[NVPTX] Initial adaptation of MCAsmStreamer/MCTargetStreamer for debug info in Cuda.

Summary:
Initial changes in interfaces of MCAsmStreamer/MCTargetStreamer for
correct debug info emission for Cuda.
1. PTX foramt does not support `.ascii` directives. Added the ability to
nullify it.
2. The initial function label must follow the first debug `.loc`
directive, not be followed by.
3. DWARF sections must be enclosed in braces.

Reviewers: hfinkel, probinson, jlebar, rafael, echristo

Subscribers: sdardis, nemanjai, llvm-commits, aprantl

Differential Revision: https://reviews.llvm.org/D40033

llvm-svn: 321178

llvm/include/llvm/MC/MCAsmInfo.h

@@ -165,7 +165,8 @@ protected:
   const char *ZeroDirective;
 
   /// This directive allows emission of an ascii string with the standard C
-  /// escape characters embedded into it.  Defaults to "\t.ascii\t"
+  /// escape characters embedded into it.  If a target doesn't support this, it
+  /// can be set to null. Defaults to "\t.ascii\t"
   const char *AsciiDirective;
 
   /// If not null, this allows for special handling of zero terminated strings

llvm/include/llvm/MC/MCStreamer.h

@@ -95,6 +95,17 @@ public:
   virtual void prettyPrintAsm(MCInstPrinter &InstPrinter, raw_ostream &OS,
                               const MCInst &Inst, const MCSubtargetInfo &STI);
 
+  virtual void emitDwarfFileDirective(StringRef Directive);
+
+  /// Update streamer for a new active section.
+  ///
+  /// This is called by PopSection and SwitchSection, if the current
+  /// section changes.
+  virtual void changeSection(const MCSection *CurSection, MCSection *Section,
+                             const MCExpr *SubSection, raw_ostream &OS);
+
+  virtual void emitValue(const MCExpr *Value);
+
   virtual void finish();
 };
 

llvm/lib/MC/MCAsmStreamer.cpp

@@ -405,9 +405,13 @@ void MCAsmStreamer::emitExplicitComments() {
 void MCAsmStreamer::ChangeSection(MCSection *Section,
                                   const MCExpr *Subsection) {
   assert(Section && "Cannot switch to a null section!");
+  if (MCTargetStreamer *TS = getTargetStreamer()) {
+    TS->changeSection(getCurrentSectionOnly(), Section, Subsection, OS);
+  } else {
     Section->PrintSwitchToSection(
         *MAI, getContext().getObjectFileInfo()->getTargetTriple(), OS,
         Subsection);
+  }
 }
 
 void MCAsmStreamer::EmitLabel(MCSymbol *Symbol, SMLoc Loc) {
@@ -796,10 +800,15 @@ void MCAsmStreamer::EmitBytes(StringRef Data) {
          "Cannot emit contents before setting section!");
   if (Data.empty()) return;
 
-  if (Data.size() == 1) {
-    OS << MAI->getData8bitsDirective();
-    OS << (unsigned)(unsigned char)Data[0];
+  // If only single byte is provided or no ascii or asciz directives is
+  // supported, emit as vector of 8bits data.
+  if (Data.size() == 1 ||
+      !(MAI->getAscizDirective() || MAI->getAsciiDirective())) {
+    const char *Directive = MAI->getData8bitsDirective();
+    for (const unsigned char C : Data.bytes()) {
+      OS << Directive << (unsigned)C;
       EmitEOL();
+    }
     return;
   }
 
@@ -884,8 +893,12 @@ void MCAsmStreamer::EmitValueImpl(const MCExpr *Value, unsigned Size,
 
   assert(Directive && "Invalid size for machine code value!");
   OS << Directive;
+  if (MCTargetStreamer *TS = getTargetStreamer()) {
+    TS->emitValue(Value);
+  } else {
     Value->print(OS, MAI);
     EmitEOL();
+  }
 }
 
 void MCAsmStreamer::EmitULEB128Value(const MCExpr *Value) {
@@ -1097,13 +1110,19 @@ unsigned MCAsmStreamer::EmitDwarfFileDirective(unsigned FileNo,
     }
   }
 
-  OS << "\t.file\t" << FileNo << ' ';
+  SmallString<128> Str;
+  raw_svector_ostream OS1(Str);
+  OS1 << "\t.file\t" << FileNo << ' ';
   if (!Directory.empty()) {
-    PrintQuotedString(Directory, OS);
-    OS << ' ';
+    PrintQuotedString(Directory, OS1);
+    OS1 << ' ';
+  }
+  PrintQuotedString(Filename, OS1);
+  if (MCTargetStreamer *TS = getTargetStreamer()) {
+    TS->emitDwarfFileDirective(OS1.str());
+  } else {
+    EmitRawText(OS1.str());
   }
-  PrintQuotedString(Filename, OS);
-  EmitEOL();
 
   return FileNo;
 }

llvm/lib/MC/MCStreamer.cpp

@@ -49,6 +49,28 @@ void MCTargetStreamer::emitLabel(MCSymbol *Symbol) {}
 
 void MCTargetStreamer::finish() {}
 
+void MCTargetStreamer::changeSection(const MCSection *CurSection,
+                                     MCSection *Section,
+                                     const MCExpr *Subsection,
+                                     raw_ostream &OS) {
+  Section->PrintSwitchToSection(
+      *Streamer.getContext().getAsmInfo(),
+      Streamer.getContext().getObjectFileInfo()->getTargetTriple(), OS,
+      Subsection);
+}
+
+void MCTargetStreamer::emitDwarfFileDirective(StringRef Directive) {
+  Streamer.EmitRawText(Directive);
+}
+
+void MCTargetStreamer::emitValue(const MCExpr *Value) {
+  SmallString<128> Str;
+  raw_svector_ostream OS(Str);
+
+  Value->print(OS, Streamer.getContext().getAsmInfo());
+  Streamer.EmitRawText(OS.str());
+}
+
 void MCTargetStreamer::emitAssignment(MCSymbol *Symbol, const MCExpr *Value) {}
 
 MCStreamer::MCStreamer(MCContext &Ctx)