On Mon, Mar 5, 2018 at 10:21 PM, Samuel Iglesias Gonsálvez <
sigles...@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 <sigles...@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.
> + /* 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. :-)
> + 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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