[WebAssembly] Add new `export_name` clang attribute for controlling wasm export names

This is equivalent to the existing `import_name` and `import_module`
attributes which control the import names in the final wasm binary
produced by lld.

This maps the existing

This attribute currently requires a string rather than using the
symbol name for a couple of reasons:

1. Avoid confusion with static and dynamic linking which is
   based on symbol name.  Exporting a function from a wasm module using
   this directive is orthogonal to both static and dynamic linking.
2. Avoids name mangling.

Differential Revision: https://reviews.llvm.org/D70520

1 files changed, 12 insertions, 0 deletions

diff --git a/llvm/lib/Target/WebAssembly/AsmParser/WebAssemblyAsmParser.cpp b/llvm/lib/Target/WebAssembly/AsmParser/WebAssemblyAsmParser.cpp
index 138ce85..1f0bdde 100644
--- a/llvm/lib/Target/WebAssembly/AsmParser/WebAssemblyAsmParser.cpp
+++ b/llvm/lib/Target/WebAssembly/AsmParser/WebAssemblyAsmParser.cpp
@@ -712,6 +712,18 @@ public:
       return expect(AsmToken::EndOfStatement, "EOL");
     }
 
+    if (DirectiveID.getString() == ".export_name") {
+      auto SymName = expectIdent();
+      if (SymName.empty())
+        return true;
+      if (expect(AsmToken::Comma, ","))
+        return true;
+      auto ExportName = expectIdent();
+      auto WasmSym = cast<MCSymbolWasm>(Ctx.getOrCreateSymbol(SymName));
+      WasmSym->setExportName(ExportName);
+      TOut.emitExportName(WasmSym, ExportName);
+    }
+
     if (DirectiveID.getString() == ".import_module") {
       auto SymName = expectIdent();
       if (SymName.empty())