[Mesa-dev] [PATCH v2 1/2] spirv: fix OpSConvert when the source is unsigned

[Samuel Iglesias Gonsálvez]

On 12/03/18 20:42, Jason Ekstrand wrote:
> On Mon, Mar 5, 2018 at 10:21 PM, Samuel Iglesias Gonsálvez
> <siglesias at igalia.com <mailto:siglesias at igalia.com>> wrote:
>
>     OpSConvert interprets the MSB of the unsigned value as the sign
>     bit and
>     extends it to the new type. If we want to preserve the value, we need
>     to use OpUConvert opcode.
>
>     v2:
>     - No need to check dst type.
>     - Fix typo in comment.
>
>     Signed-off-by: Samuel Iglesias Gonsálvez <siglesias at igalia.com
>     <mailto:siglesias at igalia.com>>
>     ---
>      src/compiler/spirv/vtn_alu.c | 18 +++++++++++++++++-
>      1 file changed, 17 insertions(+), 1 deletion(-)
>
>     diff --git a/src/compiler/spirv/vtn_alu.c
>     b/src/compiler/spirv/vtn_alu.c
>     index d0c9e316935..a5cefc35773 100644
>     --- a/src/compiler/spirv/vtn_alu.c
>     +++ b/src/compiler/spirv/vtn_alu.c
>     @@ -354,10 +354,26 @@ vtn_nir_alu_op_for_spirv_opcode(struct
>     vtn_builder *b,
>         case SpvOpConvertFToS:
>         case SpvOpConvertSToF:
>         case SpvOpConvertUToF:
>     -   case SpvOpSConvert:
>         case SpvOpFConvert:
>            return nir_type_conversion_op(src, dst,
>     nir_rounding_mode_undef);
>
>     +   case SpvOpSConvert: {
>     +      nir_alu_type src_base = (nir_alu_type)
>     nir_alu_type_get_base_type(src);
>     +      if (src_base == nir_type_uint) {
>
>
> Why are we predicating this on src_base == nir_type_uint?  It seems to
> me as if we should just ignore the source and destination type except
> for the bit size.

Right.

>  
>
>     +         /* SPIR-V expects to interpret the unsigned value as
>     signed and
>     +          * do sign extend. Return the opcode accordingly.
>     +          */
>     +         unsigned dst_bit_size = nir_alu_type_get_type_size(dst);
>     +         switch (dst_bit_size) {
>     +         case 16:   return nir_op_i2i16;
>     +         case 32:   return nir_op_i2i32;
>     +         case 64:   return nir_op_i2i64;
>
>
> This can be nir_type_int | dst_bit_size. NIR types are convenient like
> that. :-)

Oh, nice suggestion! I am going to send soon a v3 with the suggested
changes for both patches.

Thanks a lot!

Sam

>  
>
>     +         default:
>     +            vtn_fail("Invalid nir alu bit size");
>     +         }
>     +      }
>     +      return nir_type_conversion_op(src, dst,
>     nir_rounding_mode_undef);
>     +   }
>         /* Derivatives: */
>         case SpvOpDPdx:         return nir_op_fddx;
>         case SpvOpDPdy:         return nir_op_fddy;
>     --
>     2.14.1
>
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