[Bug target/113356] New: [14 Regression][aarch64] ICE in try_fuse_pair, at config/aarch64/aarch64-ldp-fusion.cc:2203 since r14-6947-g4b67ec7ff5b1aa

[Bug target/113356] New: [14 Regression][aarch64] ICE in try_fuse_pair, at config/aarch64/aarch64-ldp-fusion.cc:2203 since r14-6947-g4b67ec7ff5b1aa

[mjires at suse dot cz]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113356

            Bug ID: 113356
           Summary: [14 Regression][aarch64] ICE in try_fuse_pair, at
                    config/aarch64/aarch64-ldp-fusion.cc:2203 since
                    r14-6947-g4b67ec7ff5b1aa
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Keywords: ice-on-valid-code
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: mjires at suse dot cz
                CC: acoplan at gcc dot gnu.org
  Target Milestone: ---
            Target: aarch64

Compiling reduced testcase g++.dg/ipa/pr71207.C fails the assert added in
r14-6947-g4b67ec7ff5b1aa.

$ cat pr71207.C
struct Class1 {
  virtual ~Class1() {}
  unsigned Field1;
};
struct Class4 : virtual Class1 {};
int main() { Class4 var1; }


$ aarch64-linux-gnu-g++ pr71207.C -fnon-call-exceptions -mearly-ldp-fusion
-fno-lifetime-dse -fno-forward-propagate -Os
during RTL pass: ldp_fusion
pr71207.C: In destructor ‘virtual Class4::~Class4()’:
pr71207.C:5:8: internal compiler error: in try_fuse_pair, at
config/aarch64/aarch64-ldp-fusion.cc:2265
    5 | struct Class4 : virtual Class1 {};
      |        ^~~~~~
0x2264a33 ldp_bb_info::try_fuse_pair(bool, unsigned int, rtl_ssa::insn_info*,
rtl_ssa::insn_info*)
       
/home/mjires/git/GCC/master/gcc/config/aarch64/aarch64-ldp-fusion.cc:2265
0x2264eff ldp_bb_info::merge_pairs(std::__cxx11::list<rtl_ssa::insn_info*,
std::allocator<rtl_ssa::insn_info*> >&, std::__cxx11::list<rtl_ssa::insn_info*,
std::allocator<rtl_ssa::insn_info*> >&, bool, unsigned int)
       
/home/mjires/git/GCC/master/gcc/config/aarch64/aarch64-ldp-fusion.cc:2389
0x2265124 ldp_bb_info::transform_for_base(int, access_group&)
       
/home/mjires/git/GCC/master/gcc/config/aarch64/aarch64-ldp-fusion.cc:2422
0x226785e void
ldp_bb_info::traverse_base_map<ordered_hash_map<pair_hash<nofree_ptr_hash<rtl_ssa::def_info>,
int_hash<int, -1, -2> >, access_group,
simple_hashmap_traits<default_hash_traits<pair_hash<nofree_ptr_hash<rtl_ssa::def_info>,
int_hash<int, -1, -2> > >, access_group> >
>(ordered_hash_map<pair_hash<nofree_ptr_hash<rtl_ssa::def_info>, int_hash<int,
-1, -2> >, access_group,
simple_hashmap_traits<default_hash_traits<pair_hash<nofree_ptr_hash<rtl_ssa::def_info>,
int_hash<int, -1, -2> > >, access_group> >&)
       
/home/mjires/git/GCC/master/gcc/config/aarch64/aarch64-ldp-fusion.cc:2481
0x2265383 ldp_bb_info::transform()
       
/home/mjires/git/GCC/master/gcc/config/aarch64/aarch64-ldp-fusion.cc:2489
0x22604ca ldp_fusion_bb(rtl_ssa::bb_info*)
       
/home/mjires/git/GCC/master/gcc/config/aarch64/aarch64-ldp-fusion.cc:2717
0x2260554 ldp_fusion()
       
/home/mjires/git/GCC/master/gcc/config/aarch64/aarch64-ldp-fusion.cc:2726
0x2260666 execute
       
/home/mjires/git/GCC/master/gcc/config/aarch64/aarch64-ldp-fusion.cc:2776
Please submit a full bug report, with preprocessed source (by using
-freport-bug).
Please include the complete backtrace with any bug report.
See <https://gcc.gnu.org/bugs/> for instructions.


