[WebAssembly] Add version to object file metadata

[sbc100]

Summary

See https://github.com/WebAssembly/tool-conventions/issues/54

This change only adds a version of the metadata and doesn't try to encode
ABI information. That may come as a followup change, most likely in a new
subsection.

[sbc100]

• use version constant

[sbc100]

• add test

[ncw]

Seems sensible.

llvm/trunk/include/llvm/BinaryFormat/Wasm.h

 
 namespace llvm {
 namespace wasm {
 
 // Object file magic string.
 const char WasmMagic[] = {'\0', 'a', 's', 'm'};
 // Wasm binary format version
 const uint32_t WasmVersion = 0x1;
+// Wasm linking metadata version
+const uint32_t WasmMetadataVersion = 0x1;
 // Wasm uses a 64k page size
 const uint32_t WasmPageSize = 65536;
 
 struct WasmObjectHeader {
   StringRef Magic;
   uint32_t Version;
 };
 

 };
 
 struct WasmFunctionName {
   uint32_t Index;
   StringRef Name;
 };
 
 struct WasmLinkingData {
+  uint32_t Version;
   std::vector<WasmInitFunc> InitFunctions;
   std::vector<StringRef> Comdats;
   std::vector<WasmSymbolInfo> SymbolTable;
 };
 
 enum : unsigned {
   WASM_SEC_CUSTOM = 0,   // Custom / User-defined section
   WASM_SEC_TYPE = 1,     // Function signature declarations

llvm/trunk/include/llvm/ObjectYAML/WasmYAML.h

 struct LinkingSection : CustomSection {
   LinkingSection() : CustomSection("linking") {}
 
   static bool classof(const Section *S) {
     auto C = dyn_cast<CustomSection>(S);
     return C && C->Name == "linking";
   }
 
+  uint32_t Version;
   std::vector<SymbolInfo> SymbolTable;
   std::vector<SegmentInfo> SegmentInfos;
   std::vector<InitFunction> InitFunctions;
   std::vector<Comdat> Comdats;
 };
 
 struct TypeSection : Section {
   TypeSection() : Section(wasm::WASM_SEC_TYPE) {}

llvm/trunk/lib/MC/WasmObjectWriter.cpp

 }
 
 void WasmObjectWriter::writeLinkingMetaDataSection(
     ArrayRef<wasm::WasmSymbolInfo> SymbolInfos,
     ArrayRef<std::pair<uint16_t, uint32_t>> InitFuncs,
     const std::map<StringRef, std::vector<WasmComdatEntry>> &Comdats) {
   SectionBookkeeping Section;
   startCustomSection(Section, "linking");
-  SectionBookkeeping SubSection;
+  encodeULEB128(wasm::WasmMetadataVersion, getStream());
 
+  SectionBookkeeping SubSection;
   if (SymbolInfos.size() != 0) {
     startSection(SubSection, wasm::WASM_SYMBOL_TABLE);
     encodeULEB128(SymbolInfos.size(), getStream());
     for (const wasm::WasmSymbolInfo &Sym : SymbolInfos) {
       encodeULEB128(Sym.Kind, getStream());
       encodeULEB128(Sym.Flags, getStream());
       switch (Sym.Kind) {
       case wasm::WASM_SYMBOL_TYPE_FUNCTION:

llvm/trunk/lib/Object/WasmObjectFile.cpp

 Error WasmObjectFile::parseLinkingSection(const uint8_t *Ptr,
                                           const uint8_t *End) {
   HasLinkingSection = true;
   if (Functions.size() != FunctionTypes.size()) {
     return make_error<GenericBinaryError>(
         "Linking data must come after code section", object_error::parse_failed);
   }
 
