      bool removed = getVarInfo(I->second).removeKill(I->first);
+      assert(removed && "kill not in register's VarInfo?");
+    }
     RegistersKilled.erase(B, E);
   }
 
   /// addVirtualRegisterDead - Add information about the fact that the specified
   /// register is dead after being used by the specified instruction.
   ///
-  void addVirtualRegisterDead(unsigned IncomingReg, MachineBasicBlock *MBB,
+  void addVirtualRegisterDead(unsigned IncomingReg,
+                              MachineBasicBlock *MBB,
                               MachineInstr *MI) {
     RegistersDead.insert(std::make_pair(MI, IncomingReg));
     getVarInfo(IncomingReg).Kills.push_back(std::make_pair(MBB, MI));
   }
 
-  /// removeVirtualRegistersKilled - Remove all of the specified killed
+  /// removeVirtualRegisterDead - Remove the specified virtual
+  /// register from the live variable information. Returns true if the
+  /// variable was marked dead at the specified instruction, false
+  /// otherwise.
+  bool removeVirtualRegisterDead(unsigned reg,
+                                 MachineBasicBlock *MBB,
+                                 MachineInstr *MI) {
+    if (!getVarInfo(reg).removeKill(MI))
+      return false;
+
+    for (killed_iterator i = killed_begin(MI), e = killed_end(MI); i != e; ) {
+      if (i->second == reg)
+        RegistersKilled.erase(i++);
+      else
+        ++i;
+    }
+    return true;
+  }
+
+  /// removeVirtualRegistersDead - Remove all of the specified dead
   /// registers from the live variable information.
   void removeVirtualRegistersDead(killed_iterator B, killed_iterator E) {
     for (killed_iterator I = B; I != E; ++I)  // Remove VarInfo entries...

include/llvm/CodeGen/TwoAddressInstructionPass.h

@@ -0,0 +1,51 @@
+//===-- llvm/CodeGen/TwoAddressInstructionPass.h - Two-Address instruction pass  -*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file was developed by the LLVM research group and is distributed under
+// the University of Illinois Open Source License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements the Two-Address instruction rewriter pass. In
+// some architectures instructions have a combined source/destination
+// operand. In those cases the instruction cannot have three operands
+// as the destination is implicit (for example ADD %EAX, %EBX on the
+// IA-32). After code generation this restrictions are not handled and
+// instructions may have three operands. This pass remedies this and
+// reduces all two-address instructions to two operands.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CODEGEN_TWOADDRESSINSTRUCTIONPASS_H
+#define LLVM_CODEGEN_TWOADDRESSINSTRUCTIONPASS_H
+
+#include "llvm/CodeGen/MachineFunctionPass.h"
+#include "llvm/CodeGen/MachineBasicBlock.h"
+#include <iostream>
+#include <map>
+
+namespace llvm {
+
+    class LiveVariables;
+    class MRegisterInfo;
+
+    class TwoAddressInstructionPass : public MachineFunctionPass
+    {
+    private:
+        MachineFunction* mf_;
+        const TargetMachine* tm_;
+        const MRegisterInfo* mri_;
+        LiveVariables* lv_;
+
+    public:
+        virtual void getAnalysisUsage(AnalysisUsage &AU) const;
+
+    private:
+        /// runOnMachineFunction - pass entry point
+        bool runOnMachineFunction(MachineFunction&);
+    };
+
+} // End llvm namespace
+
+#endif

lib/CodeGen/TwoAddressInstructionPass.cpp

@@ -0,0 +1,149 @@
+//===-- TwoAddressInstructionPass.cpp - Two-Address instruction pass ------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file was developed by the LLVM research group and is distributed under
+// the University of Illinois Open Source License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements the LiveInterval analysis pass which is used
+// by the Linear Scan Register allocator. This pass linearizes the
+// basic blocks of the function in DFS order and uses the
+// LiveVariables pass to conservatively compute live intervals for
+// each virtual and physical register.
+//
+//===----------------------------------------------------------------------===//
+
+#define DEBUG_TYPE "twoaddrinstr"
+#include "llvm/CodeGen/TwoAddressInstructionPass.h"
+#include "llvm/Function.h"
+#include "llvm/CodeGen/LiveVariables.h"
+#include "llvm/CodeGen/MachineFrameInfo.h"
+#include "llvm/CodeGen/MachineFunctionPass.h"
+#include "llvm/CodeGen/MachineInstr.h"
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/CodeGen/SSARegMap.h"
+#include "llvm/Target/MRegisterInfo.h"
+#include "llvm/Target/TargetInstrInfo.h"
+#include "llvm/Target/TargetMachine.h"
+#include "llvm/Target/TargetRegInfo.h"
+#include "Support/Debug.h"
+#include "Support/Statistic.h"
+#include "Support/STLExtras.h"
+#include <iostream>
+
+using namespace llvm;
+
+namespace {
+    RegisterAnalysis<TwoAddressInstructionPass> X(
+        "twoaddressinstruction", "Two-Address instruction pass");
+
+    Statistic<> numTwoAddressInstrs("twoaddressinstruction",
+                                    "Number of two-address instructions");
+    Statistic<> numInstrsAdded("twoaddressinstruction",
+                               "Number of instructions added");
+};
+
+void TwoAddressInstructionPass::getAnalysisUsage(AnalysisUsage &AU) const
+{
+    AU.addPreserved<LiveVariables>();
+    AU.addRequired<LiveVariables>();
+    AU.addPreservedID(PHIEliminationID);
+    AU.addRequiredID(PHIEliminationID);
+    MachineFunctionPass::getAnalysisUsage(AU);
+}
+
+/// runOnMachineFunction - Reduce two-address instructions to two
+/// operands
+///
+bool TwoAddressInstructionPass::runOnMachineFunction(MachineFunction &fn) {
+    DEBUG(std::cerr << "Machine Function\n");
+    mf_ = &fn;
+    tm_ = &fn.getTarget();
+    mri_ = tm_->getRegisterInfo();
+    lv_ = &getAnalysis<LiveVariables>();
+
+    const TargetInstrInfo& tii = tm_->getInstrInfo();
+
+    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;
+
+            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();
+            bool regAisPhysical = regA < MRegisterInfo::FirstVirtualRegister;
+            bool regBisPhysical = regB < MRegisterInfo::FirstVirtualRegister;
+
+            const TargetRegisterClass* rc = regAisPhysical ?
+                mri_->getRegClass(regA) :
+                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_));
+
+            // update live variables for regA
+            if (regAisPhysical) {
+                lv_->HandlePhysRegDef(regA, prevMi);
+            }
+            else {
+                LiveVariables::VarInfo& varInfo = lv_->getVarInfo(regA);
+                varInfo.DefInst = prevMi;
+            }
+
+            // update live variables for regB
+            if (regBisPhysical) {
+                lv_->HandlePhysRegUse(regB, prevMi);
+            }
+            else {
+                if (lv_->removeVirtualRegisterKilled(regB, &*mbbi, mi))
+                    lv_->addVirtualRegisterKilled(regB, &*mbbi, prevMi);
+
+                if (lv_->removeVirtualRegisterDead(regB, &*mbbi, mi))
+                    lv_->addVirtualRegisterDead(regB, &*mbbi, 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());
+        }
+    }
+
+    return numInstrsAdded != 0;
+}