[Bug tree-optimization/69773] New: gcc ICE at -O2 and above on valid code on x86_64-linux-gnu in "assign_by_spills"

[helloqirun at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69773

            Bug ID: 69773
           Summary: gcc ICE at -O2 and above on valid code on
                    x86_64-linux-gnu in "assign_by_spills"
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: helloqirun at gmail dot com
  Target Milestone: ---

The following valid code causes an ICE when compiled with the current gcc trunk
at -O2 and above on x86_64-linux-gnu in both 32-bit and 64-bit modes.


$ 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/6.0.0/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 6.0.0 20160211 (experimental) [trunk revision 233345] (GCC)


$ gcc-trunk -c -O2 abc.c
abc.c: In function 'fn2':
abc.c:18:1: error: unable to find a register to spill
 }
 ^
abc.c:18:1: error: this is the insn:
(insn 11 30 29 3 (parallel [
            (set (reg:SI 101 [95])
                (truncate:SI (lshiftrt:DI (mult:DI (sign_extend:DI (reg:SI 102
[100]))
                            (sign_extend:DI (reg:SI 96)))
                        (const_int 32 [0x20]))))
            (clobber (reg:SI 102 [100]))
            (clobber (reg:CC 17 flags))
        ]) abc.c:8 341 {*smulsi3_highpart_1}
     (expr_list:REG_UNUSED (reg:SI 102 [100])
        (expr_list:REG_DEAD (reg:SI 96)
            (expr_list:REG_UNUSED (reg:CC 17 flags)
                (expr_list:REG_EQUAL (truncate:SI (lshiftrt:DI (mult:DI
(sign_extend:DI (reg:SI 94 [ MEM[(struct str *)&f] ]))
                                (const_int 1374389535 [0x51eb851f]))
                            (const_int 32 [0x20])))
                    (nil))))))
abc.c:18:1: internal compiler error: in assign_by_spills, at lra-assigns.c:1417
0xaf7f38 _fatal_insn(char const*, rtx_def const*, char const*, int, char
const*)
        ../../gcc/gcc/rtl-error.c:108
0x9f3575 assign_by_spills
        ../../gcc/gcc/lra-assigns.c:1417
0x9f3c23 lra_assign()
        ../../gcc/gcc/lra-assigns.c:1590
0x9ef6ab lra(_IO_FILE*)
        ../../gcc/gcc/lra.c:2322
0x9a6939 do_reload
        ../../gcc/gcc/ira.c:5395
0x9a6939 execute
        ../../gcc/gcc/ira.c:5566
Please submit a full bug report,
with preprocessed source if appropriate.


$ cat abc.c
struct str {
  int k;
} f;
int g, a;
int fn1(struct str *p1) {
  a = ({
    register __typeof__(0) c asm("rdx");
    g = p1->k / 100;
    c;
  });
  return 0;
}
int fn2() {
  struct str h = f;
  if (g)
    fn1(&h);
  return 0;
}