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List:       gcc-bugs
Subject:    [Bug tree-optimization/114902] New: wrong code at -O3 with "-fno-tree-vrp -fno-expensive-optimizatio
From:       "zhendong.su at inf dot ethz.ch via Gcc-bugs" <gcc-bugs () gcc ! gnu ! org>
Date:       2024-04-30 22:13:13
Message-ID: bug-114902-4 () http ! gcc ! gnu ! org/bugzilla/
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114902

            Bug ID: 114902
           Summary: wrong code at -O3 with "-fno-tree-vrp
                    -fno-expensive-optimizations -fno-tree-dominator-opts"
                    on x86_64-linux-gnu
           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 13.2. 

Compiler Explorer: https://godbolt.org/z/7ssP5W57E


[587] % 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 20240430 (experimental) (GCC) 
[588] % 
[588] % gcctk -O3 -fno-tree-vrp -fno-expensive-optimizations
-fno-tree-dominator-opts small.c
[589] % ./a.out
Floating point exception
[590] % 
[590] % gcctk -O3 small.c; ./a.out
[591] % 
[591] % cat small.c
volatile int a, c;
unsigned b = 1;
int main() {
  for (; a < 2; a++)
    if (a)
      for (; c < 2; c++) {
        int d = -1, e = -(-d & ~b), f = -~(1 && b % a);
        a % f || a;
        if (d <= e)
          e = a;
        a = e;
      }
  return 0;
}=


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