[Bug tree-optimization/100512] New: [12 Regression] ICE during GIMPLE pass: cddce in mark_operand_necessary, at tree-ssa-dce.c:173 (under -O2 to -Os)

[haoxintu at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100512

            Bug ID: 100512
           Summary: [12 Regression] ICE during GIMPLE pass: cddce in
                    mark_operand_necessary, at tree-ssa-dce.c:173  (under
                    -O2 to -Os)
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Keywords: ice-on-valid-code
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: haoxintu at gmail dot com
  Target Milestone: ---

Hi all.

$cat small.c
#include <stdint.h>
int a;
void b() {
  int16_t *c;
  uint16_t d = 2;
  if (0 == d) {
    uint64_t e;
    uint64_t *f = &e;
    for (;;) {
      if (e += 0 >= 0)
        for (;;)
          ;
    g:
      for (; a;) {
        int16_t i = &d;
        *c = i && *f;
      }
    }
  }
  goto g;
}


$gcc -w -O2 
during GIMPLE pass: cddce
small.c: In function ‘b’:
small.c:21:1: internal compiler error: in mark_operand_necessary, at
tree-ssa-dce.c:173
   21 | }
      | ^
0x65b30e mark_operand_necessary
        ../../gcc/tree-ssa-dce.c:173
0xc86d76 propagate_necessity
        ../../gcc/tree-ssa-dce.c:852
0xc86d76 perform_tree_ssa_dce
        ../../gcc/tree-ssa-dce.c:1673
0xc887d5 tree_ssa_cd_dce
        ../../gcc/tree-ssa-dce.c:1717
0xc887d5 execute
        ../../gcc/tree-ssa-dce.c:1789
Please submit a full bug report,
with preprocessed source if appropriate.
Please include the complete backtrace with any bug report.
See <https://gcc.gnu.org/bugs/> for instructions.
tuhaoxin@oscar-2020:~/dut-research/covsmith-test/20210502$ cat small.c
#include <stdint.h>
int a;
void b() {
  int16_t *c;
  uint16_t d = 2;
  if (0 == d) {
    uint64_t e;
    uint64_t *f = &e;
    for (;;) {
      if (e += 0 >= 0)
        for (;;)
          ;
    g:
      for (; a;) {
        int16_t i = &d;
        *c = i && *f;
      }
    }
  }
  goto g;
}

$gcc -v
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/home/tuhaoxin/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/tuhaoxin/compilers/gcc/build/
--enable-bootstrap --enable-checking=release --enable-languages=c,c++
-disable-multilib
Thread model: posix
Supported LTO compression algorithms: zlib
gcc version 12.0.0 20210510 (experimental) (GCC) 

This crash only exists in the current trunk version of GCC, and the released
versions perform well. I also tested it on an earlier GCC trunk built on
20210425, it does not crash as well. So I think it's a regression issue in
GCC-12.


Thanks,
Haoxin