From 9594e04e4e2abeb4ffd3ca134447ee9fe84f95a4 Mon Sep 17 00:00:00 2001 From: Richard Biener Date: Tue, 16 Aug 2022 14:14:55 +0200 Subject: [PATCH] Stop backwards thread discovery when leaving a loop The backward threader copier cannot deal with the situation of copying blocks belonging to different loops and will reject those paths late. The following uses this to prune path discovery, saving on compile-time. Note the off-loop block is still considered as entry edge origin. * tree-ssa-threadbackward.cc (back_threader::find_paths_to_names): Do not walk further if we are leaving the current loop. --- gcc/tree-ssa-threadbackward.cc | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/gcc/tree-ssa-threadbackward.cc b/gcc/tree-ssa-threadbackward.cc index b886027fccf..1c362839fab 100644 --- a/gcc/tree-ssa-threadbackward.cc +++ b/gcc/tree-ssa-threadbackward.cc @@ -355,6 +355,12 @@ back_threader::find_paths_to_names (basic_block bb, bitmap interesting, || maybe_register_path ())) ; + // The backwards thread copier cannot copy blocks that do not belong + // to the same loop, so when the new source of the path entry no + // longer belongs to it we don't need to search further. + else if (m_path[0]->loop_father != bb->loop_father) + ; + // Continue looking for ways to extend the path but limit the // search space along a branch else if ((overall_paths = overall_paths * EDGE_COUNT (bb->preds)) -- 2.47.2