[CodeGen] Move lowerCopy from expandPostRA to TII

[yassingh]

Summary

This will allow targets to lower their 'copy' instructions easily.

[cdevadas]

llvm/include/llvm/CodeGen/TargetInstrInfo.h

1154

Fix the comment "machine IR" -> "target specific instruction"

[arsenm]

llvm/lib/CodeGen/TargetInstrInfo.cpp

720–723

Should pass in TRI for consistency with other TRI functions

727

Don't see the point of the bool return, it just always returns true

[yassingh]

Addressed review comments.

[arsenm]

llvm/lib/CodeGen/TargetInstrInfo.cpp

723

Don't need TII, that's just this

[yassingh]

Use 'this' pointer.

[arsenm]

llvm/lib/CodeGen/TargetInstrInfo.cpp

745

You don’t need the explicit this

[yassingh]

llvm/lib/CodeGen/TargetInstrInfo.cpp

745

Just this one or 'get()' above too?

[arsenm]

llvm/lib/CodeGen/TargetInstrInfo.cpp

745

Everywhere

[yassingh]

Removed explicit 'this'

[arsenm]

llvm/lib/CodeGen/TargetInstrInfo.cpp

702

Might as well change this to start with lowercase while you're here

[barannikov88]

llvm/include/llvm/CodeGen/TargetInstrInfo.h

1154

Can't it be lowered into several instructions? The comment near copyPhysReg suggests that it can.

[arsenm]

llvm/include/llvm/CodeGen/TargetInstrInfo.h

1154

Yes, most copies are expanded to multiple instructions for amdgpu

[yassingh]

Rebase.

llvm/include/llvm/CodeGen/TargetInstrInfo.h

MachineInstr *foldMemoryOperand(MachineInstr &MI, ArrayRef<unsigned> Ops,
                                   VirtRegMap *VRM = nullptr) const;
 
   /// Same as the previous version except it allows folding of any load and
   /// store from / to any address, not just from a specific stack slot.
   MachineInstr *foldMemoryOperand(MachineInstr &MI, ArrayRef<unsigned> Ops,
                                   MachineInstr &LoadMI,
                                   LiveIntervals *LIS = nullptr) const;
 
+  /// This function defines the logic to lower COPY instruction to
+  /// target specific instruction(s).
+  void lowerCopy(MachineInstr *MI, const TargetRegisterInfo *TRI) const;
+
   /// Return true when there is potentially a faster code sequence
   /// for an instruction chain ending in \p Root. All potential patterns are
   /// returned in the \p Pattern vector. Pattern should be sorted in priority
   /// order since the pattern evaluator stops checking as soon as it finds a
   /// faster sequence.
   /// \param Root - Instruction that could be combined with one of its operands
   /// \param Patterns - Vector of possible combination patterns
   virtual bool

llvm/lib/CodeGen/ExpandPostRAPseudos.cpp

void getAnalysisUsage(AnalysisUsage &AU) const override {
     MachineFunctionPass::getAnalysisUsage(AU);
   }
 
   /// runOnMachineFunction - pass entry point
   bool runOnMachineFunction(MachineFunction&) override;
 
 private:
   bool LowerSubregToReg(MachineInstr *MI);
-  bool LowerCopy(MachineInstr *MI);
-
-  void TransferImplicitOperands(MachineInstr *MI);
 };
 } // end anonymous namespace
 
 char ExpandPostRA::ID = 0;
 char &llvm::ExpandPostRAPseudosID = ExpandPostRA::ID;
 
 INITIALIZE_PASS(ExpandPostRA, DEBUG_TYPE,
                 "Post-RA pseudo instruction expansion pass", false, false)
 
-/// TransferImplicitOperands - MI is a pseudo-instruction, and the lowered
-/// replacement instructions immediately precede it.  Copy any implicit
-/// operands from MI to the replacement instruction.
-void ExpandPostRA::TransferImplicitOperands(MachineInstr *MI) {
-  MachineBasicBlock::iterator CopyMI = MI;
-  --CopyMI;
-
-  Register DstReg = MI->getOperand(0).getReg();
-  for (const MachineOperand &MO : MI->implicit_operands()) {
-    CopyMI->addOperand(MO);
-
-    // Be conservative about preserving kills when subregister defs are
-    // involved. If there was implicit kill of a super-register overlapping the
-    // copy result, we would kill the subregisters previous copies defined.
-    if (MO.isKill() && TRI->regsOverlap(DstReg, MO.getReg()))
-      CopyMI->getOperand(CopyMI->getNumOperands() - 1).setIsKill(false);
-  }
-}
-
 bool ExpandPostRA::LowerSubregToReg(MachineInstr *MI) {
   MachineBasicBlock *MBB = MI->getParent();
   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");
 
   Register DstReg = MI->getOperand(0).getReg();
if (DstSubReg == InsReg) {
     LLVM_DEBUG(dbgs() << "subreg: " << *CopyMI);
   }
 
