Merge pull request #17071 from aschwaighofer/silgen_fix_noescape_verification_objc_exception_4.2

[4.2] SILGen: Fix no escape verification if the closure throws an exc…

Author: aschwaighofer

lib/SILGen/SILGenBridging.cpp

@@ -371,7 +371,8 @@ static void buildFuncToBlockInvokeBody(SILGenFunction &SGF,
                                        CanAnyFunctionType formalBlockType,
                                        CanSILFunctionType funcTy,
                                        CanSILFunctionType blockTy,
-                                       CanSILBlockStorageType blockStorageTy) {
+                                       CanSILBlockStorageType blockStorageTy,
+                                       bool isUnretainedClosureSafe) {
   Scope scope(SGF.Cleanups, CleanupLocation::get(loc));
   SILBasicBlock *entry = &*SGF.F.begin();
   SILFunctionConventions blockConv(blockTy, SGF.SGM.M);
@@ -395,7 +396,9 @@ static void buildFuncToBlockInvokeBody(SILGenFunction &SGF,
   auto storage = entry->createFunctionArgument(storageAddrTy);
   auto capture = SGF.B.createProjectBlockStorage(loc, storage);
   auto &funcTL = SGF.getTypeLowering(funcTy);
-  auto fn = SGF.emitLoad(loc, capture, funcTL, SGFContext(), IsNotTake);
+  auto fn = isUnretainedClosureSafe
+                ? SGF.emitManagedLoadBorrow(loc, capture)
+                : SGF.emitLoad(loc, capture, funcTL, SGFContext(), IsNotTake);
 
   // Collect the block arguments, which may have nonstandard conventions.
   assert(blockTy->getParameters().size() == funcTy->getParameters().size()
@@ -590,8 +593,11 @@ ManagedValue SILGenFunction::emitFuncToBlock(SILLocation loc,
     thunk->setGenericEnvironment(genericEnv);
     SILGenFunction thunkSGF(SGM, *thunk);
     auto loc = RegularLocation::getAutoGeneratedLocation();
+    // Not retaining the closure in the reabstraction thunk is safe if we hold
+    // another reference for the is_escaping sentinel.
     buildFuncToBlockInvokeBody(thunkSGF, loc, funcType, blockType,
-                               loweredFuncTy, loweredBlockTy, storageTy);
+                               loweredFuncTy, loweredBlockTy, storageTy,
+                               useWithoutEscapingVerifcation);
   }
 
   // Form the block on the stack.

test/Interpreter/Inputs/ObjCException.h

@@ -0,0 +1,5 @@
+#import <Foundation/Foundation.h>
+
+@interface ExceptionCatcher : NSObject
+- (NSException* _Nullable)tryBlock:(__attribute__((noescape)) void(^ _Nonnull)(void))unsafeBlock NS_SWIFT_NAME(tryBlock(_:));
+@end

test/Interpreter/Inputs/ObjCException.m

@@ -0,0 +1,13 @@
+#import "ObjCException.h"
+
+@implementation ExceptionCatcher
+- (NSException* _Nullable) tryBlock:(__attribute__((noescape)) void(^_Nonnull)(void))unsafeBlock {
+    @try {
+        unsafeBlock();
+    }
+    @catch (NSException *exception) {
+        return exception;
+    }
+    return nil;
+}
+@end

test/Interpreter/objc_throw_in_noescape_block.swift

@@ -0,0 +1,25 @@
+// RUN: %empty-directory(%t)
+//
+// RUN: %target-clang -fobjc-arc %S/Inputs/ObjCException.m -c -o %t/ObjCException.o
+// RUN: %target-build-swift -import-objc-header %S/Inputs/ObjcException.h -Xlinker %t/ObjCException.o %s -o %t/a.out
+// RUN: %target-run %t/a.out
+
+// REQUIRES: executable_test
+// REQUIRES: objc_interop
+
+import Foundation
+import StdlibUnittest
+
+var ThrowingTestSuite = TestSuite("Throwing")
+
+
+ThrowingTestSuite.test("noescape verification") {
+  let catcher = ExceptionCatcher()
+  let e = catcher.tryBlock {
+    NSException(name: NSExceptionName(rawValue: "Flames"), reason: "Fire", userInfo: nil).raise()
+  }
+  expectEqual(e!.reason, "Fire")
+}
+
+
+runAllTests()

test/SILGen/objc_thunks.swift

@@ -570,3 +570,25 @@ func registerAnsible() {
   // CHECK: function_ref @$S11objc_thunks15registerAnsibleyyFyyycSgcfU_
   Ansible.anseAsync({ completion in completion!() })
 }
+@_silgen_name("noescape")
+func noescape(f: @convention(block) () -> ())
+
+// CHECK: sil hidden @$S11objc_thunks21testObjCNoescapeThunkyyF : $@convention(thin) () -> () {
+// CHECK: [[REABSTRACT:%.*]] = function_ref @$SIeg_IyB_TR
+// CHECK: init_block_storage_header {{.*}} : $*@block_storage @callee_guaranteed () -> (), invoke [[REABSTRACT]]
+// CHECK: return
+func testObjCNoescapeThunk() {
+  noescape {
+  }
+}
+
+// Noescape verification relies on there not being a retain/release in order to
+// work in the presence of a objective c throwing implementation function.
+// CHECK: sil {{.*}} @$SIeg_IyB_TR
+// CHECK: bb0([[T0:%.*]] : @trivial $*@block_storage @callee_guaranteed () -> ()):
+// CHECK-NEXT:  [[T1:%.*]] = project_block_storage [[T0]]
+// CHECK-NEXT:  [[T2:%.*]] = load_borrow [[T1]]
+// CHECK-NEXT:  [[T3:%.*]] = apply [[T2]]()
+// CHECK-NEXT:  [[T4:%.*]] = tuple ()
+// CHECK-NEXT:  end_borrow [[T2]] from [[T1]]
+// CHECK-NEXT:  return [[T4]]