Richard Guenther wrote: > On Fri, Jul 27, 2012 at 5:24 PM, Ulrich Weigand <uweig...@de.ibm.com> wrote: > > ChangeLog: > > > > * target.def (vector_alignment): New target hook. > > * doc/tm.texi.in (TARGET_VECTOR_ALIGNMENT): Document new hook. > > * doc/tm.texi: Regenerate. > > * targhooks.c (default_vector_alignment): New function. > > * targhooks.h (default_vector_alignment): Add prototype. > > * stor-layout.c (layout_type): Use targetm.vector_alignment. > > * config/arm/arm.c (arm_vector_alignment): New function. > > (TARGET_VECTOR_ALIGNMENT): Define. > > > > * tree-vect-data-refs.c (vect_update_misalignment_for_peel): Use > > vector type alignment instead of size. > > * tree-vect-loop-manip.c (vect_do_peeling_for_loop_bound): Use > > element type size directly instead of computing it from alignment. > > Fix variable naming and comment. > > > > testsuite/ChangeLog: > > > > * lib/target-supports.exp > > (check_effective_target_vect_natural_alignment): New function. > > * gcc.dg/align-2.c: Only run on targets with natural alignment > > of vector types. > > * gcc.dg/vect/slp-25.c: Adjust tests for targets without natural > > alignment of vector types.
> > OK for mainline? > > Ok. Would it be OK to backport this to 4.7 and possibly 4.6? This patch represents a change in the ABI on ARM (the alignment could potentially affect struct member offsets, for example), which could conceivably cause incompatibilities with code compiled with older versions of GCC. We had originally decided we nevertheless want to implement this change on ARM, because: - GCC is now in compliance with the platform ABI document - the old code could actually be buggy since GCC *assumed* 16-byte alignment that wasn't actually guaranteed - code actually affected by this change ought to be rare (code using NEON vector types is rare in the first place, code using *structure members* of such types is even rarer, and code using such structures in cross-module APIs seems to be extremely rare) Nevertheless, given we do want to make this change, it would be best to roll it out as quickly as possible, to minimize the time period where people might use old (not yet fixed) compilers to generate non-ABI-compliant binaries. Thus, we think it would be good for the change to be applied to all still open release branches as well. (Note that while the patch contains changes to common code, those should be no-ops for all targets that do not implement the new hook.) Bye, Ulrich -- Dr. Ulrich Weigand GNU Toolchain for Linux on System z and Cell BE ulrich.weig...@de.ibm.com
