From a001d4f9b912362c78e38ba3ea6aeddaa97f8eb8 Mon Sep 17 00:00:00 2001 From: Segher Boessenkool Date: Tue, 29 Nov 2016 03:02:45 +0100 Subject: [PATCH] combine: Make code after a new trap unreachable (PR78342) Combine can turn a conditional trap into an unconditional trap. If it does that it should make the code after it unreachable (an unconditional trap should be the last insn in its bb, and that bb has no successors). This patch seems to work. It is hard to be sure, this is very hard to trigger. Quite a few other passes look like they need something similar as well, but I don't see anything else handling it yet either. PR rtl-optimization/78342 * combine.c: Include "cfghooks.h". (try_combine): If we create an unconditional trap, break the basic block in two just after it, and remove the edge between; also, set the *new_direct_jump_p flag so that cleanup_cfg is run. From-SVN: r242947 --- gcc/ChangeLog | 8 ++++++++ gcc/combine.c | 20 ++++++++++++++++++++ 2 files changed, 28 insertions(+) diff --git a/gcc/ChangeLog b/gcc/ChangeLog index 900f9b355d7..07bcc26b5b6 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,3 +1,11 @@ +2016-11-28 Segher Boessenkool + + PR rtl-optimization/78342 + * combine.c: Include "cfghooks.h". + (try_combine): If we create an unconditional trap, break the basic + block in two just after it, and remove the edge between; also, set + the *new_direct_jump_p flag so that cleanup_cfg is run. + 2016-11-28 Segher Boessenkool * simplify-rtx.c (simplify_truncation): Handle truncate of zero_extract diff --git a/gcc/combine.c b/gcc/combine.c index 45d4048b13d..41f69daf7f3 100644 --- a/gcc/combine.c +++ b/gcc/combine.c @@ -82,6 +82,7 @@ along with GCC; see the file COPYING3. If not see #include "target.h" #include "rtl.h" #include "tree.h" +#include "cfghooks.h" #include "predict.h" #include "df.h" #include "memmodel.h" @@ -4620,6 +4621,25 @@ try_combine (rtx_insn *i3, rtx_insn *i2, rtx_insn *i1, rtx_insn *i0, update_cfg_for_uncondjump (undobuf.other_insn); } + if (GET_CODE (PATTERN (i3)) == TRAP_IF + && XEXP (PATTERN (i3), 0) == const1_rtx) + { + basic_block bb = BLOCK_FOR_INSN (i3); + gcc_assert (bb); + remove_edge (split_block (bb, i3)); + *new_direct_jump_p = 1; + } + + if (undobuf.other_insn + && GET_CODE (PATTERN (undobuf.other_insn)) == TRAP_IF + && XEXP (PATTERN (undobuf.other_insn), 0) == const1_rtx) + { + basic_block bb = BLOCK_FOR_INSN (undobuf.other_insn); + gcc_assert (bb); + remove_edge (split_block (bb, undobuf.other_insn)); + *new_direct_jump_p = 1; + } + /* A noop might also need cleaning up of CFG, if it comes from the simplification of a jump. */ if (JUMP_P (i3) -- 2.30.2