+  LinkingData.Version = readVaruint32(Ptr);
+  if (LinkingData.Version != wasm::WasmMetadataVersion) {
+    return make_error<GenericBinaryError>(
+        "Unexpected metadata version: " + Twine(LinkingData.Version) +
+            " (Expected: " + Twine(wasm::WasmMetadataVersion) + ")",
+        object_error::parse_failed);
+  }
+
   while (Ptr < End) {
     uint8_t Type = readUint8(Ptr);
     uint32_t Size = readVaruint32(Ptr);
     const uint8_t *SubSectionEnd = Ptr + Size;
     switch (Type) {
     case wasm::WASM_SYMBOL_TABLE:
       if (Error Err = parseLinkingSectionSymtab(Ptr, SubSectionEnd))
         return Err;

llvm/trunk/lib/ObjectYAML/WasmYAML.cpp

static void sectionMapping(IO &IO, WasmYAML::NameSection &Section) {
   commonSectionMapping(IO, Section);
   IO.mapRequired("Name", Section.Name);
   IO.mapOptional("FunctionNames", Section.FunctionNames);
 }
 
 static void sectionMapping(IO &IO, WasmYAML::LinkingSection &Section) {
   commonSectionMapping(IO, Section);
   IO.mapRequired("Name", Section.Name);
+  IO.mapRequired("Version", Section.Version);
   IO.mapOptional("SymbolTable", Section.SymbolTable);
   IO.mapOptional("SegmentInfo", Section.SegmentInfos);
   IO.mapOptional("InitFunctions", Section.InitFunctions);
   IO.mapOptional("Comdats", Section.Comdats);
 }
 
 static void sectionMapping(IO &IO, WasmYAML::CustomSection &Section) {
   commonSectionMapping(IO, Section);

llvm/trunk/test/MC/WebAssembly/array-fill.ll

 ; RUN: llc -filetype=obj %s -o - | obj2yaml | FileCheck %s
 ; PR33624
 
 source_filename = "ws.c"
 target datalayout = "e-m:e-p:32:32-i64:64-n32:64-S128"
 target triple = "wasm32-unknown-unknown-wasm"
 
 %struct.bd = type { i8 }
 
 @gBd = hidden global [2 x %struct.bd] [%struct.bd { i8 1 }, %struct.bd { i8 2 }], align 1
 
 ; CHECK:        - Type:            DATA
 ; CHECK:              Content:         '0102'
 
-; CHECK:        - Type:            CUSTOM
-; CHECK-NEXT:     Name:            linking
-; CHECK-NEXT:     SymbolTable:
+; CHECK:          SymbolTable:
 ; CHECK-NEXT:       - Index:           0
 ; CHECK-NEXT:         Kind:            DATA
 ; CHECK-NEXT:         Name:            gBd
 ; CHECK-NEXT:         Flags:           [ VISIBILITY_HIDDEN ]
 ; CHECK-NEXT:         Segment:         0
 ; CHECK-NEXT:         Size:            2
 ; CHECK-NEXT:     SegmentInfo:    
 ; CHECK-NEXT:       - Index:           0
 ; CHECK-NEXT:         Name:            .data
 ; CHECK-NEXT:         Alignment:       1
 ; CHECK-NEXT:         Flags:           [ ]
 ; CHECK-NEXT: ...

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

 ; CHECK-NEXT:           Value:           8
 ; CHECK-NEXT:         Content:         ''
 ; CHECK-NEXT:       - SectionOffset:   29
 ; CHECK-NEXT:         MemoryIndex:     0
 ; CHECK-NEXT:         Offset:
 ; CHECK-NEXT:           Opcode:          I32_CONST
 ; CHECK-NEXT:           Value:           8
 ; CHECK-NEXT:         Content:         ''
-; CHECK-NEXT:   - Type:            CUSTOM
-; CHECK-NEXT:     Name:            linking
-; CHECK-NEXT:     SymbolTable:
+
+; CHECK:          SymbolTable:
 ; CHECK-NEXT:       - Index:           0
 ; CHECK-NEXT:         Kind:            DATA
 ; CHECK-NEXT:         Name:            g0
 ; CHECK-NEXT:         Flags:           [  ]
 ; CHECK-NEXT:         Segment:         0
 ; CHECK-NEXT:         Size:            4
 ; CHECK-NEXT:       - Index:           1
 ; CHECK-NEXT:         Kind:            DATA

