[WebAssembly] Add support for init functions linking metadata

Summary:
This change lays the groundwork lowering of @llvm.global_ctors
and @llvm.global_dtors for the wasm object format.  Some parts
of this patch are subset of: https://reviews.llvm.org/D40759

See https://github.com/WebAssembly/tool-conventions/issues/25

Subscribers: jfb, dschuff, jgravelle-google, aheejin, sunfish

Differential Revision: https://reviews.llvm.org/D41208

llvm-svn: 320742

2 files changed, 27 insertions, 1 deletions

diff --git a/llvm/lib/Object/WasmObjectFile.cpp b/llvm/lib/Object/WasmObjectFile.cpp
index 8d4c15abc7f..677fccc6299 100644
--- a/llvm/lib/Object/WasmObjectFile.cpp
+++ b/llvm/lib/Object/WasmObjectFile.cpp
@@ -398,6 +398,21 @@ Error WasmObjectFile::parseLinkingSection(const uint8_t *Ptr,
       }
       break;
     }
+    case wasm::WASM_INIT_FUNCS: {
+      uint32_t Count = readVaruint32(Ptr);
+      LinkingData.InitFunctions.reserve(Count);
+      for (uint32_t i = 0; i < Count; i++) {
+        wasm::WasmInitFunc Init;
+        Init.Priority = readVaruint32(Ptr);
+        Init.FunctionIndex = readVaruint32(Ptr);
+        if (!isValidFunctionIndex(Init.FunctionIndex))
+          return make_error<GenericBinaryError>("Invalid function index: " +
+                                                    Twine(Init.FunctionIndex),
+                                                object_error::parse_failed);
+        LinkingData.InitFunctions.emplace_back(Init);
+      }
+      break;
+    }
     default:
       Ptr += Size;
       break;
@@ -656,9 +671,13 @@ Error WasmObjectFile::parseExportSection(const uint8_t *Ptr, const uint8_t *End)
   return Error::success();
 }
 
+bool WasmObjectFile::isValidFunctionIndex(uint32_t Index) const {
+  return Index < FunctionTypes.size() + NumImportedFunctions;
+}
+
 Error WasmObjectFile::parseStartSection(const uint8_t *Ptr, const uint8_t *End) {
   StartFunction = readVaruint32(Ptr);
-  if (StartFunction >= FunctionTypes.size())
+  if (!isValidFunctionIndex(StartFunction))
     return make_error<GenericBinaryError>("Invalid start function",
                                           object_error::parse_failed);
   return Error::success();
diff --git a/llvm/lib/ObjectYAML/WasmYAML.cpp b/llvm/lib/ObjectYAML/WasmYAML.cpp
index c206a682b83..8687f22949a 100644
--- a/llvm/lib/ObjectYAML/WasmYAML.cpp
+++ b/llvm/lib/ObjectYAML/WasmYAML.cpp
@@ -60,6 +60,7 @@ static void sectionMapping(IO &IO, WasmYAML::LinkingSection &Section) {
   IO.mapRequired("DataSize", Section.DataSize);
   IO.mapOptional("SymbolInfo", Section.SymbolInfos);
   IO.mapOptional("SegmentInfo", Section.SegmentInfos);
+  IO.mapOptional("InitFunctions", Section.InitFunctions);
 }
 
 static void sectionMapping(IO &IO, WasmYAML::CustomSection &Section) {
@@ -359,6 +360,12 @@ void MappingTraits<WasmYAML::DataSegment>::mapping(
   IO.mapRequired("Content", Segment.Content);
 }
 
+void MappingTraits<WasmYAML::InitFunction>::mapping(
+    IO &IO, WasmYAML::InitFunction &Init) {
+  IO.mapRequired("Priority", Init.Priority);
+  IO.mapRequired("FunctionIndex", Init.FunctionIndex);
+}
+
 void MappingTraits<WasmYAML::SymbolInfo>::mapping(IO &IO,
                                                   WasmYAML::SymbolInfo &Info) {
   IO.mapRequired("Name", Info.Name);