[Bug c/68906] New: ICE at -O3 on x86_64-linux-gnu: verify_ssa failed

[chengniansun at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68906

            Bug ID: 68906
           Summary: ICE at -O3 on x86_64-linux-gnu: verify_ssa failed
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: chengniansun at gmail dot com
  Target Milestone: ---

The following 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. 


$: gcc-trunk -v
Using built-in specs.
COLLECT_GCC=gcc-trunk
COLLECT_LTO_WRAPPER=/usr/local/gcc-trunk/libexec/gcc/x86_64-pc-linux-gnu/6.0.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: ../gcc-trunk/configure --prefix=/usr/local/gcc-trunk
--enable-languages=c,c++ --disable-werror --enable-multilib
Thread model: posix
gcc version 6.0.0 20151214 (experimental) [trunk revision 231607] (GCC) 

$: 
$: gcc-trunk -c -g -O3 -m32 small.c 
small.c: In function ‘fn1’:
small.c:4:5: error: definition in block 6 does not dominate use in block 7
 int fn1() {
     ^~~

for SSA_NAME: e_14 in statement:
# DEBUG f => e_14
small.c:4:5: internal compiler error: verify_ssa failed
0xce6fe2 verify_ssa(bool, bool)
        ../../gcc-trunk/gcc/tree-ssa.c:1039
0xa1f9dd execute_function_todo
        ../../gcc-trunk/gcc/passes.c:1965
0xa2027b execute_todo
        ../../gcc-trunk/gcc/passes.c:2010
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.
$: 
$: gcc-trunk -c -g -O3 -m64 small.c 
small.c: In function ‘fn1’:
small.c:4:5: error: definition in block 6 does not dominate use in block 7
 int fn1() {
     ^~~

for SSA_NAME: e_14 in statement:
# DEBUG f => e_14
small.c:4:5: internal compiler error: verify_ssa failed
0xce6fe2 verify_ssa(bool, bool)
        ../../gcc-trunk/gcc/tree-ssa.c:1039
0xa1f9dd execute_function_todo
        ../../gcc-trunk/gcc/passes.c:1965
0xa2027b execute_todo
        ../../gcc-trunk/gcc/passes.c:2010
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 small.c
int a;
volatile int b;
short c, d;
int fn1() {
  int e;
  for (;;) {
    a = 3;
    if (c)
      continue;
    e = 0;
    for (; e > -30; e--)
      if (b) {
        int f = e;
        return d;
      }
  }
}