agx: lower export even later

so we can do reg cache opt as late as possible without losing this information.

Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/36399>

src/asahi/compiler/agx_lower_pseudo.c

@@ -124,12 +124,6 @@ lower(agx_builder *b, agx_instr *I)
       swap(b, I->src[0], I->src[1]);
       return (void *)true;
 
-   case AGX_OPCODE_EXPORT:
-      /* We already lowered exports during RA, we just need to remove them late
-       * after inserting waits.
-       */
-      return (void *)true;
-
    default:
       return NULL;
    }

src/asahi/compiler/agx_pack.c

@@ -1174,6 +1174,12 @@ agx_pack_instr(struct util_dynarray *emission, struct util_dynarray *fixups,
       break;
    }
 
+   case AGX_OPCODE_EXPORT:
+      /* Zero-byte pseudo-op. This remains until late for the benefit of
+       * register cache optimizations.
+       */
+      return;
+
    default:
       agx_pack_alu(emission, I);
       return;