http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49501
Summary: support ATTRIBUTES ALIGN in gfortran
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: enhancement
Priority: P3
Component: fortran
AssignedTo: unassig...@gcc.gnu.org
ReportedBy: stev...@alum.mit.edu
Please add support for a ATTRIBUTES ALIGN compiler directive to gfortran,
similar to the Intel Fortran compiler:
http://software.intel.com/sites/products/documentation/hpc/composerxe/en-us/fortran/mac/lref_for/source_files/rfattali.htm
Note in particular that this should also apply to allocatable arrays:
http://software.intel.com/en-us/forums/showthread.php?t=78361
Currently, there is no way to allocate 16-byte or 32-byte aligned memory in
gfortran. 16-byte aligned memory is needed for SSE/SSE2, and 32-byte aligned
memory is needed for upcoming AVX instructions. This means that allocated
memory cannot be passed to optimized SIMD routines written in low-level
languages.
It seems reasonable to follow Intel's lead here rather than to invent an
incompatible GNU extension.
Note that Bug #41209 (which requests even more complete ATTRIBUTE support,
including ALIGN) depends on this one.
Previously, Bug #24261, which requested a way to get 16-byte alignment, was
closed based on the erroneous assertion that this is a glibc/malloc bug. This
is false, because no standard C type requires more than 8-byte alignment (on
both 32-bit and 64-bit machines). Hopefully this is even more obvious now that
there is a need in numerics for 32-byte alignment (AVX instructions), which is
even farther from requirements of standard C types.
