[Bug c++/70029] New: [6 Regression] ICE with C++11 and -flto

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70029

            Bug ID: 70029
           Summary: [6 Regression] ICE with C++11 and -flto
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Keywords: ice-on-valid-code, lto
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: reichelt at gcc dot gnu.org
  Target Milestone: ---

The following valid code snippet triggers an ICE on trunk when compiled with
"-std=c++11 -g -flto":

========================================================================
struct A
{
  A();
  int foo() && __attribute__ ((__warn_unused_result__)) { return 0; }
};

A a;
========================================================================

bug.cc:7:4: error: TYPE_CANONICAL of main variant is not main variant
 A a;
    ^
 <method_type 0x7fac2957f888
    type <integer_type 0x7fac294417e0 int asm_written public type_6 SI
        size <integer_cst 0x7fac2945f0a8 constant 32>
        unit size <integer_cst 0x7fac2945f0c0 constant 4>
        align 32 symtab 692482528 alias set 2 canonical type 0x7fac294417e0
precision 32 min <integer_cst 0x7fac2945f060 -2147483648> max <integer_cst
0x7fac2945f078 2147483647>
        pointer_to_this <pointer_type 0x7fac29463930>>
    tree_4 tree_5 QI
    size <integer_cst 0x7fac2943df48 type <integer_type 0x7fac294412a0
bitsizetype> constant 8>
    unit size <integer_cst 0x7fac2943df60 type <integer_type 0x7fac294411f8
sizetype> constant 1>
    align 8 symtab 0 alias set -1 canonical type 0x7fac2957f888 method basetype
<record_type 0x7fac2957f348 A>
    arg-types <tree_list 0x7fac29576d98
        value <pointer_type 0x7fac2957f5e8 type <record_type 0x7fac2957f348 A>
            asm_written unsigned DI
            size <integer_cst 0x7fac2943de58 constant 64>
            unit size <integer_cst 0x7fac2943de70 constant 8>
            align 64 symtab 692482368 alias set -1 canonical type
0x7fac2957f5e8>
        chain <tree_list 0x7fac29451c80 value <void_type 0x7fac29463150
void>>>>
 <method_type 0x7fac2957f7e0
    type <integer_type 0x7fac294417e0 int asm_written public type_6 SI
        size <integer_cst 0x7fac2945f0a8 constant 32>
        unit size <integer_cst 0x7fac2945f0c0 constant 4>
        align 32 symtab 692482528 alias set 2 canonical type 0x7fac294417e0
precision 32 min <integer_cst 0x7fac2945f060 -2147483648> max <integer_cst
0x7fac2945f078 2147483647>
        pointer_to_this <pointer_type 0x7fac29463930>>
    QI
    size <integer_cst 0x7fac2943df48 type <integer_type 0x7fac294412a0
bitsizetype> constant 8>
    unit size <integer_cst 0x7fac2943df60 type <integer_type 0x7fac294411f8
sizetype> constant 1>
    align 8 symtab 0 alias set -1 canonical type 0x7fac2957f7e0 method basetype
<record_type 0x7fac2957f348 A>
    arg-types <tree_list 0x7fac29576d98
        value <pointer_type 0x7fac2957f5e8 type <record_type 0x7fac2957f348 A>
            asm_written unsigned DI
            size <integer_cst 0x7fac2943de58 constant 64>
            unit size <integer_cst 0x7fac2943de70 constant 8>
            align 64 symtab 692482368 alias set -1 canonical type
0x7fac2957f5e8>
        chain <tree_list 0x7fac29451c80 value <void_type 0x7fac29463150
void>>>>
 <method_type 0x7fac2957f930
    type <integer_type 0x7fac294417e0 int asm_written public type_6 SI
        size <integer_cst 0x7fac2945f0a8 constant 32>
        unit size <integer_cst 0x7fac2945f0c0 constant 4>
        align 32 symtab 692482528 alias set 2 canonical type 0x7fac294417e0
precision 32 min <integer_cst 0x7fac2945f060 -2147483648> max <integer_cst
0x7fac2945f078 2147483647>
        pointer_to_this <pointer_type 0x7fac29463930>>
    QI
    size <integer_cst 0x7fac2943df48 type <integer_type 0x7fac294412a0
bitsizetype> constant 8>
    unit size <integer_cst 0x7fac2943df60 type <integer_type 0x7fac294411f8
sizetype> constant 1>
    align 8 symtab 0 alias set -1 canonical type 0x7fac2957f888
    attributes <tree_list 0x7fac29576dc0
        purpose <identifier_node 0x7fac295948f0 __warn_unused_result__
            bindings <(nil)>
            local bindings <(nil)>>> method basetype <record_type
0x7fac2957f348 A>
    arg-types <tree_list 0x7fac29576d98
        value <pointer_type 0x7fac2957f5e8 type <record_type 0x7fac2957f348 A>
            asm_written unsigned DI
            size <integer_cst 0x7fac2943de58 constant 64>
            unit size <integer_cst 0x7fac2943de70 constant 8>
            align 64 symtab 692482368 alias set -1 canonical type
0x7fac2957f5e8>
        chain <tree_list 0x7fac29451c80 value <void_type 0x7fac29463150
void>>>>
bug.cc:7:4: internal compiler error: verify_type failed
0xfa84c2 verify_type(tree_node const*)
        ../../gcc/gcc/tree.c:13900
0xfaa34b free_lang_data_in_cgraph
        ../../gcc/gcc/tree.c:5984
0xfaa34b free_lang_data
        ../../gcc/gcc/tree.c:6014
0xfaa34b execute
        ../../gcc/gcc/tree.c:6063
Please submit a full bug report, [etc.]


This is a regression w.r.t GCC 5.3.0.
The bug makes it impossible to compile Qt (Qt 5.4.2) programs with -flto,
because QString contains such a pattern.