Add visibility flag to Wasm symbol flags

The LLVM "hidden" flag needs to be passed through the Wasm
intermediate objects in order for the linker to apply
it to the final Wasm object.

The corresponding change in LLD is here: https://github.com/WebAssembly/lld/pull/14

Patch by Nicholas Wilson

Differential Revision: https://reviews.llvm.org/D40442

llvm-svn: 319488

diff --git a/llvm/include/llvm/BinaryFormat/Wasm.h b/llvm/include/llvm/BinaryFormat/Wasm.h
index 26475c2..f3a5802 100644 (file)
--- a/llvm/include/llvm/BinaryFormat/Wasm.h
+++ b/llvm/include/llvm/BinaryFormat/Wasm.h
@@ -190,11 +190,15 @@ enum : unsigned {
 };
 
 const unsigned WASM_SYMBOL_BINDING_MASK = 0x3;
+const unsigned WASM_SYMBOL_VISIBILITY_MASK = 0x4;
 
 enum : unsigned {
   WASM_SYMBOL_BINDING_GLOBAL = 0x0,
   WASM_SYMBOL_BINDING_WEAK   = 0x1,
   WASM_SYMBOL_BINDING_LOCAL  = 0x2,
+
+  WASM_SYMBOL_VISIBILITY_DEFAULT = 0x0,
+  WASM_SYMBOL_VISIBILITY_HIDDEN = 0x4,
 };
 
 #define WASM_RELOC(name, value) name = value,

diff --git a/llvm/include/llvm/MC/MCSymbolWasm.h b/llvm/include/llvm/MC/MCSymbolWasm.h
index 9bae6c5..309ebf9 100644 (file)
--- a/llvm/include/llvm/MC/MCSymbolWasm.h
+++ b/llvm/include/llvm/MC/MCSymbolWasm.h
@@ -18,6 +18,7 @@ class MCSymbolWasm : public MCSymbol {
 private:
   bool IsFunction = false;
   bool IsWeak = false;
+  bool IsHidden = false;
   std::string ModuleName;
   SmallVector<wasm::ValType, 1> Returns;
   SmallVector<wasm::ValType, 4> Params;
@@ -45,6 +46,9 @@ public:
   bool isWeak() const { return IsWeak; }
   void setWeak(bool isWeak) { IsWeak = isWeak; }
 
+  bool isHidden() const { return IsHidden; }
+  void setHidden(bool isHidden) { IsHidden = isHidden; }
+
   const StringRef getModuleName() const { return ModuleName; }
 
   const SmallVector<wasm::ValType, 1> &getReturns() const {

diff --git a/llvm/include/llvm/Object/Wasm.h b/llvm/include/llvm/Object/Wasm.h
index e138fae..504f1b4 100644 (file)
--- a/llvm/include/llvm/Object/Wasm.h
+++ b/llvm/include/llvm/Object/Wasm.h
@@ -81,6 +81,14 @@ public:
     return Flags & wasm::WASM_SYMBOL_BINDING_MASK;
   }
 
+  bool isHidden() const {
+    return getVisibility() == wasm::WASM_SYMBOL_VISIBILITY_HIDDEN;
+  }
+
+  unsigned getVisibility() const {
+    return Flags & wasm::WASM_SYMBOL_VISIBILITY_MASK;
+  }
+
   void print(raw_ostream &Out) const {
     Out << "Name=" << Name << ", Type=" << static_cast<int>(Type)
         << ", Flags=" << Flags << " ElemIndex=" << ElementIndex

diff --git a/llvm/lib/MC/MCWasmStreamer.cpp b/llvm/lib/MC/MCWasmStreamer.cpp
index 287b7cf..ef2a562 100644 (file)
--- a/llvm/lib/MC/MCWasmStreamer.cpp
+++ b/llvm/lib/MC/MCWasmStreamer.cpp
@@ -98,10 +98,13 @@ bool MCWasmStreamer::EmitSymbolAttribute(MCSymbol *S, MCSymbolAttr Attribute) {
   case MCSA_WeakDefAutoPrivate:
   case MCSA_Invalid:
   case MCSA_IndirectSymbol:
-  case MCSA_Hidden:
   case MCSA_Protected:
     return false;
 
