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String: Add support for __memcmpeq() ABI on all targets

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No bug.

This commit adds support for __memcmpeq() as a new ABI for all
targets. In this commit __memcmpeq() is implemented only as an alias
to the corresponding targets memcmp() implementation. __memcmpeq() is
added as a new symbol starting with GLIBC_2.35 and defined in string.h
with comments explaining its behavior. Basic tests that it is callable
and works where added in string/tester.c

As discussed in the proposal "Add new ABI '__memcmpeq()' to libc"
__memcmpeq() is essentially a reserved namespace for bcmp(). The means
is shares the same specifications as memcmp() except the return value
for non-equal byte sequences is any non-zero value. This is less
strict than memcmp()'s return value specification and can be better
optimized when a boolean return is all that is needed.

__memcmpeq() is meant to only be called by compilers if they can prove
that the return value of a memcmp() call is only used for its boolean
value.

All tests in string/tester.c passed. As well build succeeds on
x86_64-linux-gnu target.
This commit is contained in:
Noah Goldstein
2021-10-21 15:54:57 -05:00
parent 8438135d34
commit 44829b3ddb
64 changed files with 120 additions and 0 deletions
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1
sysdeps/unix/sysv/linux/sparc/sparc32/libc.abilist
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@@ -2743,6 +2743,7 @@ GLIBC_2.34 tss_create F
GLIBC_2.34 tss_delete F
GLIBC_2.34 tss_get F
GLIBC_2.34 tss_set F
GLIBC_2.35 __memcmpeq F
GLIBC_2.4 _IO_fprintf F
GLIBC_2.4 _IO_printf F
GLIBC_2.4 _IO_sprintf F

1
sysdeps/unix/sysv/linux/sparc/sparc64/libc.abilist
View File

@@ -2570,6 +2570,7 @@ GLIBC_2.34 tss_create F
GLIBC_2.34 tss_delete F
GLIBC_2.34 tss_get F
GLIBC_2.34 tss_set F
GLIBC_2.35 __memcmpeq F
GLIBC_2.4 __confstr_chk F
GLIBC_2.4 __fgets_chk F
GLIBC_2.4 __fgets_unlocked_chk F