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Re: [Qemu-devel] [PATCH] target/arm: Fix sign-extension for SMLAL*
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From: |
Philippe Mathieu-Daudé |
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Subject: |
Re: [Qemu-devel] [PATCH] target/arm: Fix sign-extension for SMLAL* |
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Date: |
Fri, 13 Sep 2019 13:01:56 +0200 |
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User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.0 |
On 9/12/19 8:30 PM, Richard Henderson wrote:
> The 32-bit product should be sign-extended, not zero-extended.
>
> Fixes: ea96b374641b
> Reported-by: Laurent Desnogues <address@hidden>
> Signed-off-by: Richard Henderson <address@hidden>
Reviewed-by: Philippe Mathieu-Daudé <address@hidden>
> ---
> target/arm/translate.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/target/arm/translate.c b/target/arm/translate.c
> index 34bb280e3d..fd2f0e3048 100644
> --- a/target/arm/translate.c
> +++ b/target/arm/translate.c
> @@ -8045,7 +8045,9 @@ static bool op_smlaxxx(DisasContext *s, arg_rrrr *a,
> case 2:
> tl = load_reg(s, a->ra);
> th = load_reg(s, a->rd);
> - t1 = tcg_const_i32(0);
> + /* Sign-extend the 32-bit product to 64 bits. */
> + t1 = tcg_temp_new_i32();
> + tcg_gen_sari_i32(t1, t0, 31);
> tcg_gen_add2_i32(tl, th, tl, th, t0, t1);
> tcg_temp_free_i32(t0);
> tcg_temp_free_i32(t1);
>