Merge pull request swiftlang#39936 from DougGregor/watchos-noasyncframepointer-backdeploy-5.5

Disable the definition and use of swift_async_extendedFramePointerFlags on watchOS

Author: DougGregor

lib/Frontend/CompilerInvocation.cpp

@@ -1822,6 +1822,15 @@ static bool ParseIRGenArgs(IRGenOptions &Opts, ArgList &Args,
       Diags.diagnose(SourceLoc(), diag::error_invalid_arg_value,
                      A->getAsString(Args), A->getValue());
     }
+  } else if (Triple.isWatchOS() && !Triple.isSimulatorEnvironment()) {
+    // watchOS does not support auto async frame pointers due to bitcode, so
+    // silently override "auto" to "never" when back-deploying. This approach
+    // sacrifies async backtraces when back-deploying but prevents crashes in
+    // older tools that cannot handle the async frame bit in the frame pointer.
+    unsigned major, minor, micro;
+    Triple.getWatchOSVersion(major, minor, micro);
+    if (major < 8)
+      Opts.SwiftAsyncFramePointer = SwiftAsyncFramePointerKind::Never;
   }
 
   return false;

stdlib/public/Concurrency/Task.cpp

@@ -35,8 +35,19 @@
 #endif
 
 #if defined(SWIFT_CONCURRENCY_BACK_DEPLOYMENT)
+#include <Availability.h>
+#include <TargetConditionals.h>
+#if TARGET_OS_WATCH
+// Bitcode compilation for the watch device precludes defining the following asm
+// symbols, so we don't use them... but simulators are okay.
+#if TARGET_OS_SIMULATOR
 asm("\n .globl _swift_async_extendedFramePointerFlags" \
     "\n _swift_async_extendedFramePointerFlags = 0x0");
+#endif
+#else
+asm("\n .globl _swift_async_extendedFramePointerFlags" \
+    "\n _swift_async_extendedFramePointerFlags = 0x0");
+#endif
 #else
 #ifdef __APPLE__
 #if __POINTER_WIDTH__ == 64

test/IRGen/swift_async_extended_frame_info_watchos.swift

@@ -0,0 +1,20 @@
+// RUN: %target-swift-frontend -disable-availability-checking -target arm64_32-apple-watchos7 %s -S | %FileCheck  -check-prefix=NEVER %s
+// RUN: %target-swift-frontend -disable-availability-checking -target arm64_32-apple-watchos8 %s -S | %FileCheck  -check-prefix=ALWAYS %s
+// RUN: %target-swift-frontend -disable-availability-checking -target arm64_32-apple-watchos7  -swift-async-frame-pointer=always %s -S | %FileCheck  -check-prefix=ALWAYS %s
+// RUN: %target-swift-frontend -disable-availability-checking -target arm64_32-apple-watchos7  -swift-async-frame-pointer=never %s -S | %FileCheck  -check-prefix=NEVER %s
+// RUN: %target-swift-frontend -disable-availability-checking -target arm64_32-apple-watchos7  -swift-async-frame-pointer=auto %s -S | %FileCheck  -check-prefix=AUTO %s
+
+// REQUIRES: OS=watchos
+// REQUIRES: CPU=armv7k || CPU=arm64_32
+
+public func someAsyncFunction() async {
+}
+
+// AUTO: swift_async_extendedFramePointerFlags
+
+// ALWAYS-NOT: swift_async_extendedFramePointerFlags
+// ALWAYS: 0x1000000000000000
+// ALWAYS-NOT: swift_async_extendedFramePointerFlags
+
+// NEVER-NOT: swift_async_extendedFramePointerFlags
+// NEVER-NOT: 0x1000000000000000