[Mesa-dev] [Mesa-stable] [PATCH 5/5] amd/common: add workaround for cube map array layer clamping

[Marek Olšák]

For the series:

Reviewed-by: Marek Olšák <marek.olsak at amd.com>

Marek

On Wed, Sep 13, 2017 at 7:04 PM, Nicolai Hähnle <nhaehnle at gmail.com> wrote:
> From: Nicolai Hähnle <nicolai.haehnle at amd.com>
>
> Fixes dEQP-GLES31.functional.texture.filtering.cube_array.*
>
> Cc: mesa-stable at lists.freedesktop.org
> ---
>  src/amd/common/ac_llvm_build.c | 31 +++++++++++++++++++++++++++++--
>  1 file changed, 29 insertions(+), 2 deletions(-)
>
> diff --git a/src/amd/common/ac_llvm_build.c b/src/amd/common/ac_llvm_build.c
> index 6c010e8c3a6..8a329515b57 100644
> --- a/src/amd/common/ac_llvm_build.c
> +++ b/src/amd/common/ac_llvm_build.c
> @@ -491,22 +491,49 @@ ac_prepare_cube_coords(struct ac_llvm_context *ctx,
>                        LLVMValueRef *coords_arg,
>                        LLVMValueRef *derivs_arg)
>  {
>
>         LLVMBuilderRef builder = ctx->builder;
>         struct cube_selection_coords selcoords;
>         LLVMValueRef coords[3];
>         LLVMValueRef invma;
>
>         if (is_array && !is_lod) {
> -               coords_arg[3] = ac_build_intrinsic(ctx, "llvm.rint.f32", ctx->f32,
> -                                                  &coords_arg[3], 1, 0);
> +               LLVMValueRef tmp = coords_arg[3];
> +               tmp = ac_build_intrinsic(ctx, "llvm.rint.f32", ctx->f32, &tmp, 1, 0);
> +
> +               /* Section 8.9 (Texture Functions) of the GLSL 4.50 spec says:
> +                *
> +                *    "For Array forms, the array layer used will be
> +                *
> +                *       max(0, min(d−1, floor(layer+0.5)))
> +                *
> +                *     where d is the depth of the texture array and layer
> +                *     comes from the component indicated in the tables below.
> +                *     Workaroudn for an issue where the layer is taken from a
> +                *     helper invocation which happens to fall on a different
> +                *     layer due to extrapolation."
> +                *
> +                * VI and earlier attempt to implement this in hardware by
> +                * clamping the value of coords[2] = (8 * layer) + face.
> +                * Unfortunately, this means that the we end up with the wrong
> +                * face when clamping occurs.
> +                *
> +                * Clamp the layer earlier to work around the issue.
> +                */
> +               if (ctx->chip_class <= VI) {
> +                       LLVMValueRef ge0;
> +                       ge0 = LLVMBuildFCmp(builder, LLVMRealOGE, tmp, ctx->f32_0, "");
> +                       tmp = LLVMBuildSelect(builder, ge0, tmp, ctx->f32_0, "");
> +               }
> +
> +               coords_arg[3] = tmp;
>         }
>
>         build_cube_intrinsic(ctx, coords_arg, &selcoords);
>
>         invma = ac_build_intrinsic(ctx, "llvm.fabs.f32",
>                         ctx->f32, &selcoords.ma, 1, AC_FUNC_ATTR_READNONE);
>         invma = ac_build_fdiv(ctx, LLVMConstReal(ctx->f32, 1.0), invma);
>
>         for (int i = 0; i < 2; ++i)
>                 coords[i] = LLVMBuildFMul(builder, selcoords.stc[i], invma, "");
> --
> 2.11.0
>
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