From 44fcda9631ee94f2c28367b2d70e630de8a65734 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Marek=20Ol=C5=A1=C3=A1k?= <marek.olsak@amd.com>
Date: Mon, 26 May 2025 10:14:24 -0400
Subject: [PATCH] nir/opt_clip_cull_const: support GS

Reviewed-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/35256>
---
 src/compiler/nir/nir_opt_clip_cull_const.c | 95 +++++++++++++++++++---
 1 file changed, 85 insertions(+), 10 deletions(-)

diff --git a/src/compiler/nir/nir_opt_clip_cull_const.c b/src/compiler/nir/nir_opt_clip_cull_const.c
index 0132f0e7b83..c7d827c01de 100644
--- a/src/compiler/nir/nir_opt_clip_cull_const.c
+++ b/src/compiler/nir/nir_opt_clip_cull_const.c
@@ -15,39 +15,114 @@
  * and works best with scalar store_outputs.
  */
 
-static bool
-opt_clip_cull(nir_builder *b, nir_intrinsic_instr *intr, void *unused)
+/* Return -1 if invalid, 0 if it's a normal clip/cull distance value,
+ * and 1 if it's a no-op value.
+ */
+static int
+analyze_clip_cull_value(nir_intrinsic_instr *intr)
 {
    if (intr->intrinsic != nir_intrinsic_store_output)
-      return false;
+      return -1;
 
    const nir_io_semantics io_sem = nir_intrinsic_io_semantics(intr);
    const unsigned location = io_sem.location;
 
    if (io_sem.no_sysval_output)
-      return false;
+      return -1;
 
    if (location != VARYING_SLOT_CLIP_DIST0 && location != VARYING_SLOT_CLIP_DIST1)
-      return false;
+      return -1;
 
    nir_def *val = intr->src[0].ssa;
    for (unsigned i = 0; i < val->num_components; i++) {
       nir_scalar s = nir_scalar_resolved(val, i);
       if (!nir_scalar_is_const(s))
-         return false;
+         return 0;
       float distance = nir_scalar_as_float(s);
 
       /* NaN gets clipped, and INF after interpolation is NaN. */
       if (isnan(distance) || distance < 0.0 || distance == INFINITY)
-         return false;
+         return 0;
    }
 
-   nir_remove_sysval_output(intr, MESA_SHADER_FRAGMENT);
-   return true;
+   return 1;
+}
+
+static bool
+opt_clip_cull_vs_tes(nir_builder *b, nir_intrinsic_instr *intr, void *unused)
+{
+   if (analyze_clip_cull_value(intr) == 1) {
+      nir_remove_sysval_output(intr, MESA_SHADER_FRAGMENT);
+      return true;
+   }
+
+   return false;
+}
+
+/* The types of stores are first gathered for all stores. If a certain slot
+ * component is only written by no-op stores, they are removed.
+ */
+typedef struct {
+   bool has_normal_store[8];
+   bool has_noop_store[8];
+} gs_info;
+
+static unsigned
+get_clip_io_index(nir_intrinsic_instr *intr)
+{
+   nir_io_semantics sem = nir_intrinsic_io_semantics(intr);
+   assert(intr->intrinsic == nir_intrinsic_store_output);
+   assert(sem.location == VARYING_SLOT_CLIP_DIST0 ||
+          sem.location == VARYING_SLOT_CLIP_DIST1);
+   assert(sem.num_slots == 1);
+   assert(nir_src_as_uint(*nir_get_io_offset_src(intr)) == 0); /* no indirect */
+   assert(intr->src[0].ssa->num_components == 1); /* scalar */
+
+   return (sem.location - VARYING_SLOT_CLIP_DIST0) * 4 +
+          nir_intrinsic_component(intr);
+}
+
+static bool
+gather_clip_cull_gs(nir_builder *b, nir_intrinsic_instr *intr, void *unused)
+{
+   gs_info *info = (gs_info *)unused;
+   int r = analyze_clip_cull_value(intr);
+
+   if (r == 1)
+      info->has_noop_store[get_clip_io_index(intr)] = true;
+   else if (r == 0)
+      info->has_normal_store[get_clip_io_index(intr)] = true;
+
+   return false;
+}
+
+static bool
+opt_clip_cull_gs(nir_builder *b, nir_intrinsic_instr *intr, void *unused)
+{
+   gs_info *info = (gs_info *)unused;
+
+   if (intr->intrinsic == nir_intrinsic_store_output &&
+       (nir_intrinsic_io_semantics(intr).location == VARYING_SLOT_CLIP_DIST0 ||
+        nir_intrinsic_io_semantics(intr).location == VARYING_SLOT_CLIP_DIST1)) {
+      unsigned index = get_clip_io_index(intr);
+
+      if (info->has_noop_store[index] && !info->has_normal_store[index]) {
+         nir_remove_sysval_output(intr, MESA_SHADER_FRAGMENT);
+         return true;
+      }
+   }
+
+   return false;
 }
 
 bool
 nir_opt_clip_cull_const(nir_shader *shader)
 {
-   return nir_shader_intrinsics_pass(shader, opt_clip_cull, nir_metadata_control_flow, NULL);
+   if (shader->info.stage == MESA_SHADER_GEOMETRY) {
+      gs_info info = {0};
+      nir_shader_intrinsics_pass(shader, gather_clip_cull_gs, nir_metadata_all, &info);
+      return nir_shader_intrinsics_pass(shader, opt_clip_cull_gs, nir_metadata_all, &info);
+   } else {
+      return nir_shader_intrinsics_pass(shader, opt_clip_cull_vs_tes, nir_metadata_all, NULL);
+   }
 }