[WebAssembly] Convert to new "dylink.0" section format

This format is based on sub-sections (like the "linking" and "name"
sections) and is therefore easier to extend going forward.

spec change: https://github.com/WebAssembly/tool-conventions/pull/170
binaryen change: https://github.com/WebAssembly/binaryen/pull/4141
wabt change:  https://github.com/WebAssembly/wabt/pull/1707
emscripten change: https://github.com/emscripten-core/emscripten/pull/15019

Differential Revision: https://reviews.llvm.org/D109595

1 files changed, 52 insertions, 1 deletions

diff --git a/llvm/lib/Object/WasmObjectFile.cpp b/llvm/lib/Object/WasmObjectFile.cpp
index 9a4e246..3b1392e 100644
--- a/llvm/lib/Object/WasmObjectFile.cpp
+++ b/llvm/lib/Object/WasmObjectFile.cpp
@@ -339,7 +339,8 @@ Error WasmObjectFile::parseSection(WasmSection &Sec) {
 }
 
 Error WasmObjectFile::parseDylinkSection(ReadContext &Ctx) {
-  // See https://github.com/WebAssembly/tool-conventions/blob/master/DynamicLinking.md
+  // Legacy "dylink" section support.
+  // See parseDylink0Section for the current "dylink.0" section parsing.
   HasDylinkSection = true;
   DylinkInfo.MemorySize = readVaruint32(Ctx);
   DylinkInfo.MemoryAlignment = readVaruint32(Ctx);
@@ -349,12 +350,58 @@ Error WasmObjectFile::parseDylinkSection(ReadContext &Ctx) {
   while (Count--) {
     DylinkInfo.Needed.push_back(readString(Ctx));
   }
+
   if (Ctx.Ptr != Ctx.End)
     return make_error<GenericBinaryError>("dylink section ended prematurely",
                                           object_error::parse_failed);
   return Error::success();
 }
 
+Error WasmObjectFile::parseDylink0Section(ReadContext &Ctx) {
+  // See
+  // https://github.com/WebAssembly/tool-conventions/blob/master/DynamicLinking.md
+  HasDylinkSection = true;
+
+  const uint8_t *OrigEnd = Ctx.End;
+  while (Ctx.Ptr < OrigEnd) {
+    Ctx.End = OrigEnd;
+    uint8_t Type = readUint8(Ctx);
+    uint32_t Size = readVaruint32(Ctx);
+    LLVM_DEBUG(dbgs() << "readSubsection type=" << int(Type) << " size=" << Size
+                      << "\n");
+    Ctx.End = Ctx.Ptr + Size;
+    uint32_t Count;
+    switch (Type) {
+    case wasm::WASM_DYLINK_MEM_INFO:
+      DylinkInfo.MemorySize = readVaruint32(Ctx);
+      DylinkInfo.MemoryAlignment = readVaruint32(Ctx);
+      DylinkInfo.TableSize = readVaruint32(Ctx);
+      DylinkInfo.TableAlignment = readVaruint32(Ctx);
+      break;
+    case wasm::WASM_DYLINK_NEEDED:
+      Count = readVaruint32(Ctx);
+      while (Count--) {
+        DylinkInfo.Needed.push_back(readString(Ctx));
+      }
+      break;
+    default:
+      return make_error<GenericBinaryError>("unknown dylink.0 sub-section",
+                                            object_error::parse_failed);
+      Ctx.Ptr += Size;
+      break;
+    }
+    if (Ctx.Ptr != Ctx.End) {
+      return make_error<GenericBinaryError>(
+          "dylink.0 sub-section ended prematurely", object_error::parse_failed);
+    }
+  }
+
+  if (Ctx.Ptr != Ctx.End)
+    return make_error<GenericBinaryError>("dylink.0 section ended prematurely",
+                                          object_error::parse_failed);
+  return Error::success();
+}
+
 Error WasmObjectFile::parseNameSection(ReadContext &Ctx) {
   llvm::DenseSet<uint64_t> SeenFunctions;
   llvm::DenseSet<uint64_t> SeenGlobals;
@@ -984,6 +1031,9 @@ Error WasmObjectFile::parseCustomSection(WasmSection &Sec, ReadContext &Ctx) {
   if (Sec.Name == "dylink") {
     if (Error Err = parseDylinkSection(Ctx))
       return Err;
+  } else if (Sec.Name == "dylink.0") {
+    if (Error Err = parseDylink0Section(Ctx))
+      return Err;
   } else if (Sec.Name == "name") {
     if (Error Err = parseNameSection(Ctx))
       return Err;
@@ -1793,6 +1843,7 @@ int WasmSectionOrderChecker::getSectionOrder(unsigned ID,
   case wasm::WASM_SEC_CUSTOM:
     return StringSwitch<unsigned>(CustomSectionName)
         .Case("dylink", WASM_SEC_ORDER_DYLINK)
+        .Case("dylink.0", WASM_SEC_ORDER_DYLINK)
         .Case("linking", WASM_SEC_ORDER_LINKING)
         .StartsWith("reloc.", WASM_SEC_ORDER_RELOC)
         .Case("name", WASM_SEC_ORDER_NAME)