https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88587
--- Comment #3 from Martin Liška <marxin at gcc dot gnu.org> ---
So the problem is that new function body is copied in:
(gdb) bt
#0 __memmove_avx_unaligned_erms () at
../sysdeps/x86_64/multiarch/memmove-vec-unaligned-erms.S:342
#1 0x0000000000fd7378 in copy_node (node=node@entry=<var_decl 0x7ffff7feeab0
b>) at /home/marxin/Programming/gcc/gcc/tree.c:1183
#2 0x0000000000db07bf in copy_decl_no_change (decl=<var_decl 0x7ffff7feeab0
b>, id=0x7fffffffd5d0) at /home/marxin/Programming/gcc/gcc/tree-inline.c:5557
#3 0x0000000000db0b2d in remap_decl (decl=<optimized out>, id=0x7fffffffd5d0)
at /home/marxin/Programming/gcc/gcc/tree-inline.c:366
#4 0x0000000000db0d9d in remap_decls (decls=<optimized out>,
nonlocalized_list=0x7ffff6c60508<error reading variable: Cannot access memory
at address 0x4>, id=0x7fffffffd5d0) at
/home/marxin/Programming/gcc/gcc/tree-inline.c:656
#5 0x0000000000db29c2 in remap_block (block=0x7fffffffd498, id=0x7fffffffd5d0)
at /home/marxin/Programming/gcc/gcc/tree.h:3177
#6 0x0000000000db2a86 in remap_blocks (block=<block 0x7ffff6c602a0>,
id=0x7fffffffd5d0) at /home/marxin/Programming/gcc/gcc/tree-inline.c:736
#7 0x0000000000dbd5c8 in tree_function_versioning
(old_decl=old_decl@entry=<function_decl 0x7ffff6c5c200 a>,
new_decl=new_decl@entry=<function_decl 0x7ffff6c5c800 a.sse2.0>,
tree_map=tree_map@entry=0x0, update_clones=update_clones@entry=false,
args_to_skip=args_to_skip@entry=0x0, skip_return=skip_return@entry=false,
blocks_to_copy=<optimized out>, new_entry=<optimized out>) at
/home/marxin/Programming/gcc/gcc/tree.h:3291
#8 0x000000000093f8b1 in cgraph_node::create_version_clone_with_body
(this=this@entry=<cgraph_node * const 0x7ffff6b552d0 "a"/0>,
redirect_callers=..., redirect_callers@entry=..., tree_map=tree_map@entry=0x0,
args_to_skip=args_to_skip@entry=0x0,
skip_return=skip_return@entry=false, bbs_to_copy=bbs_to_copy@entry=0x0,
new_entry_block=<optimized out>, suffix=<optimized out>) at
/home/marxin/Programming/gcc/gcc/cgraphclones.c:1060
#9 0x00000000015d8c18 in create_target_clone (name=0x21fddc0 "sse2",
definition=<optimized out>, node=<cgraph_node * 0x7ffff6b552d0 "a"/0>) at
/home/marxin/Programming/gcc/gcc/multiple_target.c:303
#10 expand_target_clones (definition=<optimized out>, node=<optimized out>) at
/home/marxin/Programming/gcc/gcc/multiple_target.c:403
#11 ipa_target_clone () at
/home/marxin/Programming/gcc/gcc/multiple_target.c:509
#12 (anonymous namespace)::pass_target_clone::execute (this=<optimized out>) at
/home/marxin/Programming/gcc/gcc/multiple_target.c:545
#13 0x0000000000c53605 in execute_one_pass (pass=<opt_pass* 0x220d2a0
"targetclone"(65)>) at /home/marxin/Programming/gcc/gcc/passes.c:2483
#14 0x0000000000c5c0d6 in execute_ipa_pass_list (pass=<opt_pass* 0x220d2a0
"targetclone"(65)>) at /home/marxin/Programming/gcc/gcc/passes.c:2923
#15 0x0000000000939853 in ipa_passes () at
