[lld][WebAssembly] Fix bitcode LTO order in archive parsing

lld/test/wasm/lto/Inputs/comdat_ordering1.ll

@@ -0,0 +1,42 @@
+target datalayout = "e-m:e-p:32:32-p10:8:8-p20:8:8-i64:64-n32:64-S128"
+target triple = "wasm32-unknown-unknown"
+
+; Generated from this C++ code and simplified manually:
+;
+; int foo();
+; inline int unused = foo();
+;
+; int main() {
+;   return foo();
+; }
+
+$unused = comdat any
+
+@unused = linkonce_odr global i32 0, comdat, align 4
+@_ZGV6unused = linkonce_odr global i32 0, comdat($unused), align 4
+@llvm.global_ctors = appending global [1 x { i32, ptr, ptr }] [{ i32, ptr, ptr } { i32 65535, ptr @__cxx_global_var_init, ptr @unused }]
+
+define internal void @__cxx_global_var_init() comdat($unused) {
+entry:
+  %0 = load i8, ptr @_ZGV6unused, align 4
+  %1 = and i8 %0, 1
+  %guard.uninitialized = icmp eq i8 %1, 0
+  br i1 %guard.uninitialized, label %init.check, label %init.end
+
+init.check:                                       ; preds = %entry
+  store i8 1, ptr @_ZGV6unused, align 4
+  %call = call i32 @foo()
+  store i32 %call, ptr @unused, align 4
+  br label %init.end
+
+init.end:                                         ; preds = %init.check, %entry
+  ret void
+}
+
+declare i32 @foo()
+
+define i32 @main() {
+entry:
+  %call = call i32 @foo()
+  ret i32 %call
+}

lld/test/wasm/lto/Inputs/comdat_ordering2.ll

@@ -0,0 +1,39 @@
+target datalayout = "e-m:e-p:32:32-p10:8:8-p20:8:8-i64:64-n32:64-S128"
+target triple = "wasm32-unknown-unknown"
+
+; Generated from this C++ code and simplified manually:
+;
+; int foo();
+; inline int unused = foo();
+;
+; int foo() {
+;   return 42;
+; }
+
+$unused = comdat any
+
+@unused = linkonce_odr global i32 0, comdat, align 4
+@_ZGV6unused = linkonce_odr global i32 0, comdat($unused), align 4
+@llvm.global_ctors = appending global [1 x { i32, ptr, ptr }] [{ i32, ptr, ptr } { i32 65535, ptr @__cxx_global_var_init, ptr @unused }]
+
+define internal void @__cxx_global_var_init() comdat($unused) {
+entry:
+  %0 = load i8, ptr @_ZGV6unused, align 4
+  %1 = and i8 %0, 1
+  %guard.uninitialized = icmp eq i8 %1, 0
+  br i1 %guard.uninitialized, label %init.check, label %init.end
+
+init.check:                                       ; preds = %entry
+  store i8 1, ptr @_ZGV6unused, align 4
+  %call = call i32 @foo()
+  store i32 %call, ptr @unused, align 4
+  br label %init.end
+
+init.end:                                         ; preds = %init.check, %entry
+  ret void
+}
+
+define i32 @foo() {
+entry:
+  ret i32 42
+}

lld/test/wasm/lto/comdat_ordering.test

@@ -0,0 +1,19 @@
+; Check if we handle a variable (here __cxx_global_var_init) in different LTO
+; bitcode modules sharing a comdat.
+
+; RUN: llvm-as %S/Inputs/comdat_ordering1.ll -o %t1.o
+; RUN: llvm-as %S/Inputs/comdat_ordering2.ll -o %t2.o
+; RUN: llvm-ar rcs %t1.a %t1.o
+; RUN: llvm-ar rcs %t2.a %t2.o
+; RUN: wasm-ld %t1.a %t2.a -o %t.wasm --no-entry --export=main --export=__wasm_call_ctors
+; RUN: obj2yaml %t.wasm | FileCheck %s
+
+; CHECK:       - Type:            CUSTOM
+; CHECK-NEXT:    Name:            name
+; CHECK-NEXT:    FunctionNames:
+; CHECK-NEXT:      - Index:           0
+; CHECK-NEXT:        Name:            __wasm_call_ctors
+; CHECK-NEXT:      - Index:           1
+; CHECK-NEXT:        Name:            __cxx_global_var_init
+
+; CHECK-NOT:         Name:            __cxx_global_var_init.2

lld/wasm/SymbolTable.cpp

@@ -50,8 +50,10 @@ void SymbolTable::addFile(InputFile *file, StringRef symName) {
 
   // LLVM bitcode file
   if (auto *f = dyn_cast<BitcodeFile>(file)) {
-    f->parse(symName);
+    // This order, first adding to `bitcodeFiles` and then parsing is necessary.
+    // See https://github.com/llvm/llvm-project/pull/73095
     bitcodeFiles.push_back(f);
+    f->parse(symName);
     return;
   }