[Bug target/102057] New: ICE at -O2 in extract_constrain_insn, at recog.c:2670

[haoxintu at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102057

            Bug ID: 102057
           Summary: ICE at -O2 in extract_constrain_insn, at recog.c:2670
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Keywords: ice-on-valid-code
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: haoxintu at gmail dot com
  Target Milestone: ---

Hi all.

This program makes GCC ICE. I think this program is syntactically valid and GCC
should not emit any error. I found there are many fixed PRs that crash at the
same point "recog.c:2670" and similar stack information. So, I am not sure if
this is a dup case, and please kindly close it if it is.

$cat small.c
#include <stdint.h>
extern n(int f);
a, b, c, d, e, f, g, i;
fn1(int64_t j, uint16_t k) {
  uint64_t *l = c;
  int8_t m;
  if (n(f))
    if (*l) {
      int8_t o;
      uint16_t *p = &k;
      if (i) {
        int64_t q = e;
        if (q)
          for (; *p <= 5; k += o)
            ;
      }
    }
  e = 8;
  while (e--) {
    a = 7;
    while (a) {
      a -= 5;
      if (i)
        if (5 << m)
          while (i)
            i += 4;
      for (; b;)
        ;
    }
  }
  int32_t r;
  g = (d ? k : m) >> (r = 2) ?: 3;
  for (; *l; l += f++) {
    int64_t *s;
    if (*s)
      for (; j;)
        if (0 / 0)
          for (;;)
            ;
  }
}

$gcc -O2 -w -fPIC small.c
small.c: In function ‘fn1’:
small.c:41:1: error: insn does not satisfy its constraints:
   41 | }
      | ^
(insn 429 394 430 22 (parallel [
            (set (reg:CCZ 17 flags)
                (compare:CCZ (ashiftrt:SI (reg:SI 0 ax [orig:90 _12 ] [90])
                        (const_int 2 [0x2]))
                    (const_int 0 [0])))
            (set (reg:SI 41 r13 [orig:137 k ] [137])
                (ashiftrt:SI (reg:SI 0 ax [orig:90 _12 ] [90])
                    (const_int 2 [0x2])))
        ]) "small.c":32:31 740 {*ashrsi3_cmp}
     (expr_list:REG_DEAD (reg:SI 0 ax [orig:90 _12 ] [90])
        (nil)))
during RTL pass: cprop_hardreg
small.c:41:1: internal compiler error: in extract_constrain_insn, at
recog.c:2670
0x681355 _fatal_insn(char const*, rtx_def const*, char const*, int, char
const*)
        ../../gcc/rtl-error.c:108
0x68137b _fatal_insn_not_found(rtx_def const*, char const*, int, char const*)
        ../../gcc/rtl-error.c:118
0x680484 extract_constrain_insn(rtx_insn*)
        ../../gcc/recog.c:2670
0xb738ce copyprop_hardreg_forward_1
        ../../gcc/regcprop.c:825
0xb7481d execute
        ../../gcc/regcprop.c:1390
Please submit a full bug report,
with preprocessed source if appropriate.
Please include the complete backtrace with any bug report.
See <https://gcc.gnu.org/bugs/> for instructions.


$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
Thread model: posix
Supported LTO compression algorithms: zlib
gcc version 12.0.0 20210825 (experimental) (GCC)

Reproduced in Godbol: https://godbolt.org/z/EfMa7zrcj

Thanks,
Haoxin