On November 30, 2017 11:55:42 PM GMT+01:00, Jakub Jelinek <ja...@redhat.com>
wrote:
>Hi!
>
>Now that the C++ FE emits __builtin_unreachable with BUILTINS_LOCATION
>for fallthrough into end of function without returning value, we need
>to
>see those in the warn_function_return pass which is right after
>building
>cfg. While GIMPLE_CONDs conditionally jumping to __builtin_unreachable
>are
>only optimized during evrp and later, GIMPLE_SWITCH cases that branch
>to
>__builtin_unreachable are unfortunately removed already during the cfg
>cleanup in the cfg pass and thus the immediately following
>warn_function_return pass can't warn. Fixed by postponing that, e.g.
>the evrp pass does unconditional TODO_cleanup_cfg, so those will be
>optimized away pretty early (often already during ccp1).
>
>Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
OK.
Richard.
>2017-11-30 Jakub Jelinek <ja...@redhat.com>
>
> PR sanitizer/81275
> * tree-cfg.c (group_case_labels_stmt): Don't optimize away
> C++ FE implicitly added __builtin_unreachable () until -Wreturn-type
> is diagnosed.
>
> * c-c++-common/tsan/pr81275.c: New test.
>
>--- gcc/tree-cfg.c.jj 2017-11-30 11:40:38.000000000 +0100
>+++ gcc/tree-cfg.c 2017-11-30 12:01:39.496311219 +0100
>@@ -1750,7 +1750,14 @@ group_case_labels_stmt (gswitch *stmt)
>
> /* Discard cases that have an unreachable destination block. */
> if (EDGE_COUNT (base_bb->succs) == 0
>- && gimple_seq_unreachable_p (bb_seq (base_bb)))
>+ && gimple_seq_unreachable_p (bb_seq (base_bb))
>+ /* Don't optimize this if __builtin_unreachable () is the
>+ implicitly added one by the C++ FE too early, before
>+ -Wreturn-type can be diagnosed. We'll optimize it later
>+ during switchconv pass or any other cfg cleanup. */
>+ && (gimple_in_ssa_p (cfun)
>+ || (LOCATION_LOCUS (gimple_location (last_stmt (base_bb)))
>+ != BUILTINS_LOCATION)))
> {
> edge base_edge = find_edge (gimple_bb (stmt), base_bb);
> if (base_edge != NULL)
>--- gcc/testsuite/c-c++-common/tsan/pr81275.c.jj 2017-11-28
>22:23:34.000000000 +0100
>+++ gcc/testsuite/c-c++-common/tsan/pr81275.c 2017-11-30
>11:50:56.185274379 +0100
>@@ -1,7 +1,6 @@
> /* PR sanitizer/81275 */
> /* { dg-do compile } */
> /* { dg-options "-Wreturn-type -fsanitize=thread" } */
>-/* { dg-skip-if "" { c++ } { "*" } { "-O0" } } */
>
> int
> f1 (int a, int b)
>
> Jakub