$ aarch64-linux-gnu-g++ -v
Using built-in specs.
COLLECT_GCC=aarch64-linux-gnu-g++
COLLECT_LTO_WRAPPER=/home/mjires/built/master/libexec/gcc/aarch64-linux-gnu/14.0.1/lto-wrapper
Target: aarch64-linux-gnu
Configured with: /home/mjires/git/GCC/master/configure
--prefix=/home/mjires/built/master --target=aarch64-linux-gnu
--disable-bootstrap --enable-languages=c,c++,fortran --disable-multilib
--disable-libsanitizer --enable-checking : (reconfigured)
/home/mjires/git/GCC/master/configure --prefix=/home/mjires/built/master
--target=aarch64-linux-gnu --disable-bootstrap --enable-languages=c,c++,fortran
--disable-multilib --disable-libsanitizer --enable-checking
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 14.0.1 20240112 (experimental) (GCC)

[Bug target/113356] [14 Regression][aarch64] ICE in try_fuse_pair, at config/aarch64/aarch64-ldp-fusion.cc:2203 since r14-6947-g4b67ec7ff5b1aa

[acoplan at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113356

Alex Coplan <acoplan at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |ASSIGNED
     Ever confirmed|0                           |1
           Assignee|unassigned at gcc dot gnu.org      |acoplan at gcc dot gnu.org
   Last reconfirmed|                            |2024-01-12

--- Comment #1 from Alex Coplan <acoplan at gcc dot gnu.org> ---
Sigh.  Confirmed, I'll take a look.

[Bug target/113356] [14 Regression][aarch64] ICE in try_fuse_pair, at config/aarch64/aarch64-ldp-fusion.cc:2203 since r14-6947-g4b67ec7ff5b1aa

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113356

Alex Coplan <acoplan at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |ASSIGNED
     Ever confirmed|0                           |1
           Assignee|unassigned at gcc dot gnu.org      |acoplan at gcc dot gnu.org
   Last reconfirmed|                            |2024-01-12

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P3                          |P1
             Status|ASSIGNED                    |UNCONFIRMED
                 CC|                            |jakub at gcc dot gnu.org
           Assignee|acoplan at gcc dot gnu.org         |unassigned at gcc dot gnu.org
   Last reconfirmed|2024-01-12 00:00:00         |
   Target Milestone|---                         |14.0
     Ever confirmed|1                           |0

--- Comment #1 from Alex Coplan <acoplan at gcc dot gnu.org> ---
Sigh.  Confirmed, I'll take a look.

[Bug target/113356] [14 Regression][aarch64] ICE in try_fuse_pair, at config/aarch64/aarch64-ldp-fusion.cc:2203 since r14-6947-g4b67ec7ff5b1aa

[acoplan at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113356

Alex Coplan <acoplan at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
     Ever confirmed|0                           |1
   Last reconfirmed|                            |2024-01-12
             Status|UNCONFIRMED                 |ASSIGNED
           Assignee|unassigned at gcc dot gnu.org      |acoplan at gcc dot gnu.org

[Bug target/113356] [14 Regression][aarch64] ICE in try_fuse_pair, at config/aarch64/aarch64-ldp-fusion.cc:2203 since r14-6947-g4b67ec7ff5b1aa

[acoplan at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113356

--- Comment #2 from Alex Coplan <acoplan at gcc dot gnu.org> ---
So we have this IR:

    insn i8 in bb2 [ebb2] at point 18:
      +----------------------------
      |    8: [r104:DI++]=r101:DI
      |      REG_DEAD r101:DI
      |      REG_INC r104:DI
      +----------------------------
      has pre/post-modify operations
      uses:
        use of set r101:i7 (DI pseudo)
        use of set r104:i17 (DI pseudo)
          appears in a read/write context
      defines:
        set r104:i8 (DI pseudo)
          set by a pre/post-modify
          appears in a read/write context
          used by insn i13 in bb2 [ebb2] at point 24
        set mem:i8

    insn i11 in bb2 [ebb2] at point 20:
      +------------------------------------------------
      |   11: r106:DI=high(const(`_ZTV6Class1'+0x10))
      +------------------------------------------------
      defines:
        set r106:i11 (DI pseudo)
          used by insn i12 in bb2 [ebb2] at point 22

    insn i12 in bb2 [ebb2] at point 22:
      +-------------------------------------------------------
      |   12: r105:DI=r106:DI+low(const(`_ZTV6Class1'+0x10))
      |      REG_DEAD r106:DI
      |      REG_EQUAL const(`_ZTV6Class1'+0x10)
      +-------------------------------------------------------
      uses:
        use of set r106:i11 (DI pseudo)
      defines:
        set r105:i12 (DI pseudo)
          used by insn i13 in bb2 [ebb2] at point 24

    insn i13 in bb2 [ebb2] at point 24:
      +----------------------------------------
      |   13: [r104:DI]=r105:DI
      |      REG_DEAD r105:DI
      |      REG_DEAD r104:DI
      |      REG_EH_REGION 0xffffffffffffffff
      +----------------------------------------
      uses:
        use of set r104:i8 (DI pseudo)
          appears inside an address
        use of set r105:i12 (DI pseudo)
      defines:
        set mem:i13
          used by phi node mem:a7 in ebb1 at point 30

and we're trying to form (8,13).  i8 has i13 as a hazard due to the writeback
dataflow and i13 has i12 as a hazard (due to the initial fix for non-call
exceptions introducing a hazard on the previous nondebug insn).  I wonder if it
would be enough to get i

[Bug target/113356] [14 Regression][aarch64] ICE in try_fuse_pair, at config/aarch64/aarch64-ldp-fusion.cc:2203 since r14-6947-g4b67ec7ff5b1aa

[acoplan at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113356

--- Comment #3 from Alex Coplan <acoplan at gcc dot gnu.org> ---
... i13 to be a hazard w.r.t. itself, then we might not even need the clause in
the follow-up fix.  I'll investigate.

Alternatively the assert can probably be relaxed to include the previous
nondebug insn, as we're inserting after the insn in the move_range, anyway.

[Bug target/113356] [14 Regression][aarch64] ICE in try_fuse_pair, at config/aarch64/aarch64-ldp-fusion.cc:2203 since r14-6947-g4b67ec7ff5b1aa

[acoplan at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113356

Alex Coplan <acoplan at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |patch
                URL|                            |https://gcc.gnu.org/piperma
                   |                            |il/gcc-patches/2024-January
                   |                            |/643011.html

--- Comment #4 from Alex Coplan <acoplan at gcc dot gnu.org> ---
Patch posted:
https://gcc.gnu.org/pipermail/gcc-patches/2024-January/643011.html

[Bug target/113356] [14 Regression][aarch64] ICE in try_fuse_pair, at config/aarch64/aarch64-ldp-fusion.cc:2203 since r14-6947-g4b67ec7ff5b1aa

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113356

--- Comment #5 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Alex Coplan <acoplan@gcc.gnu.org>:

https://gcc.gnu.org/g:639ae543449a8d6525303458497bd4b897660ec3

commit r14-8367-g639ae543449a8d6525303458497bd4b897660ec3
Author: Alex Coplan <alex.coplan@arm.com>
Date:   Mon Jan 15 11:07:48 2024 +0000

    aarch64: Don't record hazards against paired insns [PR113356]

    For the testcase in the PR, we try to pair insns where the first has
    writeback and the second uses the updated base register.  This causes us
    to record a hazard against the second insn, thus narrowing the move
    range away from the end of the BB.

    However, it isn't meaningful to record hazards against the other insn
    in the pair, as this doesn't change which pairs can be formed, and also
    doesn't change where the pair is formed (from the perspective of
    nondebug insns).

    To see why this is the case, consider the two cases:

     - Suppoe we are finding hazards for insns[0].  If we record a hazard
       against insns[1], then range.last becomes
       insns[1]->prev_nondebug_insn (), but note that this is equivalent to
       inserting after insns[1] (since insns[1] is being changed).
     - Now consider finding hazards for insns[1].  Suppose we record
       insns[0] as a hazard.  Then we set range.first = insns[0], which is a
       no-op.

    As such, it seems better to never record hazards against the other insn
    in the pair, as we check whether the insns themselves are suitable for
    combination separately (e.g. for ldp checking that they use distinct
    transfer registers).  Avoiding unnecessarily narrowing the move range
    avoids unnecessarily re-ordering over debug insns.

    This should also mean that we can only narrow the move range away from
    the end of the BB in the case that we record a hazard for insns[0]
    against insns[1]->prev_nondebug_insn () or earlier.  This means that for
    the non-call-exceptions case, either the move range includes insns[1],
    or we reject the pair (thus the assert tripped in the PR should always
    hold).

    gcc/ChangeLog:

            PR target/113356
            * config/aarch64/aarch64-ldp-fusion.cc
(ldp_bb_info::try_fuse_pair):
            Don't record hazards against the opposite insn in the pair.

    gcc/testsuite/ChangeLog:

            PR target/113356
            * gcc.target/aarch64/pr113356.C: New test.

[Bug target/113356] [14 Regression][aarch64] ICE in try_fuse_pair, at config/aarch64/aarch64-ldp-fusion.cc:2203 since r14-6947-g4b67ec7ff5b1aa

[acoplan at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113356

Alex Coplan <acoplan at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|---                         |FIXED

--- Comment #6 from Alex Coplan <acoplan at gcc dot gnu.org> ---
Fixed, thanks for the report.