[Object][Wasm] Move WasmSymbolInfo directly into WasmSymbol (NFC) (#80219)

Move the WasmSymbolInfos from their own vector on the WasmLinkingData
directly into the WasmSymbol object. Removing the const-ref to an
external object allows the vector of WasmSymbols to be safely
expanded/reallocated; generating symbol info from the name section will
require this, as the numbers of function and data segment names are
stored separately.

This is a step toward generating symbol information from name sections
for #76107

Author: dschuff

lld/wasm/InputFiles.cpp

@@ -15,6 +15,7 @@
 #include "lld/Common/Args.h"
 #include "lld/Common/CommonLinkerContext.h"
 #include "lld/Common/Reproduce.h"
+#include "llvm/BinaryFormat/Wasm.h"
 #include "llvm/Object/Binary.h"
 #include "llvm/Object/Wasm.h"
 #include "llvm/Support/Path.h"
@@ -322,20 +323,19 @@ void ObjFile::addLegacyIndirectFunctionTableIfNeeded(
     return;
   }
 
-  auto *info = make<WasmSymbolInfo>();
-  info->Name = tableImport->Field;
-  info->Kind = WASM_SYMBOL_TYPE_TABLE;
-  info->ImportModule = tableImport->Module;
-  info->ImportName = tableImport->Field;
-  info->Flags = WASM_SYMBOL_UNDEFINED;
-  info->Flags |= WASM_SYMBOL_NO_STRIP;
-  info->ElementIndex = 0;
-  LLVM_DEBUG(dbgs() << "Synthesizing symbol for table import: " << info->Name
+  WasmSymbolInfo info;
+  info.Name = tableImport->Field;
+  info.Kind = WASM_SYMBOL_TYPE_TABLE;
+  info.ImportModule = tableImport->Module;
+  info.ImportName = tableImport->Field;
+  info.Flags = WASM_SYMBOL_UNDEFINED | WASM_SYMBOL_NO_STRIP;
+  info.ElementIndex = 0;
+  LLVM_DEBUG(dbgs() << "Synthesizing symbol for table import: " << info.Name
                     << "\n");
   const WasmGlobalType *globalType = nullptr;
   const WasmSignature *signature = nullptr;
   auto *wasmSym =
-      make<WasmSymbol>(*info, globalType, &tableImport->Table, signature);
+      make<WasmSymbol>(info, globalType, &tableImport->Table, signature);
   Symbol *sym = createUndefined(*wasmSym, false);
   // We're only sure it's a TableSymbol if the createUndefined succeeded.
   if (errorCount())

llvm/include/llvm/BinaryFormat/Wasm.h

@@ -467,11 +467,15 @@ struct WasmDebugName {
   StringRef Name;
 };
 
+// Info from the linking metadata section of a wasm object file.
 struct WasmLinkingData {
   uint32_t Version;
   std::vector<WasmInitFunc> InitFunctions;
   std::vector<StringRef> Comdats;
-  std::vector<WasmSymbolInfo> SymbolTable;
+  // The linking section also contains a symbol table. This info (represented
+  // in a WasmSymbolInfo struct) is stored inside the WasmSymbol object instead
+  // of in this structure; this allows vectors of WasmSymbols and
+  // WasmLinkingDatas to be reallocated.
 };
 
 struct WasmSignature {

llvm/include/llvm/Object/Wasm.h

@@ -43,7 +43,9 @@ class WasmSymbol {
     assert(!Signature || Signature->Kind != wasm::WasmSignature::Placeholder);
   }
 
-  const wasm::WasmSymbolInfo &Info;
+  // Symbol info as represented in the symbol's 'syminfo' entry of an object
+  // file's symbol table.
+  wasm::WasmSymbolInfo Info;
   const wasm::WasmGlobalType *GlobalType;
   const wasm::WasmTableType *TableType;
   const wasm::WasmSignature *Signature;

llvm/lib/Object/WasmObjectFile.cpp

@@ -642,9 +642,7 @@ Error WasmObjectFile::parseLinkingSectionSymtab(ReadContext &Ctx) {
   uint32_t Count = readVaruint32(Ctx);
   // Clear out any symbol information that was derived from the exports
   // section.
-  LinkingData.SymbolTable.clear();
   Symbols.clear();
-  LinkingData.SymbolTable.reserve(Count);
   Symbols.reserve(Count);
   StringSet<> SymbolNames;
 
@@ -844,9 +842,7 @@ Error WasmObjectFile::parseLinkingSectionSymtab(ReadContext &Ctx) {
       return make_error<GenericBinaryError>("duplicate symbol name " +
                                                 Twine(Info.Name),
                                             object_error::parse_failed);
-    LinkingData.SymbolTable.emplace_back(Info);
-    Symbols.emplace_back(LinkingData.SymbolTable.back(), GlobalType, TableType,
-                         Signature);
+    Symbols.emplace_back(Info, GlobalType, TableType, Signature);
     LLVM_DEBUG(dbgs() << "Adding symbol: " << Symbols.back() << "\n");
   }
 
@@ -1390,7 +1386,6 @@ Error WasmObjectFile::parseGlobalSection(ReadContext &Ctx) {
 Error WasmObjectFile::parseExportSection(ReadContext &Ctx) {
   uint32_t Count = readVaruint32(Ctx);
   Exports.reserve(Count);
-  LinkingData.SymbolTable.reserve(Count);
   Symbols.reserve(Count);
   for (uint32_t I = 0; I < Count; I++) {
     wasm::WasmExport Ex;
@@ -1455,9 +1450,7 @@ Error WasmObjectFile::parseExportSection(ReadContext &Ctx) {
     }
     Exports.push_back(Ex);
     if (Ex.Kind != wasm::WASM_EXTERNAL_MEMORY) {
-      LinkingData.SymbolTable.emplace_back(Info);
-      Symbols.emplace_back(LinkingData.SymbolTable.back(), GlobalType,
-                           TableType, Signature);
+      Symbols.emplace_back(Info, GlobalType, TableType, Signature);
       LLVM_DEBUG(dbgs() << "Adding symbol: " << Symbols.back() << "\n");
     }
   }

llvm/tools/obj2yaml/wasm2yaml.cpp

@@ -124,7 +124,8 @@ WasmDumper::dumpCustomSection(const WasmSection &WasmSec) {
     }
 
     uint32_t SymbolIndex = 0;
-    for (const wasm::WasmSymbolInfo &Symbol : Obj.linkingData().SymbolTable) {
+    for (const object::SymbolRef &Sym : Obj.symbols()) {
+      const wasm::WasmSymbolInfo &Symbol = Obj.getWasmSymbol(Sym).Info;
       WasmYAML::SymbolInfo Info;
       Info.Index = SymbolIndex++;
       Info.Kind = static_cast<uint32_t>(Symbol.Kind);