Add initial support for code metadata (#1840)

See https://github.com/WebAssembly/tool-conventions/blob/main/CodeMetadata.md  for the specification.

In particular this pr implements the following:

- Parsing code metadata sections in BinaryReader, providing appropriate callbacks that a BinaryReaderDelegate can implement:
    - BinaryReaderObjdump: show the sections in a human-readable form
    - BinaryReaderIr: add code metadata in the IR as expressions
- Parsing code metadata annotations in text format, adding them in the IR like the BinaryReaderIR does
- Writing the code metadata present in the IR in the proper sections when converting IR to binary
- Support in wasm-decompiler for showing code metadata as comments in the pseudo-code

All the features have corresponding tests.

Support for code metadata is gated through the --enable-code-metadata feature. For reading/writing in the text format, --enable-annotations is also required.

Missing features:

    Support for function-level code metadata (offset 0)
    Extensive validation in validator.cc (like making sure that all metadata instances are at the same code offset of an instruction)

1 files changed, 2 insertions, 0 deletions

diff --git a/src/expr-visitor.h b/src/expr-visitor.h
index ab7dc9e4..e00c487d 100644
--- a/src/expr-visitor.h
+++ b/src/expr-visitor.h
@@ -76,6 +76,7 @@ class ExprVisitor::Delegate {
   virtual Result OnCallExpr(CallExpr*) = 0;
   virtual Result OnCallIndirectExpr(CallIndirectExpr*) = 0;
   virtual Result OnCallRefExpr(CallRefExpr*) = 0;
+  virtual Result OnCodeMetadataExpr(CodeMetadataExpr*) = 0;
   virtual Result OnCompareExpr(CompareExpr*) = 0;
   virtual Result OnConstExpr(ConstExpr*) = 0;
   virtual Result OnConvertExpr(ConvertExpr*) = 0;
@@ -149,6 +150,7 @@ class ExprVisitor::DelegateNop : public ExprVisitor::Delegate {
   Result OnCallExpr(CallExpr*) override { return Result::Ok; }
   Result OnCallIndirectExpr(CallIndirectExpr*) override { return Result::Ok; }
   Result OnCallRefExpr(CallRefExpr*) override { return Result::Ok; }
+  Result OnCodeMetadataExpr(CodeMetadataExpr*) override { return Result::Ok; }
   Result OnCompareExpr(CompareExpr*) override { return Result::Ok; }
   Result OnConstExpr(ConstExpr*) override { return Result::Ok; }
   Result OnConvertExpr(ConvertExpr*) override { return Result::Ok; }