[WebAssembly] Make __attribute__((used)) not imply export.

Add an WASM_SYMBOL_NO_STRIP flag, so that __attribute__((used)) doesn't
need to imply exporting. When targeting Emscripten, have
WASM_SYMBOL_NO_STRIP imply exporting.

Differential Revision: https://reviews.llvm.org/D62542

llvm-svn: 370415

1 files changed, 7 insertions, 2 deletions

diff --git a/llvm/lib/MC/WasmObjectWriter.cpp b/llvm/lib/MC/WasmObjectWriter.cpp
index cb00241715a..53618887bb5 100644
--- a/llvm/lib/MC/WasmObjectWriter.cpp
+++ b/llvm/lib/MC/WasmObjectWriter.cpp
@@ -258,6 +258,7 @@ class WasmObjectWriter : public MCObjectWriter {
 
   // TargetObjectWriter wrappers.
   bool is64Bit() const { return TargetObjectWriter->is64Bit(); }
+  bool isEmscripten() const { return TargetObjectWriter->isEmscripten(); }
 
   void startSection(SectionBookkeeping &Section, unsigned SectionId);
   void startCustomSection(SectionBookkeeping &Section, StringRef Name);
@@ -1443,8 +1444,12 @@ uint64_t WasmObjectWriter::writeObject(MCAssembler &Asm,
       Flags |= wasm::WASM_SYMBOL_BINDING_LOCAL;
     if (WS.isUndefined())
       Flags |= wasm::WASM_SYMBOL_UNDEFINED;
-    if (WS.isExported())
-      Flags |= wasm::WASM_SYMBOL_EXPORTED;
+    if (WS.isNoStrip()) {
+      Flags |= wasm::WASM_SYMBOL_NO_STRIP;
+      if (isEmscripten()) {
+        Flags |= wasm::WASM_SYMBOL_EXPORTED;
+      }
+    }
     if (WS.getName() != WS.getImportName())
       Flags |= wasm::WASM_SYMBOL_EXPLICIT_NAME;