[Bug tree-optimization/121264] New: ifcombine wrong code

[kristerw at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=121264

            Bug ID: 121264
           Summary: ifcombine wrong code
           Product: gcc
           Version: 16.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: kristerw at gcc dot gnu.org
  Target Milestone: ---

The following program (from testsuite/gcc.c-torture/compile/pr103813.c) is
miscompiled for x86_64 with -O1 or higher optimization levels.

struct A { char b; char c[0x21000000]; };
struct A d;
int
foo ()
{
  return d.c[0x20000000] || d.c[1];
}

Ifcombine transforms this into the equivalent of
  return d.c[1] != 0;