asahi: Gather flat/linear shaded input info from uncompiled FS

We need to propagate shading model metadata from the FS to the VS in
order to correctly lay out the uniforms in the right order. This means
we need VS variants depending on this data.

We could use the existing shader info structure, but that applies to
compiled shaders which would introduce a dependency from the VS compile
to the FS compile. This information does not change with FS variants, so
we can introduce an agx_uncompiled_shader_info structure and gather it
early at precompilation time.

Signed-off-by: Asahi Lina <lina@asahilina.net>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/23998>

src/asahi/compiler/agx_compile.c

@@ -2094,33 +2094,60 @@ agx_gather_texcoords(nir_builder *b, nir_instr *instr, void *data)
    return false;
 }
 
+struct interp_masks {
+   uint64_t flat;
+   uint64_t linear;
+};
+
 static bool
-agx_gather_flat(nir_builder *b, nir_instr *instr, void *data)
+agx_gather_interp(nir_builder *b, nir_instr *instr, void *data)
 {
-   uint64_t *mask = data;
+   struct interp_masks *masks = data;
    if (instr->type != nir_instr_type_intrinsic)
       return false;
 
    nir_intrinsic_instr *intr = nir_instr_as_intrinsic(instr);
-   if (intr->intrinsic != nir_intrinsic_load_input)
-      return false;
 
+   if (intr->intrinsic == nir_intrinsic_load_input) {
       nir_io_semantics sem = nir_intrinsic_io_semantics(intr);
-   *mask |= BITFIELD64_BIT(sem.location);
+      masks->flat |= BITFIELD64_BIT(sem.location);
+   } else if (intr->intrinsic == nir_intrinsic_load_interpolated_input &&
+              nir_intrinsic_interp_mode(nir_src_as_intrinsic(intr->src[0])) ==
+                 INTERP_MODE_NOPERSPECTIVE) {
+      nir_io_semantics sem = nir_intrinsic_io_semantics(intr);
+      masks->linear |= BITFIELD64_BIT(sem.location);
+   }
+
    return false;
 }
 
 /*
- * Build a bit mask of varyings (by location) that are flatshaded or used as
- * texture coordinates. This information is needed by lower_mediump_io.
+ * Build a bit mask of varyings (by location) that are flatshaded and linear
+ * shaded. This information is needed by lower_mediump_io and
+ * agx_uncompiled_shader_info.
+ */
+static struct interp_masks
+agx_interp_masks(nir_shader *nir)
+{
+   assert(nir->info.stage == MESA_SHADER_FRAGMENT);
+
+   struct interp_masks masks = {0};
+   nir_shader_instructions_pass(nir, agx_gather_interp, nir_metadata_all,
+                                &masks);
+
+   return masks;
+}
+
+/*
+ * Build a bit mask of varyings (by location) that are used as texture
+ * coordinates. This information is needed by lower_mediump_io.
  */
 static uint64_t
-agx_fp32_varying_mask(nir_shader *nir)
+agx_texcoord_mask(nir_shader *nir)
 {
    assert(nir->info.stage == MESA_SHADER_FRAGMENT);
 
    uint64_t mask = 0;
-   nir_shader_instructions_pass(nir, agx_gather_flat, nir_metadata_all, &mask);
    nir_shader_instructions_pass(nir, agx_gather_texcoords, nir_metadata_all,
                                 &mask);
    return mask;
@@ -2287,8 +2314,12 @@ agx_compile_function_nir(nir_shader *nir, nir_function_impl *impl,
  * lowered here to avoid duplicate work with shader variants.
  */
 void
-agx_preprocess_nir(nir_shader *nir, bool support_lod_bias)
+agx_preprocess_nir(nir_shader *nir, bool support_lod_bias,
+                   struct agx_uncompiled_shader_info *out)
 {
+   if (out)
+      memset(out, 0, sizeof(*out));
+
    NIR_PASS_V(nir, nir_lower_vars_to_ssa);
 
    if (nir->info.stage == MESA_SHADER_VERTEX) {
@@ -2313,6 +2344,9 @@ agx_preprocess_nir(nir_shader *nir, bool support_lod_bias)
               glsl_type_size, 0);
    NIR_PASS_V(nir, nir_lower_ssbo);
    if (nir->info.stage == MESA_SHADER_FRAGMENT) {
+      uint64_t texcoord = agx_texcoord_mask(nir);
+      struct interp_masks masks = agx_interp_masks(nir);
+
       NIR_PASS_V(nir, agx_nir_lower_frag_sidefx);
 
       /* Interpolate varyings at fp16 and write to the tilebuffer at fp16. As an
@@ -2322,7 +2356,12 @@ agx_preprocess_nir(nir_shader *nir, bool support_lod_bias)
        */
       NIR_PASS_V(nir, nir_lower_mediump_io,
                  nir_var_shader_in | nir_var_shader_out,
-                 ~agx_fp32_varying_mask(nir), false);
+                 ~(masks.flat | texcoord), false);
+
+      if (out) {
+         out->inputs_flat_shaded = masks.flat;
+         out->inputs_linear_shaded = masks.linear;
+      }
    }
 
    /* Clean up deref gunk after lowering I/O */

src/asahi/compiler/agx_compile.h

@@ -76,6 +76,11 @@ union agx_varyings {
    struct agx_varyings_fs fs;
 };
 
+struct agx_uncompiled_shader_info {
+   uint64_t inputs_flat_shaded;
+   uint64_t inputs_linear_shaded;
+};
+
 struct agx_shader_info {
    union agx_varyings varyings;
 
@@ -171,7 +176,8 @@ struct agx_shader_key {
    };
 };
 
-void agx_preprocess_nir(nir_shader *nir, bool support_lod_bias);
+void agx_preprocess_nir(nir_shader *nir, bool support_lod_bias,
+                        struct agx_uncompiled_shader_info *out);
 
 bool agx_nir_lower_discard_zs_emit(nir_shader *s);
 

src/asahi/lib/agx_meta.c

@@ -17,7 +17,7 @@ agx_compile_meta_shader(struct agx_meta_cache *cache, nir_shader *shader,
    struct util_dynarray binary;
    util_dynarray_init(&binary, NULL);
 
-   agx_preprocess_nir(shader, false);
+   agx_preprocess_nir(shader, false, NULL);
    if (tib) {
       agx_nir_lower_tilebuffer(shader, tib, NULL, NULL);
       agx_nir_lower_monolithic_msaa(

src/gallium/drivers/asahi/agx_state.c

@@ -1595,7 +1595,7 @@ agx_create_shader_state(struct pipe_context *pctx,
    blob_finish(&blob);
 
    so->nir = nir;
-   agx_preprocess_nir(nir, true);
+   agx_preprocess_nir(nir, true, &so->info);
 
    /* For shader-db, precompile a shader with a default key. This could be
     * improved but hopefully this is acceptable for now.
@@ -1674,7 +1674,7 @@ agx_create_compute_state(struct pipe_context *pctx,
    blob_finish(&blob);
 
    so->nir = nir;
-   agx_preprocess_nir(nir, true);
+   agx_preprocess_nir(nir, true, &so->info);
    agx_get_shader_variant(agx_screen(pctx->screen), so, &pctx->debug, &key);
 
    /* We're done with the NIR, throw it away */

src/gallium/drivers/asahi/agx_state.h

@@ -171,6 +171,7 @@ struct agx_uncompiled_shader {
    enum pipe_shader_type type;
    const struct nir_shader *nir;
    uint8_t nir_sha1[20];
+   struct agx_uncompiled_shader_info info;
    struct hash_table *variants;
 
    /* For compute kernels */