nir: Move phi src setup to a helper.

Cleans up the ralloc/list push code all over the tree.

Reviewed-by: Matt Turner <mattst88@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/11772>

src/compiler/nir/nir_clone.c

@@ -448,23 +448,12 @@ clone_phi(clone_state *state, const nir_phi_instr *phi, nir_block *nblk)
    nir_instr_insert_after_block(nblk, &nphi->instr);
 
    foreach_list_typed(nir_phi_src, src, node, &phi->srcs) {
-      nir_phi_src *nsrc = ralloc(nphi, nir_phi_src);
-
-      /* Just copy the old source for now. */
-      memcpy(nsrc, src, sizeof(*src));
-
-      /* Since we're not letting nir_insert_instr handle use/def stuff for us,
-       * we have to set the parent_instr manually.  It doesn't really matter
-       * when we do it, so we might as well do it here.
-       */
-      nsrc->src.parent_instr = &nphi->instr;
+      nir_phi_src *nsrc = nir_phi_instr_add_src(nphi, src->pred, src->src);
 
       /* Stash it in the list of phi sources.  We'll walk this list and fix up
        * sources at the very end of clone_function_impl.
        */
       list_add(&nsrc->src.use_link, &state->phi_srcs);
-
-      exec_list_push_tail(&nphi->srcs, &nsrc->node);
    }
 
    return nphi;