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

 ; 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:            linking
+; CHECK-NEXT:    Version:         1
 ; CHECK-NEXT:    SymbolTable:
 ; CHECK-NEXT:       - Index:           0
 ; CHECK-NEXT:         Kind:            FUNCTION
 ; CHECK-NEXT:         Name:            callImport
 ; CHECK-NEXT:         Flags:           [  ]
 ; CHECK-NEXT:         Function:        1
 ; CHECK-NEXT:       - Index:           1
 ; CHECK-NEXT:         Kind:            FUNCTION

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

 ; CHECK-NEXT:           Value:           8
 ; CHECK-NEXT:         Content:         '01000000030000000700000000000000'
 ; CHECK-NEXT:       - SectionOffset:   36
 ; CHECK-NEXT:         MemoryIndex:     0
 ; CHECK-NEXT:         Offset:          
 ; CHECK-NEXT:           Opcode:          I32_CONST
 ; CHECK-NEXT:           Value:           24
 ; CHECK-NEXT:         Content:         '08000000'
-; CHECK-NEXT:   - Type:            CUSTOM
-; CHECK-NEXT:     Name:            linking
-; CHECK-NEXT:     SymbolTable:
+
+; CHECK:          SymbolTable:
 ; CHECK-NEXT:       - Index:           0
 ; CHECK-NEXT:         Kind:            DATA
 ; CHECK-NEXT:         Name:            global0
 ; CHECK-NEXT:         Flags:           [  ]
 ; CHECK-NEXT:         Segment:         0
 ; CHECK-NEXT:         Size:            4
 ; CHECK-NEXT:       - Index:           1
 ; CHECK-NEXT:         Kind:            DATA

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

 ; 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:            linking
+; CHECK-NEXT:     Version:         1
 ; CHECK-NEXT:     SymbolTable:
 ; CHECK-NEXT:       - Index:           0
 ; CHECK-NEXT:         Kind:            FUNCTION
 ; CHECK-NEXT:         Name:            .Lcall_dtors.42
 ; CHECK-NEXT:         Flags:           [ BINDING_LOCAL ]
 ; CHECK-NEXT:         Function:        5
 ; CHECK-NEXT:       - Index:           1
 ; CHECK-NEXT:         Kind:            FUNCTION

llvm/trunk/test/MC/WebAssembly/unnamed-data.ll

 ; CHECK-NEXT:       - SectionOffset:   37
 ; CHECK-NEXT:         MemoryIndex:     0
 ; CHECK-NEXT:         Offset:          
 ; CHECK-NEXT:           Opcode:          I32_CONST
 ; CHECK-NEXT:           Value:           24
 ; CHECK-NEXT:         Content:         '06000000'
 ; CHECK-NEXT:   - Type:            CUSTOM
 ; CHECK-NEXT:     Name:            linking
+; CHECK-NEXT:     Version:         1
 ; CHECK-NEXT:     SymbolTable:      
 ; CHECK-NEXT:       - Index:           0
 ; CHECK-NEXT:         Kind:            DATA
 ; CHECK-NEXT:         Name:            .L.str1
 ; CHECK-NEXT:         Flags:           [ BINDING_LOCAL ]
 ; CHECK-NEXT:         Segment:         0
 ; CHECK-NEXT:         Size:            6
 ; CHECK-NEXT:       - Index:           1

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

 ; RUN: llc -filetype=obj %s -o - | obj2yaml | FileCheck %s
 
 target triple = "wasm32-unknown-unknown-wasm"
 
 ; 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-NEXT:     Name:            linking
-; CHECK-NEXT:     SymbolTable:
+; CHECK:          SymbolTable:
 ; CHECK-NEXT:       - Index:           0
 ; CHECK-NEXT:         Kind:            FUNCTION
 ; CHECK-NEXT:         Name:            defaultVis
 ; CHECK-NEXT:         Flags:           [  ]
 ; CHECK-NEXT:         Function:        0
 ; CHECK-NEXT:       - Index:           1
 ; CHECK-NEXT:         Kind:            FUNCTION
 ; CHECK-NEXT:         Name:            hiddenVis
 ; CHECK-NEXT:         Flags:           [ VISIBILITY_HIDDEN ]
 ; CHECK-NEXT:         Function:        1
 ; CHECK-NEXT: ...

