Reland: "[lld][WebAssembly] Initial support merging string data"

This change was originally landed in: 5000a1b4b9edeb9e994f2a5b36da8d48599bea49
It was reverted in: 061e071d8c9b98526f35cad55a918a4f1615afd4

This change adds support for a new WASM_SEG_FLAG_STRINGS flag in
the object format which works in a similar fashion to SHF_STRINGS
in the ELF world.

Unlike the ELF linker this support is currently limited:
- No support for SHF_MERGE (non-string merging)
- Always do full tail merging ("lo" can be merged with "hello")
- Only support single byte strings (p2align 0)

Like the ELF linker merging is only performed at `-O1` and above.

This fixes part of https://bugs.llvm.org/show_bug.cgi?id=48828,
although crucially it doesn't not currently support debug sections
because they are not represented by data segments (they are custom
sections)

Differential Revision: https://reviews.llvm.org/D97657

1 files changed, 2 insertions, 2 deletions

diff --git a/llvm/lib/Object/WasmObjectFile.cpp b/llvm/lib/Object/WasmObjectFile.cpp
index 946721a..df64a46 100644
--- a/llvm/lib/Object/WasmObjectFile.cpp
+++ b/llvm/lib/Object/WasmObjectFile.cpp
@@ -462,7 +462,7 @@ Error WasmObjectFile::parseLinkingSection(ReadContext &Ctx) {
       for (uint32_t I = 0; I < Count; I++) {
         DataSegments[I].Data.Name = readString(Ctx);
         DataSegments[I].Data.Alignment = readVaruint32(Ctx);
-        DataSegments[I].Data.LinkerFlags = readVaruint32(Ctx);
+        DataSegments[I].Data.LinkingFlags = readVaruint32(Ctx);
       }
       break;
     }
@@ -1431,7 +1431,7 @@ Error WasmObjectFile::parseDataSection(ReadContext &Ctx) {
     // The rest of these Data fields are set later, when reading in the linking
     // metadata section.
     Segment.Data.Alignment = 0;
-    Segment.Data.LinkerFlags = 0;
+    Segment.Data.LinkingFlags = 0;
     Segment.Data.Comdat = UINT32_MAX;
     Segment.SectionOffset = Ctx.Ptr - Ctx.Start;
     Ctx.Ptr += Size;