[Bug ipa/88936] New: -fipa-pta breaks bash (incorrect optimisation of recursive static function)

[slyfox at inbox dot ru]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88936

            Bug ID: 88936
           Summary: -fipa-pta breaks bash (incorrect optimisation of
                    recursive static function)
           Product: gcc
           Version: 8.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: ipa
          Assignee: unassigned at gcc dot gnu.org
          Reporter: slyfox at inbox dot ru
                CC: marxin at gcc dot gnu.org
  Target Milestone: ---

Initially bug is observed by muffindrake on #gentoo-portage as a series of
mysterious bash failures.

Here is the minimal reproducer:

  #include <stdio.h>

  /*
   How to reproduce:

  $ gcc -O2 -Wall -fno-stack-protector           main.c -o c-bug         &&
./c-bug
  ff(1) = 1
  $ gcc -O2 -Wall -fno-stack-protector -fipa-pta main.c -o c-bug-ipa-pta &&
./c-bug-ipa-pta
  ff(1) = 3
  */

  static long bug (long depth, long * v)
  {
    if (depth == 0)
    {
      *v = 0;
      return 1;
    }

    long r = 1;
    long val = bug(depth - 1, &r);
    return 2 * r + val;
  }

  static long ff (long depth)
  {
    return bug(depth, (long*)NULL);
  }

  int main() {
    fprintf(stderr, "ff(1) = %ld\n", ff(1));
  }

Reproducible on 9.0.0 20190120, 8.2.0, 7.4.0, 6.5.0. Not reproducible on 5.5.0.
Reproducible on multiple platforms.

$ ./xgcc -B. -v
Reading specs from ./specs
COLLECT_GCC=./xgcc
COLLECT_LTO_WRAPPER=./lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: ../gcc/configure --enable-languages=c,c++ --disable-bootstrap
--with-multilib-list=m64
--prefix=/home/slyfox/dev/git/gcc-native/../gcc-native-quick-installed
--disable-nls CFLAGS='-O0 -g ' CXXFLAGS='-O0 -g '
--with-sysroot=/usr/x86_64-HEAD-linux-gnu
Thread model: posix
gcc version 9.0.0 20190120 (experimental) (GCC)