[utils][UpdateTestChecks] Warn about possible target triple mismatch (#149645)

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, 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.

1 files changed, 6 insertions, 0 deletions

diff --git a/llvm/utils/UpdateTestChecks/common.py b/llvm/utils/UpdateTestChecks/common.py
index 178c623..a5d4375 100644
--- a/llvm/utils/UpdateTestChecks/common.py
+++ b/llvm/utils/UpdateTestChecks/common.py
@@ -878,12 +878,17 @@ class FunctionTestBuilder:
         return False
 
     def process_run_line(self, function_re, scrubber, raw_tool_output, prefixes):
+        """
+        Returns the number of functions processed from the output by the regex.
+        """
         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 +1005,7 @@ class FunctionTestBuilder:
                         # 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):
         """