[RFC PATCH] x86: Ignore rounding for vcvt[, u]si2sd under r32 and vcvt[,u]dq2pd instead of reporting bad

[Jan Beulich]

On 14.01.2025 09:35, Haochen Jiang wrote:
> --- a/opcodes/i386-dis-evex-w.h
> +++ b/opcodes/i386-dis-evex-w.h
> @@ -97,7 +97,7 @@
>    },
>    /* EVEX_W_0F7A_P_1 */
>    {
> -    { "vcvtudq2pd",	{ XM, EXEvexHalfBcstXmmq }, 0 },
> +    { "vcvtudq2pd",	{ XM, EXEvexHalfBcstXmmq, EXxEVexRIG }, 0 },
>      { "vcvtuqq2pd",	{ XM, EXx, EXxEVexR }, 0 },
>    },
>    /* EVEX_W_0F7A_P_2 */
> @@ -161,7 +161,7 @@
>    },
>    /* EVEX_W_0FE6_P_1 */
>    {
> -    { "%XEvcvtdq2pd",	{ XM, EXEvexHalfBcstXmmq }, 0 },
> +    { "%XEvcvtdq2pd",	{ XM, EXEvexHalfBcstXmmq, EXxEVexRIG }, 0 },
>      { "vcvtqq2pd",	{ XM, EXx, EXxEVexR }, 0 },
>    },
>    /* EVEX_W_0FE7 */

In both of these I think EXxEVexR64 can be used, eliminating the need
for ...

> --- a/opcodes/i386-dis.c
> +++ b/opcodes/i386-dis.c
> @@ -605,6 +605,7 @@ fetch_error (const instr_info *ins)
>  #define EXxEVexR { OP_Rounding, evex_rounding_mode }
>  #define EXxEVexR64 { OP_Rounding, evex_rounding_64_mode }
>  #define EXxEVexS { OP_Rounding, evex_sae_mode }
> +#define EXxEVexRIG { OP_Rounding, evex_rounding_ignore_mode }

... this and ...

> @@ -765,6 +766,8 @@ enum
>    evex_rounding_64_mode,
>    /* Supress all exceptions.  */
>    evex_sae_mode,
> +  /* Rounding allowed, but ignored.  */
> +  evex_rounding_ignore_mode,

... this. Re-using a mode we already have also feels slightly more safe,
considering the special casing we have in place, keyed to the handler
being OP_Rounding.

Jan