   LLVM_DEBUG(dbgs() << '\n');
   MBB->erase(MI);
   return true;
 }
 
-bool ExpandPostRA::LowerCopy(MachineInstr *MI) {
-
-  if (MI->allDefsAreDead()) {
-    LLVM_DEBUG(dbgs() << "dead copy: " << *MI);
-    MI->setDesc(TII->get(TargetOpcode::KILL));
-    LLVM_DEBUG(dbgs() << "replaced by: " << *MI);
-    return true;
-  }
-
-  MachineOperand &DstMO = MI->getOperand(0);
-  MachineOperand &SrcMO = MI->getOperand(1);
-
-  bool IdentityCopy = (SrcMO.getReg() == DstMO.getReg());
-  if (IdentityCopy || SrcMO.isUndef()) {
-    LLVM_DEBUG(dbgs() << (IdentityCopy ? "identity copy: " : "undef copy:    ")
-                      << *MI);
-    // No need to insert an identity copy instruction, but replace with a KILL
-    // if liveness is changed.
-    if (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));
-      LLVM_DEBUG(dbgs() << "replaced by:   " << *MI);
-      return true;
-    }
-    // Vanilla identity copy.
-    MI->eraseFromParent();
-    return true;
-  }
-
-  LLVM_DEBUG(dbgs() << "real copy:   " << *MI);
-  TII->copyPhysReg(*MI->getParent(), MI, MI->getDebugLoc(),
-                   DstMO.getReg(), SrcMO.getReg(), SrcMO.isKill());
-
-  if (MI->getNumOperands() > 2)
-    TransferImplicitOperands(MI);
-  LLVM_DEBUG({
-    MachineBasicBlock::iterator dMI = MI;
-    dbgs() << "replaced by: " << *(--dMI);
-  });
-  MI->eraseFromParent();
-  return true;
-}
-
 /// runOnMachineFunction - Reduce subregister inserts and extracts to register
 /// copies.
 ///
 bool ExpandPostRA::runOnMachineFunction(MachineFunction &MF) {
   LLVM_DEBUG(dbgs() << "Machine Function\n"
                     << "********** EXPANDING POST-RA PSEUDO INSTRS **********\n"
                     << "********** Function: " << MF.getName() << '\n');
   TRI = MF.getSubtarget().getRegisterInfo();
for (MachineInstr &MI : llvm::make_early_inc_range(MBB)) {
       }
 
       // Expand standard pseudos.
       switch (MI.getOpcode()) {
       case TargetOpcode::SUBREG_TO_REG:
         MadeChange |= LowerSubregToReg(&MI);
         break;
       case TargetOpcode::COPY:
-        MadeChange |= LowerCopy(&MI);
+        TII->lowerCopy(&MI, TRI);
+        MadeChange = true;
         break;
       case TargetOpcode::DBG_VALUE:
         continue;
       case TargetOpcode::INSERT_SUBREG:
       case TargetOpcode::EXTRACT_SUBREG:
         llvm_unreachable("Sub-register pseudos should have been eliminated.");
       }
     }
   }
 
   return MadeChange;
 }

llvm/lib/CodeGen/TargetInstrInfo.cpp

for (MachineInstr::mmo_iterator I = LoadMI.memoperands_begin(),
                                     E = LoadMI.memoperands_end();
          I != E; ++I) {
       NewMI->addMemOperand(MF, *I);
     }
   }
   return NewMI;
 }
 
+/// transferImplicitOperands - MI is a pseudo-instruction, and the lowered
+/// replacement instructions immediately precede it.  Copy any implicit
+/// operands from MI to the replacement instruction.
+static void transferImplicitOperands(MachineInstr *MI,
+                                     const TargetRegisterInfo *TRI) {
+  MachineBasicBlock::iterator CopyMI = MI;
+  --CopyMI;
+
+  Register DstReg = MI->getOperand(0).getReg();
+  for (const MachineOperand &MO : MI->implicit_operands()) {
+    CopyMI->addOperand(MO);
+
+    // Be conservative about preserving kills when subregister defs are
+    // involved. If there was implicit kill of a super-register overlapping the
+    // copy result, we would kill the subregisters previous copies defined.
+
+    if (MO.isKill() && TRI->regsOverlap(DstReg, MO.getReg()))
+      CopyMI->getOperand(CopyMI->getNumOperands() - 1).setIsKill(false);
+  }
+}
+
+void TargetInstrInfo::lowerCopy(MachineInstr *MI,
+                                const TargetRegisterInfo *TRI) const {
+  if (MI->allDefsAreDead()) {
+    MI->setDesc(get(TargetOpcode::KILL));
+    return;
+  }
+
+  MachineOperand &DstMO = MI->getOperand(0);
+  MachineOperand &SrcMO = MI->getOperand(1);
+
+  bool IdentityCopy = (SrcMO.getReg() == DstMO.getReg());
+  if (IdentityCopy || SrcMO.isUndef()) {
+    // No need to insert an identity copy instruction, but replace with a KILL
+    // if liveness is changed.
+    if (SrcMO.isUndef() || MI->getNumOperands() > 2) {
+      // We must make sure the super-register gets killed. Replace the
+      // instruction with KILL.
+      MI->setDesc(get(TargetOpcode::KILL));
+      return;
+    }
+    // Vanilla identity copy.
+    MI->eraseFromParent();
+    return;
+  }
+
+  copyPhysReg(*MI->getParent(), MI, MI->getDebugLoc(), DstMO.getReg(),
+              SrcMO.getReg(), SrcMO.isKill());
+
+  if (MI->getNumOperands() > 2)
+    transferImplicitOperands(MI, TRI);
+  MI->eraseFromParent();
+  return;
+}
+
 bool TargetInstrInfo::hasReassociableOperands(
     const MachineInstr &Inst, const MachineBasicBlock *MBB) const {
   const MachineOperand &Op1 = Inst.getOperand(1);
   const MachineOperand &Op2 = Inst.getOperand(2);
   const MachineRegisterInfo &MRI = MBB->getParent()->getRegInfo();
 
   // We need virtual register definitions for the operands that we will
   // reassociate.