[WebAssembly][Object] Record section start offsets at start of payload (#76188)

LLVM ObjectFile currently records the start offsets of sections as the
start of the section header, whereas most other tools (WABT, emscripten,
wasm-tools) record it as the start of the section content, after the
header. This affects binutils tools such as objdump and nm, but not
compilation/assembly (since that is driven by symbols and assembler
labels which already have their values inside the section payload rather
in the header. This patch updates LLVM to match the other tools.

1 files changed, 1 insertions, 1 deletions

diff --git a/llvm/lib/Object/WasmObjectFile.cpp b/llvm/lib/Object/WasmObjectFile.cpp
index 05bd730..dfe86a4 100644
--- a/llvm/lib/Object/WasmObjectFile.cpp
+++ b/llvm/lib/Object/WasmObjectFile.cpp
@@ -265,7 +265,6 @@ static wasm::WasmTableType readTableType(WasmObjectFile::ReadContext &Ctx) {
 
 static Error readSection(WasmSection &Section, WasmObjectFile::ReadContext &Ctx,
                          WasmSectionOrderChecker &Checker) {
-  Section.Offset = Ctx.Ptr - Ctx.Start;
   Section.Type = readUint8(Ctx);
   LLVM_DEBUG(dbgs() << "readSection type=" << Section.Type << "\n");
   // When reading the section's size, store the size of the LEB used to encode
@@ -273,6 +272,7 @@ static Error readSection(WasmSection &Section, WasmObjectFile::ReadContext &Ctx,
   const uint8_t *PreSizePtr = Ctx.Ptr;
   uint32_t Size = readVaruint32(Ctx);
   Section.HeaderSecSizeEncodingLen = Ctx.Ptr - PreSizePtr;
+  Section.Offset = Ctx.Ptr - Ctx.Start;
   if (Size == 0)
     return make_error<StringError>("zero length section",
                                    object_error::parse_failed);