[WebAssembly] Fix local references to weak aliases

When weak aliases are used with in same translation
unit we need to be able to directly reference to alias
and not just the thing it is aliases.  We do this by
defining both a wasm import and a wasm export in this
case that result in a single Symbol.  This change is
a partial revert of rL314245.  A corresponding lld
change address the previous issues we had with this.

See: https://github.com/WebAssembly/tool-conventions/issues/34

Differential Revision: https://reviews.llvm.org/D41472

llvm-svn: 321242

1 files changed, 18 insertions, 9 deletions

diff --git a/llvm/lib/Object/WasmObjectFile.cpp b/llvm/lib/Object/WasmObjectFile.cpp
index 7a0c05ed8a1..d4c3b736d0e 100644
--- a/llvm/lib/Object/WasmObjectFile.cpp
+++ b/llvm/lib/Object/WasmObjectFile.cpp
@@ -303,7 +303,6 @@ Error WasmObjectFile::parseNameSection(const uint8_t *Ptr, const uint8_t *End) {
 
 void WasmObjectFile::populateSymbolTable() {
   // Add imports to symbol table
-  size_t ImportIndex = 0;
   size_t GlobalIndex = 0;
   size_t FunctionIndex = 0;
   for (const wasm::WasmImport& Import : Imports) {
@@ -312,7 +311,7 @@ void WasmObjectFile::populateSymbolTable() {
       assert(Import.Global.Type == wasm::WASM_TYPE_I32);
       SymbolMap.try_emplace(Import.Field, Symbols.size());
       Symbols.emplace_back(Import.Field, WasmSymbol::SymbolType::GLOBAL_IMPORT,
-                           ImportSection, GlobalIndex++, ImportIndex);
+                           ImportSection, GlobalIndex++);
       DEBUG(dbgs() << "Adding import: " << Symbols.back()
                    << " sym index:" << Symbols.size() << "\n");
       break;
@@ -320,14 +319,13 @@ void WasmObjectFile::populateSymbolTable() {
       SymbolMap.try_emplace(Import.Field, Symbols.size());
       Symbols.emplace_back(Import.Field,
                            WasmSymbol::SymbolType::FUNCTION_IMPORT,
-                           ImportSection, FunctionIndex++, ImportIndex);
+                           ImportSection, FunctionIndex++, Import.SigIndex);
       DEBUG(dbgs() << "Adding import: " << Symbols.back()
                    << " sym index:" << Symbols.size() << "\n");
       break;
     default:
       break;
     }
-    ImportIndex++;
   }
 
   // Add exports to symbol table
@@ -338,11 +336,22 @@ void WasmObjectFile::populateSymbolTable() {
           Export.Kind == wasm::WASM_EXTERNAL_FUNCTION
               ? WasmSymbol::SymbolType::FUNCTION_EXPORT
               : WasmSymbol::SymbolType::GLOBAL_EXPORT;
-      SymbolMap.try_emplace(Export.Name, Symbols.size());
-      Symbols.emplace_back(Export.Name, ExportType,
-                           ExportSection, Export.Index);
-      DEBUG(dbgs() << "Adding export: " << Symbols.back()
-                   << " sym index:" << Symbols.size() << "\n");
+      auto Pair = SymbolMap.try_emplace(Export.Name, Symbols.size());
+      if (Pair.second) {
+        Symbols.emplace_back(Export.Name, ExportType,
+                             ExportSection, Export.Index);
+        DEBUG(dbgs() << "Adding export: " << Symbols.back()
+                     << " sym index:" << Symbols.size() << "\n");
+      } else {
+        uint32_t SymIndex = Pair.first->second;
+        const WasmSymbol &OldSym = Symbols[SymIndex];
+        WasmSymbol NewSym(Export.Name, ExportType, ExportSection, Export.Index);
+        NewSym.setAltIndex(OldSym.ElementIndex);
+        Symbols[SymIndex] = NewSym;
+
+        DEBUG(dbgs() << "Replacing existing symbol:  " << NewSym
+                     << " sym index:" << SymIndex << "\n");
+      }
     }
   }
 }