[WebAssembly] Add linking metatdata test coverage for wasm2yaml

[sbc100]

Summary

Also, remove old/unused linking metadata enum value

[ncw]

I didn't even know yaml2obj existed! I'm sure this is fine, I don't think I can usefully review things I haven't worked on.

[sbc100]

In D41196#954452, @ncw wrote:

I didn't even know yaml2obj existed! I'm sure this is fine, I don't think I can usefully review things I haven't worked on.

No problem. Sorry, I'll try to use you only for linker-y changes

include/llvm/BinaryFormat/Wasm.h

enum class ValType {
   F32 = WASM_TYPE_F32,
   F64 = WASM_TYPE_F64,
 };
 
 // Linking metadata kinds.
 enum : unsigned {
   WASM_SYMBOL_INFO    = 0x2,
   WASM_DATA_SIZE      = 0x3,
-  WASM_DATA_ALIGNMENT = 0x4,
   WASM_SEGMENT_INFO   = 0x5,
 };
 
 const unsigned WASM_SYMBOL_BINDING_MASK       = 0x3;
 const unsigned WASM_SYMBOL_VISIBILITY_MASK    = 0x4;
 
 const unsigned WASM_SYMBOL_BINDING_GLOBAL     = 0x0;
 const unsigned WASM_SYMBOL_BINDING_WEAK       = 0x1;

test/ObjectYAML/wasm/linking_section.yaml

+# RUN: yaml2obj %s | obj2yaml | FileCheck %s
+--- !WASM
+FileHeader:
+  Version:         0x00000001
+Sections:
+  - Type:            TYPE
+    Signatures:
+      - ReturnType:      I32
+        ParamTypes:
+          - I32
+  - Type:            IMPORT
+    Imports:
+      - Module:          foo
+        Field:           bar
+        Kind:            FUNCTION
+        SigIndex:        0
+  - Type:            DATA
+    Segments:
+      - MemoryIndex:      0
+        Offset:
+          Opcode:          I32_CONST
+          Value:           4
+        Content:         '10001000'
+      - MemoryIndex:      0
+        Offset:
+          Opcode:          I32_CONST
+          Value:           8
+        Content:         '11110000'
+  - Type:            CUSTOM
+    Name:            linking
+    DataSize:        999
+    SymbolInfo:
+      - Name:            bar
+        Flags:           1
+    SegmentInfo:
+      - Index:       0
+        Alignment:   4
+        Flags:       0
+        Name:        mydata
+      - Index:       1
+        Alignment:   2
+        Flags:       1
+        Name:        moredata
+...
+# CHECK:       - Type:            CUSTOM
+# CHECK-NEXT:    Name:            linking
+# CHECK-NEXT:    DataSize:        999
+# CHECK-NEXT:    SymbolInfo:
+# CHECK-NEXT:      - Name:            bar
+# CHECK-NEXT:        Flags:           1
+# CHECK-NEXT:    SegmentInfo:
+# CHECK-NEXT:      - Index:           0
+# CHECK-NEXT:        Name:            mydata
+# CHECK-NEXT:        Alignment:       4
+# CHECK-NEXT:        Flags:           0
+# CHECK-NEXT:      - Index:           1
+# CHECK-NEXT:        Name:            moredata
+# CHECK-NEXT:        Alignment:       2
+# CHECK-NEXT:        Flags:           1
+# CHECK-NEXT: ...

tools/yaml2obj/yaml2wasm.cpp

if (Section.SymbolInfos.size()) {
     SubSection.Done();
   }
 
   // SEGMENT_NAMES subsection
   if (Section.SegmentInfos.size()) {
     encodeULEB128(wasm::WASM_SEGMENT_INFO, OS);
     encodeULEB128(Section.SegmentInfos.size(), SubSection.GetStream());
     for (const WasmYAML::SegmentInfo &SegmentInfo : Section.SegmentInfos) {
-      encodeULEB128(SegmentInfo.Index, SubSection.GetStream());
       writeStringRef(SegmentInfo.Name, SubSection.GetStream());
       encodeULEB128(SegmentInfo.Alignment, SubSection.GetStream());
       encodeULEB128(SegmentInfo.Flags, SubSection.GetStream());
     }
     SubSection.Done();
   }
   return 0;
 }