/home/marxin/Programming/gcc/gcc/cgraphunit.c:2482
#16 symbol_table::compile (this=0x7ffff6b56100) at
/home/marxin/Programming/gcc/gcc/cgraphunit.c:2618
#17 0x000000000093bbed in symbol_table::compile (this=0x7ffff6b56100) at
/home/marxin/Programming/gcc/gcc/cgraphunit.c:2863
#18 symbol_table::finalize_compilation_unit (this=0x7ffff6b56100) at
/home/marxin/Programming/gcc/gcc/cgraphunit.c:2863
#19 0x0000000000d3a62b in compile_file () at
/home/marxin/Programming/gcc/gcc/toplev.c:481
#20 0x00000000007a630a in do_compile () at
/home/marxin/Programming/gcc/gcc/toplev.c:2176
#21 toplev::main (this=this@entry=0x7fffffffd9de, argc=<optimized out>,
argc@entry=24, argv=<optimized out>, argv@entry=0x7fffffffdad8) at
/home/marxin/Programming/gcc/gcc/toplev.c:2311
#22 0x00000000007a98eb in main (argc=24, argv=0x7fffffffdad8) at
/home/marxin/Programming/gcc/gcc/main.c:39
so we copy the 'b' with copy_decl_no_change and thus we end up with same mode.
On the other hand when using target("sse2"), the V4SI mode is set here:
#0 layout_decl (decl=<result_decl 0x7ffff6b60d98>, known_align=0) at
/home/marxin/Programming/gcc/gcc/stor-layout.c:605
#1 0x0000000000fc1be2 in build_decl (loc=loc@entry=255680,
code=code@entry=RESULT_DECL, name=name@entry=<tree 0x0>, type=<void_type
0x7ffff6b740a8 void>) at /home/marxin/Programming/gcc/gcc/tree.c:5035
#2 0x00000000007cab6f in start_function (declspecs=declspecs@entry=0x225f0f0,
declarator=declarator@entry=0x225f200, attributes=<optimized out>,
attributes@entry=<tree_list 0x7ffff6c59758>) at
/home/marxin/Programming/gcc/gcc/c/c-decl.c:8991
#3 0x000000000081d8d3 in c_parser_declaration_or_fndef (parser=0x7ffff6b60d20,
fndef_ok=true, static_assert_ok=<optimized out>, empty_ok=<optimized out>,
nested=<optimized out>, start_attr_ok=<optimized out>,
objc_foreach_object_declaration=<optimized out>,
omp_declare_simd_clauses=..., oacc_routine_data=<optimized out>,
fallthru_attr_p=<optimized out>) at
/home/marxin/Programming/gcc/gcc/c/c-parser.c:2256
#4 0x00000000008252e0 in c_parser_external_declaration (parser=0x7ffff6b60d20)
at /home/marxin/Programming/gcc/gcc/c/c-parser.c:1653
#5 0x0000000000825b2a in c_parser_translation_unit (parser=<optimized out>) at
/home/marxin/Programming/gcc/gcc/c/c-parser.c:1534
#6 c_parse_file () at /home/marxin/Programming/gcc/gcc/c/c-parser.c:19807
#7 0x0000000000878de1 in c_common_parse_file () at
/home/marxin/Programming/gcc/gcc/c-family/c-opts.c:1151
#8 0x0000000000d3a3cf in compile_file () at
/home/marxin/Programming/gcc/gcc/toplev.c:456
#9 0x00000000007a630a in do_compile () at
/home/marxin/Programming/gcc/gcc/toplev.c:2176
#10 toplev::main (this=this@entry=0x7fffffffd9ce, argc=<optimized out>,
argc@entry=24, argv=<optimized out>, argv@entry=0x7fffffffdac8) at
/home/marxin/Programming/gcc/gcc/toplev.c:2311
#11 0x00000000007a98eb in main (argc=24, argv=0x7fffffffdac8) at
/home/marxin/Programming/gcc/gcc/main.c:39
So call to relayout_decl will be needed. I'm investigating..
