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[Concurrency] Add an exported symbol on Darwin that contains the frame pointer flag bit for async frames. #38290

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Merged
merged 1 commit into from
Jul 9, 2021
Merged

[Concurrency] Add an exported symbol on Darwin that contains the frame pointer flag bit for async frames. #38290

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12 changes: 12 additions & 0 deletions include/swift/Runtime/Concurrency.h
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Original file line number Diff line number Diff line change
Expand Up @@ -673,6 +673,18 @@ void swift_task_reportUnexpectedExecutor(
SWIFT_EXPORT_FROM(swift_Concurrency) SWIFT_CC(swift)
JobPriority swift_task_getCurrentThreadPriority(void);

#ifdef __APPLE__
/// A magic symbol whose address is the mask to apply to a frame pointer to
/// signal that it is an async frame. Do not try to read the actual value of
/// this global, it will crash.
///
/// On ARM64_32, the address is only 32 bits, and therefore this value covers
/// the top 32 bits of the in-memory frame pointer. On other 32-bit platforms,
/// the bit is not used and the address is always 0.
SWIFT_EXPORT_FROM(swift_Concurrency)
struct { char c; } swift_async_extendedFramePointerFlags;
#endif

}

#pragma clang diagnostic pop
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13 changes: 13 additions & 0 deletions stdlib/public/Concurrency/Task.cpp
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Expand Up @@ -34,6 +34,19 @@
#include <dlfcn.h>
#endif

#ifdef __APPLE__
#if __POINTER_WIDTH__ == 64
asm("\n .globl _swift_async_extendedFramePointerFlags" \
"\n _swift_async_extendedFramePointerFlags = 0x1000000000000000");
#elif __ARM64_ARCH_8_32__
asm("\n .globl _swift_async_extendedFramePointerFlags" \
"\n _swift_async_extendedFramePointerFlags = 0x10000000");
#else
asm("\n .globl _swift_async_extendedFramePointerFlags" \
"\n _swift_async_extendedFramePointerFlags = 0x0");
#endif
#endif // __APPLE__

using namespace swift;
using FutureFragment = AsyncTask::FutureFragment;
using TaskGroup = swift::TaskGroup;
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