[WebAssembly] Add support for weak symbols in the binary format

This also introduces the updated format for the
"linking" section which can represent extra
symbol information.  See:
https://github.com/WebAssembly/tool-conventions/pull/10

Differential Revision: https://reviews.llvm.org/D34019

llvm-svn: 305769

4 files changed, 70 insertions, 6 deletions

diff --git a/llvm/include/llvm/BinaryFormat/Wasm.h b/llvm/include/llvm/BinaryFormat/Wasm.h
index fcd8ad95704..470c20ddc7d 100644
--- a/llvm/include/llvm/BinaryFormat/Wasm.h
+++ b/llvm/include/llvm/BinaryFormat/Wasm.h
@@ -176,6 +176,11 @@ enum class ValType {
 // Linking metadata kinds.
 enum : unsigned {
   WASM_STACK_POINTER = 0x1,
+  WASM_SYMBOL_INFO  = 0x2,
+};
+
+enum : unsigned {
+  WASM_SYMBOL_FLAG_WEAK = 0x1,
 };
 
 #define WASM_RELOC(name, value) name = value,
diff --git a/llvm/include/llvm/MC/MCSymbolWasm.h b/llvm/include/llvm/MC/MCSymbolWasm.h
index 1b87095552d..7ea89629efd 100644
--- a/llvm/include/llvm/MC/MCSymbolWasm.h
+++ b/llvm/include/llvm/MC/MCSymbolWasm.h
@@ -17,6 +17,7 @@ namespace llvm {
 class MCSymbolWasm : public MCSymbol {
 private:
   bool IsFunction = false;
+  bool IsWeak = false;
   std::string ModuleName;
   SmallVector<wasm::ValType, 1> Returns;
   SmallVector<wasm::ValType, 4> Params;
@@ -39,6 +40,9 @@ public:
   bool isFunction() const { return IsFunction; }
   void setIsFunction(bool isFunc) { IsFunction = isFunc; }
 
+  bool isWeak() const { return IsWeak; }
+  void setWeak(bool isWeak) { IsWeak = isWeak; }
+
   const StringRef getModuleName() const { return ModuleName; }
 
   const SmallVector<wasm::ValType, 1> &getReturns() const { return Returns; }
diff --git a/llvm/include/llvm/Object/Wasm.h b/llvm/include/llvm/Object/Wasm.h
index 10edc461b9e..9d53131234f 100644
--- a/llvm/include/llvm/Object/Wasm.h
+++ b/llvm/include/llvm/Object/Wasm.h
@@ -19,6 +19,7 @@
 
 #include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/StringRef.h"
+#include "llvm/ADT/StringMap.h"
 #include "llvm/BinaryFormat/Wasm.h"
 #include "llvm/Object/Binary.h"
 #include "llvm/Object/ObjectFile.h"
@@ -48,7 +49,24 @@ public:
   StringRef Name;
   SymbolType Type;
   uint32_t Section;
+  uint32_t Flags = 0;
+
+  // Index into the imports, exports or functions array of the object depending
+  // on the type
   uint32_t ElementIndex;
+
+  bool isWeak() const {
+    return Flags & wasm::WASM_SYMBOL_FLAG_WEAK;
+  }
+
+  void print(raw_ostream &Out) const {
+    Out << "Name=" << Name << ", Type=" << static_cast<int>(Type)
+        << ", Flags=" << Flags;
+  }
+
+#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
+  LLVM_DUMP_METHOD void dump() const { print(dbgs()); }
+#endif
 };
 
 class WasmSection {
@@ -63,6 +81,7 @@ public:
 };
 
 class WasmObjectFile : public ObjectFile {
+
 public:
   WasmObjectFile(MemoryBufferRef Object, Error &Err);
 
@@ -176,6 +195,7 @@ private:
 
   // Custom section types
   Error parseNameSection(const uint8_t *Ptr, const uint8_t *End);
+  Error parseLinkingSection(const uint8_t *Ptr, const uint8_t *End);
   Error parseRelocSection(StringRef Name, const uint8_t *Ptr,
                           const uint8_t *End);
 
