Re: [PATCH v2 03/16] perf annotate-arm64: Generalize arm64_mov__parse to support standard operands

[James Clark <james.clark@linaro.org>]

On 07/04/2026 07:58, Namhyung Kim wrote:
> On Fri, Apr 03, 2026 at 09:47:47AM +0000, Tengda Wu wrote:
>> The current arm64_mov__parse() implementation strictly requires the
>> operand to contain a symbol suffix in the "<symbol>" format. This
>> causes the parser to fail for standard instructions that only contain
>> raw immediates or registers without symbolic annotations.
>>
>> Refactor the function to make symbol matching optional. The parser now
>> correctly extracts the target operand and only attempts to parse the
>> "<symbol>" suffix if it exists. This change also introduces better
>> handling for whitespace and comments, and adds support for multi-register
>> check via arm64__check_multi_regs(), ensuring compatibility with a
>> wider range of arm64 instruction formats.
>>
>> Signed-off-by: Tengda Wu <wutengda@huaweicloud.com>
>> ---
>>   .../perf/util/annotate-arch/annotate-arm64.c  | 85 ++++++++++++++-----
>>   1 file changed, 65 insertions(+), 20 deletions(-)
>>
>> diff --git a/tools/perf/util/annotate-arch/annotate-arm64.c b/tools/perf/util/annotate-arch/annotate-arm64.c
>> index 33080fdca125..4c42323b0c18 100644
>> --- a/tools/perf/util/annotate-arch/annotate-arm64.c
>> +++ b/tools/perf/util/annotate-arch/annotate-arm64.c
>> @@ -14,12 +14,38 @@ struct arch_arm64 {
>>   	regex_t jump_insn;
>>   };
>>   
>> +static bool arm64__check_multi_regs(const char *op)
>> +{
>> +	char *comma = strchr(op, ',');
>> +
>> +	while (comma) {
>> +		char *next = comma + 1;
>> +
>> +		next = skip_spaces(next);
>> +
>> +		/*
>> +		 * Check the first valid character after the comma:
>> +		 * - If it is '#', it indicates an immediate offset (e.g., [x1, #16]).
>> +		 * - If it is an alphabetic character, it is highly likely a
>> +		 *   register name (e.g., x, w, s, d, q, v, p, z).
>> +		 * - Special cases: Alias and control registers like sp, xzr,
>> +		 *   and wzr all start with an alphabetic character.
>> +		 */
>> +		if (*next && *next != '#' && isalpha(*next))
>> +			return true;
> 
> It seems you check any alphabet charactor after a comma for multi-regs.
> Does that mean the first component before the comma should be another
> register?
> 
>> +
>> +		comma = strchr(next, ',');
>> +	}
>> +
>> +	return false;
>> +}
>> +
>>   static int arm64_mov__parse(const struct arch *arch __maybe_unused,
>>   			    struct ins_operands *ops,
>>   			    struct map_symbol *ms __maybe_unused,
>>   			    struct disasm_line *dl __maybe_unused)
>>   {
>> -	char *s = strchr(ops->raw, ','), *target, *endptr;
>> +	char *s = strchr(ops->raw, ','), *target, *endptr, *comment, prev;
>>   
>>   	if (s == NULL)
>>   		return -1;
>> @@ -31,29 +57,48 @@ static int arm64_mov__parse(const struct arch *arch __maybe_unused,
>>   	if (ops->source.raw == NULL)
>>   		return -1;
>>   
>> -	target = ++s;
>> +	target = skip_spaces(++s);
>> +	comment = strchr(s, arch->objdump.comment_char);
>> +
>> +	if (comment != NULL)
>> +		s = comment - 1;
>> +	else
>> +		s = strchr(s, '\0') - 1;
> 
> An interesting use of strchr().  Oh, I found the strchr(3) man page
> also mentions that it's a supported use case.  TIL.
> 
> 
>> +
>> +	while (s > target && isspace(s[0]))
>> +		--s;
>> +	s++;
>> +	prev = *s;
>> +	*s = '\0';
>>   	ops->target.raw = strdup(target);
>> +	*s = prev;
>> +
>>   	if (ops->target.raw == NULL)
>>   		goto out_free_source;
>>   
>> -	ops->target.addr = strtoull(target, &endptr, 16);
>> -	if (endptr == target)
>> -		goto out_free_target;
>> -
>> -	s = strchr(endptr, '<');
>> -	if (s == NULL)
>> -		goto out_free_target;
>> -	endptr = strchr(s + 1, '>');
>> -	if (endptr == NULL)
>> -		goto out_free_target;
>> -
>> -	*endptr = '\0';
>> -	*s = ' ';
>> -	ops->target.name = strdup(s);
>> -	*s = '<';
>> -	*endptr = '>';
>> -	if (ops->target.name == NULL)
>> -		goto out_free_target;
>> +	ops->target.multi_regs = arm64__check_multi_regs(ops->target.raw);
>> +
>> +	/* Parse address followed by symbol name, e.g. "addr <symbol>" */
>> +	if (strchr(target, '<') != NULL) {
>> +		ops->target.addr = strtoull(target, &endptr, 16);
>> +		if (endptr == target)
>> +			goto out_free_target;
> 
> Hmm.. shouldn't this part be executed regardless of presence of a symbol
> name?
> 
>> +
>> +		s = strchr(endptr, '<');
>> +		if (s == NULL)
>> +			goto out_free_target;
> 
> It'd be safer to check `if (*skip_spaces(endptr) == '<')` rather than
> strchr().
> 
> 
>> +		endptr = strchr(s + 1, '>');
>> +		if (endptr == NULL)
>> +			goto out_free_target;
> 
> I'm afraid C++ programs can have symbols with <> for templates.
> Probably strrchr() would work.
> 
> Thanks,
> Namhyung
> 

Maybe a test for this function would be good to make sure it still works 
the same for old and also handles the new inputs. A lot of it looks 
quite fiddly and I didn't see any dependencies in it that would make 
testing a whole list of inputs and outputs difficult.

>> +
>> +		*endptr = '\0';
>> +		*s = ' ';
>> +		ops->target.name = strdup(s);
>> +		*s = '<';
>> +		*endptr = '>';
>> +		if (ops->target.name == NULL)
>> +			goto out_free_target;
>> +	}
>>   
>>   	return 0;
>>   
>> -- 
>> 2.34.1
>>
>