S390: Implement mempcpy with help of memcpy. [BZ #19765]

System Internals / glibc - Stefan Liebler [linux.vnet.ibm.com] - 24 May 2016 03:39 EDT

There exist optimized memcpy functions on s390, but no optimized mempcpy. This patch adds mempcpy entry points in memcpy.S files, which use the memcpy implementation. Now mempcpy itself is also an IFUNC function as memcpy is and the variants are listed in ifunc-impl-list.c.

The s390 string.h does not define _HAVE_STRING_ARCH_mempcpy. Instead mempcpy string/string.h inlines memcpy() + n. If n is constant and small enough, GCC emits instructions like mvi or mvc and avoids the function call to memcpy. If n is not constant, then memcpy is called and n is added afterwards. If _HAVE_STRING_ARCH_mempcpy would be defined, mempcpy would be called in every case.

According to PR70140 "Inefficient expansion of __builtin_mempcpy" (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70140) GCC should handle a call to mempcpy in the same way as memcpy. Then either the mempcpy macro in string/string.h has to be removed or _HAVE_STRING_ARCH_mempcpy has to be defined for S390.


[BZ #19765]
- sysdeps/s390/mempcpy.S: New File.
- sysdeps/s390/multiarch/mempcpy.c: Likewise.
- sysdeps/s390/multiarch/Makefile (sysdep_routines): Add mempcpy.
- sysdeps/s390/multiarch/ifunc-impl-list.c (__libc_ifunc_impl_list): Add mempcpy variants.
- sysdeps/s390/s390-32/memcpy.S: Add mempcpy entry point. (memcpy): Adjust to be usable from mempcpy entry point. (__memcpy_mvcle): Likewise.
- sysdeps/s390/s390-64/memcpy.S: Likewise.
- sysdeps/s390/s390-32/multiarch/memcpy-s390.S: Add entry points ____mempcpy_z196, ____mempcpy_z10 and add __GI_ symbols for mempcpy. (__memcpy_z196): Adjust to be usable from mempcpy entry point. (__memcpy_z10): Likewise.
- sysdeps/s390/s390-64/multiarch/memcpy-s390x.S: Likewise.

4c01126 S390: Implement mempcpy with help of memcpy. [BZ #19765]
ChangeLog | 18 +++++++++
sysdeps/s390/mempcpy.S | 19 ++++++++++
sysdeps/s390/multiarch/Makefile | 3 +-
sysdeps/s390/multiarch/ifunc-impl-list.c | 7 ++++
sysdeps/s390/multiarch/mempcpy.c | 26 +++++++++++++
sysdeps/s390/s390-32/memcpy.S | 50 +++++++++++++++----------
sysdeps/s390/s390-32/multiarch/memcpy-s390.S | 31 ++++++++++++++-
sysdeps/s390/s390-64/memcpy.S | 47 +++++++++++++----------
sysdeps/s390/s390-64/multiarch/memcpy-s390x.S | 29 +++++++++++++-
9 files changed, 185 insertions(+), 45 deletions(-)

Upstream: sourceware.org

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