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

 ; CHECK-NEXT:       - SectionOffset:   24
 ; CHECK-NEXT:         MemoryIndex:     0
 ; CHECK-NEXT:         Offset:
 ; CHECK-NEXT:           Opcode:          I32_CONST
 ; CHECK-NEXT:           Value:           16
 ; CHECK-NEXT:         Content:         '01000000'
 ; CHECK-NEXT:   - Type:            CUSTOM
 ; CHECK-NEXT:     Name:            linking
+; CHECK-NEXT:     Version:         1
 ; CHECK-NEXT:     SymbolTable:      
 ; CHECK-NEXT:       - Index:           0
 ; CHECK-NEXT:         Kind:            FUNCTION
 ; CHECK-NEXT:         Name:            foo
 ; CHECK-NEXT:         Flags:           [ VISIBILITY_HIDDEN ]
 ; CHECK-NEXT:         Function:        0
 ; CHECK-NEXT:       - Index:           1
 ; CHECK-NEXT:         Kind:            FUNCTION

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

 ; CHECK:        - Type:            IMPORT
 ; CHECK-NEXT:     Imports:         
 ; CHECK:            - Module:          env
 ; CHECK-NEXT:         Field:           __linear_memory
 ; CHECK:            - Module:          env
 ; CHECK-NEXT:         Field:           __indirect_function_table
 
 
-; CHECK:        - Type:            CUSTOM
-; CHECK-NEXT:     Name:            linking
-; CHECK-NEXT:     SymbolTable:      
+; CHECK:          SymbolTable:      
 ; CHECK-NEXT:       - Index:           0
 ; CHECK-NEXT:         Kind:            FUNCTION
 ; CHECK-NEXT:         Name:            weak_function
 ; CHECK-NEXT:         Flags:           [ BINDING_WEAK, VISIBILITY_HIDDEN ]
 ; CHECK-NEXT:         Function:        0
 ; CHECK-NEXT:       - Index:           1
 ; CHECK-NEXT:         Kind:            DATA
 ; CHECK-NEXT:         Name:            weak_external_data
 ; CHECK-NEXT:         Flags:           [ BINDING_WEAK, UNDEFINED ]
 ; CHECK-NEXT: ...

llvm/trunk/test/Object/obj2yaml.test

 ELF-AVR-NEXT:       Value:           0x0000000000800060
 
 
 WASM:      --- !WASM
 WASM-NEXT: FileHeader:
 WASM-NEXT:   Version:         0x00000001
 WASM:        - Type:            CUSTOM
 WASM-NEXT:     Name:            linking
+WASM-NEXT:     Version:         1
 WASM-NEXT:     SymbolTable:
 WASM-NEXT:       - Index:           0
 WASM-NEXT:         Kind:            FUNCTION
 WASM-NEXT:         Name:            main
 WASM-NEXT:         Flags:           [  ]
 WASM-NEXT:         Function:        2
 WASM-NEXT:       - Index:           1
 WASM-NEXT:         Kind:            DATA

llvm/trunk/test/Object/wasm-bad-metadata-version.yaml

+# RUN: yaml2obj %s | not llvm-objdump -h - 2>&1 | FileCheck %s
+
+!WASM
+FileHeader:
+  Version:         0x00000001
+Sections:
+  - Type:            CUSTOM
+    Name:            linking
+    Version:         0
+
+# CHECK: {{.*}}: Unexpected metadata version: 0 (Expected: 1)

