x86-64: Implement memcmp family IFUNC selectors in C

System Internals / glibc - H.J. Lu [gmail.com] - 15 June 2017 11:49 EDT

Implement memcmp family IFUNC selectors in C.

All internal calls within libc.so can use IFUNC on x86-64 since unlike x86, x86-64 supports PC-relative addressing to access the GOT entry so that it can call via PLT without using an extra register. For libc.a, we can't use IFUNC for functions which are called before IFUNC has been initialized. Use IFUNC internally reduces the icache footprint since libc.so and other codes in the process use the same implementations. This patch uses IFUNC for memcmp family functions within libc.

- sysdeps/x86_64/multiarch/Makefile (sysdep_routines): Add memcmp-sse2.
- sysdeps/x86_64/multiarch/ifunc-memcmp.h: New file.
- sysdeps/x86_64/multiarch/memcmp-sse2.S: Likewise.
- sysdeps/x86_64/multiarch/memcmp.c: Likewise.
- sysdeps/x86_64/multiarch/wmemcmp.c: Likewise.
- sysdeps/x86_64/multiarch/memcmp.S: Removed.
- sysdeps/x86_64/multiarch/wmemcmp.S: Likewise.

b91a52d x86-64: Implement memcmp family IFUNC selectors in C
ChangeLog | 12 ++++
sysdeps/x86_64/multiarch/Makefile | 1 +
sysdeps/x86_64/multiarch/ifunc-impl-list.c | 4 +-
sysdeps/x86_64/multiarch/ifunc-memcmp.h | 45 +++++++++++++
sysdeps/x86_64/multiarch/memcmp-sse2.S | 31 +++++++++
sysdeps/x86_64/multiarch/memcmp.S | 78 -----------------------
sysdeps/x86_64/multiarch/memcmp.c | 38 +++++++++++
sysdeps/x86_64/multiarch/{wmemcmp.S => wmemcmp.c} | 42 +++---------
8 files changed, 138 insertions(+), 113 deletions(-)

Upstream: sourceware.org


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