[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

3 files changed, 13 insertions, 10 deletions

diff --git a/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyAsmBackend.cpp b/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyAsmBackend.cpp
index 70b409cf4a9..8314de41021 100644
--- a/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyAsmBackend.cpp
+++ b/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyAsmBackend.cpp
@@ -31,10 +31,12 @@ namespace {
 
 class WebAssemblyAsmBackend final : public MCAsmBackend {
   bool Is64Bit;
+  bool IsEmscripten;
 
 public:
-  explicit WebAssemblyAsmBackend(bool Is64Bit)
-      : MCAsmBackend(support::little), Is64Bit(Is64Bit) {}
+  explicit WebAssemblyAsmBackend(bool Is64Bit, bool IsEmscripten)
+      : MCAsmBackend(support::little), Is64Bit(Is64Bit),
+        IsEmscripten(IsEmscripten) {}
 
   unsigned getNumFixupKinds() const override {
     return WebAssembly::NumTargetFixupKinds;
@@ -123,11 +125,11 @@ void WebAssemblyAsmBackend::applyFixup(const MCAssembler &Asm,
 
 std::unique_ptr<MCObjectTargetWriter>
 WebAssemblyAsmBackend::createObjectTargetWriter() const {
-  return createWebAssemblyWasmObjectWriter(Is64Bit);
+  return createWebAssemblyWasmObjectWriter(Is64Bit, IsEmscripten);
 }
 
 } // end anonymous namespace
 
 MCAsmBackend *llvm::createWebAssemblyAsmBackend(const Triple &TT) {
-  return new WebAssemblyAsmBackend(TT.isArch64Bit());
+  return new WebAssemblyAsmBackend(TT.isArch64Bit(), TT.isOSEmscripten());
 }
diff --git a/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyMCTargetDesc.h b/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyMCTargetDesc.h
index 7a9f59b1a4f..f2f3d20a98e 100644
--- a/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyMCTargetDesc.h
+++ b/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyMCTargetDesc.h
@@ -38,7 +38,7 @@ MCCodeEmitter *createWebAssemblyMCCodeEmitter(const MCInstrInfo &MCII);
 MCAsmBackend *createWebAssemblyAsmBackend(const Triple &TT);
 
 std::unique_ptr<MCObjectTargetWriter>
-createWebAssemblyWasmObjectWriter(bool Is64Bit);
+createWebAssemblyWasmObjectWriter(bool Is64Bit, bool IsEmscripten);
 
 namespace WebAssembly {
 enum OperandType {
diff --git a/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyWasmObjectWriter.cpp b/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyWasmObjectWriter.cpp
index f424b722b83..e7a599e3e17 100644
--- a/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyWasmObjectWriter.cpp
+++ b/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyWasmObjectWriter.cpp
@@ -31,7 +31,7 @@ using namespace llvm;
 namespace {
 class WebAssemblyWasmObjectWriter final : public MCWasmObjectTargetWriter {
 public:
-  explicit WebAssemblyWasmObjectWriter(bool Is64Bit);
+  explicit WebAssemblyWasmObjectWriter(bool Is64Bit, bool IsEmscripten);
 
 private:
   unsigned getRelocType(const MCValue &Target,
@@ -39,8 +39,9 @@ private:
 };
 } // end anonymous namespace
 
-WebAssemblyWasmObjectWriter::WebAssemblyWasmObjectWriter(bool Is64Bit)
-    : MCWasmObjectTargetWriter(Is64Bit) {}
+WebAssemblyWasmObjectWriter::WebAssemblyWasmObjectWriter(bool Is64Bit,
+                                                         bool IsEmscripten)
+    : MCWasmObjectTargetWriter(Is64Bit, IsEmscripten) {}
 
 static const MCSection *getFixupSection(const MCExpr *Expr) {
   if (auto SyExp = dyn_cast<MCSymbolRefExpr>(Expr)) {
@@ -116,6 +117,6 @@ unsigned WebAssemblyWasmObjectWriter::getRelocType(const MCValue &Target,
 }
 
 std::unique_ptr<MCObjectTargetWriter>
-llvm::createWebAssemblyWasmObjectWriter(bool Is64Bit) {
-  return std::make_unique<WebAssemblyWasmObjectWriter>(Is64Bit);
+llvm::createWebAssemblyWasmObjectWriter(bool Is64Bit, bool IsEmscripten) {
+  return std::make_unique<WebAssemblyWasmObjectWriter>(Is64Bit, IsEmscripten);
 }