[WebAssembly] Support parsing .lto_set_conditional

llvm/lib/MC/WasmObjectWriter.cpp

@@ -1785,6 +1785,18 @@ uint64_t WasmObjectWriter::writeOneObject(MCAssembler &Asm,
       WS.setIndex(InvalidIndex);
       continue;
     }
+    // In bitcode generated by split-LTO-unit mode in ThinLTO, these lines can
+    // appear:
+    // module asm ".lto_set_conditional symbolA,symbolA.[moduleId]"
+    // ...
+    // (Here [moduleId] will be replaced by a real module hash ID)
+    //
+    // Here the original symbol (symbolA here) has been renamed to the new name
+    // created by attaching its module ID, so the original symbol does not
+    // appear in the bitcode anymore, and thus not in DataLocations. We should
+    // ignore them.
+    if (WS.isData() && WS.isDefined() && !DataLocations.count(&WS))
+      continue;
     LLVM_DEBUG(dbgs() << "adding to symtab: " << WS << "\n");
 
     uint32_t Flags = 0;

llvm/test/MC/WebAssembly/lto-set-conditional.s

@@ -0,0 +1,8 @@
+# RUN: llvm-mc -triple=wasm32-unknown-unknown
+
+# Tests if `.lto_set_conditional` directives are parsed without crashing.
+.lto_set_conditional a, a.new
+.type  a.new,@function
+a.new:
+  .functype  a.new () -> ()
+  end_function