| Message ID | 20200814065855.GL2363@tucnak |
|---|---|
| State | New |
| Headers | show |
| Series | vec: Fix bootstrap on i686-linux, 32-bit darwin and AIX | expand |
On August 14, 2020 8:58:55 AM GMT+02:00, Jakub Jelinek <jakub@redhat.com> wrote: >Hi! > >As mentioned earlier, embedded_size is broken on vecs of long long, >double >etc. on some platforms, which breaks bootstrap. >E.g. on i686-linux, the problem is mostly with older GCC versions being >used >as stage1 compiler (GCC 4.8 to 7.* in particular), because alignas >(long long) >makes U 64-bit aligned, while when long long m_vecdata[1]; is in vec, >it is >only 32-bit aligned. We've tried various ways and the following one >seems >to work, use the old way (offsetof (vec, m_vecdata)) for non-class >types >as well as standard layout class types, i.e. whenever offsetof is >guaranteed >to work, and for others use the new day (in that case we don't run into >problems with long long or other scalar types and for the structure >layout >there is just a struct with a given alignment. > >Bootstrapped/regtested on x86_64-linux and i686-linux, AFAIK Iain and >David >are bootstrapping/regtesting it on 32-bit darwin and AIX and it got >through >the spots where it broke before, ok for trunk? OK. Thanks, Richard. >2020-08-14 Jakub Jelinek <jakub@redhat.com> > Jonathan Wakely <jwakely@redhat.com> > > * system.h: Include type_traits. > * vec.h (vec<T, A, vl_embed>::embedded_size): Use offsetof and asserts > on vec_stdlayout, which is conditionally a vec (for standard layout T) > and otherwise vec_embedded. > >--- gcc/system.h.jj 2020-07-28 15:39:09.984756558 +0200 >+++ gcc/system.h 2020-08-13 16:33:48.330642026 +0200 >@@ -235,6 +235,7 @@ extern int errno; > # include <cstring> > # include <new> > # include <utility> >+# include <type_traits> > #endif > > /* Some of glibc's string inlines cause warnings. Plus we'd rather >--- gcc/vec.h.jj 2020-08-13 15:41:17.221755055 +0200 >+++ gcc/vec.h 2020-08-13 16:31:42.190367975 +0200 >@@ -1283,9 +1283,11 @@ vec<T, A, vl_embed>::embedded_size (unsi > { > struct alignas (T) U { char data[sizeof (T)]; }; > typedef vec<U, A, vl_embed> vec_embedded; >- static_assert (sizeof (vec_embedded) == sizeof(vec), ""); >- static_assert (alignof (vec_embedded) == alignof(vec), ""); >- return offsetof (vec_embedded, m_vecdata) + alloc * sizeof (T); >+ typedef typename std::conditional<std::is_standard_layout<T>::value, >+ vec, vec_embedded>::type vec_stdlayout; >+ static_assert (sizeof (vec_stdlayout) == sizeof (vec), ""); >+ static_assert (alignof (vec_stdlayout) == alignof (vec), ""); >+ return offsetof (vec_stdlayout, m_vecdata) + alloc * sizeof (T); > } > > > > Jakub
--- gcc/system.h.jj 2020-07-28 15:39:09.984756558 +0200 +++ gcc/system.h 2020-08-13 16:33:48.330642026 +0200 @@ -235,6 +235,7 @@ extern int errno; # include <cstring> # include <new> # include <utility> +# include <type_traits> #endif /* Some of glibc's string inlines cause warnings. Plus we'd rather --- gcc/vec.h.jj 2020-08-13 15:41:17.221755055 +0200 +++ gcc/vec.h 2020-08-13 16:31:42.190367975 +0200 @@ -1283,9 +1283,11 @@ vec<T, A, vl_embed>::embedded_size (unsi { struct alignas (T) U { char data[sizeof (T)]; }; typedef vec<U, A, vl_embed> vec_embedded; - static_assert (sizeof (vec_embedded) == sizeof(vec), ""); - static_assert (alignof (vec_embedded) == alignof(vec), ""); - return offsetof (vec_embedded, m_vecdata) + alloc * sizeof (T); + typedef typename std::conditional<std::is_standard_layout<T>::value, + vec, vec_embedded>::type vec_stdlayout; + static_assert (sizeof (vec_stdlayout) == sizeof (vec), ""); + static_assert (alignof (vec_stdlayout) == alignof (vec), ""); + return offsetof (vec_stdlayout, m_vecdata) + alloc * sizeof (T); }