[CodeGen] Move lowerCopy from expandPostRA to TII

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

Reviewed By: arsenm

Differential Revision: https://reviews.llvm.org/D152261

llvm/include/llvm/CodeGen/TargetInstrInfo.h

@@ -1150,6 +1150,10 @@ public:
                                   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

llvm/lib/CodeGen/ExpandPostRAPseudos.cpp

@@ -47,9 +47,6 @@ public:
 
 private:
   bool LowerSubregToReg(MachineInstr *MI);
-  bool LowerCopy(MachineInstr *MI);
-
-  void TransferImplicitOperands(MachineInstr *MI);
 };
 } // end anonymous namespace
 
@@ -59,25 +56,6 @@ 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()) &&
@@ -137,50 +115,6 @@ bool ExpandPostRA::LowerSubregToReg(MachineInstr *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.
 ///
@@ -211,7 +145,8 @@ bool ExpandPostRA::runOnMachineFunction(MachineFunction &MF) {
         MadeChange |= LowerSubregToReg(&MI);
         break;
       case TargetOpcode::COPY:
-        MadeChange |= LowerCopy(&MI);
+        TII->lowerCopy(&MI, TRI);
+        MadeChange = true;
         break;
       case TargetOpcode::DBG_VALUE:
         continue;

llvm/lib/CodeGen/TargetInstrInfo.cpp

@@ -696,6 +696,61 @@ MachineInstr *TargetInstrInfo::foldMemoryOperand(MachineInstr &MI,
   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);