3 files changed, 28 insertions, 2 deletions
diff --git a/mesonbuild/compilers/c.py b/mesonbuild/compilers/c.py
index e27eb90..f3ed9e8 100644
--- a/mesonbuild/compilers/c.py
+++ b/mesonbuild/compilers/c.py
@@ -133,7 +133,7 @@ class AppleClangCCompiler(ClangCCompiler):
     _C18_VERSION = '>=11.0.0'
 
 
-class EmscriptenCCompiler(BasicLinkerIsCompilerMixin, LinkerEnvVarsMixin, EmscriptenMixin, ClangCCompiler):
+class EmscriptenCCompiler(EmscriptenMixin, BasicLinkerIsCompilerMixin, LinkerEnvVarsMixin, ClangCCompiler):
     def __init__(self, exelist, version, for_machine: MachineChoice,
                  is_cross: bool, info: 'MachineInfo', exe_wrapper=None, **kwargs):
         if not is_cross:
diff --git a/mesonbuild/compilers/cpp.py b/mesonbuild/compilers/cpp.py
index f6f4cfc..2a244e9 100644
--- a/mesonbuild/compilers/cpp.py
+++ b/mesonbuild/compilers/cpp.py
@@ -201,7 +201,7 @@ class AppleClangCPPCompiler(ClangCPPCompiler):
     pass
 
 
-class EmscriptenCPPCompiler(BasicLinkerIsCompilerMixin, LinkerEnvVarsMixin, EmscriptenMixin, ClangCPPCompiler):
+class EmscriptenCPPCompiler(EmscriptenMixin, BasicLinkerIsCompilerMixin, LinkerEnvVarsMixin, ClangCPPCompiler):
     def __init__(self, exelist, version, for_machine: MachineChoice,
                  is_cross: bool, info: 'MachineInfo', exe_wrapper=None, **kwargs):
         if not is_cross:
diff --git a/mesonbuild/compilers/mixins/emscripten.py b/mesonbuild/compilers/mixins/emscripten.py
index 36a757a..ee86ce4 100644
--- a/mesonbuild/compilers/mixins/emscripten.py
+++ b/mesonbuild/compilers/mixins/emscripten.py
@@ -17,8 +17,13 @@
 import os.path
 import typing as T
 
+from ... import coredata
 from ...mesonlib import MesonException
 
+if T.TYPE_CHECKING:
+    from ..environment import Environment
+
+
 class EmscriptenMixin:
 
     def get_option_link_args(self, options):
@@ -45,3 +50,24 @@ class EmscriptenMixin:
         else:
             suffix = 'wasm'
         return os.path.join(dirname, 'output.' + suffix)
+
+    def thread_flags(self, env: 'Environment') -> T.List[str]:
+        return ['-s', 'USE_PTHREADS=1']
+
+    def thread_link_flags(self, env: 'Environment') -> T.List[str]:
+        args = ['-s', 'USE_PTHREADS=1']
+        count = env.coredata.compiler_options[self.for_machine]['{}_thread_count'.format(self.language)].value  # type: int
+        if count:
+            args.extend(['-s', 'PTHREAD_POOL_SIZE={}'.format(count)])
+        return args
+
+    def get_options(self):
+        opts = super().get_options()
+        opts.update({
+            '{}_thread_count'.format(self.language): coredata.UserIntegerOption(
+                'Number of threads to use in web assembly, set to 0 to disable',
+                (0, None, 4),  # Default was picked at random
+            ),
+        })
+
+        return opts