Remove PTHREAD_HINT_NUM_CORES (#10166)

We can assume almost all browsers have
navigator.hardwareConcurrency these days, and
basically all those where we can use pthreads (so
not IE11).

Author: kripken

site/source/docs/porting/pthreads.rst

@@ -18,8 +18,7 @@ Compiling with pthreads enabled
 By default, support for pthreads is not enabled. To enable code generation for pthreads, the following command line flags exist:
 
 - Pass the compiler flag ``-s USE_PTHREADS=1`` when compiling any .c/.cpp files, AND when linking to generate the final output .js file.
-- Optionally, pass the linker flag ``-s PTHREAD_POOL_SIZE=<integer>`` to specify a predefined pool of web workers to populate at page preRun time before application main() is called. This is important because if the workers do not already exist then we may need to wait for the next browser event iteration for certain things, see below. (If -1 is passed to both PTHREAD_POOL_SIZE and PTHREAD_HINT_NUM_CORES, then a popup dialog will ask the user the size of the pool, which is useful for testing.)
-- Optionally, pass the linker flag ``-s PTHREAD_HINT_NUM_CORES=<integer>`` to choose what the function emscripten_num_logical_cores(); will return if navigator.hardwareConcurrency is not supported. If -1 is specified here, a popup dialog will be shown at startup to let the user specify the value that is returned here. This can be helpful in order to dynamically test how an application behaves with different values here.
+- Optionally, pass the linker flag ``-s PTHREAD_POOL_SIZE=<integer>`` to specify a predefined pool of web workers to populate at page preRun time before application main() is called. This is important because if the workers do not already exist then we may need to wait for the next browser event iteration for certain things, see below.
 
 There should be no other changes required. In C/C++ code, the preprocessor check ``#ifdef __EMSCRIPTEN_PTHREADS__`` can be used to detect whether Emscripten is currently targeting pthreads.
 

src/library_pthread.js

@@ -582,20 +582,12 @@ var LibraryPThread = {
     }
   },
 
-  _num_logical_cores__deps: ['emscripten_force_num_logical_cores'],
-  _num_logical_cores: '{{{ makeStaticAlloc(4) }}}; HEAPU32[__num_logical_cores>>2] = navigator["hardwareConcurrency"] || ' + {{{ PTHREAD_HINT_NUM_CORES }}},
-
   emscripten_has_threading_support: function() {
     return typeof SharedArrayBuffer !== 'undefined';
   },
 
-  emscripten_num_logical_cores__deps: ['_num_logical_cores'],
   emscripten_num_logical_cores: function() {
-    return {{{ makeGetValue('__num_logical_cores', 0, 'i32') }}};
-  },
-
-  emscripten_force_num_logical_cores: function(cores) {
-    {{{ makeSetValue('__num_logical_cores', 0, 'cores', 'i32') }}};
+    return navigator['hardwareConcurrency'];
   },
 
   {{{ USE_LSAN || USE_ASAN ? 'emscripten_builtin_' : '' }}}pthread_create__deps: ['_spawn_thread', 'pthread_getschedparam', 'pthread_self', 'memalign'],

src/preamble.js

@@ -780,43 +780,6 @@ var memoryInitializer = null;
 #include "memoryprofiler.js"
 #endif
 
