On Fri, Nov 20, 2015 at 2:17 PM, Jason Merrill <ja...@redhat.com> wrote: > On 11/20/2015 01:52 PM, H.J. Lu wrote: >> >> On Tue, Nov 17, 2015 at 4:22 AM, Richard Biener >> <richard.guent...@gmail.com> wrote: >>> >>> On Tue, Nov 17, 2015 at 12:01 PM, H.J. Lu <hjl.to...@gmail.com> wrote: >>>> >>>> Empty record should be returned and passed the same way in C and C++. >>>> This patch adds LANG_HOOKS_EMPTY_RECORD_P for C++ empty class, which >>>> defaults to return false. For C++, LANG_HOOKS_EMPTY_RECORD_P is defined >>>> to is_really_empty_class, which returns true for C++ empty classes. For >>>> LTO, we stream out a bit to indicate if a record is empty and we store >>>> it in TYPE_LANG_FLAG_0 when streaming in. get_ref_base_and_extent is >>>> changed to set bitsize to 0 for empty records. Middle-end and x86 >>>> backend are updated to ignore empty records for parameter passing and >>>> function value return. Other targets may need similar changes. >>> >>> >>> Please avoid a new langhook for this and instead claim a bit in >>> tree_type_common >>> like for example restrict_flag (double-check it is unused for >>> non-pointers). >> >> >> There is no bit in tree_type_common I can overload. restrict_flag is >> checked for non-pointers to issue an error when it is used on >> non-pointers: >> >> >> /export/gnu/import/git/sources/gcc/gcc/testsuite/g++.dg/template/qualttp20.C:19:38: >> error: ‘__restrict__’ qualifiers cannot be applied to ‘AS::L’ >> typedef typename T::L __restrict__ r;// { dg-error "'__restrict__' >> qualifiers cannot" "" } > > > The C++ front end only needs to check TYPE_RESTRICT for this purpose on > front-end-specific type codes like TEMPLATE_TYPE_PARM; cp_type_quals could > handle that specifically if you change TYPE_RESTRICT to only apply to > pointers. >
restrict_flag is also checked in this case: [hjl@gnu-6 gcc]$ cat x.i struct dummy { }; struct dummy foo (struct dummy __restrict__ i) { return i; } [hjl@gnu-6 gcc]$ gcc -S x.i -Wall x.i:4:13: error: invalid use of ‘restrict’ foo (struct dummy __restrict__ i) ^ x.i:4:13: error: invalid use of ‘restrict’ [hjl@gnu-6 gcc]$ restrict_flag can't also be used to indicate `i' is an empty record. H.J.