Mesa (main): zink: handle max_vertices=0 in geometry shader

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Module: Mesa
Branch: main
Commit: 5b58f8df538f9bb7489486d262a6e603ddfa1f65
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=5b58f8df538f9bb7489486d262a6e603ddfa1f65

Author: Mike Blumenkrantz <michael.blumenkrantz at gmail.com>
Date:   Mon Jul 11 12:04:22 2022 -0400

zink: handle max_vertices=0 in geometry shader

this is a weird corner case where glsl permits a zero value, so clamp to 1
and then don't emit any vertices to avoid driver hangs

affects:
dEQP-GL45-ES31.functional.geometry_shading.emit.points_emit_0_end_0

cc: mesa-stable

Reviewed-by: Dave Airlie <airlied at redhat.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/17639>

---

 src/gallium/drivers/zink/nir_to_spirv/nir_to_spirv.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/src/gallium/drivers/zink/nir_to_spirv/nir_to_spirv.c b/src/gallium/drivers/zink/nir_to_spirv/nir_to_spirv.c
index f206e5287d1..768f1e439aa 100644
--- a/src/gallium/drivers/zink/nir_to_spirv/nir_to_spirv.c
+++ b/src/gallium/drivers/zink/nir_to_spirv/nir_to_spirv.c
@@ -3060,8 +3060,9 @@ emit_intrinsic(struct ntv_context *ctx, nir_intrinsic_instr *intr)
        */
       if (ctx->sinfo)
          emit_so_outputs(ctx, ctx->sinfo);
-      spirv_builder_emit_vertex(&ctx->builder, nir_intrinsic_stream_id(intr),
-                                ctx->nir->info.stage == MESA_SHADER_GEOMETRY && util_bitcount(ctx->nir->info.gs.active_stream_mask) > 1);
+      if (ctx->nir->info.gs.vertices_out) //skip vertex emission if !vertices_out
+         spirv_builder_emit_vertex(&ctx->builder, nir_intrinsic_stream_id(intr),
+                                   ctx->nir->info.stage == MESA_SHADER_GEOMETRY && util_bitcount(ctx->nir->info.gs.active_stream_mask) > 1);
       break;
 
    case nir_intrinsic_set_vertex_and_primitive_count:
@@ -4336,7 +4337,7 @@ nir_to_spirv(struct nir_shader *s, const struct zink_shader_info *sinfo, uint32_
                                            s->info.gs.invocations);
       spirv_builder_emit_exec_mode_literal(&ctx.builder, entry_point,
                                            SpvExecutionModeOutputVertices,
-                                           s->info.gs.vertices_out);
+                                           MAX2(s->info.gs.vertices_out, 1));
       break;
    case MESA_SHADER_COMPUTE:
       if (s->info.shared_size)