linux-kernel - Re: [PATCH] perf: use default compiler mode by default

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Date:	Sun, 22 Nov 2009 13:59:17 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	"Michael S. Tsirkin" <mst@...hat.com>
Cc:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Paul Mackerras <paulus@...ba.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] perf: use default compiler mode by default


* Michael S. Tsirkin <mst@...hat.com> wrote:

> gcc with no flags typically is a sane default for systems to use, and
> looking at the running kernel is probably broken for cross-builds
> anyway, so let's not do this.  Add EXTRA_CFLAGS so that users can
> override default gcc mode if they want to.
> 
> Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
> ---
>  tools/perf/Makefile |   20 +++-----------------
>  1 files changed, 3 insertions(+), 17 deletions(-)
> 
> diff --git a/tools/perf/Makefile b/tools/perf/Makefile
> index d0bdaf2..ab35b0f 100644
> --- a/tools/perf/Makefile
> +++ b/tools/perf/Makefile
> @@ -148,6 +148,8 @@ all::
>  # broken, or spawning external process is slower than built-in grep perf has).
>  #
>  # Define LDFLAGS=-static to build a static binary.
> +#
> +# Define EXTRA_CFLAGS=-m64 or EXTRA_CFLAGS=-m32 as appropriate for cross-builds.
>  
>  PERF-VERSION-FILE: .FORCE-PERF-VERSION-FILE
>  	@$(SHELL_PATH) util/PERF-VERSION-GEN
> @@ -160,22 +162,6 @@ uname_R := $(shell sh -c 'uname -r 2>/dev/null || echo not')
>  uname_P := $(shell sh -c 'uname -p 2>/dev/null || echo not')
>  uname_V := $(shell sh -c 'uname -v 2>/dev/null || echo not')
>  
> -#
> -# Add -m32 for cross-builds:
> -#
> -ifdef NO_64BIT
> -  MBITS := -m32
> -else
> -  #
> -  # If we're on a 64-bit kernel (except ia64), use -m64:
> -  #
> -  ifneq ($(uname_M),ia64)
> -    ifneq ($(patsubst %64,%,$(uname_M)),$(uname_M))
> -      MBITS := -m64
> -    endif
> -  endif
> -endif

iirc PowerPC had some trouble in this area. Paulus?

	Ingo
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