Merge pull request #10506 from apple/unique-test-output-dirs

Speculative fix for test output race conditions

@gparker42 is going to verify that it allows us to re-enable parallel device testing.

Author: Dave Abrahams

test/lit.cfg

@@ -144,15 +144,28 @@ class SwiftTest(lit.formats.ShTest, object):
         self.skipped_tests = set()
 
     def before_test(self, test, litConfig):
+        _, tmp_base = lit.TestRunner.getTempPaths(test)
+        
+        # Apparently despite the docs, tmpDir is not actually unique for each test, but
+        # tmpBase is.  Remove it here and add a tmpBase substitution in before_test.
+        # Speculative fix for rdar://32928464.
+        try:
+            percentT_index = [x[0] for x in test.config.substitutions].index('%T')
+        except ValueError: pass
+        else:
+            test.config.substitutions.pop(percentT_index)
+
+            test.config.substitutions.append(
+                ('%T', '$(mkdir -p %r && echo %r)' % (tmp_base, tmp_base)))
+
         if self.coverage_mode:
             # FIXME: The compiler crashers run so fast they fill up the
             # merger's queue (and therefore the build bot's disk)
             if 'crasher' in test.getSourcePath():
                 test.config.environment["LLVM_PROFILE_FILE"] = os.devnull
                 self.skipped_tests.add(test.getSourcePath())
                 return
-
-            _, tmp_base = lit.TestRunner.getTempPaths(test)
+            
             if self.coverage_mode == "NOT_MERGED":
                 profdir = tmp_base + '.profdir'
                 if not os.path.exists(profdir):