[Mesa-dev] [PATCH 31/59] intel/compiler: fix ddx and ddy for 16-bit float

[Jason Ekstrand]

On Tue, Dec 4, 2018 at 1:18 AM Iago Toral Quiroga <itoral at igalia.com> wrote:

> We were assuming 32-bit elements.
> ---
>  src/intel/compiler/brw_fs_generator.cpp | 34 +++++++++++++------------
>  1 file changed, 18 insertions(+), 16 deletions(-)
>
> diff --git a/src/intel/compiler/brw_fs_generator.cpp
> b/src/intel/compiler/brw_fs_generator.cpp
> index 08dd83dded7..bffd9bc4787 100644
> --- a/src/intel/compiler/brw_fs_generator.cpp
> +++ b/src/intel/compiler/brw_fs_generator.cpp
> @@ -1259,7 +1259,7 @@ fs_generator::generate_ddx(const fs_inst *inst,
>     struct brw_reg src0 = src;
>     struct brw_reg src1 = src;
>
> -   src0.subnr   = sizeof(float);
> +   src0.subnr   = type_sz(src.type);
>

Should this be "+="?  I think this is broken if we're SIMD8 and in the
second half of a register.


>     src0.vstride = vstride;
>     src0.width   = width;
>     src0.hstride = BRW_HORIZONTAL_STRIDE_0;
> @@ -1278,23 +1278,25 @@ void
>  fs_generator::generate_ddy(const fs_inst *inst,
>                             struct brw_reg dst, struct brw_reg src)
>  {
> +   const uint32_t type_size = type_sz(src.type);
> +
>     if (inst->opcode == FS_OPCODE_DDY_FINE) {
>        /* produce accurate derivatives */
>        if (devinfo->gen >= 11) {
>           src = stride(src, 0, 2, 1);
> -         struct brw_reg src_0  = byte_offset(src,  0 * sizeof(float));
> -         struct brw_reg src_2  = byte_offset(src,  2 * sizeof(float));
> -         struct brw_reg src_4  = byte_offset(src,  4 * sizeof(float));
> -         struct brw_reg src_6  = byte_offset(src,  6 * sizeof(float));
> -         struct brw_reg src_8  = byte_offset(src,  8 * sizeof(float));
> -         struct brw_reg src_10 = byte_offset(src, 10 * sizeof(float));
> -         struct brw_reg src_12 = byte_offset(src, 12 * sizeof(float));
> -         struct brw_reg src_14 = byte_offset(src, 14 * sizeof(float));
> -
> -         struct brw_reg dst_0  = byte_offset(dst,  0 * sizeof(float));
> -         struct brw_reg dst_4  = byte_offset(dst,  4 * sizeof(float));
> -         struct brw_reg dst_8  = byte_offset(dst,  8 * sizeof(float));
> -         struct brw_reg dst_12 = byte_offset(dst, 12 * sizeof(float));
> +         struct brw_reg src_0  = byte_offset(src,  0 * type_size);
> +         struct brw_reg src_2  = byte_offset(src,  2 * type_size);
> +         struct brw_reg src_4  = byte_offset(src,  4 * type_size);
> +         struct brw_reg src_6  = byte_offset(src,  6 * type_size);
> +         struct brw_reg src_8  = byte_offset(src,  8 * type_size);
> +         struct brw_reg src_10 = byte_offset(src, 10 * type_size);
> +         struct brw_reg src_12 = byte_offset(src, 12 * type_size);
> +         struct brw_reg src_14 = byte_offset(src, 14 * type_size);
> +
> +         struct brw_reg dst_0  = byte_offset(dst,  0 * type_size);
> +         struct brw_reg dst_4  = byte_offset(dst,  4 * type_size);
> +         struct brw_reg dst_8  = byte_offset(dst,  8 * type_size);
> +         struct brw_reg dst_12 = byte_offset(dst, 12 * type_size);
>
>           brw_push_insn_state(p);
>           brw_set_default_exec_size(p, BRW_EXECUTE_4);
> @@ -1323,8 +1325,8 @@ fs_generator::generate_ddy(const fs_inst *inst,
>        /* replicate the derivative at the top-left pixel to other pixels */
>        struct brw_reg src0 = stride(src, 4, 4, 0);
>        struct brw_reg src1 = stride(src, 4, 4, 0);
> -      src0.subnr = 0 * sizeof(float);
> -      src1.subnr = 2 * sizeof(float);
> +      src0.subnr = 0 * type_size;
> +      src1.subnr = 2 * type_size;
>

Again, +=?  Or, better yet, maybe byte_offset().


>
>        brw_ADD(p, dst, negate(src0), src1);
>     }
> --
> 2.17.1
>
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