use md5 (faster) and avoid locking to check cache

Author: inorton

clcache.py

@@ -138,16 +138,15 @@ def computeKey(self, compilerBinary, commandLine):
         normalizedCmdLine = self._normalizedCommandLine(commandLine)
 
         stat = os.stat(compilerBinary)
-        sha = hashlib.sha1()
-        sha.update(str(stat.st_mtime))
-        sha.update(str(stat.st_size))
-        sha.update(' '.join(normalizedCmdLine))
-        sha.update(preprocessedSourceCode)
-        return sha.hexdigest()
+        h = hashlib.md5()
+        h.update(str(stat.st_mtime))
+        h.update(str(stat.st_size))
+        h.update(' '.join(normalizedCmdLine))
+        h.update(preprocessedSourceCode)
+        return h.hexdigest()
 
     def hasEntry(self, key):
-        with self.lock:
-            return os.path.exists(self.cachedObjectName(key))
+        return os.path.exists(self.cachedObjectName(key))
 
     def setEntry(self, key, objectFileName, compilerOutput):
         with self.lock: