[Bug tree-optimization/103209] New: [12 Regression] wrong code at -O1 on x86_64-linux-gnu

[Bug tree-optimization/103209] New: [12 Regression] wrong code at -O1 on x86_64-linux-gnu

[haoxintu at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103209

            Bug ID: 103209
           Summary: [12 Regression] wrong code at -O1 on x86_64-linux-gnu
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Keywords: wrong-code
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: haoxintu at gmail dot com
  Target Milestone: ---

Hi all.

It seems to be a recent regression issue.

$cat small.c
#include <stdio.h>
#include <stdint.h>

int32_t a[6];
int64_t b;
int32_t *c;
int32_t **d = &c;
int64_t *e = &b;
int32_t **const *f = &d;
int32_t **const **g = &f;
int32_t *h();
static int16_t j();
static uint32_t k(int8_t, const int32_t *, int64_t);
static uint32_t l() {
  int32_t *m = &a[3];
  int32_t n = 0;
  int8_t o = 0;
  int32_t *p[] = {&n, &n, &n, &n};
  uint32_t q[6][1][2] = {};
  for (o = 0; o <= 1; o = 6)
    if (h(j(k(3, 0, q[2][0][0]), &n), n) == p[3])
      *m = *e;
  return 0;
}
int32_t *h(uint32_t, int32_t) { return ***g; }
int16_t j(uint32_t, int32_t *r) { **f = r; }
uint32_t k(int8_t, const int32_t *, int64_t) { *e = 3; return 0;}
int main() {
  int i = 0;
  l();
  for (i = 0; i < 6; i++){
    if (i == 3)
        printf("%d\n", a[i]);
  }
  return 0;
}

$gcc -O1 small.c ; ./a.out
0

$gcc -O0 small.c ; ./a.out
3

$gcc -O2 small.c ; ./a.out
3

$gcc -v
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/home/haoxin/haoxin-data/compilers/gcc/build/libexec/gcc/x86_64-pc-linux-gnu/12.0.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with:../configure
--prefix=/home/haoxin/haoxin-data/compilers/gcc/build/ --enable-bootstrap
--enable-checking=release --enable-languages=c,c++ --enable-multilib :
(reconfigured) ../configure
--prefix=/home/haoxin/haoxin-data/compilers/gcc/build/ --enable-bootstrap
--enable-checking=release --enable-multilib --enable-languages=c,c++,lto
--no-create --no-recursion
Thread model: posix
Supported LTO compression algorithms: zlib
gcc version 12.0.0 20211112 (experimental) (GCC) 

Thanks,
Haoxin

[Bug tree-optimization/103209] [12 Regression] wrong code at -O1 on x86_64-linux-gnu since r12-4324-g008e7397dad971c0

[marxin at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103209

Martin Liška <marxin at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|                            |2021-11-12
             Status|UNCONFIRMED                 |NEW
            Summary|[12 Regression] wrong code  |[12 Regression] wrong code
                   |at -O1 on x86_64-linux-gnu  |at -O1 on x86_64-linux-gnu
                   |                            |since
                   |                            |r12-4324-g008e7397dad971c0
     Ever confirmed|0                           |1
                 CC|                            |hubicka at gcc dot gnu.org,
                   |                            |marxin at gcc dot gnu.org

--- Comment #1 from Martin Liška <marxin at gcc dot gnu.org> ---
Started with r12-4324-g008e7397dad971c0.

[Bug tree-optimization/103209] [12 Regression] wrong code at -O1 on x86_64-linux-gnu since r12-4324-g008e7397dad971c0

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103209

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P3                          |P1
   Target Milestone|---                         |12.0

[Bug tree-optimization/103209] [12 Regression] wrong code at -O1 on x86_64-linux-gnu since r12-4324-g008e7397dad971c0

[hubicka at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103209

Jan Hubicka <hubicka at gcc dot gnu.org> changed:

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

--- Comment #2 from Jan Hubicka <hubicka at gcc dot gnu.org> ---
mine.

[Bug tree-optimization/103209] [12 Regression] wrong code at -O1 on x86_64-linux-gnu since r12-4324-g008e7397dad971c0

[hubicka at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103209

--- Comment #3 from Jan Hubicka <hubicka at gcc dot gnu.org> ---
This is bug I introduced to tree-ssa-structalias where I reversed order of
flags which deterine global memory read and writes. So pure functions are
handled as functions writting global memory but not reading it.  I am very
surprised it took so long to show as wrong code.

diff --git a/gcc/tree-ssa-structalias.c b/gcc/tree-ssa-structalias.c
index 153ddf57a61..34fd47fdf47 100644
--- a/gcc/tree-ssa-structalias.c
+++ b/gcc/tree-ssa-structalias.c
@@ -4996,7 +4996,7 @@ find_func_aliases_for_call (struct function *fn, gcall
*t)
         reachable from their arguments, but they are not an escape
         point for reachable memory of their arguments.  */
       else if (flags & (ECF_PURE|ECF_LOOPING_CONST_OR_PURE))
-       handle_rhs_call (t, &rhsc, implicit_pure_eaf_flags, true, false);
+       handle_rhs_call (t, &rhsc, implicit_pure_eaf_flags, false, true);
       /* If the call is to a replaceable operator delete and results
         from a delete expression as opposed to a direct call to
         such operator, then the effects for PTA (in particular

[Bug tree-optimization/103209] [12 Regression] wrong code at -O1 on x86_64-linux-gnu since r12-4324-g008e7397dad971c0

[marxin at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103209

--- Comment #4 from Martin Liška <marxin at gcc dot gnu.org> ---
Wow, what a bug :P

[Bug tree-optimization/103209] [12 Regression] wrong code at -O1 on x86_64-linux-gnu since r12-4324-g008e7397dad971c0

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103209

--- Comment #5 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Jan Hubicka <hubicka@gcc.gnu.org>:

https://gcc.gnu.org/g:4d2d5565a0953eaa829d10006baf007cf33bab89

commit r12-5217-g4d2d5565a0953eaa829d10006baf007cf33bab89
Author: Jan Hubicka <jh@suse.cz>
Date:   Fri Nov 12 23:55:50 2021 +0100

    Fix wrong code with pure functions

    I introduced bug into find_func_aliases_for_call in handling pure
functions.
    Instead of reading global memory pure functions are believed to write
global
    memory.  This results in misoptimization of the testcase at -O1.

    The change to pta-callused.c updates the template for new behaviour of the
    constraint generation. We copy nonlocal memory to calluse which is correct
but
    also not strictly necessary because later we take care to add nonlocal_p
flag
    manually.

    gcc/ChangeLog:

            PR tree-optimization/103209
            * tree-ssa-structalias.c (find_func_aliases_for_call): Fix
            use of handle_rhs_call

    gcc/testsuite/ChangeLog:

            PR tree-optimization/103209
            * gcc.dg/tree-ssa/pta-callused.c: Update template.
            * gcc.c-torture/execute/pr103209.c: New test.

[Bug tree-optimization/103209] [12 Regression] wrong code at -O1 on x86_64-linux-gnu since r12-4324-g008e7397dad971c0

[hubicka at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103209

Jan Hubicka <hubicka at gcc dot gnu.org> changed:

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

--- Comment #6 from Jan Hubicka <hubicka at gcc dot gnu.org> ---
Fixed.