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

[Justin Holewinski]

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.

http://llvm-reviews.chandlerc.com/D1210

Files:
  include/llvm/CodeGen/AsmPrinter.h
  lib/CodeGen/AsmPrinter/AsmPrinter.cpp
  lib/Target/NVPTX/NVPTXAsmPrinter.cpp
  lib/Target/NVPTX/NVPTXAsmPrinter.h
  test/CodeGen/NVPTX/implicit-def.ll

Index: include/llvm/CodeGen/AsmPrinter.h
===================================================================
--- include/llvm/CodeGen/AsmPrinter.h
+++ include/llvm/CodeGen/AsmPrinter.h
@@ -284,6 +284,10 @@
     virtual bool
     isBlockOnlyReachableByFallthrough(const MachineBasicBlock *MBB) const;
 
+    /// emitImplicitDef - Targets can override this to customize the output of
+    /// IMPLICIT_DEF instructions in verbose mode.
+    virtual void emitImplicitDef(const MachineInstr *MI) const;
+
     //===------------------------------------------------------------------===//
     // Symbol Lowering Routines.
     //===------------------------------------------------------------------===//
Index: lib/CodeGen/AsmPrinter/AsmPrinter.cpp
===================================================================
--- lib/CodeGen/AsmPrinter/AsmPrinter.cpp
+++ lib/CodeGen/AsmPrinter/AsmPrinter.cpp
@@ -529,11 +529,11 @@
 
 /// 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) {
@@ -723,7 +723,7 @@
         }
         break;
       case TargetOpcode::IMPLICIT_DEF:
-        if (isVerbose()) emitImplicitDef(II, *this);
+        if (isVerbose()) emitImplicitDef(II);
         break;
       case TargetOpcode::KILL:
         if (isVerbose()) emitKill(II, *this);
Index: lib/Target/NVPTX/NVPTXAsmPrinter.cpp
===================================================================
--- lib/Target/NVPTX/NVPTXAsmPrinter.cpp
+++ lib/Target/NVPTX/NVPTXAsmPrinter.cpp
@@ -452,6 +452,19 @@
   VRegMapping.clear();
 }
 
+void NVPTXAsmPrinter::emitImplicitDef(const MachineInstr *MI) const {
+  unsigned RegNo = MI->getOperand(0).getReg();
+  const TargetRegisterInfo *TRI = TM.getRegisterInfo();
+  if (TRI->isVirtualRegister(RegNo)) {
+    OutStreamer.AddComment(Twine("implicit-def: ") +
+      getVirtualRegisterName(RegNo));
+  } else {
+    OutStreamer.AddComment(Twine("implicit-def: ") +
+      TM.getRegisterInfo()->getName(RegNo));
+  }
+  OutStreamer.AddBlankLine();
+}
+
 void NVPTXAsmPrinter::emitKernelFunctionDirectives(const Function &F,
                                                    raw_ostream &O) const {
   // If the NVVM IR has some of reqntid* specified, then output
@@ -503,23 +516,30 @@
     O << ".minnctapersm " << mincta << "\n";
 }
 
-void NVPTXAsmPrinter::getVirtualRegisterName(unsigned vr, bool isVec,
-                                             raw_ostream &O) {
-  const TargetRegisterClass *RC = MRI->getRegClass(vr);
+std::string
+NVPTXAsmPrinter::getVirtualRegisterName(unsigned Reg) const {
+  const TargetRegisterClass *RC = MRI->getRegClass(Reg);
+
+  std::string Name;
+  raw_string_ostream NameStr(Name);
 
-  DenseMap<unsigned, unsigned> &regmap = VRegMapping[RC];
-  unsigned mapped_vr = regmap[vr];
+  VRegRCMap::const_iterator I = VRegMapping.find(RC);
+  assert(I != VRegMapping.end() && "Bad register class");
+  const DenseMap<unsigned, unsigned> &RegMap = I->second;
 
-  if (!isVec) {
-    O << getNVPTXRegClassStr(RC) << mapped_vr;
-    return;
-  }
-  report_fatal_error("Bad register!");
+  VRegMap::const_iterator VI = RegMap.find(Reg);
+  assert(VI != RegMap.end() && "Bad virtual register");
+  unsigned MappedVR = VI->second;
+
+  NameStr << getNVPTXRegClassStr(RC) << MappedVR;
+
+  NameStr.flush();
+  return Name;
 }
 
-void NVPTXAsmPrinter::emitVirtualRegister(unsigned int vr, bool isVec,
+void NVPTXAsmPrinter::emitVirtualRegister(unsigned int vr,
                                           raw_ostream &O) {
-  getVirtualRegisterName(vr, isVec, O);
+  O << getVirtualRegisterName(vr);
 }
 
 void NVPTXAsmPrinter::printVecModifiedImmediate(
@@ -564,10 +584,10 @@
         O << getRegisterName(MO.getReg());
     } else {
       if (!Modifier)
-        emitVirtualRegister(MO.getReg(), false, O);
+        emitVirtualRegister(MO.getReg(), O);
       else {
         if (strcmp(Modifier, "vecfull") == 0)
-          emitVirtualRegister(MO.getReg(), true, O);
+          emitVirtualRegister(MO.getReg(), O);
         else
           llvm_unreachable(
               "Don't know how to handle the modifier on virtual register.");
Index: lib/Target/NVPTX/NVPTXAsmPrinter.h
===================================================================
--- lib/Target/NVPTX/NVPTXAsmPrinter.h
+++ lib/Target/NVPTX/NVPTXAsmPrinter.h
@@ -188,6 +188,7 @@
   void EmitFunctionEntryLabel();
   void EmitFunctionBodyStart();
   void EmitFunctionBodyEnd();
+  void emitImplicitDef(const MachineInstr *MI) const;
 
   void EmitInstruction(const MachineInstr *);
 
@@ -217,7 +218,7 @@
   void emitGlobals(const Module &M);
   void emitHeader(Module &M, raw_ostream &O);
   void emitKernelFunctionDirectives(const Function &F, raw_ostream &O) const;
-  void emitVirtualRegister(unsigned int vr, bool isVec, raw_ostream &O);
+  void emitVirtualRegister(unsigned int vr, raw_ostream &);
   void emitFunctionExternParamList(const MachineFunction &MF);
   void emitFunctionParamList(const Function *, raw_ostream &O);
   void emitFunctionParamList(const MachineFunction &MF, raw_ostream &O);
@@ -297,7 +298,7 @@
 
   bool ignoreLoc(const MachineInstr &);
 
-  virtual void getVirtualRegisterName(unsigned, bool, raw_ostream &);
+  std::string getVirtualRegisterName(unsigned) const;
 
   DebugLoc prevDebugLoc;
   void emitLineNumberAsDotLoc(const MachineInstr &);
Index: test/CodeGen/NVPTX/implicit-def.ll
===================================================================
--- /dev/null
+++ test/CodeGen/NVPTX/implicit-def.ll
@@ -0,0 +1,9 @@
+; RUN: llc < %s -march=nvptx -mcpu=sm_20 | FileCheck %s
+
+; CHECK: // implicit-def: %f[[F0:[0-9]+]]
+; CHECK: add.f32         %f{{[0-9]+}}, %f{{[0-9]+}}, %f[[F0]];
+define float @foo(float %a) {
+  %ret = fadd float %a, undef
+  ret float %ret
+}
+
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