Merge pull request swiftlang#30633 from aschwaighofer/arm64e_does_not_backdeploy

arm64e does not back-deploy

Author: aschwaighofer

lib/Basic/Platform.cpp

@@ -397,6 +397,9 @@ swift::getSwiftRuntimeCompatibilityVersionForTarget(
     const llvm::Triple &Triple) {
   unsigned Major, Minor, Micro;
 
+  if (Triple.getArchName() == "arm64e")
+    return llvm::VersionTuple(5, 3);
+
   if (Triple.isMacOSX()) {
     Triple.getMacOSXVersion(Major, Minor, Micro);
     if (Major == 10) {

test/IRGen/autolink-runtime-compatibility-arm64e.swift

@@ -0,0 +1,10 @@
+// REQUIRES: CPU=arm64e,OS=ios
+
+// Doesn't autolink compatibility library because target OS doesn't need it
+// RUN: %target-swift-frontend -target arm64e-apple-ios11.0  -emit-ir -parse-stdlib %s | %FileCheck -check-prefix=NO-FORCE-LOAD %s
+
+public func foo() {}
+
+// NO-FORCE-LOAD-NOT: FORCE_LOAD
+// NO-FORCE-LOAD-NOT: !{!"-lswiftCompatibility50"}
+// NO-FORCE-LOAD-NOT: !{!"-lswiftCompatibilityDynamicReplacements"}