[WebAssembly] Model weakly defined symbols as wasm exports

Previously these were being included as both imports and
exports, with the import being satisfied by the export
(or some strong symbol) at runtime.  However proved
unnecessary and actually complicated linking as it meant
there was not a 1-to-1 mapping between a wasm function
/global index and a linker symbol.

Differential Revision: https://reviews.llvm.org/D38246

llvm-svn: 314245

diff --git a/llvm/lib/MC/WasmObjectWriter.cpp b/llvm/lib/MC/WasmObjectWriter.cpp
index f17801a..d7a9895 100644 (file)
--- a/llvm/lib/MC/WasmObjectWriter.cpp
+++ b/llvm/lib/MC/WasmObjectWriter.cpp
@@ -1036,7 +1036,7 @@ void WasmObjectWriter::writeObject(MCAssembler &Asm,
       registerFunctionType(WS);
 
     // If the symbol is not defined in this translation unit, import it.
-    if (!WS.isDefined(/*SetUsed=*/false) || WS.isVariable()) {
+    if (!WS.isDefined(/*SetUsed=*/false)) {
       WasmImport Import;
       Import.ModuleName = WS.getModuleName();
       Import.FieldName = WS.getName();
@@ -1268,6 +1268,7 @@ void WasmObjectWriter::writeObject(MCAssembler &Asm,
     uint32_t Index = SymbolIndices.find(ResolvedSym)->second;
     DEBUG(dbgs() << "  -> index:" << Index << "\n");
 
+    SymbolIndices[&WS] = Index;
     WasmExport Export;
     Export.FieldName = WS.getName();
     Export.Index = Index;

diff --git a/llvm/lib/Object/WasmObjectFile.cpp b/llvm/lib/Object/WasmObjectFile.cpp
index c320b91..1954335 100644 (file)
--- a/llvm/lib/Object/WasmObjectFile.cpp
+++ b/llvm/lib/Object/WasmObjectFile.cpp
@@ -337,19 +337,11 @@ void WasmObjectFile::populateSymbolTable() {
           Export.Kind == wasm::WASM_EXTERNAL_FUNCTION
               ? WasmSymbol::SymbolType::FUNCTION_EXPORT
               : WasmSymbol::SymbolType::GLOBAL_EXPORT;
-      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;
-        Symbols[SymIndex] =
-            WasmSymbol(Export.Name, ExportType, ExportSection, Export.Index);
-        DEBUG(dbgs() << "Replacing existing symbol:  " << Symbols[SymIndex]
-                     << " sym index:" << SymIndex << "\n");
-      }
+      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");
     }
   }
 }

