Switch default backend from 'fastcomp' to 'upstream'

When users as for 'latest' or just '1.39.0' we now default to the
upstream llvm backend.

For versions before 1.39.0 we continue to default to fastcomp.

Fixes: emscripten-core/emscripten#5488

Author: sbc100

emsdk.py

@@ -1941,7 +1941,7 @@ def find_used_python():
 
 
 def version_key(ver):
-  return list(map(int, re.split('[._-]', ver)))
+  return tuple(map(int, re.split('[._-]', ver)))
 
 
 # A sort function that is compatible with both Python 2 and Python 3 using a
@@ -2710,14 +2710,29 @@ def extract_bool_arg(name):
 
   releases_info = load_releases_info()['releases']
 
+  def report_upstream_by_default():
+    print('''\
+** NOTICE **: The default SDK changed from `fastcomp` to `upstream`.
+If you have problems, or wish to revert back to fastcomp for some other reason
+you can add `-fastcomp` to explitly install that fastcomp-based
+SDK. .e.g ./emsdk install latest-fastcomp.
+''', file=sys.stderr)
+
   # Replace meta-packages with the real package names.
   if cmd in ('update', 'install', 'activate'):
     for i in range(2, len(sys.argv)):
       arg = sys.argv[i]
-      if arg in ('latest', 'sdk-latest', 'latest-64bit', 'sdk-latest-64bit', 'latest-fastcomp', 'latest-releases-fastcomp'):
+      if arg in ('latest', 'sdk-latest', 'latest-64bit', 'sdk-latest-64bit'):
+        # This is effectly the default SDK
+        report_upstream_by_default()
+        sys.argv[i] = str(find_latest_releases_sdk('upstream'))
+      elif arg in ('latest-fastcomp', 'latest-releases-fastcomp'):
         sys.argv[i] = str(find_latest_releases_sdk('fastcomp'))
       elif arg in ('latest-upstream', 'latest-clang-upstream', 'latest-releases-upstream'):
         sys.argv[i] = str(find_latest_releases_sdk('upstream'))
+      elif arg in ('tot', 'sdk-tot'):
+        report_upstream_by_default()
+        sys.argv[i] = str(find_tot_sdk('upstream'))
       elif arg == 'tot-upstream':
         sys.argv[i] = str(find_tot_sdk('upstream'))
       elif arg in ('tot-fastcomp', 'sdk-nightly-latest'):
@@ -2728,17 +2743,23 @@ def extract_bool_arg(name):
         #   x.y.z[-(upstream|fastcomp_])
         #   sdk-x.y.z[-(upstream|fastcomp_])-64bit
         # TODO: support short notation for old builds too?
-        upstream = False
+        backend = None
         if '-upstream' in arg:
           arg = arg.replace('-upstream', '')
-          upstream = True
+          backend = 'upstream'
         elif '-fastcomp' in arg:
           arg = arg.replace('-fastcomp', '')
-          upstream = False
+          backend = 'fastcomp'
         arg = arg.replace('sdk-', '').replace('-64bit', '').replace('tag-', '')
         release_hash = releases_info.get(arg, None) or releases_info.get('sdk-' + arg + '-64bit')
         if release_hash:
-          sys.argv[i] = 'sdk-releases-%s-%s-64bit' % ('upstream' if upstream else 'fastcomp', release_hash)
+          if backend is None:
+            if version_key(arg) >= (1, 39, 0):
+              report_upstream_by_default()
+              backend = 'upstream'
+            else:
+              backend = 'fastcomp'
+          sys.argv[i] = 'sdk-releases-%s-%s-64bit' % (backend, release_hash)
 
   if cmd == 'list':
     print('')
@@ -2747,12 +2768,12 @@ def extract_bool_arg(name):
       print('The *recommended* precompiled SDK download is %s (%s).' % (find_latest_releases_version(), find_latest_releases_hash()))
       print()
       print('To install/activate it, use one of:')
-      print('         latest                  [default (fastcomp) backend]')
-      print('         latest-upstream         [upstream LLVM wasm backend]')
+      print('         latest                  [default (llvm) backend]')
+      print('         latest-fastcomp         [legacy (fastcomp) backend]')
       print('')
       print('Those are equivalent to installing/activating the following:')
       print('         %s' % find_latest_releases_version())
-      print('         %s-upstream' % find_latest_releases_version())
+      print('         %s-fastcomp' % find_latest_releases_version())
       print('')
     else:
       print('Warning: your platform does not have precompiled SDKs available.')
@@ -2764,7 +2785,6 @@ def extract_bool_arg(name):
     releases_versions.reverse()
     for ver in releases_versions:
       print('         %s' % ver)
-      print('         %s-upstream' % ver)
     print()
 
     # Use array to work around the lack of being able to mutate from enclosing

test.py

@@ -61,8 +61,8 @@ def hack_emsdk(marker, replacement):
 # Tests
 
 print('test .emscripten contents (latest was installed/activated in test.sh)')
-assert 'fastcomp' in open(os.path.expanduser('~/.emscripten')).read()
-assert 'upstream' not in open(os.path.expanduser('~/.emscripten')).read()
+assert 'fastcomp' not in open(os.path.expanduser('~/.emscripten')).read()
+assert 'upstream' in open(os.path.expanduser('~/.emscripten')).read()
 
 print('building proper system libraries')
 
@@ -114,23 +114,22 @@ def run_emsdk(cmd):
 else:
   emsdk = './emsdk'
 
-test_lib_building(fastcomp_emcc, use_asmjs_optimizer=True)
+test_lib_building(upstream_emcc, use_asmjs_optimizer=True)
 
 print('update')
 run_emsdk('update-tags')
 
-print('test latest-releases-upstream')
-run_emsdk('install latest-upstream')
-run_emsdk('activate latest-upstream')
+print('test latest-releases-fastcomp')
+run_emsdk('install latest-fastcomp')
+run_emsdk('activate latest-fastcomp')
 
-test_lib_building(upstream_emcc, use_asmjs_optimizer=False)
+test_lib_building(fastcomp_emcc, use_asmjs_optimizer=False)
 assert open(os.path.expanduser('~/.emscripten')).read().count('LLVM_ROOT') == 1
-assert 'upstream' in open(os.path.expanduser('~/.emscripten')).read()
-assert 'fastcomp' not in open(os.path.expanduser('~/.emscripten')).read()
-
+assert 'upstream' not in open(os.path.expanduser('~/.emscripten')).read()
+assert 'fastcomp' in open(os.path.expanduser('~/.emscripten')).read()
 
 print('verify version')
-checked_call_with_output(upstream_emcc + ' -v', TAGS['latest'], stderr=subprocess.STDOUT)
+checked_call_with_output(fastcomp_emcc + ' -v', TAGS['latest'], stderr=subprocess.STDOUT)
 
 print('clear cache')
 check_call(upstream_emcc + ' --clear-cache')
@@ -160,8 +159,8 @@ def run_emsdk(cmd):
 print('another install must re-download')
 checked_call_with_output(emsdk + ' install 1.38.33', expected='Downloading:', unexpected='already exist in destination')
 run_emsdk('activate 1.38.33')
-assert 'fastcomp' in open(os.path.expanduser('~/.emscripten')).read()
-assert 'upstream' not in open(os.path.expanduser('~/.emscripten')).read()
+assert 'upstream' in open(os.path.expanduser('~/.emscripten')).read()
+assert 'fastcomp' not in open(os.path.expanduser('~/.emscripten')).read()
 
 print('test specific release (new, full name)')
 run_emsdk('install sdk-1.38.33-upstream-64bit')