[Bug symtab/29105] new DWARF reader still slow

["cvs-commit at gcc dot gnu.org" <sourceware-bugzilla@sourceware.org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=29105

--- Comment #27 from cvs-commit at gcc dot gnu.org <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Tom Tromey <tromey@sourceware.org>:

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=55fc1623f942fba10362cb199f9356d75ca5835b

commit 55fc1623f942fba10362cb199f9356d75ca5835b
Author: Tom Tromey <tromey@adacore.com>
Date:   Thu Nov 3 13:49:17 2022 -0600

    Add name canonicalization for C

    PR symtab/29105 shows a number of situations where symbol lookup can
    result in the expansion of too many CUs.

    What happens is that lookup_signed_typename will try to look up a type
    like "signed int".  In cooked_index_functions::expand_symtabs_matching,
    when looping over languages, the C++ case will canonicalize this type
    name to be "int" instead.  Then this method will proceed to expand
    every CU that has an entry for "int" -- i.e., nearly all of them.  A
    crucial component of this is that the caller, objfile::lookup_symbol,
    does not do this canonicalization, so when it tries to find the symbol
    for "signed int", it fails -- causing the loop to continue.

    This patch fixes the problem by introducing name canonicalization for
    C.  The idea here is that, by making C and C++ agree on the canonical
    name when a symbol name can have multiple spellings, we avoid the bad
    behavior in objfile::lookup_symbol (and any other such code -- I don't
    know if there is any).

    Unlike C++, C only has a few situations where canonicalization is
    needed.  And, in particular, due to the lack of overloading (thus
    avoiding any issues in linespec) and due to the way c-exp.y works, I
    think that no canonicalization is needed during symbol lookup -- only
    during symtab construction.  This explains why lookup_name_info is not
    touched.

    The stabs reader is modified on a "best effort" basis.

    The DWARF reader needed one small tweak in dwarf2_name to avoid a
    regression in dw2-unusual-field-names.exp.  I think this is adequately
    explained by the comment, but basically this is a scenario that should
    not occur in real code, only the gdb test suite.

    lookup_signed_typename is simplified.  It used to search for two
    different type names, but now gdb can search just for the canonical
    form.

    gdb.dwarf2/enum-type.exp needed a small tweak, because the
    canonicalizer turns "unsigned integer" into "unsigned int integer".
    It seems better here to use the correct C type name.

    Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=29105
    Tested-by: Simon Marchi <simark@simark.ca>
    Reviewed-by: Andrew Burgess <aburgess@redhat.com>

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