panfrost: Assign varying buffers dynamically

Rather than hardcoding certain varying buffer indices "by convention",
work it out at draw time. This added flexibility is needed for
futureproofing and will be enable streamout.

Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>

2 files changed, 23 insertions, 36 deletions

diff --git a/src/gallium/drivers/panfrost/pan_assemble.c b/src/gallium/drivers/panfrost/pan_assemble.c
index dd877056d3b..337f97bddbd 100644
--- a/src/gallium/drivers/panfrost/pan_assemble.c
+++ b/src/gallium/drivers/panfrost/pan_assemble.c
@@ -141,28 +141,22 @@ panfrost_shader_compile(
                 /* Check for special cases, otherwise assume general varying */
 
                 if (location == VARYING_SLOT_POS) {
-                        v.index = 1;
                         v.format = MALI_VARYING_POS;
                 } else if (location == VARYING_SLOT_PSIZ) {
-                        v.index = 2;
                         v.format = MALI_R16F;
                         v.swizzle = default_vec1_swizzle;
 
                         state->writes_point_size = true;
                 } else if (location == VARYING_SLOT_PNTC) {
-                        v.index = 3;
                         v.format = MALI_RG16F;
                         v.swizzle = default_vec2_swizzle;
 
                         state->reads_point_coord = true;
                 } else if (location == VARYING_SLOT_FACE) {
-                        v.index = 4;
                         v.format = MALI_R32I;
                         v.swizzle = default_vec1_swizzle;
 
                         state->reads_face = true;
-                } else {
-                        v.index = 0;
                 }
 
                 state->varyings[i] = v;
diff --git a/src/gallium/drivers/panfrost/pan_varyings.c b/src/gallium/drivers/panfrost/pan_varyings.c
index b918d1426c4..b4ed512917a 100644
--- a/src/gallium/drivers/panfrost/pan_varyings.c
+++ b/src/gallium/drivers/panfrost/pan_varyings.c
@@ -60,6 +60,20 @@ panfrost_emit_front_face(union mali_attr *slot)
 
 /* Given a shader and buffer indices, link varying metadata together */
 
+static bool
+is_special_varying(gl_varying_slot loc)
+{
+        switch (loc) {
+        case VARYING_SLOT_POS:
+        case VARYING_SLOT_PSIZ:
+        case VARYING_SLOT_PNTC:
+        case VARYING_SLOT_FACE:
+                return true;
+        default:
+                return false;
+        }
+}
+
 static void
 panfrost_emit_varying_meta(
                 void *outptr, struct panfrost_shader_state *ss,
@@ -115,19 +129,9 @@ panfrost_emit_varying_descriptor(
         struct panfrost_transfer trans = panfrost_allocate_transient(ctx,
                                          vs_size + fs_size);
 
-        /*
-         * Assign ->src_offset now that we know about all the general purpose
-         * varyings that will be used by the fragment and vertex shaders.
-         */
         for (unsigned i = 0; i < vs->tripipe->varying_count; i++) {
-                /*
-                 * General purpose varyings have ->index set to 0, skip other
-                 * entries.
-                 */
-                if (vs->varyings[i].index)
-                        continue;
-
-                vs->varyings[i].src_offset = 16 * (num_gen_varyings++);
+                if (!is_special_varying(vs->varyings_loc[i]))
+                        vs->varyings[i].src_offset = 16 * (num_gen_varyings++);
         }
 
         for (unsigned i = 0; i < fs->tripipe->varying_count; i++) {
@@ -177,15 +181,14 @@ panfrost_emit_varying_descriptor(
         memcpy(trans.cpu, vs->varyings, vs_size);
         memcpy(trans.cpu + vs_size, fs->varyings, fs_size);
 
-        /* Buffer indices must be in this order per our convention */
         union mali_attr varyings[PIPE_MAX_ATTRIBS];
-        unsigned idx = 0;
 
+        unsigned idx = 0;
         signed general = idx++;
         signed gl_Position = idx++;
-        signed gl_PointSize = (vs->writes_point_size || fs->reads_point_coord || fs->reads_face) ? (idx++) : -1;
-        signed gl_PointCoord = (fs->reads_point_coord || fs->reads_face) ? (idx++) : -1;
-        signed gl_FrontFacing = (fs->reads_face) ? (idx++) : -1;
+        signed gl_PointSize = vs->writes_point_size ? (idx++) : -1;
+        signed gl_PointCoord = fs->reads_point_coord ? (idx++) : -1;
+        signed gl_FrontFacing = fs->reads_face ? (idx++) : -1;
 
         panfrost_emit_varyings(ctx, &varyings[general], num_gen_varyings * 16,
                                vertex_count);
@@ -196,26 +199,16 @@ panfrost_emit_varying_descriptor(
                                        sizeof(float) * 4, vertex_count);
 
 
-        if (vs->writes_point_size || fs->reads_point_coord) {
-                /* fp16 vec1 gl_PointSize */
+        if (vs->writes_point_size)
                 ctx->payloads[PIPE_SHADER_FRAGMENT].primitive_size.pointer =
                         panfrost_emit_varyings(ctx, &varyings[gl_PointSize],
                                                2, vertex_count);
-        } else if (fs->reads_face) {
-                /* Dummy to advance index */
-                ++idx;
-        }
 
-        if (fs->reads_point_coord) {
-                /* Special descriptor */
+        if (fs->reads_point_coord)
                 panfrost_emit_point_coord(&varyings[gl_PointCoord]);
-        } else if (fs->reads_face) {
-                ++idx;
-        }
 
-        if (fs->reads_face) {
+        if (fs->reads_face)
                 panfrost_emit_front_face(&varyings[gl_FrontFacing]);
-        }
 
         /* Let's go ahead and link varying meta to the buffer in question, now
          * that that information is available */