@@ -190,13 +210,22 @@ private:
   std::vector<wasm::WasmExport> Exports;
   std::vector<wasm::WasmElemSegment> ElemSegments;
   std::vector<wasm::WasmDataSegment> DataSegments;
-  std::vector<WasmSymbol> Symbols;
   std::vector<wasm::WasmFunction> Functions;
+  std::vector<WasmSymbol> Symbols;
   ArrayRef<uint8_t> CodeSection;
   uint32_t StartFunction = -1;
+
+  StringMap<uint32_t> SymbolMap;
 };
 
 } // end namespace object
+
+inline raw_ostream &operator<<(raw_ostream &OS,
+                               const object::WasmSymbol &Sym) {
+  Sym.print(OS);
+  return OS;
+}
+
 } // end namespace llvm
 
 #endif // LLVM_OBJECT_WASM_H
diff --git a/llvm/include/llvm/ObjectYAML/WasmYAML.h b/llvm/include/llvm/ObjectYAML/WasmYAML.h
index 447dbd7a603..74f5664c43a 100644
--- a/llvm/include/llvm/ObjectYAML/WasmYAML.h
+++ b/llvm/include/llvm/ObjectYAML/WasmYAML.h
@@ -112,8 +112,13 @@ struct Signature {
   ValueType ReturnType;
 };
 
+struct SymbolInfo {
+  StringRef Name;
+  uint32_t Flags;
+};
+
 struct Section {
-  Section(SectionType SecType) : Type(SecType) {}
+  explicit Section(SectionType SecType) : Type(SecType) {}
   virtual ~Section();
 
   SectionType Type;
@@ -121,20 +126,36 @@ struct Section {
 };
 
 struct CustomSection : Section {
-  CustomSection() : Section(wasm::WASM_SEC_CUSTOM) {}
+  explicit CustomSection(StringRef Name)
+      : Section(wasm::WASM_SEC_CUSTOM), Name(Name) {}
   static bool classof(const Section *S) {
     return S->Type == wasm::WASM_SEC_CUSTOM;
   }
 
   StringRef Name;
   yaml::BinaryRef Payload;
+};
+
+struct NameSection : CustomSection {
+  NameSection() : CustomSection("name") {}
+  static bool classof(const Section *S) {
+    auto C = dyn_cast<CustomSection>(S);
+    return C && C->Name == "name";
+  }
 
-  // The follow is used by the "name" custom section.
-  // TODO(sbc): Add support for more then just functions names.  The wasm
-  // name section can support multiple sub-sections.
   std::vector<NameEntry> FunctionNames;
 };
 
+struct LinkingSection : CustomSection {
+  LinkingSection() : CustomSection("linking") {}
+  static bool classof(const Section *S) {
+    auto C = dyn_cast<CustomSection>(S);
+    return C && C->Name == "linking";
+  }
+
+  std::vector<SymbolInfo> SymbolInfos;
+};
+
 struct TypeSection : Section {
   TypeSection() : Section(wasm::WASM_SEC_TYPE) {}
   static bool classof(const Section *S) {
@@ -256,6 +277,7 @@ LLVM_YAML_IS_SEQUENCE_VECTOR(llvm::WasmYAML::Function)
 LLVM_YAML_IS_SEQUENCE_VECTOR(llvm::WasmYAML::LocalDecl)
 LLVM_YAML_IS_SEQUENCE_VECTOR(llvm::WasmYAML::Relocation)
 LLVM_YAML_IS_SEQUENCE_VECTOR(llvm::WasmYAML::NameEntry)
+LLVM_YAML_IS_SEQUENCE_VECTOR(llvm::WasmYAML::SymbolInfo)
 LLVM_YAML_IS_FLOW_SEQUENCE_VECTOR(uint32_t)
 
 namespace llvm {
@@ -329,6 +351,10 @@ template <> struct MappingTraits<WasmYAML::ElemSegment> {
   static void mapping(IO &IO, WasmYAML::ElemSegment &Segment);
 };
 
+template <> struct MappingTraits<WasmYAML::SymbolInfo> {
+  static void mapping(IO &IO, WasmYAML::SymbolInfo &Info);
+};
+
 template <> struct ScalarEnumerationTraits<WasmYAML::ValueType> {
   static void enumeration(IO &IO, WasmYAML::ValueType &Type);
 };