Add TargetInstrInfo::isMoveInstr() to support coalescing in register

allocation.

llvm-svn: 10633

include/llvm/Target/TargetInstrInfo.h

@@ -214,6 +214,16 @@ public:
     return get(Opcode).Flags & M_TERMINATOR_FLAG;
   }
 
+  //
+  // Return true if the instruction is a register to register move and
+  // leave the source and dest operands in the passed parameters.
+  //
+  virtual bool isMoveInstr(const MachineInstr& MI,
+                           unsigned& sourceReg,
+                           unsigned& destReg) const {
+    return false;
+  }
+
   // Check if an instruction can be issued before its operands are ready,
   // or if a subsequent instruction that uses its result can be issued
   // before the results are ready.

lib/Target/X86/X86InstrInfo.cpp

@@ -51,3 +51,18 @@ bool X86InstrInfo::isNOPinstr(const MachineInstr &MI) const {
   return false;
 }
 
+bool X86InstrInfo::isMoveInstr(const MachineInstr& MI,
+                               unsigned& sourceReg,
+                               unsigned& destReg) const {
+  MachineOpCode oc = MI.getOpcode();
+  if (oc == X86::MOVrr8 || oc == X86::MOVrr16 || oc == X86::MOVrr32) {
+      assert(MI.getNumOperands() == 2 &&
+             MI.getOperand(0).isRegister() &&
+             MI.getOperand(1).isRegister() &&
+             "invalid register-register move instruction");
+      sourceReg = MI.getOperand(1).getAllocatedRegNum();
+      destReg = MI.getOperand(0).getAllocatedRegNum();
+      return true;
+  }
+  return false;
+}

lib/Target/X86/X86InstrInfo.h

@@ -169,6 +169,14 @@ public:
   ///
   MachineInstr* createNOPinstr() const;
 
+  //
+  // Return true if the instruction is a register to register move and
+  // leave the source and dest operands in the passed parameters.
+  //
+  virtual bool isMoveInstr(const MachineInstr& MI,
+                           unsigned& sourceReg,
+                           unsigned& destReg) const;
+
   /// isNOPinstr - not having a special NOP opcode, we need to know if a given
   /// instruction is interpreted as an `official' NOP instr, i.e., there may be
   /// more than one way to `do nothing' but only one canonical way to slack off.