llvm/trunk/test/ObjectYAML/wasm/code_section.yaml

Functions:
         Body:            418080808000210020002101200111808080800000210220020F0B
       - Index:              1
         Locals:
          - Type:            I32
            Count:           1
         Body:            108180808000210020000F0B
   - Type:            CUSTOM
     Name:            linking
+    Version:         1
     SymbolTable:
       - Index:           0
         Kind:            FUNCTION
         Name:            func1
         Flags:           [  ]
         Function:        0
       - Index:           1
         Kind:            FUNCTION

llvm/trunk/test/ObjectYAML/wasm/data_section.yaml

Relocations:
         Offset:          0x00000006
         Addend:          8
       - Type:            R_WEBASSEMBLY_MEMORY_ADDR_I32
         Index:           0
         Offset:          0x00000006
         Addend:          -6
   - Type:            CUSTOM
     Name:            linking
+    Version:         1
     SymbolTable:
       - Index:           0
         Kind:            DATA
         Name:            dataSymbol
         Flags:           [  ]
         Segment:         0
         Offset:          0
         Size:            4

llvm/trunk/test/ObjectYAML/wasm/invalid_global_weak.yaml

 # RUN: yaml2obj < %s | not obj2yaml 2>&1 | FileCheck %s
 
 --- !WASM
 FileHeader:
   Version:         0x00000001
 Sections:
   - Type:            IMPORT
     Imports:
       - Module:          fiz
         Field:           imported_global
         Kind:            GLOBAL
         GlobalType:      I32
         GlobalMutable:   false
   - Type:            CUSTOM
     Name:            linking
+    Version:         1
     SymbolTable:
       - Index:           0
         Kind:            GLOBAL
         Name:            imported_global
         Flags:           [ BINDING_WEAK, UNDEFINED ]
         Global:          0
 ...
 
 # CHECK: Error reading file: <stdin>: undefined weak global symbol

llvm/trunk/test/ObjectYAML/wasm/linking_section.yaml

Segments:
         Content:         '10001000'
       - MemoryIndex:      0
         Offset:
           Opcode:          I32_CONST
           Value:           8
         Content:         '11110000'
   - Type:            CUSTOM
     Name:            linking
+    Version:         1
     SymbolTable:
       - Index:           0
         Kind:            FUNCTION
         Name:            bar
         Flags:           [ BINDING_WEAK, UNDEFINED ]
         Function:        0
     SegmentInfo:
       - Index:       0
         Alignment:   4
         Flags:       [ ]
         Name:        mydata
       - Index:       1
         Alignment:   2
         Flags:       [ ]
         Name:        moredata
     InitFunctions:
       - Priority:      1
         Symbol:        0
 ...
-# CHECK:       - Type:            CUSTOM
-# CHECK-NEXT:    Name:            linking
-# CHECK-NEXT:    SymbolTable:
+# CHECK:         SymbolTable:
 # CHECK-NEXT:      - Index:           0
 # CHECK-NEXT:        Kind:            FUNCTION
 # CHECK-NEXT:        Name:            bar
 # CHECK-NEXT:        Flags:           [ BINDING_WEAK, UNDEFINED ]
 # CHECK-NEXT:        Function:        0
 # CHECK-NEXT:    SegmentInfo:
 # CHECK-NEXT:      - Index:           0
 # CHECK-NEXT:        Name:            mydata

llvm/trunk/test/ObjectYAML/wasm/weak_symbols.yaml

Functions:
       - Index:           0
         Locals:
         Body:            00
       - Index:           1
         Locals:
         Body:            00
   - Type:            CUSTOM
     Name:            linking
+    Version:         1
     SymbolTable:
       - Index:           0
         Kind:            FUNCTION
         Name:            function_export
         Flags:           [ BINDING_WEAK ]
         Function:        0
       - Index:           1
         Kind:            GLOBAL

llvm/trunk/test/tools/llvm-nm/wasm/exports.yaml

Segments:
       - SectionOffset:   6
         MemoryIndex:     0
         Offset:
           Opcode:          I32_CONST
           Value:           0
         Content:         '616263'
   - Type:            CUSTOM
     Name:            linking
+    Version:         1
     SymbolTable:
        - Index:           0
          Kind:            FUNCTION
          Name:            fexport
          Flags:           [  ]
          Function:        0
        - Index:           1
          Kind:            GLOBAL

