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[WebAssembly] Make tag attribute's encoding uint8 

This changes the encoding of the `attribute` field, which currently only
contains the value `0` denoting this tag is for an exception, from
`varuint32` to `uint8`. This field is effectively unused at the moment
and reserved for future use, and it is not likely to need `varuint32`
even in future.
See https://github.com/WebAssembly/exception-handling/pull/162.

This does not change any encoded binaries because `0` is encoded in the
same way both in `varuint32` and `uint8`.

Reviewed By: tlively

Differential Revision: https://reviews.llvm.org/D104571
This commit is contained in:
Heejin Ahn 2021-06-18 14:41:01 -07:00
parent bff2b9adbc
commit 1c7b841088
3 changed files with 6 additions and 6 deletions
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4
llvm/include/llvm/BinaryFormat/Wasm.h
View File

@ -103,7 +103,7 @@ struct WasmGlobal {
struct WasmTagType {
// Kind of tag. Currently only WASM_TAG_ATTRIBUTE_EXCEPTION is possible.
uint32_t Attribute;
uint8_t Attribute;
uint32_t SigIndex;
};
@ -363,7 +363,7 @@ enum WasmSegmentFlag : unsigned {
};
// Kinds of tag attributes.
enum WasmTagAttribute : unsigned {
enum WasmTagAttribute : uint8_t {
WASM_TAG_ATTRIBUTE_EXCEPTION = 0x0,
};

4
llvm/lib/MC/WasmObjectWriter.cpp
View File

@ -814,7 +814,7 @@ void WasmObjectWriter::writeImportSection(ArrayRef<wasm::WasmImport> Imports,
encodeULEB128(NumElements, W->OS); // initial
break;
case wasm::WASM_EXTERNAL_TAG:
encodeULEB128(Import.Tag.Attribute, W->OS);
W->OS << char(Import.Tag.Attribute);
encodeULEB128(Import.Tag.SigIndex, W->OS);
break;
default:
@ -848,7 +848,7 @@ void WasmObjectWriter::writeTagSection(ArrayRef<wasm::WasmTagType> Tags) {
encodeULEB128(Tags.size(), W->OS);
for (const wasm::WasmTagType &Tag : Tags) {
encodeULEB128(Tag.Attribute, W->OS);
W->OS << char(Tag.Attribute);
encodeULEB128(Tag.SigIndex, W->OS);
}

4
llvm/lib/Object/WasmObjectFile.cpp
View File

@ -1066,7 +1066,7 @@ Error WasmObjectFile::parseImportSection(ReadContext &Ctx) {
}
case wasm::WASM_EXTERNAL_TAG:
NumImportedTags++;
Im.Tag.Attribute = readVarint32(Ctx);
Im.Tag.Attribute = readUint8(Ctx);
Im.Tag.SigIndex = readVarint32(Ctx);
break;
default:
@ -1143,7 +1143,7 @@ Error WasmObjectFile::parseTagSection(ReadContext &Ctx) {
while (Count--) {
wasm::WasmTag Tag;
Tag.Index = NumImportedTags + Tags.size();
Tag.Type.Attribute = readVaruint32(Ctx);
Tag.Type.Attribute = readUint8(Ctx);
Tag.Type.SigIndex = readVaruint32(Ctx);
Tags.push_back(Tag);
}