[llvm] [UpdateTestChecks] Don't fail silently when conflicting CHECK lines means no checks are generated for some functions (PR #159321)

[Alex Bradbury via llvm-commits]

================
@@ -918,14 +919,51 @@ def __init__(self, run_list, flags, scrubber_args, path, ginfo):
                 self._global_var_dict.update({prefix: dict()})
 
     def finish_and_get_func_dict(self):
-        for prefix in self.get_failed_prefixes():
-            warn(
-                "Prefix %s had conflicting output from different RUN lines for all functions in test %s"
-                % (
-                    prefix,
-                    self._path,
+        all_funcs = set()
+        for prefix in self._func_dict:
+            all_funcs.update(self._func_dict[prefix].keys())
+
+        warnings_to_print = collections.defaultdict(list)
+        for func in sorted(list(all_funcs)):
+            for i, run_info in enumerate(self._run_list):
+                prefixes = run_info[0]
+                if not prefixes:
+                    continue
+
+                # Check if this RUN line produces this function at all.
+                run_contains_func = True
+                for p in prefixes:
+                    if func not in self._func_dict.get(p, {}):
+                        run_contains_func = False
+                        break
+                if not run_contains_func:
+                    continue
+
+                # Check if this RUN line can print any checks for this
+                # function. It can't if all of its prefixes have conflicting
+                # (None) output.
+                can_print_for_this_run = False
+                for p in prefixes:
+                    if self._func_dict[p].get(func) is not None:
+                        can_print_for_this_run = True
+                        break
+
+                if not can_print_for_this_run:
+                    warnings_to_print[func].append((i, prefixes))
+
+        for func, warning_info in warnings_to_print.items():
+            conflict_strs = []
+            for run_index, prefixes in warning_info:
+                conflict_strs.append(
+                    "RUN #{} (prefixes: {})".format(run_index + 1, ", ".join(prefixes))
----------------
asb wrote:

Thanks, I'd seen plenty of format in this file so was conservative but I see now there's a number of fstring usages too. I've updated the string formatting appropriately.

https://github.com/llvm/llvm-project/pull/159321