[Bug c++/79664] New: ICE with #pragma omp parallel in constexpr function

["reichelt at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79664

            Bug ID: 79664
           Summary: ICE with #pragma omp parallel in constexpr function
           Product: gcc
           Version: 7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: reichelt at gcc dot gnu.org
  Target Milestone: ---

The following code snippet (compiled with "-std=c++1y -fopenmp")
triggers an ICE since GCC 5.1.0:

==================================
constexpr int foo()
{
  int i = 0;
#pragma omp parallel for
  for ( i=0; i<10; ++i ) ;

  return 0;
}
==================================

bug.cc: In function 'constexpr int foo()':
bug.cc:8:1: sorry, unimplemented: unexpected AST of kind omp_parallel
 }
 ^
bug.cc:8:1: internal compiler error: in potential_constant_expression_1, at
cp/constexpr.c:4496
0x8531e4 potential_constant_expression_1
        ../../gcc-5.1.0/gcc/cp/constexpr.c:4496
0x852c8d potential_constant_expression_1
        ../../gcc-5.1.0/gcc/cp/constexpr.c:4102
0x853c00 potential_rvalue_constant_expression(tree_node*)
        ../../gcc-5.1.0/gcc/cp/constexpr.c:4521
0x853c00 register_constexpr_fundef(tree_node*, tree_node*)
        ../../gcc-5.1.0/gcc/cp/constexpr.c:782
0x67d445 maybe_save_function_definition
        ../../gcc-5.1.0/gcc/cp/decl.c:14095
0x67d445 finish_function(int)
        ../../gcc-5.1.0/gcc/cp/decl.c:14219
0x76c9c9 cp_parser_function_definition_after_declarator
        ../../gcc-5.1.0/gcc/cp/parser.c:23489
0x76d863 cp_parser_function_definition_from_specifiers_and_declarator
        ../../gcc-5.1.0/gcc/cp/parser.c:23395
0x76d863 cp_parser_init_declarator
        ../../gcc-5.1.0/gcc/cp/parser.c:17072
0x76f915 cp_parser_simple_declaration
        ../../gcc-5.1.0/gcc/cp/parser.c:11607
0x7693a3 cp_parser_block_declaration
        ../../gcc-5.1.0/gcc/cp/parser.c:11481
0x773249 cp_parser_declaration
        ../../gcc-5.1.0/gcc/cp/parser.c:11378
0x7718da cp_parser_declaration_seq_opt
        ../../gcc-5.1.0/gcc/cp/parser.c:11264
0x771bef cp_parser_translation_unit
        ../../gcc-5.1.0/gcc/cp/parser.c:4100
0x771bef c_parse_file()
        ../../gcc-5.1.0/gcc/cp/parser.c:33192
0x8a8ed2 c_common_parse_file()
        ../../gcc-5.1.0/gcc/c-family/c-opts.c:1057
Please submit a full bug report, [etc.]