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Detect if 8-bit atomics are available.

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In some rare cases (older compiler, e.g. gcc 4.2 w/ MIPS), 8-bit atomics might
be unavailable.  Detect such cases so that we can workaround.
This commit is contained in:
Qi Wang 2019-03-07 15:58:26 -08:00 committed by Qi Wang
parent 14d3686c9f
commit 06f0850427
3 changed files with 39 additions and 0 deletions
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25
configure.ac
View File

@ -1896,6 +1896,19 @@ JE_COMPILABLE([GCC __atomic atomics], [
], [je_cv_gcc_atomic_atomics])
if test "x${je_cv_gcc_atomic_atomics}" = "xyes" ; then
AC_DEFINE([JEMALLOC_GCC_ATOMIC_ATOMICS])
dnl check for 8-bit atomic support
JE_COMPILABLE([GCC 8-bit __atomic atomics], [
], [
unsigned char x = 0;
int val = 1;
int y = __atomic_fetch_add(&x, val, __ATOMIC_RELAXED);
int after_add = (int)x;
return after_add == 1;
], [je_cv_gcc_u8_atomic_atomics])
if test "x${je_cv_gcc_u8_atomic_atomics}" = "xyes" ; then
AC_DEFINE([JEMALLOC_GCC_U8_ATOMIC_ATOMICS])
fi
fi
dnl ============================================================================
@ -1910,6 +1923,18 @@ JE_COMPILABLE([GCC __sync atomics], [
], [je_cv_gcc_sync_atomics])
if test "x${je_cv_gcc_sync_atomics}" = "xyes" ; then
AC_DEFINE([JEMALLOC_GCC_SYNC_ATOMICS])
dnl check for 8-bit atomic support
JE_COMPILABLE([GCC 8-bit __sync atomics], [
], [
unsigned char x = 0;
int before_add = __sync_fetch_and_add(&x, 1);
int after_add = (int)x;
return (before_add == 0) && (after_add == 1);
], [je_cv_gcc_u8_sync_atomics])
if test "x${je_cv_gcc_u8_sync_atomics}" = "xyes" ; then
AC_DEFINE([JEMALLOC_GCC_U8_SYNC_ATOMICS])
fi
fi
dnl ============================================================================

7
include/jemalloc/internal/atomic.h
View File

@ -3,10 +3,17 @@
#define ATOMIC_INLINE JEMALLOC_ALWAYS_INLINE
#define JEMALLOC_U8_ATOMICS
#if defined(JEMALLOC_GCC_ATOMIC_ATOMICS)
# include "jemalloc/internal/atomic_gcc_atomic.h"
# if !defined(JEMALLOC_GCC_U8_ATOMIC_ATOMICS)
# undef JEMALLOC_U8_ATOMICS
# endif
#elif defined(JEMALLOC_GCC_SYNC_ATOMICS)
# include "jemalloc/internal/atomic_gcc_sync.h"
# if !defined(JEMALLOC_GCC_U8_SYNC_ATOMICS)
# undef JEMALLOC_U8_ATOMICS
# endif
#elif defined(_MSC_VER)
# include "jemalloc/internal/atomic_msvc.h"
#elif defined(JEMALLOC_C11_ATOMICS)

7
include/jemalloc/internal/jemalloc_internal_defs.h.in
View File

@ -48,9 +48,16 @@
/* Defined if GCC __atomic atomics are available. */
#undef JEMALLOC_GCC_ATOMIC_ATOMICS
/* and the 8-bit variant support. */
#undef JEMALLOC_GCC_U8_ATOMIC_ATOMICS
/* Defined if GCC __sync atomics are available. */
#undef JEMALLOC_GCC_SYNC_ATOMICS
/* and the 8-bit variant support. */
#undef JEMALLOC_GCC_U8_SYNC_ATOMICS
/* Defined if 8-bit atomics are supported. */
/*
* Defined if __builtin_clz() and __builtin_clzl() are available.