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Re: [patch, powerpc] increase array alignment for Altivec
- From: Mike Stump <mrs at mrs dot kithrup dot com>
- To: David Edelsohn <dje dot gcc at gmail dot com>
- Cc: Bill Schmidt <wschmidt at linux dot vnet dot ibm dot com>, Sandra Loosemore <sandra at codesourcery dot com>, GCC Patches <gcc-patches at gcc dot gnu dot org>
- Date: Thu, 23 May 2013 10:59:36 -0700
- Subject: Re: [patch, powerpc] increase array alignment for Altivec
- References: <CAGWvnynN5o0uiTS-ERo+oy9PRboe2u+=8UN4v-U5CmWV1GgDAw at mail dot gmail dot com> <519BEBD1 dot 3090109 at codesourcery dot com> <CAGWvnyma77XtxbTEasQbqXmLhGRZuOBFJsXLUyY7Wdd_Mw5JBg at mail dot gmail dot com> <519BFFAD dot 9000102 at codesourcery dot com> <CAGWvnykcxe=Lx7f98z++jzezDxC-wx_cqVQVexqvgoVs8Gbdcw at mail dot gmail dot com> <1369312180 dot 14043 dot 50 dot camel at gnopaine> <519E2DBA dot 3060204 at codesourcery dot com> <1369322318 dot 14043 dot 52 dot camel at gnopaine> <CAGWvny=UYFS9sGPbSKFvTq8amR2MgYRQ8O9crb_gLe=fSwtgcw at mail dot gmail dot com>
On May 23, 2013, at 9:17 AM, David Edelsohn <dje.gcc@gmail.com> wrote:
> I want to have a version of the patch committed. The only question now
> is how much of the patch can be committed without exposing potential
> incompatibilities between different object files.
The hard part is to know when for certain, the data will be used. As long as we know for certain the data will be used, we can up the alignment on the data (not the type). No link once, no comdat, no weak would be a start. The question in my mind, is it sufficient? Some linkers will maximize the alignments of all instances of data, some won't. I was thinking darwin would, but GNU ld would not. ! TREE_PUBLIC (decl) || (! DECL_WEAK (decl) && ! DECL_COMDAT (decl) && ! DECL_COMDAT_GROUP && DECL_COMMON (decl) …) now, I say that, but am aware of the predicate routines in varasm.c. decl_replaceable_p, decl_binds_to_current_def_p, binds_local_p, resolution_to_local_definition_p… certainly one of them should fit nicely, maybe.