linux-kernel - Re: [PATCH] perf/annotate: Use architecture-agnostic register limit

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Message-ID: <CAP-5=fXVFBewYhSmjVCGTbzEN82apECRLRnSeit8rqydCBJ1bg@mail.gmail.com>
Date: Tue, 23 Sep 2025 12:11:27 -0700
From: Ian Rogers <irogers@...gle.com>
To: Suchit Karunakaran <suchitkarunakaran@...il.com>
Cc: peterz@...radead.org, mingo@...hat.com, acme@...nel.org, 
	namhyung@...nel.org, mark.rutland@....com, alexander.shishkin@...ux.intel.com, 
	jolsa@...nel.org, adrian.hunter@...el.com, kan.liang@...ux.intel.com, 
	linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org, 
	skhan@...uxfoundation.org
Subject: Re: [PATCH] perf/annotate: Use architecture-agnostic register limit

On Tue, Sep 23, 2025 at 10:43 AM Suchit Karunakaran
<suchitkarunakaran@...il.com> wrote:
>
> Remove the arch-specific guard around TYPE_STATE_MAX_REGS and define it
> as 32 for all architectures. The architecture that perf is built on may
> not match the architecture that produced the perf.data file, so relying
> on __powerpc__ or similar is fragile. Using 32 as a fixed upper bound is
> safe since it is greater than the previous maximum of 16.
> Add a comment to clarify that TYPE_STATE_MAX_REGS is an arch-independent
> maximum rather than a build-time choice.
>
> Suggested-by: Ian Rogers <irogers@...gle.com>
> Signed-off-by: Suchit Karunakaran <suchitkarunakaran@...il.com>

Reviewed-by: Ian Rogers <irogers@...gle.com>

Thanks,
Ian

> ---
>  tools/perf/util/annotate-data.h | 13 ++++++++-----
>  1 file changed, 8 insertions(+), 5 deletions(-)
>
> diff --git a/tools/perf/util/annotate-data.h b/tools/perf/util/annotate-data.h
> index 541fee1a5f0a..1f76885facb0 100644
> --- a/tools/perf/util/annotate-data.h
> +++ b/tools/perf/util/annotate-data.h
> @@ -189,12 +189,15 @@ struct type_state_stack {
>         u8 kind;
>  };
>
> -/* FIXME: This should be arch-dependent */
> -#ifdef __powerpc__
> +/*
> + * Maximum number of registers tracked in type_state.
> + *
> + * This limit must cover all supported architectures, since perf
> + * may analyze perf.data files generated on systems with a different
> + * register set. Use 32 as a safe upper bound instead of relying on
> + * build-arch specific values.
> + */
>  #define TYPE_STATE_MAX_REGS  32
> -#else
> -#define TYPE_STATE_MAX_REGS  16
> -#endif
>
>  /*
>   * State table to maintain type info in each register and stack location.
> --
> 2.51.0
>