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From: "Paul E. McKenney via lttng-dev" <lttng-dev@lists.lttng.org>
To: Michael Jeanson <mjeanson@efficios.com>
Cc: lttng-dev@lists.lttng.org
Subject: Re: [lttng-dev] [PATCH urcu 4/4] Don't force a target and optimization level on ARMv7
Date: Tue, 15 Dec 2020 08:39:41 -0800	[thread overview]
Message-ID: <20201215163941.GA2657@paulmck-ThinkPad-P72> (raw)
In-Reply-To: <20201215162850.78638-4-mjeanson@efficios.com>

On Tue, Dec 15, 2020 at 11:28:50AM -0500, Michael Jeanson wrote:
> We shouldn't force a specific target cpu for the compiler on ARMv7 but
> let the system or the user choose it. If some of our code depends on a
> specific target CPU features, it should be compile tested.
> 
> Also remove the default optimisation level of O1, it's potentially a
> workaround to an early armv7 compiler performance problem and anyway
> most builds will have an optimisation level flag set in the CFLAGS which
> will override this one.

Indeed, the original was based on advice from ARM that has undoubtedly
changed over time, so...

> Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
> Cc: Paul E. McKenney <paulmck@kernel.org>

Acked-by: Paul E. McKenney <paulmck@kernel.org>

> Change-Id: I1d1bb5cc0fa0be8f8b1d6a9ad7bf063809be1aef
> ---
>  configure.ac | 4 ----
>  1 file changed, 4 deletions(-)
> 
> diff --git a/configure.ac b/configure.ac
> index daa967a..f477425 100644
> --- a/configure.ac
> +++ b/configure.ac
> @@ -119,10 +119,6 @@ AS_CASE([$host],[*-cygwin*],
>  	[AM_CONDITIONAL(USE_CYGWIN, false)]
>  )
>  
> -AS_IF([test "$host_cpu" = "armv7l"],[
> -	AM_CFLAGS="$AM_CFLAGS -mcpu=cortex-a9 -mtune=cortex-a9 -O1"
> -])
> -
>  # Search for clock_gettime
>  AC_SEARCH_LIBS([clock_gettime], [rt], [
>  	AC_DEFINE([CONFIG_RCU_HAVE_CLOCK_GETTIME], [1])
> -- 
> 2.29.2
> 
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  reply	other threads:[~2020-12-15 16:39 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-12-15 16:28 [lttng-dev] [PATCH urcu 1/4] Cleanup: Move ARM specific code to urcu/arch/arm.h Michael Jeanson via lttng-dev
2020-12-15 16:28 ` [lttng-dev] [PATCH urcu 2/4] Blacklist GCC 4.4.0, 4.4.1 and 4.4.2 on ARM Michael Jeanson via lttng-dev
2020-12-17 13:29   ` Mathieu Desnoyers via lttng-dev
2020-12-15 16:28 ` [lttng-dev] [PATCH urcu 3/4] Use DMB only on ARMv7 Michael Jeanson via lttng-dev
2020-12-17 13:29   ` Mathieu Desnoyers via lttng-dev
2020-12-15 16:28 ` [lttng-dev] [PATCH urcu 4/4] Don't force a target and optimization level " Michael Jeanson via lttng-dev
2020-12-15 16:39   ` Paul E. McKenney via lttng-dev [this message]
2020-12-17 13:30   ` Mathieu Desnoyers via lttng-dev
2020-12-17 13:29 ` [lttng-dev] [PATCH urcu 1/4] Cleanup: Move ARM specific code to urcu/arch/arm.h Mathieu Desnoyers via lttng-dev

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