[lit] Use multiprocessing by default on Windows

Apparently nobody evaluated multiprocessing on Windows since Daniel
enabled multiprocessing on Unix in r193279. It works so far as I can
tell.

Today this is worth about an 8x speedup (631.29s to 73.25s) on my 24
core Windows machine. Hopefully this will improve Windows buildbot cycle
time, where currently it takes more time to run check-all than it does
to self-host with assertions enabled:
http://lab.llvm.org:8011/builders/clang-x86-windows-msvc2015/builds/20
  build stage 2 ninja all ( 28 mins, 22 secs )
  ninja check 2 stage 2   ( 37 mins, 38 secs )

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@280382 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/utils/lit/lit/main.py b/utils/lit/lit/main.py
index 50927e2..30ae8b3 100755 (executable)
--- a/utils/lit/lit/main.py
+++ b/utils/lit/lit/main.py
@@ -132,10 +132,6 @@ def sort_by_incremental_cache(run):
     run.tests.sort(key = lambda t: sortIndex(t))
 
 def main(builtinParameters = {}):
-    # Use processes by default on Unix platforms.
-    isWindows = platform.system() == 'Windows'
-    useProcessesIsDefault = not isWindows
-
     global options
     from optparse import OptionParser, OptionGroup
     parser = OptionParser("usage: %prog [options] {file-or-path}")
@@ -243,10 +239,10 @@ def main(builtinParameters = {}):
                       action="store_true", default=False)
     group.add_option("", "--use-processes", dest="useProcesses",
                       help="Run tests in parallel with processes (not threads)",
-                      action="store_true", default=useProcessesIsDefault)
+                      action="store_true", default=True)
     group.add_option("", "--use-threads", dest="useProcesses",
                       help="Run tests in parallel with threads (not processes)",
-                      action="store_false", default=useProcessesIsDefault)
+                      action="store_false", default=True)
     parser.add_option_group(group)
 
     (opts, args) = parser.parse_args()
@@ -286,6 +282,7 @@ def main(builtinParameters = {}):
         # Default is zero
         maxIndividualTestTime = 0
 
+    isWindows = platform.system() == 'Windows'
 
     # Create the global config object.
     litConfig = lit.LitConfig.LitConfig(