[NVPTX] Fix DWARF section printing

There was a lot of changes to MC recently, so I'm no longer sure what is
the root cause here, but the NVPTX DWARF printing was printing an
extra closing brace, causing the PTX to be invalid. This should fix it
by only printing the closing brace when the printer has already seen an
opening brace for a DWARF section.

Author: Mogball

llvm/lib/Target/NVPTX/MCTargetDesc/NVPTXTargetStreamer.cpp

@@ -88,8 +88,10 @@ void NVPTXTargetStreamer::changeSection(const MCSection *CurSection,
   assert(!SubSection && "SubSection is not null!");
   const MCObjectFileInfo *FI = getStreamer().getContext().getObjectFileInfo();
   // Emit closing brace for DWARF sections only.
-  if (isDwarfSection(FI, CurSection))
+  if (isDwarfSection(FI, CurSection) && HasDWARFSections) {
+    HasDWARFSections = false;
     OS << "\t}\n";
+  }
   if (isDwarfSection(FI, Section)) {
     // Emit DWARF .file directives in the outermost scope.
     outputDwarfFileDirectives();
@@ -100,6 +102,7 @@ void NVPTXTargetStreamer::changeSection(const MCSection *CurSection,
     // DWARF sections are enclosed into braces - emit the open one.
     OS << "\t{\n";
     HasSections = true;
+    HasDWARFSections = true;
   }
 }
 

llvm/lib/Target/NVPTX/MCTargetDesc/NVPTXTargetStreamer.h

@@ -19,6 +19,7 @@ class NVPTXTargetStreamer : public MCTargetStreamer {
 private:
   SmallVector<std::string, 4> DwarfFiles;
   bool HasSections = false;
+  bool HasDWARFSections = false;
 
 public:
   NVPTXTargetStreamer(MCStreamer &S);

llvm/test/DebugInfo/NVPTX/cu-range-hole.ll

@@ -36,7 +36,7 @@
 ; CHECK: $L__func_end2:
 ; CHECK: }
 
-; CHECK: .file 1 "{{.*}}b.c"
+; CHECK-NEXT: .file 1 "{{.*}}b.c"
 
 ; Function Attrs: nounwind uwtable
 define i32 @b(i32 %c) #0 !dbg !5 {