Make AsmPrinter::emitImplicitDef a virtual method so targets can emit custom comments for implicit defs

For NVPTX, this fixes a crash where the emitImplicitDef implementation was expecting physical registers,
while NVPTX uses virtual registers (with a couple of exceptions).  Now, the implicit def comment will be
emitted as a true PTX register name. Other targets can use this to customize the output of implicit def
comments.

Fixes PR17519

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@192444 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/AsmPrinter/AsmPrinter.cpp b/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
index 4b5edec..60f1bff 100644
--- a/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
+++ b/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
@@ -527,11 +527,11 @@
 
 /// emitImplicitDef - This method emits the specified machine instruction
 /// that is an implicit def.
-static void emitImplicitDef(const MachineInstr *MI, AsmPrinter &AP) {
+void AsmPrinter::emitImplicitDef(const MachineInstr *MI) const {
   unsigned RegNo = MI->getOperand(0).getReg();
-  AP.OutStreamer.AddComment(Twine("implicit-def: ") +
-                            AP.TM.getRegisterInfo()->getName(RegNo));
-  AP.OutStreamer.AddBlankLine();
+  OutStreamer.AddComment(Twine("implicit-def: ") +
+                         TM.getRegisterInfo()->getName(RegNo));
+  OutStreamer.AddBlankLine();
 }
 
 static void emitKill(const MachineInstr *MI, AsmPrinter &AP) {
@@ -721,7 +721,7 @@
         }
         break;
       case TargetOpcode::IMPLICIT_DEF:
-        if (isVerbose()) emitImplicitDef(II, *this);
+        if (isVerbose()) emitImplicitDef(II);
         break;
       case TargetOpcode::KILL:
         if (isVerbose()) emitKill(II, *this);