[WebAssembly] Add version of linking section (to match llvm-side change)

[sbc100]

Summary

See: https://reviews.llvm.org/D46069

[ncw]

Seems sensible.

test/wasm/Inputs/globals.yaml

Functions:
         Locals:
         Body:            2381808080000B
     Relocations:
       - Type:            R_WEBASSEMBLY_GLOBAL_INDEX_LEB
         Index:           1
         Offset:          0x00000004
   - Type:            CUSTOM
     Name:            linking
+    Version:         1
     SymbolTable:
       - Index:           0
         Kind:            GLOBAL
         Name:            unused_global
         Flags:           [ VISIBILITY_HIDDEN ]
         Global:          0
       - Index:           1
         Kind:            GLOBAL

test/wasm/Inputs/undefined-globals.yaml

Functions:
         Locals:
         Body:            2381808080000B
     Relocations:
       - Type:            R_WEBASSEMBLY_GLOBAL_INDEX_LEB
         Index:           1
         Offset:          0x00000004
   - Type:            CUSTOM
     Name:            linking
+    Version:         1
     SymbolTable:
       - Index:           0
         Kind:            GLOBAL
         Name:            unused_undef_global
         Flags:           [ VISIBILITY_HIDDEN, UNDEFINED ]
         Global:          0
       - Index:           1
         Kind:            GLOBAL

test/wasm/data-layout.ll

 ; RELOC-NEXT:         Content:         '20000000'
 ; RELOC-NEXT:       - SectionOffset:   55
 ; RELOC-NEXT:         MemoryIndex:     0
 ; RELOC-NEXT:         Offset:
 ; RELOC-NEXT:           Opcode:          I32_CONST
 ; RELOC-NEXT:           Value:           40
 ; RELOC-NEXT:         Content:         68656C6C6F0A00
 
-; RELOC:        - Type:            CUSTOM
-; RELOC-NEXT:     Name:            linking
-; RELOC-NEXT:     SymbolTable:
+; RELOC:          SymbolTable:
 ; RELOC-NEXT:       - Index:           0
 ; RELOC-NEXT:         Kind:            DATA
 ; RELOC-NEXT:         Name:            foo
 ; RELOC-NEXT:         Flags:           [ VISIBILITY_HIDDEN ]
 ; RELOC-NEXT:         Segment:         0
 ; RELOC-NEXT:         Size:            4
 ; RELOC-NEXT:       - Index:           1
 ; RELOC-NEXT:         Kind:            DATA

test/wasm/init-fini.ll

 ; CHECK-NEXT:       - Index:           22
 ; CHECK-NEXT:         Name:            .Lregister_call_dtors.2002
 ; CHECK-NEXT: ...
 
 
 ; RUN: wasm-ld --check-signatures -r %t.o %t.global-ctor-dtor.o -o %t.reloc.wasm
 ; RUN: obj2yaml %t.reloc.wasm | FileCheck -check-prefix=RELOC %s
 
-; RELOC:          Name:            linking
-; RELOC-NEXT:     SymbolTable:
+; RELOC:          SymbolTable:
 ; RELOC-NEXT:       - Index:           0
 ; RELOC-NEXT:         Kind:            FUNCTION
 ; RELOC-NEXT:         Name:            func1
 ; RELOC-NEXT:         Flags:           [ VISIBILITY_HIDDEN ]
 ; RELOC-NEXT:         Function:        2
 ; RELOC-NEXT:       - Index:           1
 ; RELOC-NEXT:         Kind:            FUNCTION
 ; RELOC-NEXT:         Name:            func2

test/wasm/locals-duplicate.test

 ; RELOC-NEXT:       - SectionOffset:   32
 ; RELOC-NEXT:         MemoryIndex:     0
 ; RELOC-NEXT:         Offset:
 ; RELOC-NEXT:           Opcode:          I32_CONST
 ; RELOC-NEXT:           Value:           16
 ; RELOC-NEXT:         Content:         '0000000000000000'
 ; RELOC-NEXT:   - Type:            CUSTOM
 ; RELOC-NEXT:     Name:            linking
+; RELOC-NEXT:     Version:         1
 ; RELOC-NEXT:     SymbolTable:
 ; RELOC-NEXT:       - Index:           0
 ; RELOC-NEXT:         Kind:            FUNCTION
 ; RELOC-NEXT:         Name:            colliding_func1
 ; RELOC-NEXT:         Flags:           [ BINDING_LOCAL ]
 ; RELOC-NEXT:         Function:        0
 ; RELOC-NEXT:       - Index:           1
 ; RELOC-NEXT:         Kind:            FUNCTION

