From 54e505d0446f86b7ad383acbb8e5501f20872b64 Mon Sep 17 00:00:00 2001 From: Martin Jambor Date: Sat, 9 Mar 2024 00:47:22 +0100 Subject: [PATCH] ipa: Avoid excessive removing of SSAs (PR 113757) PR 113757 shows that the code which was meant to debug-reset and remove SSAs defined by LHSs of calls redirected to __builtin_unreachable can trigger also when speculative devirtualization creates a call to a noreturn function (and since it is noreturn, it does not bother dealing with its return value). What is more, it seems that the code handling this case is not really necessary. I feel slightly idiotic about this because I have a feeling that I added it because of a failing test-case but I can neither find the testcase nor a reason why the code in cgraph_edge::redirect_call_stmt_to_callee would not be sufficient (it turns the SSA name into a default-def, a bit like IPA-SRA, but any code dominated by a call to a noreturn is not dangerous when it comes to its side-effects). So this patch just removes the handling. gcc/ChangeLog: 2024-02-07 Martin Jambor PR ipa/113757 * tree-inline.cc (redirect_all_calls): Remove code adding SSAs to id->killed_new_ssa_names. gcc/testsuite/ChangeLog: 2024-02-07 Martin Jambor PR ipa/113757 * g++.dg/ipa/pr113757.C: New test. --- gcc/testsuite/g++.dg/ipa/pr113757.C | 14 ++++++++++++++ gcc/tree-inline.cc | 14 ++------------ 2 files changed, 16 insertions(+), 12 deletions(-) create mode 100644 gcc/testsuite/g++.dg/ipa/pr113757.C diff --git a/gcc/testsuite/g++.dg/ipa/pr113757.C b/gcc/testsuite/g++.dg/ipa/pr113757.C new file mode 100644 index 000000000000..885d4010a100 --- /dev/null +++ b/gcc/testsuite/g++.dg/ipa/pr113757.C @@ -0,0 +1,14 @@ +// { dg-do compile } +// { dg-options "-O2 -fPIC" } +// { dg-require-effective-target fpic } + +long size(); +struct ll { virtual int hh(); }; +ll *slice_owner; +int ll::hh() { __builtin_exit(0); } +int nn() { + if (size()) + return 0; + return slice_owner->hh(); +} +int (*a)() = nn; diff --git a/gcc/tree-inline.cc b/gcc/tree-inline.cc index f0a067f5812a..eebcea8a0290 100644 --- a/gcc/tree-inline.cc +++ b/gcc/tree-inline.cc @@ -2984,23 +2984,13 @@ redirect_all_calls (copy_body_data * id, basic_block bb) gimple *stmt = gsi_stmt (si); if (is_gimple_call (stmt)) { - tree old_lhs = gimple_call_lhs (stmt); struct cgraph_edge *edge = id->dst_node->get_edge (stmt); if (edge) { if (!id->killed_new_ssa_names) id->killed_new_ssa_names = new hash_set (16); - gimple *new_stmt - = cgraph_edge::redirect_call_stmt_to_callee (edge, - id->killed_new_ssa_names); - if (old_lhs - && TREE_CODE (old_lhs) == SSA_NAME - && !gimple_call_lhs (new_stmt)) - /* In case of IPA-SRA removing the LHS, the name should have - been already added to the hash. But in case of redirecting - to builtin_unreachable it was not and the name still should - be pruned from debug statements. */ - id->killed_new_ssa_names->add (old_lhs); + cgraph_edge::redirect_call_stmt_to_callee (edge, + id->killed_new_ssa_names); if (stmt == last && id->call_stmt && maybe_clean_eh_stmt (stmt)) gimple_purge_dead_eh_edges (bb); -- 2.47.2