With NGG, empty waves may still be required to export data.

This fixes dEQP-VK.ycbcr.format.*_unorm.geometry_*.

Signed-off-by: Samuel Pitoiset <samuel.pitoi...@gmail.com>
---
 src/amd/vulkan/radv_nir_to_llvm.c | 31 ++++++++++++++++++++++++++++++-
 1 file changed, 30 insertions(+), 1 deletion(-)

diff --git a/src/amd/vulkan/radv_nir_to_llvm.c 
b/src/amd/vulkan/radv_nir_to_llvm.c
index 3e18303879e..7e623414adc 100644
--- a/src/amd/vulkan/radv_nir_to_llvm.c
+++ b/src/amd/vulkan/radv_nir_to_llvm.c
@@ -4448,8 +4448,37 @@ LLVMModuleRef ac_translate_nir_to_llvm(struct 
ac_llvm_compiler *ac_llvm,
                        declare_esgs_ring(&ctx);
                }
 
-               if (i)
+               bool nested_barrier = false;
+
+               if (i) {
+                       if (shaders[i]->info.stage == MESA_SHADER_GEOMETRY &&
+                           ctx.options->key.vs_common_out.as_ngg) {
+                               nested_barrier = false;
+                       } else {
+                               nested_barrier = true;
+                       }
+               }
+
+               if (nested_barrier) {
+                       /* Execute a barrier before the second shader in
+                        * a merged shader.
+                        *
+                        * Execute the barrier inside the conditional block,
+                        * so that empty waves can jump directly to s_endpgm,
+                        * which will also signal the barrier.
+                        *
+                        * This is possible in gfx9, because an empty wave
+                        * for the second shader does not participate in
+                        * the epilogue. With NGG, empty waves may still
+                        * be required to export data (e.g. GS output vertices),
+                        * so we cannot let them exit early.
+                        *
+                        * If the shader is TCS and the TCS epilog is present
+                        * and contains a barrier, it will wait there and then
+                        * reach s_endpgm.
+                       */
                        ac_emit_barrier(&ctx.ac, ctx.stage);
+               }
 
                nir_foreach_variable(variable, &shaders[i]->outputs)
                        scan_shader_output_decl(&ctx, variable, shaders[i], 
shaders[i]->info.stage);
-- 
2.22.0

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