Mandatory Inlining: Set ApplyOptions correctly in TypeSubstCloner

When we inline an async function called via 'apply [noasync]' or
'try_apply [noasync]', we must in turn set the '[noasync]' flag
on any async functions that the inlined function calls.

Author: slavapestov

include/swift/SIL/ApplySite.h

@@ -452,7 +452,7 @@ class ApplySite {
     case ApplySiteKind::TryApplyInst:
       return cast<TryApplyInst>(Inst)->getApplyOptions();
     case ApplySiteKind::PartialApplyInst:
-      llvm_unreachable("Unhandled case");
+      return ApplyOptions();
     }
   }
   /// Return whether the given apply is of a formally-throwing function

include/swift/SIL/TypeSubstCloner.h

@@ -54,6 +54,7 @@ class TypeSubstCloner : public SILClonerWithScopes<ImplClass> {
     SubstitutionMap Subs;
     SmallVector<SILValue, 8> Args;
     SubstitutionMap RecursiveSubs;
+    ApplyOptions ApplyOpts;
 
   public:
     ApplySiteCloningHelper(ApplySite AI, TypeSubstCloner &Cloner)
@@ -67,6 +68,14 @@ class TypeSubstCloner : public SILClonerWithScopes<ImplClass> {
       // Remap substitutions.
       Subs = Cloner.getOpSubstitutionMap(AI.getSubstitutionMap());
 
+      // If we're inlining a [noasync] function, make sure any calls inside it
+      // are marked as [noasync] as appropriate.
+      ApplyOpts = AI.getApplyOptions();
+      if (!Builder.getFunction().isAsync() &&
+          SubstCalleeSILType.castTo<SILFunctionType>()->isAsync()) {
+        ApplyOpts |= ApplyFlags::DoesNotAwait;
+      }
+
       if (!Cloner.Inlining) {
         FunctionRefInst *FRI = dyn_cast<FunctionRefInst>(AI.getCallee());
         if (FRI && FRI->getReferencedFunction() == AI.getFunction() &&
@@ -123,6 +132,10 @@ class TypeSubstCloner : public SILClonerWithScopes<ImplClass> {
     SubstitutionMap getSubstitutions() const {
       return Subs;
     }
+
+    ApplyOptions getApplyOptions() const {
+      return ApplyOpts;
+    }
   };
 
 public:
@@ -214,7 +227,7 @@ class TypeSubstCloner : public SILClonerWithScopes<ImplClass> {
         getBuilder().createApply(getOpLocation(Inst->getLoc()),
                                  Helper.getCallee(), Helper.getSubstitutions(),
                                  Helper.getArguments(),
-                                 Inst->getApplyOptions(),
+                                 Helper.getApplyOptions(),
                                  GenericSpecializationInformation::create(
                                    Inst, getBuilder()));
     // Specialization can return noreturn applies that were not identified as
@@ -234,7 +247,7 @@ class TypeSubstCloner : public SILClonerWithScopes<ImplClass> {
         Helper.getSubstitutions(), Helper.getArguments(),
         getOpBasicBlock(Inst->getNormalBB()),
         getOpBasicBlock(Inst->getErrorBB()),
-        Inst->getApplyOptions(),
+        Helper.getApplyOptions(),
         GenericSpecializationInformation::create(
           Inst, getBuilder()));
     recordClonedInstruction(Inst, N);

test/SILOptimizer/mandatory_inlining_reasync.swift

@@ -0,0 +1,25 @@
+// RUN: %target-swift-frontend -emit-sil -enable-experimental-concurrency %s | %FileCheck %s
+
+@_transparent
+func reasyncFunction(_ value: Optional<Int>, _ fn: () async throws -> Int) reasync rethrows -> Int {
+  switch value {
+  case .some(let x): return x
+  case .none: return try await fn()
+  }
+}
+
+// CHECK-LABEL: sil hidden @$s26mandatory_inlining_reasync20callsReasyncFunctionSiyF : $@convention(thin) () -> Int {
+// CHECK: [[FN:%.*]] = function_ref @$s26mandatory_inlining_reasync20callsReasyncFunctionSiyFSiyXEfU_ : $@convention(thin) () -> Int
+// CHECK-NEXT: [[CONV:%.*]] = convert_function [[FN]] : $@convention(thin) () -> Int to $@convention(thin) @noescape () -> Int
+// CHECK-NEXT: [[THICK:%.*]] = thin_to_thick_function [[CONV]] : $@convention(thin) @noescape () -> Int to $@noescape @callee_guaranteed () -> Int
+// CHECK-NEXT: br bb1
+
+// CHECK: bb1:
+// CHECK-NEXT: [[RESULT:%.*]] = apply [[THICK]]() : $@noescape @callee_guaranteed () -> Int
+// CHECK-NEXT:  br bb2
+
+// CHECK: bb2:
+// CHECK-NEXT:  return [[RESULT]] : $Int
+func callsReasyncFunction() -> Int {
+  return reasyncFunction(nil, { return 321 } )
+}