test/wasm/many-functions.ll

 ; CHECK-NEXT:       - SectionOffset:   15
 ; CHECK-NEXT:         MemoryIndex:     0
 ; CHECK-NEXT:         Offset:
 ; CHECK-NEXT:           Opcode:          I32_CONST
 ; CHECK-NEXT:           Value:           4
 ; 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:            f1
 ; CHECK-NEXT:         Flags:           [  ]
 ; CHECK-NEXT:         Function:        0
 ; CHECK-NEXT:       - Index:           1
 ; CHECK-NEXT:         Kind:            DATA

test/wasm/relocatable.ll

 ; CHECK-NEXT:       - SectionOffset:   54
 ; CHECK-NEXT:         MemoryIndex:     0
 ; CHECK-NEXT:         Offset:
 ; CHECK-NEXT:           Opcode:          I32_CONST
 ; CHECK-NEXT:           Value:           28
 ; 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:            hello
 ; CHECK-NEXT:         Flags:           [ VISIBILITY_HIDDEN ]
 ; CHECK-NEXT:         Function:        3
 ; CHECK-NEXT:       - Index:           1
 ; CHECK-NEXT:         Kind:            DATA

test/wasm/stack-pointer.ll

 ; CHECK-NEXT:         Index:           1
 ; CHECK-NEXT:         Offset:          0x00000004
 ; CHECK-NEXT:     Functions:
 ; CHECK-NEXT:       - Index:           0
 ; CHECK-NEXT:         Locals:
 ; CHECK-NEXT:         Body:            23808080800041106B1A41000B
 ; 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:            _start
 ; CHECK-NEXT:         Flags:           [  ]
 ; CHECK-NEXT:         Function:        0
 ; CHECK-NEXT:       - Index:           1
 ; CHECK-NEXT:         Kind:            GLOBAL

test/wasm/weak-alias.ll

 ; RELOC-NEXT:         Body:            23808080800041106B220024808080800020004181808080003602081081808080002101200041106A24808080800020010B
 ; RELOC-NEXT:       - Index:           5
 ; RELOC-NEXT:         Locals:
 ; RELOC-NEXT:           - Type:            I32
 ; RELOC-NEXT:             Count:           2
 ; RELOC-NEXT:         Body:            23808080800041106B220024808080800020004181808080003602081081808080002101200041106A24808080800020010B
 ; RELOC-NEXT:   - Type:            CUSTOM
 ; RELOC-NEXT:     Name:            linking
+; RELOC-NEXT:     Version:         1
 ; RELOC-NEXT:     SymbolTable:
 ; RELOC-NEXT:       - Index:           0
 ; RELOC-NEXT:         Kind:            FUNCTION
 ; RELOC-NEXT:         Name:            _start
 ; RELOC-NEXT:         Flags:           [  ]
 ; RELOC-NEXT:         Function:        0
 ; RELOC-NEXT:       - Index:           1
 ; RELOC-NEXT:         Kind:            FUNCTION

wasm/Writer.cpp

 
 // Create the custom "linking" section containing linker metadata.
 // This is only created when relocatable output is requested.
 void Writer::createLinkingSection() {
   SyntheticSection *Section =
       createSyntheticSection(WASM_SEC_CUSTOM, "linking");
   raw_ostream &OS = Section->getStream();
 
-  if (!Config->Relocatable)
-    return;
+  writeUleb128(OS, WasmMetadataVersion, "Version");
 
   if (!SymtabEntries.empty()) {
     SubSection Sub(WASM_SYMBOL_TABLE);
     writeUleb128(Sub.OS, SymtabEntries.size(), "num symbols");
 
     for (const Symbol *Sym : SymtabEntries) {
       assert(Sym->isDefined() || Sym->isUndefined());
       WasmSymbolType Kind = Sym->getWasmType();