nir: add nir_instr_rewrite_deref

Allows modifying a texture instruction's texture and sampler derefs.

Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>

src/compiler/nir/nir.c

@@ -1509,6 +1509,19 @@ nir_instr_rewrite_dest(nir_instr *instr, nir_dest *dest, nir_dest new_dest)
       src_add_all_uses(dest->reg.indirect, instr, NULL);
 }
 
+void
+nir_instr_rewrite_deref(nir_instr *instr, nir_deref_var **deref,
+                        nir_deref_var *new_deref)
+{
+   if (*deref)
+      visit_deref_src(*deref, remove_use_cb, NULL);
+
+   *deref = new_deref;
+
+   if (*deref)
+      visit_deref_src(*deref, add_use_cb, instr);
+}
+
 /* note: does *not* take ownership of 'name' */
 void
 nir_ssa_def_init(nir_instr *instr, nir_ssa_def *def,