+  case MCSA_Hidden:
+    Symbol->setHidden(true);
+    break;
+
   case MCSA_Weak:
   case MCSA_WeakReference:
     Symbol->setWeak(true);

diff --git a/llvm/lib/MC/WasmObjectWriter.cpp b/llvm/lib/MC/WasmObjectWriter.cpp
index 6e9088b..42521ac 100644 (file)
--- a/llvm/lib/MC/WasmObjectWriter.cpp
+++ b/llvm/lib/MC/WasmObjectWriter.cpp
@@ -1180,10 +1180,14 @@ void WasmObjectWriter::writeObject(MCAssembler &Asm,
                  << S.isExternal() << " isTemporary=" << S.isTemporary()
                  << " isFunction=" << WS.isFunction()
                  << " isWeak=" << WS.isWeak()
+                 << " isHidden=" << WS.isHidden()
                  << " isVariable=" << WS.isVariable() << "\n");
 
-    if (WS.isWeak())
-      SymbolFlags.emplace_back(WS.getName(), wasm::WASM_SYMBOL_BINDING_WEAK);
+    if (WS.isWeak() || WS.isHidden()) {
+      uint32_t Flags = (WS.isWeak() ? wasm::WASM_SYMBOL_BINDING_WEAK : 0) |
+          (WS.isHidden() ? wasm::WASM_SYMBOL_VISIBILITY_HIDDEN : 0);
+      SymbolFlags.emplace_back(WS.getName(), Flags);
+    }
 
     if (WS.isVariable())
       continue;

diff --git a/llvm/lib/Object/WasmObjectFile.cpp b/llvm/lib/Object/WasmObjectFile.cpp
index 86ce9c2..70ac598 100644 (file)
--- a/llvm/lib/Object/WasmObjectFile.cpp
+++ b/llvm/lib/Object/WasmObjectFile.cpp
@@ -378,7 +378,7 @@ Error WasmObjectFile::parseLinkingSection(const uint8_t *Ptr,
         Symbols[SymIndex].Flags = Flags;
         DEBUG(dbgs() << "Set symbol flags index:"
                      << SymIndex << " name:"
-                     << Symbols[SymIndex].Name << " exptected:"
+                     << Symbols[SymIndex].Name << " expected:"
                      << Symbol << " flags: " << Flags << "\n");
       }
       break;
@@ -766,6 +766,8 @@ uint32_t WasmObjectFile::getSymbolFlags(DataRefImpl Symb) const {
     Result |= SymbolRef::SF_Weak;
   if (!Sym.isLocal())
     Result |= SymbolRef::SF_Global;
+  if (Sym.isHidden())
+    Result |= SymbolRef::SF_Hidden;
 
   switch (Sym.Type) {
   case WasmSymbol::SymbolType::FUNCTION_IMPORT:

diff --git a/llvm/test/MC/WebAssembly/visibility.ll b/llvm/test/MC/WebAssembly/visibility.ll
new file mode 100644 (file)
index 0000000..b445bf4
--- /dev/null
+++ b/llvm/test/MC/WebAssembly/visibility.ll
@@ -0,0 +1,23 @@
+; RUN: llc -mtriple wasm32-unknown-unknown-wasm -filetype=obj %s -o - | obj2yaml | FileCheck %s
+
+; Function with __attribute__((visibility("default")))
+define void @defaultVis() #0 {
+entry:
+  ret void
+}
+
+; Function with __attribute__((visibility("hidden")))
+define hidden void @hiddenVis() #0 {
+entry:
+  ret void
+}
+
+; CHECK:        - Type:            CUSTOM
+
+; CHECK:        - Type:            CUSTOM
+; CHECK-NEXT:     Name:            linking
+; CHECK-NEXT:     DataSize:        0
+; CHECK-NEXT:     SymbolInfo:
+; CHECK-NEXT:       - Name:            hiddenVis
+; CHECK-NEXT:         Flags:           4
+; CHECK-NEXT: ...