llvm/trunk/test/tools/llvm-nm/wasm/imports.yaml

Imports:
         SigIndex:        0
       - Module:          env
         Field:           gimport
         Kind:            GLOBAL
         GlobalType:      I32
         GlobalMutable:   false
   - Type:            CUSTOM
     Name:            linking
+    Version:         1
     SymbolTable:
        - Index:           0
          Kind:            FUNCTION
          Name:            fimport
          Flags:           [ UNDEFINED ]
          Function:        0
        - Index:           1
          Kind:            GLOBAL

llvm/trunk/test/tools/llvm-nm/wasm/weak-symbols.yaml

Segments:
       - SectionOffset:   6
         MemoryIndex:     0
         Offset:
           Opcode:          I32_CONST
           Value:           0
         Content:         '616263'
   - Type:            CUSTOM
     Name:            linking
+    Version:         1
     SymbolTable:
        - Index:           0
          Kind:            DATA
          Name:            weak_defined_data
          Flags:           [ BINDING_WEAK ]
          Segment:         0
          Size:            3
        - Index:           1

llvm/trunk/test/tools/llvm-objdump/wasm.txt

 # RUN: llvm-objdump -h %p/Inputs/trivial.obj.wasm | FileCheck %s
 
 # CHECK:      Sections:
 # CHECK-NEXT: Idx Name          Size      Address          Type
 # CHECK-NEXT:  0 TYPE          0000000e 0000000000000000
 # CHECK-NEXT:  1 IMPORT        0000005d 0000000000000000
 # CHECK-NEXT:  2 FUNCTION      00000002 0000000000000000
 # CHECK-NEXT:  3 CODE          00000019 0000000000000000 TEXT
 # CHECK-NEXT:  4 DATA          0000001c 0000000000000000 DATA
-# CHECK-NEXT:  5 linking       0000004d 0000000000000000
+# CHECK-NEXT:  5 linking       00000051 0000000000000000
 # CHECK-NEXT:  6 reloc.CODE    0000000c 0000000000000000
 
 # RUN: llvm-objdump -p %p/Inputs/trivial.obj.wasm | FileCheck %s -check-prefix CHECK-HEADER
 
 # CHECK-HEADER: Program Header:
 # CHECK-HEADER: Version: 0x1
 
 # RUN: llvm-objdump -s --section=CODE %p/Inputs/trivial.obj.wasm | FileCheck %s -check-prefix CHECK-SECTIONS
 
 # CHECK-SECTIONS: Contents of section CODE:
 # CHECK-SECTIONS: 0000 01170041 80808080 00108080 8080001a  ...A............
 # CHECK-SECTIONS: 0010 10818080 80004100 0b                 ......A..

llvm/trunk/test/tools/llvm-readobj/sections.test

 WASM-NEXT:         Name: .rodata..L.str
 WASM-NEXT:         Size: 13
 WASM-NEXT:         Offset: 0
 WASM-NEXT:       }
 WASM-NEXT:     ]
 WASM-NEXT:   }
 WASM-NEXT:   Section {
 WASM-NEXT:     Type: CUSTOM (0x0)
-WASM-NEXT:     Size: 57
+WASM-NEXT:     Size: 61
 WASM-NEXT:     Offset: 191
 WASM-NEXT:     Name: linking
 WASM-NEXT:   }
 WASM-NEXT:   Section {
 WASM-NEXT:     Type: CUSTOM (0x0)
 WASM-NEXT:     Size: 12
-WASM-NEXT:     Offset: 262
+WASM-NEXT:     Offset: 266
 WASM-NEXT:     Name: reloc.CODE
 WASM-NEXT:   }
 WASM-NEXT: ]

