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atomic: let Clang always use atomic_load_n if available.

(Apple's Clang reports itself as GCC 4.2.1 in preprocessor macros--the final
GNU C compiler Apple shipped--as of the macOS 10.12 SDK.)
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icculus committed Apr 13, 2017
1 parent 2bf79c2 commit 8c00de57f6858b5cdf1cd0930198937ac41bb050
Showing with 15 additions and 2 deletions.
  1. +15 −2 src/atomic/SDL_atomic.c
@@ -35,6 +35,19 @@
#include <atomic.h>
#endif

/* The __atomic_load_n() intrinsic showed up in different times for different compilers. */
#if defined(HAVE_GCC_ATOMICS)
# if defined(__clang__)
# if __has_builtin(__atomic_load_n)
# define HAVE_ATOMIC_LOAD_N 1
# endif
# elif defined(__GNUC__)
# if (__GNUC__ >= 5)
# define HAVE_ATOMIC_LOAD_N 1
# endif
# endif
#endif

/*
If any of the operations are not provided then we must emulate some
of them. That means we need a nice implementation of spin locks
@@ -211,7 +224,7 @@ SDL_AtomicAdd(SDL_atomic_t *a, int v)
int
SDL_AtomicGet(SDL_atomic_t *a)
{
#if defined(HAVE_GCC_ATOMICS) && (__GNUC__ >= 5)
#ifdef HAVE_ATOMIC_LOAD_N
return __atomic_load_n(&a->value, __ATOMIC_SEQ_CST);
#else
int value;
@@ -225,7 +238,7 @@ SDL_AtomicGet(SDL_atomic_t *a)
void *
SDL_AtomicGetPtr(void **a)
{
#if defined(HAVE_GCC_ATOMICS) && (__GNUC__ >= 5)
#ifdef HAVE_ATOMIC_LOAD_N
return __atomic_load_n(a, __ATOMIC_SEQ_CST);
#else
void *value;

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