lit: Bring back -Dtool=xxx feature lost in r313928

llvm-svn: 319139

llvm/utils/lit/lit/llvm/subst.py

@@ -12,9 +12,14 @@ class FindTool(object):
         self.name = name
 
     def resolve(self, config, dirs):
-        command = lit.util.which(self.name, dirs)
-        if not command:
-            return None
+        # Check for a user explicitely overriding a tool.  This allows:
+        #     llvm-lit -D llc="llc -enable-misched -verify-machineinstrs"
+        command = config.lit_config.params.get(self.name)
+        if command is None:
+            # Then check out search paths.
+            command = lit.util.which(self.name, dirs)
+            if not command:
+                return None
 
         if self.name == 'llc' and os.environ.get('LLVM_ENABLE_MACHINE_VERIFIER') == '1':
             command += ' -verify-machineinstrs'