[Bug tree-optimization/115226] New: ICE on valid code at -O3 on x86_64-linux-gnu: verify_ssa failed

[Bug tree-optimization/115226] New: ICE on valid code at -O3 on x86_64-linux-gnu: verify_ssa failed

[zhendong.su at inf dot ethz.ch]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115226

            Bug ID: 115226
           Summary: ICE on valid code at -O3 on x86_64-linux-gnu:
                    verify_ssa failed
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: zhendong.su at inf dot ethz.ch
  Target Milestone: ---

It appears to be a recent regression as it doesn't reproduce with 14.1 and
earlier. 

Compiler Explorer: https://godbolt.org/z/EK1hn9n4s


[538] % gcctk -v
Using built-in specs.
COLLECT_GCC=gcctk
COLLECT_LTO_WRAPPER=/local/suz-local/software/local/gcc-trunk/libexec/gcc/x86_64-pc-linux-gnu/15.0.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: ../gcc-trunk/configure --disable-bootstrap
--enable-checking=yes --prefix=/local/suz-local/software/local/gcc-trunk
--enable-sanitizers --enable-languages=c,c++ --disable-werror --enable-multilib
Thread model: posix
Supported LTO compression algorithms: zlib
gcc version 15.0.0 20240525 (experimental) (GCC) 
[539] % 
[539] % gcctk -O3 small.c 
small.c: In function ‘main’:
small.c:3:5: error: stmt with wrong VUSE
    3 | int main() {
      |     ^~~~
# .MEM_4 = VDEF <.MEM_15>
a = 0;
expected .MEM_2
during GIMPLE pass: unswitch
small.c:3:5: internal compiler error: verify_ssa failed
0x140b2be verify_ssa(bool, bool)
        ../../gcc-trunk/gcc/tree-ssa.cc:1203
0x102deb5 execute_function_todo
        ../../gcc-trunk/gcc/passes.cc:2096
0x102e71e execute_todo
        ../../gcc-trunk/gcc/passes.cc:2143
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.
[540] % 
[540] % cat small.c
extern void c();
int a, b;
int main() {
  while (b) {
    int d, e = 0, *f = &a;
    *f = 1;
    e = 1 >> d ? : 1 << d;
    if (e)
      a = 0;
    c();
  }
  return 0;
}

[Bug tree-optimization/115226] [15 regression] ICE on valid code at -O3 on x86_64-linux-gnu: verify_ssa failed

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115226

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|                            |2024-05-26
           Keywords|                            |ice-on-valid-code
            Version|unknown                     |15.0
                 CC|                            |rguenth at gcc dot gnu.org
   Target Milestone|---                         |15.0
     Ever confirmed|0                           |1
             Status|UNCONFIRMED                 |NEW

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Confirmed. One of the sinking changes looks like exposed this latent bug in
unswitch.

[Bug tree-optimization/115226] [15 regression] ICE on valid code at -O3 on x86_64-linux-gnu: verify_ssa failed

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115226

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Assignee|unassigned at gcc dot gnu.org      |rguenth at gcc dot gnu.org
             Status|NEW                         |ASSIGNED

--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
I will have a look.

[Bug tree-optimization/115226] [15 regression] ICE on valid code at -O3 on x86_64-linux-gnu: verify_ssa failed

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115226

--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
It's interesting that SSA verification does not catch a missing virtual PHI
from sinking.

[Bug tree-optimization/115226] [15 regression] ICE on valid code at -O3 on x86_64-linux-gnu: verify_ssa failed

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115226

--- Comment #4 from Richard Biener <rguenth at gcc dot gnu.org> ---
It's another case where we "skip" a killing def when sinking a store.  Here
there's a conditional merge of both paths, again violating the virtual
operand update constraint.

[Bug tree-optimization/115226] [15 regression] ICE on valid code at -O3 on x86_64-linux-gnu: verify_ssa failed

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115226

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jakub at gcc dot gnu.org
           Priority|P3                          |P1

--- Comment #5 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Started with r15-815-g5b9b3bae33cae7fca2e3c3e3028be6b8bee9b698

[Bug tree-optimization/115226] [15 regression] ICE on valid code at -O3 on x86_64-linux-gnu: verify_ssa failed

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115226

--- Comment #6 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Richard Biener <rguenth@gcc.gnu.org>:

https://gcc.gnu.org/g:f9fbb47987efc8b5261e4cc36613c928a8693493

commit r15-850-gf9fbb47987efc8b5261e4cc36613c928a8693493
Author: Richard Biener <rguenther@suse.de>
Date:   Mon May 27 09:40:19 2024 +0200

    tree-optimization/115220 - fix store sinking virtual operand constraints

    The following makes sure the virtual operand updating when sinking
    stores works for the case we ignore paths to kills.  The final
    sink location might not post-dominate the original stmt location
    which would require inserting of a virtual PHI which we do not support.

            PR tree-optimization/115220
            PR tree-optimization/115226
            * tree-ssa-sink.cc (statement_sink_location): When ignoring
            paths to kills when sinking stores make sure the final
            sink location is still post-dominated by the original one.
            Otherwise we'd need to insert a PHI node to merge virtual operands.

            * gcc.dg/torture/pr115220.c: New testcase.
            * gcc.dg/torture/pr115226.c: New testcase.

[Bug tree-optimization/115226] [15 regression] ICE on valid code at -O3 on x86_64-linux-gnu: verify_ssa failed

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115226

Richard Biener <rguenth at gcc dot gnu.org> changed:

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

--- Comment #7 from Richard Biener <rguenth at gcc dot gnu.org> ---
Fixed.

[Bug tree-optimization/115226] [15 regression] ICE on valid code at -O3 on x86_64-linux-gnu: verify_ssa failed

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115226

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |dcb314 at hotmail dot com

--- Comment #8 from Richard Biener <rguenth at gcc dot gnu.org> ---
*** Bug 115243 has been marked as a duplicate of this bug. ***