Bug 84566

Summary:	error: qsort comparator not anti-commutative: -1, -1 on aarch64 in sched1
Product:	gcc	Reporter:	Martin Liška <marxin>
Component:	rtl-optimization	Assignee:	Not yet assigned to anyone <unassigned>
Status:	RESOLVED FIXED
Severity:	normal	CC:	abel, amonakov
Priority:	P3
Version:	8.0
Target Milestone:	---
See Also:	https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99469
Host:	x86_64-unknown-linux-gnu	Target:	aarch64-linux-gnu
Build:		Known to work:
Known to fail:		Last reconfirmed:	2018-02-26 00:00:00
Bug Depends on:
Bug Blocks:	82407, 85099

Description Martin Liška 2018-02-26 08:48:36 UTC

Following ICEs:

$ aarch64-linux-gnu-g++ /home/marxin/Programming/gcc/gcc/testsuite/g++.old-deja/g++.other/crash15.C /dev/null -mcpu=cortex-a35 -O2 -fselective-scheduling
/home/marxin/Programming/gcc/gcc/testsuite/g++.old-deja/g++.other/crash15.C: In function ‘void test05()’:
/home/marxin/Programming/gcc/gcc/testsuite/g++.old-deja/g++.other/crash15.C:43:1: error: qsort comparator not anti-commutative: -1, -1
 }
 ^
during RTL pass: sched1
/home/marxin/Programming/gcc/gcc/testsuite/g++.old-deja/g++.other/crash15.C:43:1: internal compiler error: qsort checking failed
0x5e693a qsort_chk_error
	.././../gcc/vec.c:201
0x15781dd qsort_chk(void*, unsigned long, unsigned long, int (*)(void const*, void const*))
	.././../gcc/vec.c:255
0xd77de4 vec<_expr*, va_heap, vl_embed>::qsort(int (*)(void const*, void const*))
	.././../gcc/vec.h:1054
0xd77de4 vec<_expr*, va_heap, vl_ptr>::qsort(int (*)(void const*, void const*))
	.././../gcc/vec.h:1816
0xd77de4 fill_vec_av_set
	.././../gcc/sel-sched.c:3953
0xd78df3 fill_ready_list
	.././../gcc/sel-sched.c:4027
0xd78df3 find_best_expr
	.././../gcc/sel-sched.c:4387
0xd78df3 fill_insns
	.././../gcc/sel-sched.c:5544
0xd7af80 schedule_on_fences
	.././../gcc/sel-sched.c:7361
0xd7af80 sel_sched_region_2
	.././../gcc/sel-sched.c:7499
0xd7d4b1 sel_sched_region_1
	.././../gcc/sel-sched.c:7541
0xd7d4b1 sel_sched_region(int)
	.././../gcc/sel-sched.c:7642
0xd7da99 run_selective_scheduling()
	.././../gcc/sel-sched.c:7718
0xd5a45d rest_of_handle_sched
	.././../gcc/sched-rgn.c:3715
0xd5a45d execute
	.././../gcc/sched-rgn.c:3825

Comment 1 Alexander Monakov 2018-02-26 11:07:26 UTC

Sorry, I cannot reproduce this. I've built a cross-compiler from today's trunk via 'configure --target aarch64-linux-gnu && make all-gcc' (i.e. just to cc1plus, no binutils etc.) and it doesn't abort.

If possible please add 'g++ -v' output, svn revision, and any other info that can help me reproduce the issue.

Comment 2 Alexander Monakov 2018-02-26 11:10:25 UTC

Bah, built a wrong branch, not the trunk. I'll recheck later, sorry for the noise.

Comment 3 Alexander Monakov 2018-02-26 13:31:26 UTC

Confirmed. Our comparator breaks here:

  /* Prefer SCHED_GROUP_P insns to any others.  */
  if (SCHED_GROUP_P (tmp_insn) != SCHED_GROUP_P (tmp2_insn))
    {
      if (VINSN_UNIQUE_P (tmp_vinsn) && VINSN_UNIQUE_P (tmp2_vinsn))
        return SCHED_GROUP_P (tmp2_insn) ? 1 : -1;

      /* Now uniqueness means SCHED_GROUP_P is set, because schedule groups
         cannot be cloned.  */
      if (VINSN_UNIQUE_P (tmp2_vinsn))
        return 1;
      return -1;
    }

when we have two non-unique insns such that one is in a sched group. That is not supposed to happen actually, since SCHED_GROUP_P should imply VINSN_UNIQUE_P. This invariant is broken when sched_macro_fuse_insns sets SCHED_GROUP_P without looking at deps->readonly.

So while we could get rid of the issue by rewriting the problematic sel-sched code in terms of SCHED_GROUP_P only, lack of deps->readonly check for macro-fusion seems like a bigger issue and should be fixed too.

Comment 4 Alexander Monakov 2018-04-11 14:36:35 UTC

Author: amonakov
Date: Wed Apr 11 14:36:04 2018
New Revision: 259322

URL: https://gcc.gnu.org/viewcvs?rev=259322&root=gcc&view=rev
Log:
sched-deps: respect deps->readonly in macro-fusion (PR 84566)

	PR rtl-optimization/84566
	* sched-deps.c (sched_analyze_insn): Check deps->readonly when invoking
	sched_macro_fuse_insns.



Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/sched-deps.c

Comment 5 Alexander Monakov 2018-04-11 14:47:50 UTC

Fixed.