[Bug target/107183] [10/11/12/13 Regression] -fcompare-debug failure (length) with -fsanitize=float-cast-overflow since r7-5708-gcfd719e7769fd43f
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107183 --- Comment #8 from CVS Commits --- The releases/gcc-11 branch has been updated by Jakub Jelinek : https://gcc.gnu.org/g:d92cbc49eac263e32ff5eaabffd3efe2324502d2 commit r11-10386-gd92cbc49eac263e32ff5eaabffd3efe2324502d2 Author: Jakub Jelinek Date: Sun Nov 20 17:42:42 2022 +0100 reg-stack: Fix a -fcompare-debug bug in reg-stack [PR107183] As the following testcase shows, the swap_rtx_condition function in reg-stack can result in different code generation between -g and -g0. The function is doing the changes as it goes, so does analysis and changes together, which makes it harder to deal with DEBUG_INSNs, where normally analysis phase ignores them and the later phase doesn't. swap_rtx_condition walks instructions two different ways, one is using next_flags_user function which stops on non-call instructions that mention the flags register, and the other is a loop on fnstsw where it stops on instructions mentioning it and tries to find sahf instruction that uses it (in both cases calls stop it and so does end of basic block). Now both of these currently stop on DEBUG_INSNs that mention the flags register resp. the fnstsw result register. On success the function recurses on next flags user instruction if still live and if the recursion failed, reverts the changes it did too and fails. If it were just for the next_flags_user case, the fix could be just not doing INSN_CODE (insn) = -1; if (recog_memoized (insn) == -1) fail = 1; on DEBUG_INSNs (assuming all changes to those are fine), swap_rtx_condition_1 just changes one comparison to a different one. But due to the possibility of fnstsw result being used in theory before sahf in some DEBUG_INSNs, this patch takes a different approach. swap_rtx_condition has now a new argument and two modes. The first mode is when debug_seen is >= 0, in this case both next_flags_user and the loop for fnstsw -> sahf will ignore but note DEBUG_INSNs (that mention flags register or fnstsw result). If no such DEBUG_INSN is found during the whole call including recursive invocations (so e.g. for -g0 but probably most often for -g as well), it behaves as before, if it returns true all the changes are done and nothing further needs to be done later. If any DEBUG_INSNs are seen along the way, even when returning success all the changes are reverted, so it just reports that the function would be successful if DEBUG_INSNs were ignored. In this case, compare_for_stack_reg needs to call it again in debug_seen = -1 mode, which tells the function to update everything including DEBUG_INSNs. For the fnstsw -> sahf case which I hope will be very rare I just reset the DEBUG_INSNs, I don't really know how to express it easily otherwise. For the rest swap_rtx_condition_1 is done even on the DEBUG_INSNs. 2022-11-20 Jakub Jelinek PR target/107183 * reg-stack.c (next_flags_user): Add DEBUG_SEEN argument. If >= 0 and a DEBUG_INSN would be otherwise returned, set DEBUG_SEEN to 1 and ignore it. (swap_rtx_condition): Add DEBUG_SEEN argument. In >= 0 mode only set DEBUG_SEEN to 1 if problematic DEBUG_ISNSs were seen and revert all changes on success in that case. Don't try to recog_memoized DEBUG_INSNs. (compare_for_stack_reg): Adjust swap_rtx_condition caller. If it returns true and debug_seen is 1, call swap_rtx_condition again with debug_seen -1. * gcc.dg/ubsan/pr107183.c: New test. (cherry picked from commit 6b5c98c1c0003bd470a4428bede6c862637a94b8)
[Bug target/107183] [10/11/12/13 Regression] -fcompare-debug failure (length) with -fsanitize=float-cast-overflow since r7-5708-gcfd719e7769fd43f
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107183 --- Comment #7 from CVS Commits --- The releases/gcc-12 branch has been updated by Jakub Jelinek : https://gcc.gnu.org/g:196cb25ddbc6c4fae5e7b1c0a09f32f59bdabaa8 commit r12-8922-g196cb25ddbc6c4fae5e7b1c0a09f32f59bdabaa8 Author: Jakub Jelinek Date: Sun Nov 20 17:42:42 2022 +0100 reg-stack: Fix a -fcompare-debug bug in reg-stack [PR107183] As the following testcase shows, the swap_rtx_condition function in reg-stack can result in different code generation between -g and -g0. The function is doing the changes as it goes, so does analysis and changes together, which makes it harder to deal with DEBUG_INSNs, where normally analysis phase ignores them and the later phase doesn't. swap_rtx_condition walks instructions two different ways, one is using next_flags_user function which stops on non-call instructions that mention the flags register, and the other is a loop on fnstsw where it stops on instructions mentioning it and tries to find sahf instruction that uses it (in both cases calls stop it and so does end of basic block). Now both of these currently stop on DEBUG_INSNs that mention the flags register resp. the fnstsw result register. On success the function recurses on next flags user instruction if still live and if the recursion failed, reverts the changes it did too and fails. If it were just for the next_flags_user case, the fix could be just not doing INSN_CODE (insn) = -1; if (recog_memoized (insn) == -1) fail = 1; on DEBUG_INSNs (assuming all changes to those are fine), swap_rtx_condition_1 just changes one comparison to a different