nir: return early when lowering a return at the end of a function

Otherwise we create unused conditional return flags and things
get unnecessarily ugly fast when lowering nested functions.

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

diff --git a/src/compiler/nir/nir_lower_returns.c b/src/compiler/nir/nir_lower_returns.c
index 423192adb8a2286dd395f0522466c84e4cf6fe18..3ea69e25204855b1cc79157d0083ab8b4353e2e1 100644 (file)
--- a/src/compiler/nir/nir_lower_returns.c
+++ b/src/compiler/nir/nir_lower_returns.c
@@ -180,6 +180,12 @@ lower_returns_in_block(nir_block *block, struct lower_returns_state *state)
 
    nir_instr_remove(&jump->instr);
 
+   /* If this is a return in the last block of the function there is nothing
+    * more to do once its removed.
+    */
+   if (block == nir_impl_last_block(state->builder.impl))
+      return true;
+
    nir_builder *b = &state->builder;
 
    /* Set the return flag */