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122 lines
4.1 KiB
Diff
122 lines
4.1 KiB
Diff
From 5d150ee111c222f09e78f4f88540964476327844 Mon Sep 17 00:00:00 2001
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From: Nathan Froyd <froydnj@mozilla.com>
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Date: Mon, 4 May 2015 13:38:41 -0400
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Subject: Support new-style __atomic_* primitives
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Recent versions of GCC/clang feature a new set of compiler intrinsics
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for performing atomic operations, motivated by the operations needed to
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support the C++11 memory model. These intrinsics are more flexible than
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the old __sync_* intrinstics and offer efficient support for atomic load
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and store operations.
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Having the load appear atomic to the compiler is particular important
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for tools like ThreadSanitizer so they don't report false positives on
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memory operations that we intend to be atomic.
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Patch from Nathan Froyd <froydnj@mozilla.com>
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diff --git a/src/cairo-atomic-private.h b/src/cairo-atomic-private.h
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index 327fed1..11b2887 100644
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--- a/src/cairo-atomic-private.h
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+++ b/src/cairo-atomic-private.h
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@@ -53,6 +53,96 @@
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CAIRO_BEGIN_DECLS
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+/* C++11 atomic primitives were designed to be more flexible than the
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+ * __sync_* family of primitives. Despite the name, they are available
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+ * in C as well as C++. The motivating reason for using them is that
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+ * for _cairo_atomic_{int,ptr}_get, the compiler is able to see that
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+ * the load is intended to be atomic, as opposed to the __sync_*
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+ * version, below, where the load looks like a plain load. Having
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+ * the load appear atomic to the compiler is particular important for
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+ * tools like ThreadSanitizer so they don't report false positives on
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+ * memory operations that we intend to be atomic.
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+ */
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+#if HAVE_CXX11_ATOMIC_PRIMITIVES
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+
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+#define HAS_ATOMIC_OPS 1
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+
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+typedef int cairo_atomic_int_t;
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+
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+static cairo_always_inline cairo_atomic_int_t
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+_cairo_atomic_int_get (cairo_atomic_int_t *x)
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+{
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+ return __atomic_load_n(x, __ATOMIC_SEQ_CST);
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+}
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+
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+static cairo_always_inline void *
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+_cairo_atomic_ptr_get (void **x)
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+{
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+ return __atomic_load_n(x, __ATOMIC_SEQ_CST);
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+}
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+
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+# define _cairo_atomic_int_inc(x) ((void) __atomic_fetch_add(x, 1, __ATOMIC_SEQ_CST))
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+# define _cairo_atomic_int_dec(x) ((void) __atomic_fetch_sub(x, 1, __ATOMIC_SEQ_CST))
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+# define _cairo_atomic_int_dec_and_test(x) (__atomic_fetch_sub(x, 1, __ATOMIC_SEQ_CST) == 1)
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+
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+#if SIZEOF_VOID_P==SIZEOF_INT
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+typedef int cairo_atomic_intptr_t;
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+#elif SIZEOF_VOID_P==SIZEOF_LONG
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+typedef long cairo_atomic_intptr_t;
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+#elif SIZEOF_VOID_P==SIZEOF_LONG_LONG
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+typedef long long cairo_atomic_intptr_t;
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+#else
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+#error No matching integer pointer type
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+#endif
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+
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+static cairo_always_inline cairo_bool_t
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+_cairo_atomic_int_cmpxchg_impl(cairo_atomic_int_t *x,
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+ cairo_atomic_int_t oldv,
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+ cairo_atomic_int_t newv)
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+{
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+ cairo_atomic_int_t expected = oldv;
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+ return __atomic_compare_exchange_n(x, &expected, newv, 0, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST);
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+}
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+
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+#define _cairo_atomic_int_cmpxchg(x, oldv, newv) \
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+ _cairo_atomic_int_cmpxchg_impl(x, oldv, newv)
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+
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+static cairo_always_inline cairo_atomic_int_t
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+_cairo_atomic_int_cmpxchg_return_old_impl(cairo_atomic_int_t *x,
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+ cairo_atomic_int_t oldv,
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+ cairo_atomic_int_t newv)
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+{
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+ cairo_atomic_int_t expected = oldv;
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+ (void) __atomic_compare_exchange_n(x, &expected, newv, 0, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST);
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+ return expected;
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+}
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+
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+#define _cairo_atomic_int_cmpxchg_return_old(x, oldv, newv) \
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+ _cairo_atomic_int_cmpxchg_return_old_impl(x, oldv, newv)
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+
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+static cairo_always_inline cairo_bool_t
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+_cairo_atomic_ptr_cmpxchg_impl(void **x, void *oldv, void *newv)
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+{
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+ void *expected = oldv;
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+ return __atomic_compare_exchange_n(x, &expected, newv, 0, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST);
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+}
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+
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+#define _cairo_atomic_ptr_cmpxchg(x, oldv, newv) \
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+ _cairo_atomic_ptr_cmpxchg_impl(x, oldv, newv)
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+
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+static cairo_always_inline void *
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+_cairo_atomic_ptr_cmpxchg_return_old_impl(void **x, void *oldv, void *newv)
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+{
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+ void *expected = oldv;
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+ (void) __atomic_compare_exchange_n(x, &expected, newv, 0, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST);
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+ return expected;
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+}
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+
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+#define _cairo_atomic_ptr_cmpxchg_return_old(x, oldv, newv) \
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+ _cairo_atomic_ptr_cmpxchg_return_old_impl(x, oldv, newv)
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+
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+#endif
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+
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#if HAVE_INTEL_ATOMIC_PRIMITIVES
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#define HAS_ATOMIC_OPS 1
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--
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cgit v0.10.2
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