[WebAssembly] Symbol changes #4e: remove object file name section

[ncw]

Summary

As requested, here's another commit to remove the "name" section from llc and clang object files.

LLD is unaffected, no changes needed there. LLD continues to write out a name section, using the symbol names.

Resolves issue: https://github.com/WebAssembly/tool-conventions/issues/37

[sunfish]

Makes sense. With the direction all the symbol-table things are headed, using the name section as a kind of secondary symbol name is indeed confusing.

In the future, we may add the ability to produce wasm files with the name section containing demangled symbol names, which is more of the intended use for the name section, however we don't need to figure that out now.

llvm/trunk/lib/MC/WasmObjectWriter.cpp

void writeImportSection(ArrayRef<WasmImport> Imports, uint32_t DataSize,
                           uint32_t NumElements);
   void writeFunctionSection(ArrayRef<WasmFunction> Functions);
   void writeGlobalSection();
   void writeExportSection(ArrayRef<WasmExport> Exports);
   void writeElemSection(ArrayRef<uint32_t> TableElems);
   void writeCodeSection(const MCAssembler &Asm, const MCAsmLayout &Layout,
                         ArrayRef<WasmFunction> Functions);
   void writeDataSection(ArrayRef<WasmDataSegment> Segments);
-  void writeNameSection(ArrayRef<WasmFunction> Functions,
-                        ArrayRef<WasmImport> Imports);
   void writeCodeRelocSection();
   void writeDataRelocSection();
   void writeLinkingMetaDataSection(
       ArrayRef<WasmDataSegment> Segments, uint32_t DataSize,
       ArrayRef<std::pair<StringRef, uint32_t>> SymbolFlags,
       ArrayRef<std::pair<uint16_t, uint32_t>> InitFuncs,
       const std::map<StringRef, std::vector<WasmComdatEntry>>& Comdats);
 
void WasmObjectWriter::writeDataSection(ArrayRef<WasmDataSegment> Segments) {
   }
 
   // Apply fixups.
   applyRelocations(DataRelocations, Section.ContentsOffset);
 
   endSection(Section);
 }
 
-void WasmObjectWriter::writeNameSection(ArrayRef<WasmFunction> Functions,
-                                        ArrayRef<WasmImport> Imports) {
-  uint32_t TotalFunctions = NumFunctionImports + Functions.size();
-  if (TotalFunctions == 0)
-    return;
-
-  SectionBookkeeping Section;
-  startSection(Section, wasm::WASM_SEC_CUSTOM, "name");
-  SectionBookkeeping SubSection;
-  startSection(SubSection, wasm::WASM_NAMES_FUNCTION);
-
-  encodeULEB128(TotalFunctions, getStream());
-  uint32_t Index = 0;
-  for (const WasmImport &Import : Imports) {
-    if (Import.Kind == wasm::WASM_EXTERNAL_FUNCTION) {
-      encodeULEB128(Index, getStream());
-      writeString(Import.FieldName);
-      ++Index;
-    }
-  }
-  for (const WasmFunction &Func : Functions) {
-    encodeULEB128(Index, getStream());
-    writeString(Func.Sym->getName());
-    ++Index;
-  }
-
-  endSection(SubSection);
-  endSection(Section);
-}
-
 void WasmObjectWriter::writeCodeRelocSection() {
   // See: https://github.com/WebAssembly/tool-conventions/blob/master/Linking.md
   // for descriptions of the reloc sections.
 
   if (CodeRelocations.empty())
     return;
 
   SectionBookkeeping Section;
void WasmObjectWriter::writeObject(MCAssembler &Asm,
   writeFunctionSection(Functions);
   // Skip the "table" section; we import the table instead.
   // Skip the "memory" section; we import the memory instead.
   writeGlobalSection();
   writeExportSection(Exports);
   writeElemSection(TableElems);
   writeCodeSection(Asm, Layout, Functions);
   writeDataSection(DataSegments);
-  writeNameSection(Functions, Imports);
   writeCodeRelocSection();
   writeDataRelocSection();
   writeLinkingMetaDataSection(DataSegments, DataSize, SymbolFlags,
                               InitFuncs, Comdats);
 
