[WebAssembly] Ensure all .debug_XXX section has proper symbol names

[yurydelendik]

Summary

Updated wasm section symbols names to match section name, and ensure all
referenced sections will have a symbol (per DWARF spec v3, Figure 43)

[sbc100]

lgtm. I have a followup CL to clean this up even more but this is a good intermediate change.

[sbc100]

Is there some reason this doesn't effect any of our tests? Can we modify one of the tests pick up this change?

[sbc100]

I added a test to verify that the name of the section and the begin symol were matching

llvm/trunk/lib/MC/MCObjectFileInfo.cpp

void MCObjectFileInfo::initWasmMCObjectFileInfo(const Triple &T) {
   TextSection = Ctx->getWasmSection(".text", SectionKind::getText());
   DataSection = Ctx->getWasmSection(".data", SectionKind::getData());
 
   // TODO: Set the section types and flags.
   DwarfLineSection = Ctx->getWasmSection(".debug_line", SectionKind::getMetadata(), ".debug_line");
   DwarfLineStrSection =
       Ctx->getWasmSection(".debug_line_str", SectionKind::getMetadata());
   DwarfStrSection = Ctx->getWasmSection(".debug_str", SectionKind::getMetadata(), ".debug_str");
-  DwarfLocSection = Ctx->getWasmSection(".debug_loc", SectionKind::getMetadata());
-  DwarfAbbrevSection = Ctx->getWasmSection(".debug_abbrev", SectionKind::getMetadata(), ".section_abbrev");
+  DwarfLocSection = Ctx->getWasmSection(
+      ".debug_loc", SectionKind::getMetadata(), ".debug_loc");
+  DwarfAbbrevSection = Ctx->getWasmSection(
+      ".debug_abbrev", SectionKind::getMetadata(), ".debug_abbrev");
   DwarfARangesSection = Ctx->getWasmSection(".debug_aranges", SectionKind::getMetadata());
-  DwarfRangesSection = Ctx->getWasmSection(".debug_ranges", SectionKind::getMetadata(), ".debug_range");
+  DwarfRangesSection = Ctx->getWasmSection(
+      ".debug_ranges", SectionKind::getMetadata(), ".debug_ranges");
   DwarfMacinfoSection = Ctx->getWasmSection(".debug_macinfo", SectionKind::getMetadata(), ".debug_macinfo");
   DwarfAddrSection = Ctx->getWasmSection(".debug_addr", SectionKind::getMetadata());
   DwarfCUIndexSection = Ctx->getWasmSection(".debug_cu_index", SectionKind::getMetadata());
   DwarfTUIndexSection = Ctx->getWasmSection(".debug_tu_index", SectionKind::getMetadata());
   DwarfInfoSection = Ctx->getWasmSection(".debug_info", SectionKind::getMetadata(), ".debug_info");
   DwarfFrameSection = Ctx->getWasmSection(".debug_frame", SectionKind::getMetadata());
   DwarfPubNamesSection = Ctx->getWasmSection(".debug_pubnames", SectionKind::getMetadata());
   DwarfPubTypesSection = Ctx->getWasmSection(".debug_pubtypes", SectionKind::getMetadata());

llvm/trunk/lib/MC/WasmObjectWriter.cpp

if (Section.isWasmData()) {
 
       StringRef Name = SectionName;
 
       // For user-defined custom sections, strip the prefix
       if (Name.startswith(".custom_section."))
         Name = Name.substr(strlen(".custom_section."));
 
       MCSymbol* Begin = Sec.getBeginSymbol();
-      if (Begin)
+      if (Begin) {
         WasmIndices[cast<MCSymbolWasm>(Begin)] = CustomSections.size();
+        if (Name != Begin->getName())
+          report_fatal_error("section name and begin symbol should match: " +
+                             Twine(Name));
+      }
       CustomSections.emplace_back(Name, &Section);
     }
   }
 
   // Populate WasmIndices and DataLocations for defined symbols.
   for (const MCSymbol &S : Asm.symbols()) {
     // Ignore unnamed temporary symbols, which aren't ever exported, imported,
     // or used in relocations.