radv/llvm: Emit s_barrier at the beginning of NGG non-GS shaders.

This is to fix a hang that can potentially happen when not every
wave had launched when a gs_alloc_req is executed.

Cc: mesa-stable
Signed-off-by: Timur Kristóf <timur.kristof@gmail.com>
Reviewed-by: Rhys Perry <pendingchaos02@gmail.com>
Reviewed-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/10837>

src/amd/vulkan/radv_nir_to_llvm.c

@@ -3077,6 +3077,10 @@ ac_translate_nir_to_llvm(struct ac_llvm_compiler *ac_llvm, struct nir_shader *co
          LLVMSetInitializer(ctx.gs_ngg_scratch, LLVMGetUndef(asi32));
          LLVMSetAlignment(ctx.gs_ngg_scratch, 4);
       }
+
+      /* GFX10 hang workaround - there needs to be an s_barrier before gs_alloc_req always */
+      if (ctx.ac.chip_class == GFX10 && shader_count == 1)
+         ac_build_s_barrier(&ctx.ac);
    }
 
    for (int shader_idx = 0; shader_idx < shader_count; ++shader_idx) {