The following valid code causes an ICE when compiled with the current gcc trunk at -O3 on x86_64-linux-gnu in both 32-bit and 64-bit modes.

It appears to be a 7 regression.


$ gcc-trunk -v
Using built-in specs.
COLLECT_GCC=gcc-trunk
COLLECT_LTO_WRAPPER=/home/absozero/trunk/root-gcc/libexec/gcc/x86_64-pc-linux-gnu/7.0.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: ../gcc/configure --prefix=/home/absozero/trunk/root-gcc --enable-languages=c,c++ --disable-werror --enable-multilib
Thread model: posix
gcc version 7.0.0 20160608 (experimental) [trunk revision 237212] (GCC)


$ gcc-trunk -O3 abc.c
abc.c: In function ‘fn1’:
abc.c:3:6: internal compiler error: Segmentation fault
 void fn1() {
      ^~~
0xb635cf crash_signal
	../../gcc/gcc/toplev.c:335
0xcbe6bb ei_container
	../../gcc/gcc/basic-block.h:393
0xcbe6bb ei_end_p
	../../gcc/gcc/basic-block.h:429
0xcbe6bb ei_cond
	../../gcc/gcc/basic-block.h:479
0xcbe6bb find_uses_to_rename_bb
	../../gcc/gcc/tree-ssa-loop-manip.c:442
0xcc0a5e find_uses_to_rename
	../../gcc/gcc/tree-ssa-loop-manip.c:476
0xcc0a5e rewrite_into_loop_closed_ssa_1(bitmap_head*, unsigned int, int, loop*)
	../../gcc/gcc/tree-ssa-loop-manip.c:642
0xca5b30 tree_unroll_loops_completely(bool, bool)
	../../gcc/gcc/tree-ssa-loop-ivcanon.c:1388
0xca6030 execute
	../../gcc/gcc/tree-ssa-loop-ivcanon.c:1531
Please submit a full bug report,
with preprocessed source if appropriate.
Please include the complete backtrace with any bug report.
See <http://gcc.gnu.org/bugs.html> for instructions.


$ cat abc.c
short a;
long b;
void fn1() {
  int c = a = 1;
  for (; a; a++) {
    for (; 9 <= 8;)
      for (;;) {
        a = 20;
        for (; a <= 35; a++)
          ;
      line:;
      }
    if ((c += 264487869) == 9) {
      unsigned *d = 0;
      for (; b;)
        d = (unsigned *)&c;
      if (d)
        for (;;)
          ;
    }
  }
  goto line;
}