May or may not be related to PR 54844:

This little piece of code has recently started to produce an ICE on mainline:
..............................
template <bool> class X {};

template <typename T> struct A {
    X<(sizeof(T)<sizeof(long double))> x;
};

A<int> a;
..............................

> c++ -c numerics/a.cc 
numerics/a.cc: In instantiation of 'struct A<int>':
numerics/a.cc:7:8:   required from here
numerics/a.cc:4:24: internal compiler error: in tsubst_copy, at cp/pt.c:12387
     X<(sizeof(T)<sizeof(long double))> x;
                        ^
linux-vdso.so.1: No such file or directory
0x596d03 tsubst_copy
        ../../mainline/gcc/cp/pt.c:12387
0x586762 tsubst_copy_and_build(tree_node*, tree_node*, int, tree_node*, bool, bool)
        ../../mainline/gcc/cp/pt.c:13514
0x585b81 tsubst_copy_and_build(tree_node*, tree_node*, int, tree_node*, bool, bool)
        ../../mainline/gcc/cp/pt.c:13539
0x585602 tsubst_copy_and_build(tree_node*, tree_node*, int, tree_node*, bool, bool)
        ../../mainline/gcc/cp/pt.c:13494
0x58e6a4 tsubst_expr
        ../../mainline/gcc/cp/pt.c:13194
0x5a1002 tsubst_template_arg
        ../../mainline/gcc/cp/pt.c:9039
0x5a75e2 tsubst_template_args
        ../../mainline/gcc/cp/pt.c:9489
0x5add71 tsubst_aggr_type
        ../../mainline/gcc/cp/pt.c:9686
0x59e773 tsubst(tree_node*, tree_node*, int, tree_node*)
        ../../mainline/gcc/cp/pt.c:11039
0x599216 tsubst_decl
        ../../mainline/gcc/cp/pt.c:10329
0x59eb8c tsubst(tree_node*, tree_node*, int, tree_node*)
        ../../mainline/gcc/cp/pt.c:10965
0x5c4a5c instantiate_class_template_1
        ../../mainline/gcc/cp/pt.c:8778
0x5c4a5c instantiate_class_template(tree_node*)
        ../../mainline/gcc/cp/pt.c:9020
0x64eb2b complete_type(tree_node*)
        ../../mainline/gcc/cp/typeck.c:134
0x54b548 start_decl_1(tree_node*, bool)
        ../../mainline/gcc/cp/decl.c:4621
0x5675e1 start_decl(cp_declarator const*, cp_decl_specifier_seq*, int, tree_node*, tree_node*, tree_node**)
        ../../mainline/gcc/cp/decl.c:4584
0x6415dc cp_parser_init_declarator
        ../../mainline/gcc/cp/parser.c:15887
0x641f6f cp_parser_simple_declaration
        ../../mainline/gcc/cp/parser.c:10560
0x63ce27 cp_parser_block_declaration
        ../../mainline/gcc/cp/parser.c:10441
0x647f3b cp_parser_declaration
        ../../mainline/gcc/cp/parser.c:10338
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.


Best
 W.