[embedded] Enable read-only static array promotion in embedded mode

Author: kubamracek

lib/IRGen/IRGenModule.cpp

@@ -2091,7 +2091,7 @@ bool IRGenModule::canMakeStaticObjectReadOnly(SILType objectType) {
 
   // TODO: Support constant static arrays on other platforms, too.
   // See also the comment in GlobalObjects.cpp.
-  if (!Triple.isOSDarwin())
+  if (!Triple.isOSDarwin() && !Context.LangOpts.hasFeature(Feature::Embedded))
     return false;
 
   auto *clDecl = objectType.getClassOrBoundGenericClass();

test/embedded/static-object-non-darwin.swift

@@ -0,0 +1,26 @@
+// RUN: %target-swift-frontend -target armv7em-none-none-eabi -parse-as-library -module-name main -O -emit-ir %s -enable-experimental-feature Embedded -Xllvm -link-embedded-runtime=0 | %FileCheck %s
+// RUN: %target-swift-frontend -target armv7em-none-none-eabi -parse-as-library -module-name main -Osize -emit-ir %s -enable-experimental-feature Embedded -Xllvm -link-embedded-runtime=0 | %FileCheck %s
+
+// REQUIRES: swift_in_compiler
+// REQUIRES: optimized_stdlib
+// REQUIRES: OS=macosx || OS=linux-gnu
+// REQUIRES: CODEGENERATOR=ARM
+// REQUIRES: embedded_stdlib_cross_compiling
+
+let pots = [41,52,99,1,4,4]
+
+public enum ValidState {
+    case yes
+    case no
+    case undefined
+}
+
+public func checkPot(i: UInt8, testValue: UInt8) -> ValidState {
+    guard i < pots.count else { return .undefined }
+    return pots[Int(i)] < testValue ? .yes : .no
+}
+
+// CHECK: @"$s4main4pots_Wz" = {{.*}}global i32 0
+// CHECK: @"$ss20__StaticArrayStorageCN" = {{.*}}global ptr null
+// CHECK: @"$s4main4pots_WZTv_r" = {{.*}}constant %Ts23_ContiguousArrayStorageCySiG_tailelems0 {{.*}}@"$ss20__StaticArrayStorageCN"
+// CHECK: @"$s4main4potsSaySiGvp" = {{.*}}constant %TSa {{.*}}@"$s4main4pots_WZTv_r"