-#if USE_PTHREADS && PTHREAD_HINT_NUM_CORES < 0
-if (!ENVIRONMENT_IS_PTHREAD) addOnPreRun(function() {
-  addRunDependency('pthreads_querycores');
-
-  var bg = document.createElement('div');
-  bg.style = "position: absolute; top: 0%; left: 0%; width: 100%; height: 100%; background-color: black; z-index:1001; -moz-opacity: 0.8; opacity:.80; filter: alpha(opacity=80);";
-  var div = document.createElement('div');
-  var default_num_cores = navigator.hardwareConcurrency || 4;
-  var hwConcurrency = navigator.hardwareConcurrency ? ("says " + navigator.hardwareConcurrency) : "is not available";
-  var html = '<div style="width: 100%; text-align:center;"> Thread setup</div> <br /> Number of logical cores: <input type="number" style="width: 50px;" value="'
-    + default_num_cores + '" min="1" max="32" id="thread_setup_num_logical_cores"></input> <br /><span style="font-size: 75%;">(<span style="font-family: monospace;">navigator.hardwareConcurrency</span> '
-    + hwConcurrency + ')</span> <br />';
-#if PTHREAD_POOL_SIZE < 0
-  html += 'PThread pool size: <input type="number" style="width: 50px;" value="'
-    + default_num_cores + '" min="1" max="32" id="thread_setup_pthread_pool_size"></input> <br />';
-#endif
-  html += ' <br /> <input type="button" id="thread_setup_button_go" value="Go"></input>';
-  div.innerHTML = html;
-  div.style = 'position: absolute; top: 35%; left: 35%; width: 30%; height: 150px; padding: 16px; border: 16px solid gray; background-color: white; z-index:1002; overflow: auto;';
-  document.body.appendChild(bg);
-  document.body.appendChild(div);
-  var goButton = document.getElementById('thread_setup_button_go');
-  goButton.onclick = function() {
-    var num_logical_cores = parseInt(document.getElementById('thread_setup_num_logical_cores').value);
-    _emscripten_force_num_logical_cores(num_logical_cores);
-#if PTHREAD_POOL_SIZE < 0
-    var pthread_pool_size = parseInt(document.getElementById('thread_setup_pthread_pool_size').value);
-    PThread.allocateUnusedWorkers(pthread_pool_size, function() { removeRunDependency('pthreads_querycores'); });
-#else
-    removeRunDependency('pthreads_querycores');
-#endif
-    document.body.removeChild(bg);
-    document.body.removeChild(div);
-  }
-});
-#endif
-
 #if PTHREAD_POOL_SIZE > 0 && PTHREAD_POOL_DELAY_LOAD != 1
 // To work around https://bugzilla.mozilla.org/show_bug.cgi?id=1049079, warm up a worker pool before starting up the application.
 if (!ENVIRONMENT_IS_PTHREAD) addOnPreRun(function() { if (typeof SharedArrayBuffer !== 'undefined') { addRunDependency('pthreads'); PThread.allocateUnusedWorkers({{{PTHREAD_POOL_SIZE}}}, function() { removeRunDependency('pthreads'); }); }});

src/settings.js

@@ -1393,11 +1393,6 @@ var PTHREAD_POOL_DELAY_LOAD = 0;
 // local vars in asm.js/wasm code.
 var DEFAULT_PTHREAD_STACK_SIZE = 2*1024*1024;
 
-// Specifies the value returned by the function emscripten_num_logical_cores()
-// if navigator.hardwareConcurrency is not supported. Pass in a negative number
-// to show a popup dialog at startup so the user can configure this dynamically.
-var PTHREAD_HINT_NUM_CORES = 4;
-
 // True when building with --threadprofiler
 var PTHREADS_PROFILING = 0;
 

tests/pthread/test_pthread_num_logical_cores.cpp

@@ -3819,11 +3819,6 @@ def test_pthread_iostream(self):
   def test_pthread_setspecific_mainthread(self):
     self.btest(path_from_root('tests', 'pthread', 'test_pthread_setspecific_mainthread.cpp'), expected='0', args=['-s', 'TOTAL_MEMORY=64MB', '-O3', '-s', 'USE_PTHREADS=1'], also_asmjs=True)
 
-  # Test the -s PTHREAD_HINT_NUM_CORES=x command line variable.
-  @requires_threads
-  def test_pthread_num_logical_cores(self):
-    self.btest(path_from_root('tests', 'pthread', 'test_pthread_num_logical_cores.cpp'), expected='0', args=['-O3', '-s', 'USE_PTHREADS=1', '-s', 'PTHREAD_HINT_NUM_CORES=2'], also_asmjs=True)
-
   # Test that pthreads have access to filesystem.
   @requires_threads
   def test_pthread_file_io(self):