SIL: create hop_to_executor instructions with "auto-generated" debug locations.

Those instructions should not be "visible" for debugging and for diagnostic messages.

Fixes a wrong "unreachable code" warning.

https://bugs.swift.org/browse/SR-14873
rdar://80237870

Author: eeckstein

include/swift/SIL/SILLocation.h

@@ -333,6 +333,13 @@ class SILLocation {
   /// Marks the location as coming from auto-generated body.
   void markAutoGenerated() { kindAndFlags.fields.autoGenerated = true; }
 
+  /// Returns this location with the auto-generated flag set.
+  SILLocation asAutoGenerated() const {
+    SILLocation loc = *this;
+    loc.markAutoGenerated();
+    return loc;
+  }
+
   /// Returns true if the location represents an artificially generated
   /// body, such as thunks or default destructors.
   ///

lib/SILGen/SILGenConstructor.cpp

@@ -677,7 +677,7 @@ void SILGenFunction::emitConstructorPrologActorHop(
 
   if (auto executor = emitExecutor(loc, *maybeIso, None)) {
     ExpectedExecutor = *executor;
-    B.createHopToExecutor(loc, *executor, /*mandatory*/ false);
+    B.createHopToExecutor(loc.asAutoGenerated(), *executor, /*mandatory*/ false);
   }
 }
 

lib/SILGen/SILGenProlog.cpp

@@ -668,7 +668,7 @@ ExecutorBreadcrumb SILGenFunction::emitHopToTargetExecutor(
   // If we're calling from an actor method ourselves, then we'll want to hop
   // back to our own actor.
   auto breadcrumb = ExecutorBreadcrumb(emitGetCurrentExecutor(loc));
-  B.createHopToExecutor(loc, executor, /*mandatory*/ false);
+  B.createHopToExecutor(loc.asAutoGenerated(), executor, /*mandatory*/ false);
   return breadcrumb;
 }
 
@@ -710,7 +710,7 @@ void SILGenFunction::emitHopToActorValue(SILLocation loc, ManagedValue actor) {
       "Builtin.hopToActor must be in an actor-independent function");
   }
   SILValue executor = emitLoadActorExecutor(loc, actor);
-  B.createHopToExecutor(loc, executor, /*mandatory*/ true);
+  B.createHopToExecutor(loc.asAutoGenerated(), executor, /*mandatory*/ true);
 }
 
 void SILGenFunction::emitPreconditionCheckExpectedExecutor(
@@ -741,7 +741,7 @@ void SILGenFunction::emitPreconditionCheckExpectedExecutor(
 
 void ExecutorBreadcrumb::emit(SILGenFunction &SGF, SILLocation loc) {
   if (Executor)
-    SGF.B.createHopToExecutor(loc, Executor, /*mandatory*/ false);
+    SGF.B.createHopToExecutor(loc.asAutoGenerated(), Executor, /*mandatory*/ false);
 }
 
 SILValue SILGenFunction::emitGetCurrentExecutor(SILLocation loc) {

lib/SILOptimizer/Mandatory/DefiniteInitialization.cpp

@@ -818,7 +818,7 @@ static void injectHopToExecutorAfter(SILLocation loc,
       if (needsBorrow)
         actor = b.createBeginBorrow(loc, actor);
 
-      b.createHopToExecutor(loc, actor, /*mandatory=*/false);
+      b.createHopToExecutor(loc.asAutoGenerated(), actor, /*mandatory=*/false);
 
       if (needsBorrow)
         b.createEndBorrow(loc, actor);

test/Concurrency/hop_to_executor_unreachable_code.swift

@@ -0,0 +1,17 @@
+// RUN: %target-swift-frontend -disable-availability-checking -emit-sil -verify %s
+
+// REQUIRES: concurrency
+
+// Check that the inserted hop-to-executor instructions don't cause a false
+// "unreachable code" warning.
+
+@MainActor
+func bye() -> Never {
+    print("bye")
+    fatalError()
+}
+
+func testit() async {
+    await bye()
+}
+