[utils][UpdateTestChecks] Warn about possible target triple mismatch

Aims to improve error reporting by printing a warning if the target function regex that has been selected finds no matches. For example, a `-mtriple=arm64-apple-darwin` runline, which is not a real triple looking forward (as it doesn't encode an actual OS), would map to the `arm64` prefix by `update_llc_test_checks.py` and wouldn't match Apple's function layout, generating some not understandable garbage checks.

The implementation changes `common.process_run_line` to return an abstract indicator of number of functions processed, without breaking the drivers. Then `update_llc_test_checks.py` prints a driver specific error message.

Author: tomershafir

llvm/utils/UpdateTestChecks/common.py

@@ -881,9 +881,12 @@ def process_run_line(self, function_re, scrubber, raw_tool_output, prefixes):
         build_global_values_dictionary(
             self._global_var_dict, raw_tool_output, prefixes, self._ginfo
         )
+        
+        processed_func_count = 0
         for m in function_re.finditer(raw_tool_output):
             if not m:
                 continue
+            processed_func_count += 1
             func = m.group("func")
             body = m.group("body")
             # func_name_separator is the string that is placed right after function name at the
@@ -1000,6 +1003,7 @@ def process_run_line(self, function_re, scrubber, raw_tool_output, prefixes):
                         # preprocesser directives to exclude individual functions from some
                         # RUN lines.
                         self._func_dict[prefix][func] = None
+        return processed_func_count        
 
     def processed_prefixes(self, prefixes):
         """

llvm/utils/update_llc_test_checks.py

@@ -142,7 +142,8 @@ def update_test(ti: common.TestInfo):
             triple = common.get_triple_from_march(march_in_cmd)
 
         scrubber, function_re = output_type.get_run_handler(triple)
-        builder.process_run_line(function_re, scrubber, raw_tool_output, prefixes)
+        if not builder.process_run_line(function_re, scrubber, raw_tool_output, prefixes):
+            common.warn("Couldn't match any function. Possibly the wrong target triple has been provided")
         builder.processed_prefixes(prefixes)
 
     func_dict = builder.finish_and_get_func_dict()