Only link crtbegin library when building with pthreads enabled (#26690)

In particular the function defined in this library are not needed when
building with just `-sWASM_WORKERS`.

Author: sbc100

.circleci/config.yml

@@ -216,7 +216,7 @@ commands:
           command: |
             ls -l ~/cache/sysroot/lib/wasm32-emscripten || echo "no build"
             ls -l ~/cache/sysroot/include/emscripten/heap.h
-            cat ~/cache/sysroot/lib/wasm32-emscripten/crtbegin.o.ccache-log
+            cat ~/cache/sysroot/lib/wasm32-emscripten/crtbegin-mt.o.ccache-log
             date
             cat ~/cache/build/libcompiler_rt/absvdi2.o.ccache-log
             ccache -s

embuilder.py

@@ -91,7 +91,7 @@
     'libstandalonewasm-nocatch',
     'crt1',
     'crt1_proxy_main',
-    'crtbegin',
+    'crtbegin-mt',
     'libunwind-legacyexcept',
     'libunwind-wasmexcept',
     'libnoexit',
@@ -117,7 +117,7 @@
     'libGL-mt-emu-webgl2-getprocaddr',
     'libGL-mt-emu-webgl2-ofb-getprocaddr',
     'libsockets_proxy',
-    'crtbegin',
+    'crtbegin-mt',
     'libsanitizer_common_rt',
     'libubsan_rt',
     'libwasm_workers-debug',

test/codesize/audio_worklet_wasm.expected.js

@@ -229,12 +229,12 @@ function ha(a) {
 function y() {
     Z = {
         g: ha,
-        b: Q,
+        c: Q,
         h: R,
         e: aa,
         i: ba,
         f: ca,
-        c: da,
+        b: da,
         a: v,
         d: fa
     };

test/codesize/hello_wasm_worker_wasm.expected.js

@@ -55,10 +55,10 @@ function B() {
 
 function k() {
     E = {
-        e: t,
+        d: t,
         c: w,
         b: x,
-        d: y,
+        e: y,
         f: A,
         g: B,
         a: g

test/codesize/test_minimal_runtime_code_size_audio_worklet.json

@@ -4,7 +4,7 @@
   "a.js": 4446,
   "a.js.gz": 2299,
   "a.wasm": 1393,
-  "a.wasm.gz": 933,
+  "a.wasm.gz": 931,
   "total": 6354,
-  "total_gz": 3587
+  "total_gz": 3585
 }

test/codesize/test_minimal_runtime_code_size_hello_wasm_worker.json

@@ -3,8 +3,8 @@
   "a.html.gz": 355,
   "a.js": 952,
   "a.js.gz": 601,
-  "a.wasm": 2638,
+  "a.wasm": 2640,
   "a.wasm.gz": 1476,
-  "total": 4105,
+  "total": 4107,
   "total_gz": 2432
 }

tools/system_libs.py

@@ -1609,8 +1609,10 @@ def can_use(self):
     return super().can_use() and settings.PROXY_TO_PTHREAD
 
 
-class crtbegin(MuslInternalLibrary):
-  name = 'crtbegin'
+class crtbegin_mt(MuslInternalLibrary):
+  # This library defines _emscripten_tls_init/_emscripten_tls_free which are linked into
+  # every module (i.e. not just the main module).
+  name = 'crtbegin-mt'
   cflags = ['-pthread']
   src_dir = 'system/lib/pthread'
   src_files = ['emscripten_tls_init.c']
@@ -1621,7 +1623,7 @@ def get_ext(self):
     return '.o'
 
   def can_use(self):
-    return super().can_use() and settings.SHARED_MEMORY
+    return super().can_use() and settings.PTHREADS
 
 
 class libcxxabi(ExceptionLibrary, MTLibrary, DebugLibrary):
@@ -2331,8 +2333,8 @@ def add_library(libname, whole_archive=False):
     libs_to_link.append((lib.get_link_flag(), whole_archive or need_whole_archive))
 
   if not options.nostartfiles:
-    if settings.SHARED_MEMORY:
-      add_library('crtbegin')
+    if settings.PTHREADS:
+      add_library('crtbegin-mt')
 
     if not settings.SIDE_MODULE:
       if settings.STANDALONE_WASM: