[Mesa-dev] [PATCH v3] intel/compiler: fix 16-bit int brw_negate_immediate and brw_abs_immediate

[Jason Ekstrand]

Rb

On May 2, 2018 16:44:52 Jose Maria Casanova Crespo <jmcasanova at igalia.com> 
wrote:

> From Intel Skylake PRM, vol 07, "Immediate" section (page 768):
>
> "For a word, unsigned word, or half-float immediate data,
> software must replicate the same 16-bit immediate value to both
> the lower word and the high word of the 32-bit immediate field
> in a GEN instruction."
>
> This fixes the int16/uint16 negate and abs immediates that weren't
> taking into account the replication in lower and upper words.
>
> v2: Integer cases are different to Float cases. (Jason Ekstrand)
>    Included reference to PRM (Jose Maria Casanova)
> v3: Make explicit uint32_t casting for left shift (Jason Ekstrand)
>    Split half float implementation. (Jason Ekstrand)
>    Fix brw_abs_immediate (Jose Maria Casanova)
>
> Cc: "18 . 0 18 . 1" <mesa-stable at lists.freedesktop.org>
> ---
> src/intel/compiler/brw_shader.cpp | 12 ++++++++----
> 1 file changed, 8 insertions(+), 4 deletions(-)
>
> diff --git a/src/intel/compiler/brw_shader.cpp 
> b/src/intel/compiler/brw_shader.cpp
> index 9cdf9fcb23d..284c2e8233c 100644
> --- a/src/intel/compiler/brw_shader.cpp
> +++ b/src/intel/compiler/brw_shader.cpp
> @@ -580,9 +580,11 @@ brw_negate_immediate(enum brw_reg_type type, struct 
> brw_reg *reg)
>       reg->d = -reg->d;
>       return true;
>    case BRW_REGISTER_TYPE_W:
> -   case BRW_REGISTER_TYPE_UW:
> -      reg->d = -(int16_t)reg->ud;
> +   case BRW_REGISTER_TYPE_UW: {
> +      uint16_t value = -(int16_t)reg->ud;
> +      reg->ud = value | (uint32_t)value << 16;
>       return true;
> +   }
>    case BRW_REGISTER_TYPE_F:
>       reg->f = -reg->f;
>       return true;
> @@ -618,9 +620,11 @@ brw_abs_immediate(enum brw_reg_type type, struct 
> brw_reg *reg)
>    case BRW_REGISTER_TYPE_D:
>       reg->d = abs(reg->d);
>       return true;
> -   case BRW_REGISTER_TYPE_W:
> -      reg->d = abs((int16_t)reg->ud);
> +   case BRW_REGISTER_TYPE_W: {
> +      uint16_t value = abs((int16_t)reg->ud);
> +      reg->ud = value | (uint32_t)value << 16;
>       return true;
> +   }
>    case BRW_REGISTER_TYPE_F:
>       reg->f = fabsf(reg->f);
>       return true;
> --
> 2.14.3