diff --git a/llvm/test/MC/WebAssembly/weak-alias.ll b/llvm/test/MC/WebAssembly/weak-alias.ll
index 8db83e4..bdaaef7 100644 (file)
--- a/llvm/test/MC/WebAssembly/weak-alias.ll
+++ b/llvm/test/MC/WebAssembly/weak-alias.ll
@@ -29,42 +29,48 @@ entry:
 ; CHECK-NEXT:       - Index:           0
 ; CHECK-NEXT:         ReturnType:      I32
 ; CHECK-NEXT:         ParamTypes:      
-
-; CHECK:        - Type:            IMPORT
-; CHECK-NEXT:     Imports:         
-; CHECK-NEXT:       - Module:          env
-; CHECK-NEXT:         Field:           foo_alias
-; CHECK-NEXT:         Kind:            FUNCTION
-; CHECK-NEXT:         SigIndex:        0
-; CHECK-NEXT:       - Module:          env
-; CHECK-NEXT:         Field:           bar_alias
-; CHECK-NEXT:         Kind:            GLOBAL
-; CHECK-NEXT:         GlobalType:      I32
-; CHECK-NEXT:         GlobalMutable:   false
-
-; CHECK:        - Type:            FUNCTION
+; CHECK-NEXT:   - Type:            FUNCTION
 ; CHECK-NEXT:     FunctionTypes:   [ 0, 0 ]
-
-; CHECK:        - Type:            EXPORT
+; CHECK-NEXT:   - Type:            TABLE
+; CHECK-NEXT:     Tables:          
+; CHECK-NEXT:       - ElemType:        ANYFUNC
+; CHECK-NEXT:         Limits:          
+; CHECK-NEXT:           Initial:         0x00000000
+; CHECK-NEXT:   - Type:            MEMORY
+; CHECK-NEXT:     Memories:        
+; CHECK-NEXT:       - Initial:         0x00000001
+; CHECK-NEXT:   - Type:            GLOBAL
+; CHECK-NEXT:     Globals:         
+; CHECK-NEXT:       - Type:            I32
+; CHECK-NEXT:         Mutable:         false
+; CHECK-NEXT:         InitExpr:        
+; CHECK-NEXT:           Opcode:          I32_CONST
+; CHECK-NEXT:           Value:           0
+; CHECK-NEXT:       - Type:            I32
+; CHECK-NEXT:         Mutable:         false
+; CHECK-NEXT:         InitExpr:        
+; CHECK-NEXT:           Opcode:          I32_CONST
+; CHECK-NEXT:           Value:           8
+; CHECK-NEXT:   - Type:            EXPORT
 ; CHECK-NEXT:     Exports:         
 ; CHECK-NEXT:       - Name:            call_alias
 ; CHECK-NEXT:         Kind:            FUNCTION
-; CHECK-NEXT:         Index:           1
+; CHECK-NEXT:         Index:           0
 ; CHECK-NEXT:       - Name:            foo
 ; CHECK-NEXT:         Kind:            FUNCTION
-; CHECK-NEXT:         Index:           2
+; CHECK-NEXT:         Index:           1
 ; CHECK-NEXT:       - Name:            bar
 ; CHECK-NEXT:         Kind:            GLOBAL
-; CHECK-NEXT:         Index:           1
+; CHECK-NEXT:         Index:           0
 ; CHECK-NEXT:       - Name:            bar_alias_address
 ; CHECK-NEXT:         Kind:            GLOBAL
-; CHECK-NEXT:         Index:           2
+; CHECK-NEXT:         Index:           1
 ; CHECK-NEXT:       - Name:            foo_alias
 ; CHECK-NEXT:         Kind:            FUNCTION
-; CHECK-NEXT:         Index:           2
+; CHECK-NEXT:         Index:           1
 ; CHECK-NEXT:       - Name:            bar_alias
 ; CHECK-NEXT:         Kind:            GLOBAL
-; CHECK-NEXT:         Index:           1
+; CHECK-NEXT:         Index:           0
 
 ; CHECK:        - Type:            DATA
 ; CHECK-NEXT:     Relocations:     
@@ -89,10 +95,8 @@ entry:
 ; CHECK-NEXT:     Name:            name
 ; CHECK-NEXT:     FunctionNames:   
 ; CHECK-NEXT:       - Index:           0
-; CHECK-NEXT:         Name:            foo_alias
-; CHECK-NEXT:       - Index:           1
 ; CHECK-NEXT:         Name:            call_alias
-; CHECK-NEXT:       - Index:           2
+; CHECK-NEXT:       - Index:           1
 ; CHECK-NEXT:         Name:            foo
 ; CHECK-NEXT:   - Type:            CUSTOM
 ; CHECK-NEXT:     Name:            linking
@@ -111,12 +115,11 @@ entry:
 ; CHECK-NEXT: ...
 
 ; CHECK-SYMS: SYMBOL TABLE:
-; CHECK-SYMS-NEXT: 00000000 g     F name       foo_alias
-; CHECK-SYMS-NEXT: 00000001 g     F name       call_alias
-; CHECK-SYMS-NEXT: 00000002 g     F name       foo
-; CHECK-SYMS-NEXT: 00000002 gw    F EXPORT     foo_alias
-; CHECK-SYMS-NEXT: 00000000 gw      EXPORT     bar_alias
-; CHECK-SYMS-NEXT: 00000001 g     F EXPORT     call_alias
-; CHECK-SYMS-NEXT: 00000002 g     F EXPORT     foo
+; CHECK-SYMS-NEXT: 00000000 g     F name       call_alias
+; CHECK-SYMS-NEXT: 00000001 g     F name       foo
+; CHECK-SYMS-NEXT: 00000000 g     F EXPORT     call_alias
+; CHECK-SYMS-NEXT: 00000001 g     F EXPORT     foo
 ; CHECK-SYMS-NEXT: 00000000 g       EXPORT     bar
 ; CHECK-SYMS-NEXT: 00000008 g       EXPORT     bar_alias_address
+; CHECK-SYMS-NEXT: 00000001 gw    F EXPORT     foo_alias
+; CHECK-SYMS-NEXT: 00000000 gw      EXPORT     bar_alias