one. But due to the possibility of fnstsw result being used in theory before sahf in some DEBUG_INSNs, this patch takes a different approach. swap_rtx_condition has now a new argument and two modes. The first mode is when debug_seen is >= 0, in this case both next_flags_user and the loop for fnstsw -> sahf will ignore but note DEBUG_INSNs (that mention flags register or fnstsw result). If no such DEBUG_INSN is found during the whole call including recursive invocations (so e.g. for -g0 but probably most often for -g as well), it behaves as before, if it returns true all the changes are done and nothing further needs to be done later. If any DEBUG_INSNs are seen along the way, even when returning success all the changes are reverted, so it just reports that the function would be successful if DEBUG_INSNs were ignored. In this case, compare_for_stack_reg needs to call it again in debug_seen = -1 mode, which tells the function to update everything including DEBUG_INSNs. For the fnstsw -> sahf case which I hope will be very rare I just reset the DEBUG_INSNs, I don't really know how to express it easily otherwise. For the rest swap_rtx_condition_1 is done even on the DEBUG_INSNs. 2022-11-20 Jakub Jelinek PR target/107183 * reg-stack.cc (next_flags_user): Add DEBUG_SEEN argument. If >= 0 and a DEBUG_INSN would be otherwise returned, set DEBUG_SEEN to 1 and ignore it. (swap_rtx_condition): Add DEBUG_SEEN argument. In >= 0 mode only set DEBUG_SEEN to 1 if problematic DEBUG_ISNSs were seen and revert all changes on success in that case. Don't try to recog_memoized DEBUG_INSNs. (compare_for_stack_reg): Adjust swap_rtx_condition caller. If it returns true and debug_seen is 1, call swap_rtx_condition again with debug_seen -1. * gcc.dg/ubsan/pr107183.c: New test. (cherry picked from commit 6b5c98c1c0003bd470a4428bede6c862637a94b8)
[Bug target/107183] [10/11/12/13 Regression] -fcompare-debug failure (length) with -fsanitize=float-cast-overflow since r7-5708-gcfd719e7769fd43f
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107183 --- Comment #6 from CVS Commits --- The master branch has been updated by Jakub Jelinek : https://gcc.gnu.org/g:6b5c98c1c0003bd470a4428bede6c862637a94b8 commit r13-4175-g6b5c98c1c0003bd470a4428bede6c862637a94b8 Author: Jakub Jelinek Date: Sun Nov 20 17:42:42 2022 +0100 reg-stack: Fix a -fcompare-debug bug in reg-stack [PR107183] As the following testcase shows, the swap_rtx_condition function in reg-stack can result in different code generation between -g and -g0. The function is doing the changes as it goes, so does analysis and changes together, which makes it harder to deal with DEBUG_INSNs, where normally analysis phase ignores them and the later phase doesn't. swap_rtx_condition walks instructions two different ways, one is using next_flags_user function which stops on non-call instructions that mention the flags register, and the other is a loop on fnstsw where it stops on instructions mentioning it and tries to find sahf instruction that uses it (in both cases calls stop it and so does end of basic block). Now both of these currently stop on DEBUG_INSNs that mention the flags register resp. the fnstsw result register. On success the function recurses on next flags user instruction if still live and if the recursion failed, reverts the changes it did too and fails. If it were just for the next_flags_user case, the fix could be just not doing INSN_CODE (insn) = -1; if (recog_memoized (insn) == -1) fail = 1; on DEBUG_INSNs (assuming all changes to those are fine), swap_rtx_condition_1 just changes one comparison to a different one. But due to the possibility of fnstsw result being used in theory before sahf in some DEBUG_INSNs, this patch takes a different approach. swap_rtx_condition has now a new argument and two modes. The first mode is when debug_seen is >= 0, in this case both next_flags_user and the loop for fnstsw -> sahf will ignore but note DEBUG_INSNs (that mention flags register or fnstsw result). If no such DEBUG_INSN is found during the whole call including recursive invocations (so e.g. for -g0 but probably most often for -g as well), it behaves as before, if it returns true all the changes are done and nothing further needs to be done later. If any DEBUG_INSNs are seen along the way, even when returning success all the changes are reverted, so it just reports that the function would be successful if DEBUG_INSNs were ignored. In this case, compare_for_stack_reg needs to call it again in debug_seen = -1 mode, which tells the function to update everything including DEBUG_INSNs. For the fnstsw -> sahf case which I hope will be very rare I just reset the DEBUG_INSNs, I don't really know how to express it easily otherwise. For the rest swap_rtx_condition_1 is done even on the DEBUG_INSNs. 2022-11-20 Jakub Jelinek PR target/107183 * reg-stack.cc (next_flags_user): Add DEBUG_SEEN argument. If >= 0 and a DEBUG_INSN would be otherwise returned, set DEBUG_SEEN to 1 and ignore it. (swap_rtx_condition): Add DEBUG_SEEN argument. In >= 0 mode only set DEBUG_SEEN to 1 if problematic DEBUG_ISNSs were seen and revert all changes on success in that case. Don't try to recog_memoized DEBUG_INSNs. (compare_for_stack_reg): Adjust swap_rtx_condition caller. If it returns true and debug_seen is 1, call swap_rtx_condition again with debug_seen -1. * gcc.dg/ubsan/pr107183.c: New test.