   // TODO: Translate the .comment section to the output.
   // TODO: Translate debug sections to the output.
 }
 
 std::unique_ptr<MCObjectWriter>
 llvm::createWasmObjectWriter(std::unique_ptr<MCWasmObjectTargetWriter> MOTW,
                              raw_pwrite_stream &OS) {
   return llvm::make_unique<WasmObjectWriter>(std::move(MOTW), OS);
 }

llvm/trunk/test/MC/WebAssembly/comdat.ll

 ; CHECK-NEXT:    Segments:
 ; CHECK-NEXT:      - SectionOffset:   6
 ; CHECK-NEXT:        MemoryIndex:     0
 ; CHECK-NEXT:        Offset:
 ; CHECK-NEXT:          Opcode:          I32_CONST
 ; CHECK-NEXT:          Value:           0
 ; CHECK-NEXT:        Content:         '616263'
 ; CHECK-NEXT:  - Type:            CUSTOM
-; CHECK-NEXT:    Name:            name
-; CHECK-NEXT:    FunctionNames:
-; CHECK-NEXT:      - Index:           0
-; CHECK-NEXT:        Name:            funcImport
-; CHECK-NEXT:      - Index:           1
-; CHECK-NEXT:        Name:            callImport
-; CHECK-NEXT:      - Index:           2
-; CHECK-NEXT:        Name:            basicInlineFn
-; CHECK-NEXT:      - Index:           3
-; CHECK-NEXT:        Name:            sharedFn
-; CHECK-NEXT:  - Type:            CUSTOM
 ; CHECK-NEXT:    Name:            linking
 ; CHECK-NEXT:    DataSize:        3
 ; CHECK-NEXT:    SymbolInfo:
 ; CHECK-NEXT:      - Name:            basicInlineFn
 ; CHECK-NEXT:        Flags:           [ BINDING_WEAK ]
 ; CHECK-NEXT:      - Name:            sharedFn
 ; CHECK-NEXT:        Flags:           [ BINDING_WEAK ]
 ; CHECK-NEXT:      - Name:            constantData

llvm/trunk/test/MC/WebAssembly/global-ctor-dtor.ll

 ; CHECK-NEXT:     Segments:        
 ; CHECK-NEXT:       - SectionOffset:   6
 ; CHECK-NEXT:         MemoryIndex:     0
 ; CHECK-NEXT:         Offset:          
 ; CHECK-NEXT:           Opcode:          I32_CONST
 ; CHECK-NEXT:           Value:           0
 ; CHECK-NEXT:         Content:         '01040000'
 ; CHECK-NEXT:   - Type:            CUSTOM
-; CHECK-NEXT:     Name:            name
-; CHECK-NEXT:     FunctionNames:   
-; CHECK-NEXT:       - Index:           0
-; CHECK-NEXT:         Name:            func3
-; CHECK-NEXT:       - Index:           1
-; CHECK-NEXT:         Name:            __cxa_atexit
-; CHECK-NEXT:       - Index:           2
-; CHECK-NEXT:         Name:            func2
-; CHECK-NEXT:       - Index:           3
-; CHECK-NEXT:         Name:            func1
-; CHECK-NEXT:       - Index:           4
-; CHECK-NEXT:         Name:            func0
-; CHECK-NEXT:       - Index:           5
-; CHECK-NEXT:         Name:            .Lcall_dtors.42
-; CHECK-NEXT:       - Index:           6
-; CHECK-NEXT:         Name:            .Lregister_call_dtors.42
-; CHECK-NEXT:       - Index:           7
-; CHECK-NEXT:         Name:            .Lcall_dtors
-; CHECK-NEXT:       - Index:           8
-; CHECK-NEXT:         Name:            .Lregister_call_dtors
-; CHECK-NEXT:   - Type:            CUSTOM
 ; CHECK-NEXT:     Name:            linking
 ; CHECK-NEXT:     DataSize:        4
 ; CHECK-NEXT:     SymbolInfo:      
 ; CHECK-NEXT:       - Name:            __dso_handle
 ; CHECK-NEXT:         Flags:           [ BINDING_WEAK, VISIBILITY_HIDDEN ]
 ; CHECK-NEXT:       - Name:            .Lcall_dtors.42
 ; CHECK-NEXT:         Flags:           [ BINDING_LOCAL ]
 ; CHECK-NEXT:       - Name:            .Lregister_call_dtors.42

llvm/trunk/test/MC/WebAssembly/sections.ll

 ; CHECK:  Section {
 ; CHECK:    Type: CODE (0xA)
 ; CHECK:  }
 ; CHECK:  Section {
 ; CHECK:    Type: DATA (0xB)
 ; CHECK:  }
 ; CHECK:  Section {
 ; CHECK:    Type: CUSTOM (0x0)
-; CHECK:    Name: name
-; CHECK:  }
-; CHECK:  Section {
-; CHECK:    Type: CUSTOM (0x0)
 ; CHECK:    Name: reloc.CODE
 ; CHECK:  }
 ; CHECK:]
 

llvm/trunk/test/MC/WebAssembly/visibility.ll

 ; RUN: llc -mtriple wasm32-unknown-unknown-wasm -filetype=obj %s -o - | obj2yaml | FileCheck %s
 
