middle-end: Avoid using DECL_UID in ASM_FORMAT_PRIVATE_NAME [PR94223]

middle-end: Avoid using DECL_UID in ASM_FORMAT_PRIVATE_NAME [PR94223]

As mentioned in the PR, we don't guarantee DECL_UID to be the same between
corresponding decls in -g and -g0 builds, -g can create more decls and all
that is guaranteed is that the DECL_UIDs of the corresponding decls compare
the same.
The following testcase gets a -fcompare-debug failure because these
functions use DECL_UID as the number in ASM_FORMAT_PRIVATE_NAME.

The patch fixes it by using just a sequential number there instead.
I don't think this can be called during PCH writing, this only happens for
non-public decls and the C/C++ FEs shouldn't mangling those at that point
(furthermore C++ FE uses a different set_decl_assembler_name hook and this
one is something only the gimplifier calls on C.NNNN temporaries.

2020-03-25  Jakub Jelinek  <jakub@redhat.com>

	PR c++/94223
	* langhooks.c (lhd_set_decl_assembler_name): Use a static ulong
	counter instead of DECL_UID.

	* lto-lang.c (lto_set_decl_assembler_name): Use a static ulong
	counter instead of DECL_UID.

	* g++.dg/opt/pr94223.C: New test.