llvm/trunk/tools/obj2yaml/wasm2yaml.cpp

for (const llvm::wasm::WasmFunctionName &Func: Obj.debugNames()) {
       WasmYAML::NameEntry NameEntry;
       NameEntry.Name = Func.Name;
       NameEntry.Index = Func.Index;
       NameSec->FunctionNames.push_back(NameEntry);
     }
     CustomSec = std::move(NameSec);
   } else if (WasmSec.Name == "linking") {
     std::unique_ptr<WasmYAML::LinkingSection> LinkingSec = make_unique<WasmYAML::LinkingSection>();
+    LinkingSec->Version = Obj.linkingData().Version;
+
     ArrayRef<StringRef> Comdats = Obj.linkingData().Comdats;
     for (StringRef ComdatName : Comdats)
       LinkingSec->Comdats.emplace_back(WasmYAML::Comdat{ComdatName, {}});
     for (auto &Func : Obj.functions()) {
       if (Func.Comdat != UINT32_MAX) {
         LinkingSec->Comdats[Func.Comdat].Entries.emplace_back(
                 WasmYAML::ComdatEntry{wasm::WASM_COMDAT_FUNCTION, Func.Index});
       }
     }
+
     uint32_t SegmentIndex = 0;
     for (const object::WasmSegment &Segment : Obj.dataSegments()) {
       if (!Segment.Data.Name.empty()) {
         WasmYAML::SegmentInfo SegmentInfo;
         SegmentInfo.Name = Segment.Data.Name;
         SegmentInfo.Index = SegmentIndex;
         SegmentInfo.Alignment = Segment.Data.Alignment;
         SegmentInfo.Flags = Segment.Data.Flags;
         LinkingSec->SegmentInfos.push_back(SegmentInfo);
       }
       if (Segment.Data.Comdat != UINT32_MAX) {
         LinkingSec->Comdats[Segment.Data.Comdat].Entries.emplace_back(
             WasmYAML::ComdatEntry{wasm::WASM_COMDAT_DATA, SegmentIndex});
       }
       SegmentIndex++;
     }
+
     uint32_t SymbolIndex = 0;
     for (const wasm::WasmSymbolInfo &Symbol : Obj.linkingData().SymbolTable) {
       WasmYAML::SymbolInfo Info;
       Info.Index = SymbolIndex++;
       Info.Kind = static_cast<uint32_t>(Symbol.Kind);
       Info.Name = Symbol.Name;
       Info.Flags = Symbol.Flags;
       switch (Symbol.Kind) {
       case wasm::WASM_SYMBOL_TYPE_DATA:
         Info.DataRef = Symbol.DataRef;
         break;
       case wasm::WASM_SYMBOL_TYPE_FUNCTION:
       case wasm::WASM_SYMBOL_TYPE_GLOBAL:
         Info.ElementIndex = Symbol.ElementIndex;
         break;
       }
       LinkingSec->SymbolTable.emplace_back(Info);
     }
+
     for (const wasm::WasmInitFunc &Func : Obj.linkingData().InitFunctions) {
       WasmYAML::InitFunction F{Func.Priority, Func.Symbol};
       LinkingSec->InitFunctions.emplace_back(F);
     }
+
     CustomSec = std::move(LinkingSec);
   } else {
     CustomSec = make_unique<WasmYAML::CustomSection>(WasmSec.Name);
   }
   CustomSec->Payload = yaml::BinaryRef(WasmSec.Content);
   return CustomSec;
 }
 

llvm/trunk/tools/yaml2obj/yaml2wasm.cpp

public:
 
   raw_ostream& GetStream() {
     return StringStream;
   }
 };
 
 int WasmWriter::writeSectionContent(raw_ostream &OS, WasmYAML::LinkingSection &Section) {
   writeStringRef(Section.Name, OS);
+  encodeULEB128(Section.Version, OS);
 
   SubSectionWriter SubSection(OS);
 
   // SYMBOL_TABLE subsection
   if (Section.SymbolTable.size()) {
     writeUint8(OS, wasm::WASM_SYMBOL_TABLE);
 
     encodeULEB128(Section.SymbolTable.size(), SubSection.GetStream());