zink: Fix RelaxedPrecision decoration of texture samples.

You can't do it unless GL called the sampler mediump.  Also, the spirv
says "For image-sampling operations, decorations can appear on both the
sampling instruction and the image variable being sampled.  If either is
decorated, they both should be decorated, and if both are decorated their
decorations must match. If only one is decorated, the sampling instruction
can behave either as if both were decorated or neither were decorated." so
emit it on the declaration too.

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/18960>

diff --git a/src/gallium/drivers/zink/nir_to_spirv/nir_to_spirv.c b/src/gallium/drivers/zink/nir_to_spirv/nir_to_spirv.c
index 39de2b4..b189c3b 100644 (file)
--- a/src/gallium/drivers/zink/nir_to_spirv/nir_to_spirv.c
+++ b/src/gallium/drivers/zink/nir_to_spirv/nir_to_spirv.c
@@ -65,6 +65,7 @@ struct ntv_context {
    SpvId samplers[PIPE_MAX_SAMPLERS];
    unsigned char sampler_array_sizes[PIPE_MAX_SAMPLERS];
    unsigned samplers_used : PIPE_MAX_SAMPLERS;
+   unsigned samplers_used_mediump : PIPE_MAX_SAMPLERS;
    SpvId entry_ifaces[PIPE_MAX_SHADER_INPUTS * 4 + PIPE_MAX_SHADER_OUTPUTS * 4];
    size_t num_entry_ifaces;
 
@@ -965,6 +966,7 @@ emit_image(struct ntv_context *ctx, struct nir_variable *var, bool bindless)
    bool is_sampler = glsl_type_is_sampler(type);
    SpvId image_type = get_bare_image_type(ctx, var, is_sampler);
    SpvId var_type = is_sampler ? spirv_builder_type_sampled_image(&ctx->builder, image_type) : image_type;
+   bool mediump = (var->data.precision == GLSL_PRECISION_MEDIUM || var->data.precision == GLSL_PRECISION_LOW);
 
    int index = var->data.driver_location;
    assert(!is_sampler || (!(ctx->samplers_used & (1 << index))));
@@ -984,6 +986,11 @@ emit_image(struct ntv_context *ctx, struct nir_variable *var, bool bindless)
    SpvId var_id = spirv_builder_emit_var(&ctx->builder, pointer_type,
                                          SpvStorageClassUniformConstant);
 
+   if (mediump) {
+      spirv_builder_emit_decoration(&ctx->builder, var_id,
+                                    SpvDecorationRelaxedPrecision);
+   }
+
    if (var->name)
       spirv_builder_emit_name(&ctx->builder, var_id, var->name);
 
@@ -998,6 +1005,8 @@ emit_image(struct ntv_context *ctx, struct nir_variable *var, bool bindless)
       ctx->sampler_types[index] = image_type;
       ctx->samplers[index] = var_id;
       ctx->samplers_used |= 1 << index;
+      if (mediump)
+         ctx->samplers_used_mediump |= 1 << index;
    } else {
       ctx->image_types[index] = image_type;
       ctx->images[index] = var_id;
@@ -2848,6 +2857,7 @@ emit_image_deref_load(struct ntv_context *ctx, nir_intrinsic_instr *intr)
    SpvId img_var = get_src(ctx, &intr->src[0]);
    nir_deref_instr *deref = nir_src_as_deref(intr->src[0]);
    nir_variable *var = deref->deref_type == nir_deref_type_var ? deref->var : get_var_from_image(ctx, img_var);
+   bool mediump = (var->data.precision == GLSL_PRECISION_MEDIUM || var->data.precision == GLSL_PRECISION_LOW);
    SpvId img_type = var->data.bindless ? get_bare_image_type(ctx, var, false) : ctx->image_types[var->data.driver_location];
    const struct glsl_type *type = glsl_without_array(var->type);
    SpvId base_type = get_glsl_basetype(ctx, glsl_get_sampler_result_type(type));
@@ -2862,6 +2872,12 @@ emit_image_deref_load(struct ntv_context *ctx, nir_intrinsic_instr *intr)
                                  img, coord, 0, sample, 0, sparse);
    if (sparse)
       result = extract_sparse_load(ctx, result, dest_type, &intr->dest.ssa);
+
+   if (!sparse && mediump) {
+      spirv_builder_emit_decoration(&ctx->builder, result,
+                                    SpvDecorationRelaxedPrecision);
+   }
+
    store_dest(ctx, &intr->dest, result, nir_type_float);
 }
 
@@ -3676,8 +3692,10 @@ emit_tex(struct ntv_context *ctx, nir_tex_instr *tex)
                                                const_offset, offset, min_lod, tex->is_sparse);
    }
 
-   spirv_builder_emit_decoration(&ctx->builder, result,
-                                 SpvDecorationRelaxedPrecision);
+   if (!bindless_var && (ctx->samplers_used_mediump & (1 << tex->texture_index))) {
+      spirv_builder_emit_decoration(&ctx->builder, result,
+                                    SpvDecorationRelaxedPrecision);
+   }
 
    if (tex->is_sparse)
       result = extract_sparse_load(ctx, result, actual_dest_type, &tex->dest.ssa);