Re: [PATCH v2 05/14] perf cs-etm: Use the recorded instruction size for A32 and A64

[James Clark]

On 23/09/2026 16:21, Leo Yan wrote:
> Use packet->last_instr_size in cs_etm__instr_size() instead of a
> hard-coded value, allowing the decoder to supply the instruction size.
>
> Keep per-address decoding for T32. A range can mix 16-bit and 32-bit
> instructions, so last_instr_size describes only the final instruction
> and cannot determine the size at an arbitrary address in the range.
>
> Assisted-by: Codex:gpt-6
> Signed-off-by: Leo Yan <leo.yan@xxxxxxx>
> ---
>   tools/perf/util/cs-etm.c | 3 +--
>   1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/tools/perf/util/cs-etm.c b/tools/perf/util/cs-etm.c
> index 2d1ab34f7b6b5a6331005c16c6a418d123c815eb..0163d93ac2d537a2190536e77d24628b4d707751 100644
> --- a/tools/perf/util/cs-etm.c
> +++ b/tools/perf/util/cs-etm.c
> @@ -1358,8 +1358,7 @@ static inline int cs_etm__instr_size(struct cs_etm_queue *etmq,
>   	if (packet->isa == CS_ETM_ISA_T32)
>   		return cs_etm__t32_instr_size(etmq, tidq, packet, addr);
>   
> -	/* Otherwise, 4-byte instruction size for A32/A64 */
> -	return 4;
> +	return packet->last_instr_size;

Why not use last_instr_size for CS_ETM_ISA_T32 too? I'm wondering how 
and when this change actually makes a difference? last_instr_size isn't 
any better than '4' for any instruction in the range other than the last 
one, so it's not clear what the issue is.

>   }
>   
>   static inline u64 cs_etm__first_executed_instr(struct cs_etm_packet *packet)