pan/bi: Add some helpers an an info field for needing the extended FIFO

The logic here is a bit scattered around and is about to get more
complicated.  This adds a helper which better documents the interactions
as well as an info field to make the driver's life easier.

Reviewed-by: Olivia Lee <olivia.lee@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/38504>

src/panfrost/compiler/bifrost_compile.c

@@ -1410,8 +1410,12 @@ bi_emit_store_vary(bi_builder *b, nir_intrinsic_instr *instr)
             /* We don't patch these offsets in the no_psiz variant, so if
              * multiview is enabled we can't switch to the basic format by
              * using no_psiz */
-            bool extended_position_fifo = b->shader->nir->info.outputs_written &
-               (VARYING_BIT_LAYER | VARYING_BIT_PSIZ);
+            const uint64_t outputs = b->shader->nir->info.outputs_written;
+            bool extended_position_fifo =
+               valhal_writes_extended_fifo(outputs, false, true);
+            /* Must be the same with and without no_psiz */
+            assert(valhal_writes_extended_fifo(outputs, true, true) ==
+                   extended_position_fifo);
             unsigned position_fifo_stride = extended_position_fifo ? 8 : 4;
             index_offset += view_index * position_fifo_stride;
          }
@@ -6860,10 +6864,10 @@ bi_compile_variant(nir_shader *nir,
 
       if (idvs == BI_IDVS_ALL) {
          /* Varying shader is only enabled if we can have any kind of varying
-          * written (that mean not position, layer or point size) */
+          * written (that mean not position, or an extended FIFO attribute) */
          info->vs.secondary_enable =
             (nir->info.outputs_written &
-             ~(VARYING_BIT_POS | VARYING_BIT_LAYER | VARYING_BIT_PSIZ)) != 0;
+             ~(VARYING_BIT_POS | VALHAL_EX_FIFO_VARYING_BITS)) != 0;
       }
    }
 

src/panfrost/compiler/bifrost_compile.h

@@ -92,6 +92,33 @@ void bifrost_compile_shader_nir(nir_shader *nir,
                                 struct util_dynarray *binary,
                                 struct pan_shader_info *info);
 
+#define VALHAL_EX_FIFO_VARYING_BITS \
+   (VARYING_BIT_PSIZ | VARYING_BIT_LAYER)
+
+static inline bool
+valhal_writes_extended_fifo(uint64_t outputs_written,
+                            bool no_psiz, bool multiview)
+{
+   uint64_t ex_fifo_written = outputs_written & VALHAL_EX_FIFO_VARYING_BITS;
+   if (ex_fifo_written == 0)
+      return false;
+
+   /* Multiview shaders depend on the FIFO format for indexing per-view
+    * output writes. We don't currently patch these offsets in the no_psiz
+    * variant, so we need the extended format, regardless of point size.
+    */
+   if (multiview)
+      return true;
+
+   /* If we're not rendering in points mode, the no_psiz variant has point
+    * size write patched out for us.
+    */
+   if (no_psiz)
+      ex_fifo_written &= ~VARYING_BIT_PSIZ;
+
+   return ex_fifo_written != 0;
+}
+
 #define DEFINE_OPTIONS(arch)                                                   \
    static const nir_shader_compiler_options bifrost_nir_options_v##arch = {    \
       .lower_scmp = true,                                                      \

src/panfrost/lib/pan_shader.c

@@ -95,6 +95,10 @@ pan_shader_compile(nir_shader *s, struct pan_compile_inputs *inputs,
       info->vs.writes_point_size =
          s->info.outputs_written & VARYING_BIT_PSIZ;
 
+      info->vs.needs_extended_fifo = arch >= 9 &&
+         valhal_writes_extended_fifo(s->info.outputs_written,
+                                     true, inputs->view_mask != 0);
+
       if (arch >= 9) {
          info->varyings.output_count =
             util_last_bit(s->info.outputs_written >> VARYING_SLOT_VAR0);

src/panfrost/util/pan_ir.h

@@ -246,6 +246,11 @@ struct pan_shader_info {
       struct {
          bool writes_point_size;
 
+         /* True if this shader needs the extended FIFO format for
+          * more than just point size.
+          */
+         bool needs_extended_fifo;
+
          /* If the primary shader writes point size, the Valhall
           * driver may need a variant that does not write point
           * size. Offset to such a shader in the program binary.

src/panfrost/vulkan/csf/panvk_vX_cmd_draw.c

@@ -2153,15 +2153,8 @@ set_tiler_idvs_flags(struct cs_builder *b, struct panvk_cmd_buffer *cmdbuf,
    bool writes_point_size =
       vs->info.vs.writes_point_size &&
       ia->primitive_topology == VK_PRIMITIVE_TOPOLOGY_POINT_LIST;
-   bool multiview = cmdbuf->state.gfx.render.view_mask;
    bool writes_layer = vs->info.outputs_written & VARYING_BIT_LAYER;
-
-   /* Multiview shaders depend on the FIFO format for indexing per-view
-    * output writes. We don't currently patch these offsets in the no_psiz
-    * variant, so we still need the extended format even though the shader
-    * does not write point size. */
-   bool extended_fifo = writes_point_size || writes_layer ||
-                        (vs->info.vs.writes_point_size && multiview);
+   bool extended_fifo = writes_point_size || vs->info.vs.needs_extended_fifo;
 
    bool dirty = gfx_state_dirty(cmdbuf, VS) || fs_user_dirty(cmdbuf) ||
                 dyn_gfx_state_dirty(cmdbuf, IA_PRIMITIVE_RESTART_ENABLE) ||