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Date: Thu, 13 Sep 2012 23:22:02 +0200
From: Aurelien Jarno <aurelien@aurel32.net>
Message-ID: <20120913212202.GA833@ohm.aurel32.net>
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Subject: Re: [Qemu-devel] [PATCH 3/4] tcg/i386: Remove unused registers from
 tcg_target_call_iarg_regs
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To: Stefan Weil <sw@weilnetz.de>
Cc: Peter Maydell <peter.maydell@linaro.org>, Alexander Graf <agraf@suse.de>, qemu-devel@nongnu.org, Blue Swirl <blauwirbel@gmail.com>, Richard Henderson <rth@twiddle.net>

On Thu, Sep 13, 2012 at 07:37:45PM +0200, Stefan Weil wrote:
> 32 bit x86 hosts don't need registers for helper function arguments
> because they use the default stack based calling convention.
> 
> Removing the registers allows simpler code for function
> tcg_target_get_call_iarg_regs_count.
> 
> Signed-off-by: Stefan Weil <sw@weilnetz.de>
> ---
>  tcg/i386/tcg-target.c |   10 ++--------
>  1 file changed, 2 insertions(+), 8 deletions(-)
> 
> diff --git a/tcg/i386/tcg-target.c b/tcg/i386/tcg-target.c
> index ef63967..375d87d 100644
> --- a/tcg/i386/tcg-target.c
> +++ b/tcg/i386/tcg-target.c
> @@ -75,9 +75,7 @@ static const int tcg_target_call_iarg_regs[] = {
>      TCG_REG_R8,
>      TCG_REG_R9,
>  #else
> -    TCG_REG_EAX,
> -    TCG_REG_EDX,
> -    TCG_REG_ECX
> +    /* 32 bit mode uses stack based calling convention (GCC default). */
>  #endif
>  };
>  
> @@ -127,11 +125,7 @@ static void patch_reloc(uint8_t *code_ptr, int type,
>  /* maximum number of register used for input function arguments */
>  static inline int tcg_target_get_call_iarg_regs_count(int flags)
>  {
> -    if (TCG_TARGET_REG_BITS == 64) {
> -        return ARRAY_SIZE(tcg_target_call_iarg_regs);
> -    }
> -
> -    return 0;
> +    return ARRAY_SIZE(tcg_target_call_iarg_regs);
>  }
>  
>  /* parse target specific constraints */
> -- 
> 1.7.10
> 
> 

Reviewed-by: Aurelien Jarno <aurelien@aurel32.net>


-- 
Aurelien Jarno                          GPG: 1024D/F1BCDB73
aurelien@aurel32.net                 http://www.aurel32.net