tools: update list of references to not include symbold used by __assert_func calls

On xtensa architecture, the call to __assert_func uses a reference to __func__ that can
sometimes be placed in flash. Since the __asert_func can be called from functions in IRAM
the check_callgraph script can report an error when checking for invalid calls from IRAM
to flash sections. However, the __asert_func prevents this scenario at runtime so the
check_callgraph script reports a 'flas positive' situation. For this reasson, all references
to __func__$x found prior to a call to __assert_func are droped in the parsing of the rtl files.

components/heap/test/CMakeLists.txt

@@ -12,6 +12,7 @@ if(CONFIG_COMPILER_DUMP_RTL_FILES)
                       find-refs
                       --from-sections=.iram0.text
                       --to-sections=.flash.text,.flash.rodata
+                      --ignore-symbols=__func__/__assert_func,__func__/heap_caps_alloc_failed
                       --exit-code
                       DEPENDS ${elf_file_name}
                       )

tools/ci/check_callgraph.py

@@ -95,6 +95,11 @@ class Reference(object):
         )
 
 
+class IgnorePair():
+    def __init__(self, pair: str) -> None:
+        self.symbol, self.function_call = pair.split('/')
+
+
 class ElfInfo(object):
     def __init__(self, elf_file: BinaryIO) -> None:
         self.elf_file = elf_file
@@ -159,7 +164,7 @@ class ElfInfo(object):
         return None
 
 
-def load_rtl_file(rtl_filename: str, tu_filename: str, functions: List[RtlFunction]) -> None:
+def load_rtl_file(rtl_filename: str, tu_filename: str, functions: List[RtlFunction], ignore_pairs: List[IgnorePair]) -> None:
     last_function: Optional[RtlFunction] = None
     for line in open(rtl_filename):
         # Find function definition
@@ -175,6 +180,17 @@ def load_rtl_file(rtl_filename: str, tu_filename: str, functions: List[RtlFuncti
             match = re.match(CALL_REGEX, line)
             if match:
                 target = match.group('target')
+
+                # if target matches on of the IgnorePair function_call attributes, remove
+                # the last occurrence of the associated symbol from the last_function.refs list.
+                call_matching_pairs = [pair for pair in ignore_pairs if pair.function_call == target]
+                if call_matching_pairs and last_function and last_function.refs:
+                    for pair in call_matching_pairs:
+                        ignored_symbols = [ref for ref in last_function.refs if pair.symbol in ref]
+                        if ignored_symbols:
+                            last_ref = ignored_symbols.pop()
+                            last_function.refs = [ref for ref in last_function.refs if last_ref != ref]
+
                 if target not in last_function.calls:
                     last_function.calls.append(target)
                 continue
@@ -304,12 +320,12 @@ def match_rtl_funcs_to_symbols(rtl_functions: List[RtlFunction], elfinfo: ElfInf
     return symbols, refs
 
 
-def get_symbols_and_refs(rtl_list: List[str], elf_file: BinaryIO) -> Tuple[List[Symbol], List[Reference]]:
+def get_symbols_and_refs(rtl_list: List[str], elf_file: BinaryIO, ignore_pairs: List[IgnorePair]) -> Tuple[List[Symbol], List[Reference]]:
     elfinfo = ElfInfo(elf_file)
 
     rtl_functions: List[RtlFunction] = []
     for file_name in rtl_list:
-        load_rtl_file(file_name, file_name, rtl_functions)
+        load_rtl_file(file_name, file_name, rtl_functions, ignore_pairs)
 
     return match_rtl_funcs_to_symbols(rtl_functions, elfinfo)
 
@@ -361,6 +377,10 @@ def main() -> None:
     find_refs_parser.add_argument(
         '--to-sections', help='comma-separated list of target sections'
     )
+    find_refs_parser.add_argument(
+        '--ignore-symbols', help='comma-separated list of symbol/function_name pairs. \
+                                  This will force the parser to ignore the symbol preceding the call to function_name'
+    )
     find_refs_parser.add_argument(
         '--exit-code',
         action='store_true',
@@ -384,7 +404,11 @@ def main() -> None:
     if not rtl_list:
         raise RuntimeError('No RTL files specified')
 
-    _, refs = get_symbols_and_refs(rtl_list, args.elf_file)
+    ignore_pairs = []
+    for pair in args.ignore_symbols.split(',') if args.ignore_symbols else []:
+        ignore_pairs.append(IgnorePair(pair))
+
+    _, refs = get_symbols_and_refs(rtl_list, args.elf_file, ignore_pairs)
 
     if args.action == 'find-refs':
         from_sections = args.from_sections.split(',') if args.from_sections else []