 ; Function with __attribute__((visibility("default")))
 define void @defaultVis() #0 {
 entry:
   ret void
 }
 
 ; Function with __attribute__((visibility("hidden")))
 define hidden void @hiddenVis() #0 {
 entry:
   ret void
 }
 
 ; CHECK:        - Type:            CUSTOM
-
-; CHECK:        - Type:            CUSTOM
 ; CHECK-NEXT:     Name:            linking
 ; CHECK-NEXT:     DataSize:        0
 ; CHECK-NEXT:     SymbolInfo:
 ; CHECK-NEXT:       - Name:            hiddenVis
 ; CHECK-NEXT:         Flags:           [ VISIBILITY_HIDDEN ]
 ; CHECK-NEXT: ...

llvm/trunk/test/MC/WebAssembly/weak-alias.ll

 ; CHECK-NEXT:       - SectionOffset:   15
 ; CHECK-NEXT:         MemoryIndex:     0
 ; CHECK-NEXT:         Offset:          
 ; CHECK-NEXT:           Opcode:          I32_CONST
 ; CHECK-NEXT:           Value:           8
 ; CHECK-NEXT:         Content:         '01000000'
 
 ; CHECK:        - Type:            CUSTOM
-; CHECK-NEXT:     Name:            name
-; CHECK-NEXT:     FunctionNames:   
-; CHECK-NEXT:       - Index:           0
-; CHECK-NEXT:         Name:            foo_alias
-; CHECK-NEXT:       - Index:           1
-; CHECK-NEXT:         Name:            foo
-; CHECK-NEXT:       - Index:           2
-; CHECK-NEXT:         Name:            call_direct
-; CHECK-NEXT:       - Index:           3
-; CHECK-NEXT:         Name:            call_alias
-; CHECK-NEXT:       - Index:           4
-; CHECK-NEXT:         Name:            call_direct_ptr
-; CHECK-NEXT:       - Index:           5
-; CHECK-NEXT:         Name:            call_alias_ptr
-; CHECK-NEXT:   - Type:            CUSTOM
 ; CHECK-NEXT:     Name:            linking
 ; CHECK-NEXT:     DataSize:        20
 ; CHECK-NEXT:     SymbolInfo:      
 ; CHECK-NEXT:       - Name:            foo_alias
 ; CHECK-NEXT:         Flags:           [ BINDING_WEAK, VISIBILITY_HIDDEN ]
 ; CHECK-NEXT:       - Name:            bar_alias
 ; CHECK-NEXT:         Flags:           [ BINDING_WEAK, VISIBILITY_HIDDEN ]
 ; CHECK-NEXT:       - Name:            foo

llvm/trunk/test/MC/WebAssembly/weak.ll

 ; CHECK:            - Module:          env
 ; CHECK-NEXT:         Field:           weak_external_data
 ; CHECK-NEXT:         Kind:            GLOBAL
 ; CHECK-NEXT:         GlobalType:      I32
 ; CHECK-NEXT:         GlobalMutable:   false
 
 
 ; CHECK:        - Type:            CUSTOM
-; CHECK-NEXT:     Name:            name
-; CHECK-NEXT:     FunctionNames:   
-; CHECK-NEXT:       - Index:           0
-; CHECK-NEXT:         Name:            weak_function
-; CHECK-NEXT:   - Type:            CUSTOM
 ; CHECK-NEXT:     Name:            linking
 ; CHECK-NEXT:     DataSize:        0
 ; CHECK-NEXT:     SymbolInfo:      
 ; CHECK-NEXT:       - Name:            weak_external_data
 ; CHECK-NEXT:         Flags:           [ BINDING_WEAK ]
 ; CHECK-NEXT:       - Name:            weak_function
 ; CHECK-NEXT:         Flags:           [ BINDING_WEAK, VISIBILITY_HIDDEN ]
 ; CHECK-NEXT: ...