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Re: [Qemu-devel] [PATCH v2] tcg: fix dead computation for repeated input

From: Richard Henderson
Subject: Re: [Qemu-devel] [PATCH v2] tcg: fix dead computation for repeated input arguments
Date: Thu, 21 May 2015 12:54:21 -0700
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.7.0

On 05/21/2015 12:35 PM, Aurelien Jarno wrote:
> When the same temp is used twice or more as an input argument to a TCG
> instruction, the dead computation code doesn't recognize the second use
> as a dead temp. This is because the temp is marked as live in the same
> loop where dead inputs are checked.
> The fix is to split the loop in two parts. This avoid emitting a move
> and using a register for the movcond instruction when used as "move if
> true" on x86-64. This might bring more improvements on RISC TCG targets
> which don't have outputs aliased to inputs.
> Cc: Richard Henderson <address@hidden>
> Signed-off-by: Aurelien Jarno <address@hidden>
> ---
>  tcg/tcg.c | 14 +++++++++++---
>  1 file changed, 11 insertions(+), 3 deletions(-)

Reviewed-by: Richard Henderson <address@hidden>


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