From 9e4c57f7a69d7060612c83867ecff61a719b97af Mon Sep 17 00:00:00 2001 From: Richard Biener Date: Mon, 24 Feb 2025 09:45:28 +0100 Subject: [PATCH] tree-optimization/118973 - stray abnormal edge after DCE DCE preserves stmts performing abnormal control flow transfer but currently has an exception for replaceable allocations and cxa_atexit calls. That results in a broken CFG since DCE isn't set up to prune abnormal edges possibly hanging off those. While we could try to add this handling, the following is the safe fix at this point and more suitable for backporting. PR tree-optimization/118973 * tree-ssa-dce.cc (mark_stmt_if_obviously_necessary): Calls that alter control flow in unpredictable ways need to be preserved. * g++.dg/torture/pr118973.C: New testcase. --- gcc/testsuite/g++.dg/torture/pr118973.C | 10 ++++++++++ gcc/tree-ssa-dce.cc | 8 ++++---- 2 files changed, 14 insertions(+), 4 deletions(-) create mode 100644 gcc/testsuite/g++.dg/torture/pr118973.C diff --git a/gcc/testsuite/g++.dg/torture/pr118973.C b/gcc/testsuite/g++.dg/torture/pr118973.C new file mode 100644 index 00000000000..8cb9e4b023a --- /dev/null +++ b/gcc/testsuite/g++.dg/torture/pr118973.C @@ -0,0 +1,10 @@ +// { dg-do compile } + +int foo() __attribute__((returns_twice)); + +void a() +{ + int a; + if(foo()) new int; + &a; +} diff --git a/gcc/tree-ssa-dce.cc b/gcc/tree-ssa-dce.cc index be21a2d0b50..18af81866b7 100644 --- a/gcc/tree-ssa-dce.cc +++ b/gcc/tree-ssa-dce.cc @@ -391,15 +391,15 @@ mark_stmt_if_obviously_necessary (gimple *stmt, bool aggressive) { gcall *call = as_a (stmt); - /* Never elide a noreturn call we pruned control-flow for. */ - if ((gimple_call_flags (call) & ECF_NORETURN) - && gimple_call_ctrl_altering_p (call)) + /* Never elide a noreturn call we pruned control-flow for. + Same for statements that can alter control flow in unpredictable + ways. */ + if (gimple_call_ctrl_altering_p (call)) { mark_stmt_necessary (call, true); return; } - if (is_removable_allocation_p (call, false)) return; -- 2.47.2