Reland "[WebAssembly] Add visibility flag to Wasm symbol flags""

[sbc100]

Summary

Original change was rL319488.

This was reverted rL319602 due to a gcc 7.1 warning.

include/llvm/BinaryFormat/Wasm.h

 enum : unsigned {
   WASM_STACK_POINTER  = 0x1,
   WASM_SYMBOL_INFO    = 0x2,
   WASM_DATA_SIZE      = 0x3,
   WASM_DATA_ALIGNMENT = 0x4,
   WASM_SEGMENT_INFO   = 0x5,
 };
 
-const unsigned WASM_SYMBOL_BINDING_MASK = 0x3;
+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,
-};
+const unsigned WASM_SYMBOL_BINDING_GLOBAL     = 0x0;
+const unsigned WASM_SYMBOL_BINDING_WEAK       = 0x1;
+const unsigned WASM_SYMBOL_BINDING_LOCAL      = 0x2;
+const unsigned WASM_SYMBOL_VISIBILITY_DEFAULT = 0x0;
+const unsigned WASM_SYMBOL_VISIBILITY_HIDDEN  = 0x4;
 
 #define WASM_RELOC(name, value) name = value,
 
 enum : unsigned {
 #include "WasmRelocs/WebAssembly.def"
 };
 
 #undef WASM_RELOC

include/llvm/MC/MCSymbolWasm.h

 #include "llvm/MC/MCSymbol.h"
 
 namespace llvm {
 
 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;
   bool ParamsSet = false;
   bool ReturnsSet = false;
 
   /// An expression describing how to calculate the size of a symbol. If a
   /// symbol has no size this field will be NULL.
public:
   void setSize(const MCExpr *SS) { SymbolSize = SS; }
 
   bool isFunction() const { return IsFunction; }
   void setIsFunction(bool isFunc) { IsFunction = isFunc; }
 
   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 {
     assert(ReturnsSet);
     return Returns;
   }
 
   void setReturns(SmallVectorImpl<wasm::ValType> &&Rets) {

include/llvm/Object/Wasm.h

public:
   bool isLocal() const {
     return getBinding() == wasm::WASM_SYMBOL_BINDING_LOCAL;
   }
 
   unsigned getBinding() const {
     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
         << ", ImportIndex=" << ImportIndex;
   }
 
 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
   LLVM_DUMP_METHOD void dump() const { print(dbgs()); }

lib/MC/MCWasmStreamer.cpp

bool MCWasmStreamer::EmitSymbolAttribute(MCSymbol *S, MCSymbolAttr Attribute) {
   case MCSA_LazyReference:
   case MCSA_Reference:
   case MCSA_SymbolResolver:
   case MCSA_PrivateExtern:
   case MCSA_WeakDefinition:
   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);
     Symbol->setExternal(true);
     break;
 
   case MCSA_Global:
     Symbol->setExternal(true);

lib/MC/WasmObjectWriter.cpp

if (S.isTemporary() && S.getName().empty())
       continue;
 
     const auto &WS = static_cast<const MCSymbolWasm &>(S);
     DEBUG(dbgs() << "MCSymbol: '" << S << "'"
                  << " isDefined=" << S.isDefined() << " isExternal="
                  << 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;
 
     unsigned Index;
 
     if (WS.isFunction()) {
       if (WS.isDefined(/*SetUsed=*/false)) {

lib/Object/WasmObjectFile.cpp

case wasm::WASM_SYMBOL_INFO: {
               "Invalid symbol name in linking section: " + Symbol,
               object_error::parse_failed);
         }
         uint32_t SymIndex = iter->second;
         assert(SymIndex < Symbols.size());
         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;
     }
     case wasm::WASM_DATA_SIZE:
       LinkingData.DataSize = readVaruint32(Ptr);
       break;
     case wasm::WASM_SEGMENT_INFO: {
uint32_t WasmObjectFile::getSymbolFlags(DataRefImpl Symb) const {
   uint32_t Result = SymbolRef::SF_None;
   const WasmSymbol &Sym = getWasmSymbol(Symb);
 
   DEBUG(dbgs() << "getSymbolFlags: ptr=" << &Sym << " " << Sym << "\n");
   if (Sym.isWeak())
     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:
     Result |= SymbolRef::SF_Undefined | SymbolRef::SF_Executable;
     break;
   case WasmSymbol::SymbolType::FUNCTION_EXPORT:
     Result |= SymbolRef::SF_Executable;
     break;

test/MC/WebAssembly/visibility.ll

+; 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: ...