[lld][WebAssembly] Honor --no-export-dynamic even with -shared

[sbc100]

• add test

[ruiu]

LGTM

lld/test/wasm/shared-export-dynamic.ll

19–20

nit: delete trailing blank lines

lld/wasm/Driver.cpp

362

Maybe removing this temporary variable and directly using config->shared is little simpler?

[sbc100]

• feedback

[MaskRay]

This is a nice change! Unfortunately GNU linkers don't suppress symbols in -shared --no-export-dynamic mode...

lld/test/wasm/shared-export-dynamic.ll

+; RUN: llc -relocation-model=pic -filetype=obj %s -o %t.o
+
+; By default all `default` symbols should be exported
+; RUN: wasm-ld -shared -o %t.wasm %t.o
+; RUN: obj2yaml %t.wasm | FileCheck %s -check-prefix=DEFAULT
+; DEFAULT: foo
+
+; Verify that `--no-export-dynamic` works with `-shared`
+; RUN: wasm-ld -shared --no-export-dynamic -o %t2.wasm %t.o
+; RUN: obj2yaml %t2.wasm | FileCheck %s -check-prefix=NO-EXPORT
+; NO-EXPORT-NOT: foo
+
+target triple = "wasm32-unknown-emscripten"
+
+define default i32 @foo() {
+entry:
+  ret i32 0
+}
+
+

lld/wasm/Driver.cpp

static void readConfigs(opt::InputArgList &args) {
   config->checkFeatures =
       args.hasFlag(OPT_check_features, OPT_no_check_features, true);
   config->compressRelocations = args.hasArg(OPT_compress_relocations);
   config->demangle = args.hasFlag(OPT_demangle, OPT_no_demangle, true);
   config->disableVerify = args.hasArg(OPT_disable_verify);
   config->emitRelocs = args.hasArg(OPT_emit_relocs);
   config->entry = getEntry(args);
   config->exportAll = args.hasArg(OPT_export_all);
-  config->exportDynamic = args.hasFlag(OPT_export_dynamic,
-      OPT_no_export_dynamic, false);
   config->exportTable = args.hasArg(OPT_export_table);
   errorHandler().fatalWarnings =
       args.hasFlag(OPT_fatal_warnings, OPT_no_fatal_warnings, false);
   config->importMemory = args.hasArg(OPT_import_memory);
   config->sharedMemory = args.hasArg(OPT_shared_memory);
   config->passiveSegments = args.hasFlag(
       OPT_passive_segments, OPT_active_segments, config->sharedMemory);
   config->importTable = args.hasArg(OPT_import_table);
static void readConfigs(opt::InputArgList &args) {
   threadsEnabled = args.hasFlag(OPT_threads, OPT_no_threads, true);
 
   config->initialMemory = args::getInteger(args, OPT_initial_memory, 0);
   config->globalBase = args::getInteger(args, OPT_global_base, 1024);
   config->maxMemory = args::getInteger(args, OPT_max_memory, 0);
   config->zStackSize =
       args::getZOptionValue(args, OPT_z, "stack-size", WasmPageSize);
 
+  // exportDynamic default to true when building with `-shared`
+  bool exportDynamicDefault = config->shared;
+  config->exportDynamic = args.hasFlag(
+      OPT_export_dynamic, OPT_no_export_dynamic, exportDynamicDefault);
+
   if (auto *arg = args.getLastArg(OPT_features)) {
     config->features =
         llvm::Optional<std::vector<std::string>>(std::vector<std::string>());
     for (StringRef s : arg->getValues())
       config->features->push_back(s);
   }
 }
 
 // Some Config members do not directly correspond to any particular
 // command line options, but computed based on other Config values.
 // This function initialize such members. See Config.h for the details
 // of these values.
 static void setConfigs() {
   config->isPic = config->pie || config->shared;
 
   if (config->isPic) {
     if (config->exportTable)
       error("-shared/-pie is incompatible with --export-table");
     config->importTable = true;
   }
 
   if (config->shared) {
     config->importMemory = true;
-    config->exportDynamic = true;
     config->allowUndefined = true;
   }
 }
 
 // Some command line options or some combinations of them are not allowed.
 // This function checks for such errors.
 static void checkOptions(opt::InputArgList &args) {
   if (!config->stripDebug && !config->stripAll && config->compressRelocations)