[Bug target/107183] [10/11/12/13 Regression] -fcompare-debug failure (length) with -fsanitize=float-cast-overflow since r7-5708-gcfd719e7769fd43f
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107183 Jakub Jelinek changed: What|Removed |Added Assignee|unassigned at gcc dot gnu.org |jakub at gcc dot gnu.org Status|NEW |ASSIGNED --- Comment #5 from Jakub Jelinek --- Created attachment 53926 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=53926=edit gcc13-pr107183.patch Untested fix.
[Bug target/107183] [10/11/12/13 Regression] -fcompare-debug failure (length) with -fsanitize=float-cast-overflow since r7-5708-gcfd719e7769fd43f
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107183
--- Comment #4 from Jakub Jelinek ---
Seems the bug is in swap_rtx_condition.
It is called on:
(insn 10023 10021 10024 4 (set (reg:CCFP 17 flags)
(unspec:CCFP [
(compare:CCFP (reg:XF 9 st(1) [orig:84 _3 ] [84])
(reg:XF 8 st [107]))
] UNSPEC_NOTRAP)) "pr107183.c":6:18 discrim 1 45 {*cmpiuxf_i387}
(expr_list:REG_DEAD (reg:XF 9 st(1) [orig:84 _3 ] [84])
(expr_list:REG_DEAD (reg:XF 8 st [107])
(nil
on the first next_flags_user call in the function it sets insn to:
(insn 10110 10024 10111 4 (set (reg:QI 3 bx [105])
(unordered:QI (reg:CCFP 17 flags)
(const_int 0 [0]))) "pr107183.c":6:18 discrim 1 949 {*setcc_qi}
(nil))
(still the same between -g and -g0, but already that one could differ),
but then next_flags_user (the 3rd one in the function) finds
(debug_insn 4 10029 10030 4 (var_location:SI D#1 (if_then_else:SI (uneq
(reg:CCFP 17 flags)
(const_int 0 [0]))
(reg:SI 3 bx [105])
(reg:SI 0 ax [111]))) -1
(nil))
with -g and
(insn 10030 10029 10032 4 (set (reg:SI 3 bx [orig:90 iftmp.0_9 ] [90])
(if_then_else:SI (uneq (reg:CCFP 17 flags)
(const_int 0 [0]))
(reg:SI 3 bx [105])
(reg:SI 0 ax [111]))) "pr107183.c":6:18 discrim 1 1269
{*movsicc_noc}
(expr_list:REG_DEAD (reg:CCFP 17 flags)
(expr_list:REG_DEAD (reg:SI 0 ax [111])
(expr_list:REG_EQUAL (if_then_else:SI (uneq (reg:CCFP 17 flags)
(const_int 0 [0]))
(reg:SI 3 bx [105])
(const_int 1 [0x1]))
(nil)
with -g0.
[Bug target/107183] [10/11/12/13 Regression] -fcompare-debug failure (length) with -fsanitize=float-cast-overflow since r7-5708-gcfd719e7769fd43f
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107183 Richard Biener changed: What|Removed |Added Priority|P3 |P2
[Bug target/107183] [10/11/12/13 Regression] -fcompare-debug failure (length) with -fsanitize=float-cast-overflow since r7-5708-gcfd719e7769fd43f
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107183 --- Comment #3 from Andrew Pinski --- (In reply to Martin Liška from comment #2) > Likely started with r7-5708-gcfd719e7769fd43f. Exposed by
[Bug target/107183] [10/11/12/13 Regression] -fcompare-debug failure (length) with -fsanitize=float-cast-overflow since r7-5708-gcfd719e7769fd43f
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107183 Martin Liška changed: What|Removed |Added Last reconfirmed||2022-10-10 Status|UNCONFIRMED |NEW Summary|[10/11/12/13 Regression]|[10/11/12/13 Regression] |-fcompare-debug failure |-fcompare-debug failure |(length) with |(length) with |-fsanitize=float-cast-overf |-fsanitize=float-cast-overf |low |low since ||r7-5708-gcfd719e7769fd43f CC||jakub at gcc dot gnu.org, ||marxin at gcc dot gnu.org Ever confirmed|0 |1 --- Comment #2 from Martin Liška --- Likely started with r7-5708-gcfd719e7769fd43f.
