[clang][WebAssembly] Link crt1 even in case of -shared

This allows -mexec-model=reactor -shared produces a library module
with _initialize entrypoint, which is preferrable over __wasm_call_ctors.

This partially reverts https://reviews.llvm.org/D153293

Discussion: dicej/component-linking-demo#3

Reviewed By: sbc100

Differential Revision: https://reviews.llvm.org/D156205

clang/lib/Driver/ToolChains/WebAssembly.cpp

@@ -77,31 +77,43 @@ void wasm::Linker::ConstructJob(Compilation &C, const JobAction &JA,
   Args.AddAllArgs(CmdArgs, options::OPT_u);
   ToolChain.AddFilePathLibArgs(Args, CmdArgs);
 
-  const char *Crt1 = "crt1.o";
+  bool IsCommand = true;
+  const char *Crt1;
   const char *Entry = nullptr;
 
-  // If crt1-command.o exists, it supports new-style commands, so use it.
-  // Otherwise, use the old crt1.o. This is a temporary transition measure.
-  // Once WASI libc no longer needs to support LLVM versions which lack
-  // support for new-style command, it can make crt1.o the same as
-  // crt1-command.o. And once LLVM no longer needs to support WASI libc
-  // versions before that, it can switch to using crt1-command.o.
-  if (ToolChain.GetFilePath("crt1-command.o") != "crt1-command.o")
-    Crt1 = "crt1-command.o";
+  // When -shared is specified, use the reactor exec model unless
+  // specified otherwise.
+  if (Args.hasArg(options::OPT_shared))
+    IsCommand = false;
 
   if (const Arg *A = Args.getLastArg(options::OPT_mexec_model_EQ)) {
     StringRef CM = A->getValue();
     if (CM == "command") {
-      // Use default values.
+      IsCommand = true;
     } else if (CM == "reactor") {
-      Crt1 = "crt1-reactor.o";
-      Entry = "_initialize";
+      IsCommand = false;
     } else {
       ToolChain.getDriver().Diag(diag::err_drv_invalid_argument_to_option)
           << CM << A->getOption().getName();
     }
   }
-  if (!Args.hasArg(options::OPT_nostdlib, options::OPT_nostartfiles, options::OPT_shared))
+
+  if (IsCommand) {
+    // If crt1-command.o exists, it supports new-style commands, so use it.
+    // Otherwise, use the old crt1.o. This is a temporary transition measure.
+    // Once WASI libc no longer needs to support LLVM versions which lack
+    // support for new-style command, it can make crt1.o the same as
+    // crt1-command.o. And once LLVM no longer needs to support WASI libc
+    // versions before that, it can switch to using crt1-command.o.
+    Crt1 = "crt1.o";
+    if (ToolChain.GetFilePath("crt1-command.o") != "crt1-command.o")
+      Crt1 = "crt1-command.o";
+  } else {
+    Crt1 = "crt1-reactor.o";
+    Entry = "_initialize";
+  }
+
+  if (!Args.hasArg(options::OPT_nostdlib, options::OPT_nostartfiles))
     CmdArgs.push_back(Args.MakeArgString(ToolChain.GetFilePath(Crt1)));
   if (Entry) {
     CmdArgs.push_back(Args.MakeArgString("--entry"));

clang/test/Driver/wasm-toolchain.c

@@ -33,19 +33,19 @@
 // LINK_KNOWN: "-cc1" {{.*}} "-o" "[[temp:[^"]*]]"
 // LINK_KNOWN: wasm-ld{{.*}}" "-L/foo/lib/wasm32-wasi" "crt1.o" "[[temp]]" "-lc" "{{.*[/\\]}}libclang_rt.builtins-wasm32.a" "-o" "a.out"
 
-// -shared should be passed through to `wasm-ld` and not include crt1.o with a known OS.
+// -shared should be passed through to `wasm-ld` and include crt1-reactor.o with a known OS.
 
-// RUN: %clang -### -shared --target=wasm32-wasi --sysroot=/foo %s 2>&1 \
+// RUN: %clang -### -shared -mexec-model=reactor --target=wasm32-wasi --sysroot=/foo %s 2>&1 \
 // RUN:   | FileCheck -check-prefix=LINK_KNOWN_SHARED %s
 // LINK_KNOWN_SHARED: "-cc1" {{.*}} "-o" "[[temp:[^"]*]]"
-// LINK_KNOWN_SHARED: wasm-ld{{.*}}" "-L/foo/lib/wasm32-wasi" "-shared" "[[temp]]" "-lc" "{{.*[/\\]}}libclang_rt.builtins-wasm32.a" "-o" "a.out"
+// LINK_KNOWN_SHARED: wasm-ld{{.*}}" "-L/foo/lib/wasm32-wasi" "crt1-reactor.o" "--entry" "_initialize" "-shared" "[[temp]]" "-lc" "{{.*[/\\]}}libclang_rt.builtins-wasm32.a" "-o" "a.out"
 
-// -shared should be passed through to `wasm-ld` and not include crt1.o with an unknown OS.
+// -shared should be passed through to `wasm-ld` and include crt1-reactor.o with an unknown OS.
 
-// RUN: %clang -### -shared --target=wasm32-unknown-unknown --sysroot=/foo %s 2>&1 \
+// RUN: %clang -### -shared -mexec-model=reactor --target=wasm32-unknown-unknown --sysroot=/foo %s 2>&1 \
 // RUN:   | FileCheck -check-prefix=LINK_UNKNOWN_SHARED %s
 // LINK_UNKNOWN_SHARED: "-cc1" {{.*}} "-o" "[[temp:[^"]*]]"
-// LINK_UNKNOWN_SHARED: wasm-ld{{.*}}" "-shared" "[[temp]]" "-lc" "{{.*[/\\]}}libclang_rt.builtins-wasm32.a" "-o" "a.out"
+// LINK_UNKNOWN_SHARED: wasm-ld{{.*}}" "crt1-reactor.o" "--entry" "_initialize" "-shared" "[[temp]]" "-lc" "{{.*[/\\]}}libclang_rt.builtins-wasm32.a" "-o" "a.out"
 
 // A basic C link command-line with optimization with known OS.