[WebAssembly] Add more test coverage for reloctions against section symbols

The only known user of this relocation type and symbol type is
the debug info sections, but we were not testing the `--relocatable`
output path.

This change adds a minimal test case to cover relocations against
section symbols includes `--relocatable` output.

Differential Revision: https://reviews.llvm.org/D61623

llvm-svn: 360110

lld/test/wasm/section-symbol-relocs.yaml

@@ -0,0 +1,51 @@
+# RUN: yaml2obj %s -o %t.o
+# RUN: llc -filetype=obj  %S/Inputs/custom.ll -o %t2.o
+# RUN: wasm-ld --no-entry -o - %t2.o %t.o | obj2yaml | FileCheck %s
+# RUN: wasm-ld -r --no-entry -o - %t2.o %t.o | obj2yaml | FileCheck %s -check-prefix=RELOC
+
+--- !WASM
+FileHeader:
+  Version:         0x00000001
+Sections:
+  - Type:            CUSTOM
+    Name:            green
+    Payload:         'AA0000000000000000'
+    Relocations:
+      - Type:            R_WASM_SECTION_OFFSET_I32
+        Index:           0
+        Offset:          0x00000001
+      - Type:            R_WASM_SECTION_OFFSET_I32
+        Index:           1
+        Offset:          0x00000005
+  - Type:            CUSTOM
+    Name:            red
+    Payload:         'BB0000000000000000'
+  - Type:            CUSTOM
+    Name:            linking
+    Version:         2
+    SymbolTable:
+      - Index:           0
+        Kind:            SECTION
+        Section:         0
+        Flags:           [ BINDING_LOCAL ]
+      - Index:           1
+        Kind:            SECTION
+        Section:         1
+        Flags:           [ BINDING_LOCAL ]
+...
+
+# CHECK:        Name:            green
+# CHECK-NEXT:   Payload:         626172717578AA0600000003000000
+# CHECK:        Name:            red
+# CHECK-NEXT:   Payload:         666F6FBB0000000000000000
+
+# RELOC:        Relocations:
+# RELOC-NEXT:       - Type:            R_WASM_SECTION_OFFSET_I32
+# RELOC-NEXT:         Index:           0
+# RELOC-NEXT:         Offset:          0x00000007
+# RELOC-NEXT:         Addend:          6
+# RELOC-NEXT:       - Type:            R_WASM_SECTION_OFFSET_I32
+# RELOC-NEXT:         Index:           1
+# RELOC-NEXT:         Offset:          0x0000000B
+# RELOC-NEXT:         Addend:          3
+# RELOC-NEXT:    Name:            green

llvm/lib/ObjectYAML/WasmYAML.cpp

@@ -484,7 +484,8 @@ void MappingTraits<WasmYAML::SymbolInfo>::mapping(IO &IO,
                                                   WasmYAML::SymbolInfo &Info) {
   IO.mapRequired("Index", Info.Index);
   IO.mapRequired("Kind", Info.Kind);
-  IO.mapRequired("Name", Info.Name);
+  if (Info.Kind != wasm::WASM_SYMBOL_TYPE_SECTION)
+    IO.mapRequired("Name", Info.Name);
   IO.mapRequired("Flags", Info.Flags);
   if (Info.Kind == wasm::WASM_SYMBOL_TYPE_FUNCTION) {
     IO.mapRequired("Function", Info.ElementIndex);

llvm/tools/yaml2obj/yaml2wasm.cpp

@@ -532,11 +532,6 @@ int WasmWriter::writeRelocSection(raw_ostream &OS, WasmYAML::Section &Sec,
     break;
   case wasm::WASM_SEC_CUSTOM: {
     auto CustomSection = dyn_cast<WasmYAML::CustomSection>(&Sec);
-    if (!CustomSection->Name.startswith(".debug_")) {
-      llvm_unreachable("not yet implemented (only for debug sections)");
-      return 1;
-    }
-
     writeStringRef(("reloc." + CustomSection->Name).str(), OS);
     break;
   }