[Bug rtl-optimization/86222] New: ICE in final_scan_insn_1 calling strncmp() with a bound of PTRDIFF_MAX + 1

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86222

            Bug ID: 86222
           Summary: ICE in final_scan_insn_1 calling strncmp() with a
                    bound of PTRDIFF_MAX + 1
           Product: gcc
           Version: 8.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: rtl-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: msebor at gcc dot gnu.org
  Target Milestone: ---

The following test case was reduced from a powerpc-ibm-aix7.2 ICE in the
gcc.dg/attr-nonstring-3.c test case added in r261704:

$ cat c.i && /ssd/build/powerpc-ibm-aix7.2/gcc-8-branch/gcc/xgcc -B
/ssd/build/powerpc-ibm-aix7.2/gcc-8-branch/gcc -S -O2 -Wall -Wextra
-fdump-tree-optimized=/dev/stdout c.i
typedef typeof (sizeof 0) size_t;

extern int strncmp (const char*, const char*, size_t);

int f (void)
{
  size_t n = 0x7fffffffL;   // PTRDIFF_MAX

  extern char a[];
  extern char b[16];
  return strncmp (a, b, n + 1);
}

;; Function f (f, funcdef_no=0, decl_uid=2619, cgraph_uid=0, symbol_order=0)

f ()
{
  int _2;

  <bb 2> [local count: 1073741825]:
  _2 = strncmp (&a, &b, 2147483648); [tail call]
  return _2;

}


c.i: In function ‘f’:
c.i:12:1: error: could not split insn
 }
 ^
(insn 116 118 194 (set (reg:SI 5 5)
        (const_int -2147483680 [0xffffffff7fffffe0])) "c.i":11 485
{*movsi_internal1}
     (nil))
during RTL pass: final
c.i:12:1: internal compiler error: in final_scan_insn_1, at final.c:3142
0xfed675 _fatal_insn(char const*, rtx_def const*, char const*, int, char
const*)
        /src/gcc/8-branch/gcc/rtl-error.c:108
0xb5c13c final_scan_insn_1
        /src/gcc/8-branch/gcc/final.c:3142
0xb5c7a9 final_scan_insn(rtx_insn*, _IO_FILE*, int, int, int*)
        /src/gcc/8-branch/gcc/final.c:3221
0xb58a26 final_1
        /src/gcc/8-branch/gcc/final.c:2091
0xb616ce rest_of_handle_final
        /src/gcc/8-branch/gcc/final.c:4674
0xb61b56 execute
        /src/gcc/8-branch/gcc/final.c:4748
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