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misc/cgo/test: use __atomic intrinsics instead of __sync

GCC has supported the __atomic intrinsics since 4.7, and clang
supports them as well. They are better than the __sync intrinsics in
that they specify a memory model and, more importantly for our purposes,
they are reliably implemented either in the compiler or in libatomic.

Change-Id: I5e0036ea3300f65c28b1c3d1f3b93fb61c1cd646
Reviewed-on: https://go-review.googlesource.com/c/go/+/193603
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Than McIntosh <thanm@google.com>
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ianlancetaylor committed Sep 5, 2019
1 parent e3d3e11 commit b4924870f4b8302aba051a506bb499fad99b464e
Showing with 5 additions and 23 deletions.
  1. +5 −23 misc/cgo/test/testx.go
@@ -83,33 +83,18 @@ extern void f7665(void);
void issue7978cb(void);
#if defined(__APPLE__) && defined(__arm__)
// on Darwin/ARM, libSystem doesn't provide implementation of the __sync_fetch_and_add
// primitive, and although gcc supports it, it doesn't inline its definition.
// Clang could inline its definition, so we require clang on Darwin/ARM.
#if defined(__clang__)
#define HAS_SYNC_FETCH_AND_ADD 1
#else
#define HAS_SYNC_FETCH_AND_ADD 0
#endif
#else
#define HAS_SYNC_FETCH_AND_ADD 1
#endif
// use ugly atomic variable sync since that doesn't require calling back into
// Go code or OS dependencies
static void issue7978c(uint32_t *sync) {
#if HAS_SYNC_FETCH_AND_ADD
while(__sync_fetch_and_add(sync, 0) != 0)
while(__atomic_load_n(sync, __ATOMIC_SEQ_CST) != 0)
;
__sync_fetch_and_add(sync, 1);
while(__sync_fetch_and_add(sync, 0) != 2)
__atomic_add_fetch(sync, 1, __ATOMIC_SEQ_CST);
while(__atomic_load_n(sync, __ATOMIC_SEQ_CST) != 2)
;
issue7978cb();
__sync_fetch_and_add(sync, 1);
while(__sync_fetch_and_add(sync, 0) != 6)
__atomic_add_fetch(sync, 1, __ATOMIC_SEQ_CST);
while(__atomic_load_n(sync, __ATOMIC_SEQ_CST) != 6)
;
#endif
}
// issue 8331 part 2 - part 1 in test.go
@@ -496,9 +481,6 @@ func test7978(t *testing.T) {
if runtime.Compiler == "gccgo" {
t.Skip("gccgo can not do stack traces of C code")
}
if C.HAS_SYNC_FETCH_AND_ADD == 0 {
t.Skip("clang required for __sync_fetch_and_add support on darwin/arm")
}
debug.SetTraceback("2")
issue7978sync = 0
go issue7978go()

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