Mesa (main): panfrost: Create transform feedback shaders

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Module: Mesa
Branch: main
Commit: a510a94b02449c3ecb9fad043a28fc8641ab66c8
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=a510a94b02449c3ecb9fad043a28fc8641ab66c8

Author: Alyssa Rosenzweig <alyssa at collabora.com>
Date:   Thu Jun  2 10:51:16 2022 -0400

panfrost: Create transform feedback shaders

Valhall has no architectural support for transform feedback. So if a vertex
shader uses transform feedback, we need to split the shader into two: a pure
vertex stage and a compute-like transform feedback stage. This splitting
resembles the splitting we do for IDVS.

When compiling a vertex shader that uses transform feedback on Bifrost, also
compile the transform feedback variant. That variant (marked by internal=true)
will get its stores lowered by the NIR pass introduced earlier in this series.

Signed-off-by: Alyssa Rosenzweig <alyssa at collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/15720>

---

 src/gallium/drivers/panfrost/pan_assemble.c | 13 +++++++++++++
 src/gallium/drivers/panfrost/pan_context.c  |  7 +++++++
 src/gallium/drivers/panfrost/pan_context.h  |  3 +++
 3 files changed, 23 insertions(+)

diff --git a/src/gallium/drivers/panfrost/pan_assemble.c b/src/gallium/drivers/panfrost/pan_assemble.c
index 21141e930bd..ae86112b26e 100644
--- a/src/gallium/drivers/panfrost/pan_assemble.c
+++ b/src/gallium/drivers/panfrost/pan_assemble.c
@@ -47,6 +47,19 @@ panfrost_shader_compile(struct pipe_screen *pscreen,
 
         nir_shader *s = nir_shader_clone(NULL, ir);
 
+        if (dev->arch >= 6 && s->xfb_info && !s->info.internal) {
+                /* Create compute shader doing transform feedback */
+                nir_shader *xfb = nir_shader_clone(NULL, s);
+                xfb->info.name = ralloc_asprintf(xfb, "%s at xfb", xfb->info.name);
+                xfb->info.internal = true;
+
+                state->xfb = calloc(1, sizeof(struct panfrost_shader_state));
+                panfrost_shader_compile(pscreen, shader_pool, desc_pool, xfb, state->xfb);
+
+                /* Main shader no longer uses XFB */
+                s->info.has_transform_feedback_varyings = false;
+        }
+
         /* Lower this early so the backends don't have to worry about it */
         if (s->info.stage == MESA_SHADER_FRAGMENT) {
                 NIR_PASS_V(s, nir_lower_fragcolor, state->key.fs.nr_cbufs);
diff --git a/src/gallium/drivers/panfrost/pan_context.c b/src/gallium/drivers/panfrost/pan_context.c
index 3efc48294d6..304107f45c4 100644
--- a/src/gallium/drivers/panfrost/pan_context.c
+++ b/src/gallium/drivers/panfrost/pan_context.c
@@ -342,6 +342,13 @@ panfrost_delete_shader_state(
                 panfrost_bo_unreference(shader_state->bin.bo);
                 panfrost_bo_unreference(shader_state->state.bo);
                 panfrost_bo_unreference(shader_state->linkage.bo);
+
+                if (shader_state->xfb) {
+                        panfrost_bo_unreference(shader_state->xfb->bin.bo);
+                        panfrost_bo_unreference(shader_state->xfb->state.bo);
+                        panfrost_bo_unreference(shader_state->xfb->linkage.bo);
+                        free(shader_state->xfb);
+                }
         }
 
         simple_mtx_destroy(&cso->lock);
diff --git a/src/gallium/drivers/panfrost/pan_context.h b/src/gallium/drivers/panfrost/pan_context.h
index 415ba5f28ed..0145e94e886 100644
--- a/src/gallium/drivers/panfrost/pan_context.h
+++ b/src/gallium/drivers/panfrost/pan_context.h
@@ -290,6 +290,9 @@ struct panfrost_shader_state {
 
         struct pan_shader_info info;
 
+        /* Attached transform feedback program, if one exists */
+        struct panfrost_shader_state *xfb;
+
         /* Linked varyings, for non-separable programs */
         struct pan_linkage linkage;