diff --git a/src/asahi/compiler/agx_nir.h b/src/asahi/compiler/agx_nir.h
index db1ddea1111..4ef3a326299 100644
--- a/src/asahi/compiler/agx_nir.h
+++ b/src/asahi/compiler/agx_nir.h
@@ -15,5 +15,6 @@ bool agx_nir_lower_algebraic_late(struct nir_shader *shader);
 bool agx_nir_fuse_algebraic_late(struct nir_shader *shader);
 bool agx_nir_fence_images(struct nir_shader *shader);
 bool agx_nir_lower_multisampled_image_store(struct nir_shader *s);
+void agx_nir_lower_layer(struct nir_shader *s);
 
 #endif
diff --git a/src/asahi/compiler/agx_nir_lower_layer.c b/src/asahi/compiler/agx_nir_lower_layer.c
new file mode 100644
index 00000000000..4d606ce952b
--- /dev/null
+++ b/src/asahi/compiler/agx_nir_lower_layer.c
@@ -0,0 +1,67 @@
+/*
+ * Copyright 2023 Valve Corporation
+ * SPDX-License-Identifier: MIT
+ */
+
+#include "compiler/nir/nir.h"
+#include "compiler/nir/nir_builder.h"
+#include "agx_nir.h"
+
+void
+agx_nir_lower_layer(nir_shader *s)
+{
+   assert(s->info.stage == MESA_SHADER_VERTEX);
+   if (!(s->info.outputs_written & (VARYING_BIT_LAYER | VARYING_BIT_VIEWPORT)))
+      return;
+
+   /* Writes are in the last block, search */
+   nir_function_impl *impl = nir_shader_get_entrypoint(s);
+   nir_block *last = nir_impl_last_block(impl);
+
+   nir_def *layer = NULL, *viewport = NULL;
+   nir_cursor last_cursor;
+
+   nir_foreach_instr(instr, last) {
+      if (instr->type != nir_instr_type_intrinsic)
+         continue;
+
+      nir_intrinsic_instr *store = nir_instr_as_intrinsic(instr);
+      if (store->intrinsic != nir_intrinsic_store_output)
+         continue;
+
+      nir_io_semantics sem = nir_intrinsic_io_semantics(store);
+      nir_def *value = store->src[0].ssa;
+
+      if (sem.location == VARYING_SLOT_LAYER) {
+         assert(layer == NULL && "only written once");
+         layer = value;
+      } else if (sem.location == VARYING_SLOT_VIEWPORT) {
+         assert(viewport == NULL && "only written once");
+         viewport = value;
+      } else {
+         continue;
+      }
+
+      last_cursor = nir_after_instr(&store->instr);
+
+      /* Leave the store as a varying-only, no sysval output */
+      sem.no_sysval_output = true;
+      nir_intrinsic_set_io_semantics(store, sem);
+   }
+
+   assert((layer || viewport) && "metadata inconsistent with program");
+
+   /* Pack together and write out */
+   nir_builder b = nir_builder_at(last_cursor);
+
+   nir_def *zero = nir_imm_intN_t(&b, 0, 16);
+   nir_def *packed =
+      nir_pack_32_2x16_split(&b, layer ? nir_u2u16(&b, layer) : zero,
+                             viewport ? nir_u2u16(&b, viewport) : zero);
+
+   /* Written with a sysval-only store, no varying output */
+   nir_store_output(&b, packed, nir_imm_int(&b, 0),
+                    .io_semantics.location = VARYING_SLOT_LAYER,
+                    .io_semantics.num_slots = 1,
+                    .io_semantics.no_varying = true);
+}
diff --git a/src/asahi/compiler/meson.build b/src/asahi/compiler/meson.build
index 3a985fbdb60..8130dbb3eb8 100644
--- a/src/asahi/compiler/meson.build
+++ b/src/asahi/compiler/meson.build
@@ -14,6 +14,7 @@ libasahi_agx_files = files(
   'agx_nir_lower_discard_zs_emit.c',
   'agx_nir_lower_texture.c',
   'agx_nir_lower_interpolation.c',
+  'agx_nir_lower_layer.c',
   'agx_nir_lower_load_mask.c',
   'agx_nir_lower_shared_bitsize.c',
   'agx_nir_opt_preamble.c',