[generic-specializer] Fix for specializations which are no-return functions

lib/SILOptimizer/Utils/Generics.cpp

@@ -1670,10 +1670,19 @@ static ApplySite replaceWithSpecializedCallee(ApplySite AI,
                                       Arguments, A->isNonThrowing());
     if (StoreResultTo) {
       assert(substConv.useLoweredAddresses());
-      // Store the direct result to the original result address.
-      fixUsedVoidType(A, Loc, Builder);
-      Builder.createStore(Loc, NewAI, StoreResultTo,
-                          StoreOwnershipQualifier::Unqualified);
+      if (!CalleeSILSubstFnTy.isNoReturnFunction()) {
+        // Store the direct result to the original result address.
+        fixUsedVoidType(A, Loc, Builder);
+        Builder.createStore(Loc, NewAI, StoreResultTo,
+                            StoreOwnershipQualifier::Unqualified);
+      } else {
+        Builder.createUnreachable(Loc);
+        // unreachable should be the terminator instruction.
+        // So, split the current basic block right after the
+        // inserted unreachable instruction.
+        Builder.getInsertionPoint()->getParent()->split(
+            Builder.getInsertionPoint());
+      }
     }
     A->replaceAllUsesWith(NewAI);
     return NewAI;

test/SILOptimizer/specialize.sil

@@ -527,3 +527,58 @@ bb0(%0 : $Builtin.RawPointer):
   %5 = tuple ()
   return %5 : $()
 }
+
+// invokeGenericClosure<A>(todo:)
+sil [noinline] @invokeGenericClosure : $@convention(thin) <R> (@owned @callee_owned () -> (@out R, @error Error)) -> (@out R, @error Error) {
+bb0(%0 : $*R, %1 : $@callee_owned () -> (@out R, @error Error)):
+  debug_value %1 : $@callee_owned () -> (@out R, @error Error), let, name "todo", argno 1 // id: %2
+  debug_value undef : $Error, var, name "$error", argno 2 // id: %3
+  strong_retain %1 : $@callee_owned () -> (@out R, @error Error) // id: %4
+  try_apply %1(%0) : $@callee_owned () -> (@out R, @error Error), normal bb1, error bb2 // id: %5
+
+bb1(%6 : $()):                                    // Preds: bb0
+  strong_release %1 : $@callee_owned () -> (@out R, @error Error) // id: %7
+  %8 = tuple ()                                   // user: %9
+  return %8 : $()                                 // id: %9
+
+// %10                                            // user: %12
+bb2(%10 : $Error):                                // Preds: bb0
+  strong_release %1 : $@callee_owned () -> (@out R, @error Error) // id: %11
+  throw %10 : $Error                              // id: %12
+} // end sil function 'invokeGenericClosure'
+
+sil public_external @error : $@convention(thin) () -> Never
+
+// action()
+sil @action : $@convention(thin) () -> Never
+
+// thunk for @callee_owned () -> (@unowned Never, @error @owned Error)
+sil @action_thunk : $@convention(thin) (@owned @callee_owned () -> (Never, @error Error)) -> (@out Never, @error Error)
+
+// Check that in a case where a generic specialization is a non-return function,
+// the return value is not stored after the call and an unreachable instruction
+// is inserted as a terminator of a basic block.
+//
+// CHECK-LABEL: sil @testGenericClosureSpecialization
+// Call of the generic specialization of invokeGenericClosure<Never>
+// CHECK: function_ref @_T020invokeGenericClosures5NeverO_Tg5 : $@convention(thin) (@owned @callee_owned () -> (@out Never, @error Error)) -> (Never, @error Error)
+// CHECK: apply [nothrow]
+// CHECK: unreachable
+// CHECK: end sil function 'testGenericClosureSpecialization'
+sil @testGenericClosureSpecialization : $@convention(thin) () -> @error Error {
+bb0:
+  // function_ref invokeGenericClosure<A>(todo:)
+  %1 = function_ref @invokeGenericClosure : $@convention(thin) <τ_0_0> (@owned @callee_owned () -> (@out τ_0_0, @error Error)) -> (@out τ_0_0, @error Error)
+  %2 = alloc_stack $Never
+  // function_ref action()
+  %3 = function_ref @action : $@convention(thin) () -> Never
+  %4 = thin_to_thick_function %3 : $@convention(thin) () -> Never to $@callee_owned () -> Never
+  %5 = convert_function %4 : $@callee_owned () -> Never to $@callee_owned () -> (Never, @error Error)
+  // function_ref thunk for @callee_owned () -> (@unowned Never, @error @owned Error)
+  %6 = function_ref @action_thunk : $@convention(thin) (@owned @callee_owned () -> (Never, @error Error)) -> (@out Never, @error Error)
+  %7 = partial_apply %6(%5) : $@convention(thin) (@owned @callee_owned () -> (Never, @error Error)) -> (@out Never, @error Error)
+  %8 = apply [nothrow] %1<Never>(%2, %7) : $@convention(thin) <τ_0_0> (@owned @callee_owned () -> (@out τ_0_0, @error Error)) -> (@out τ_0_0, @error Error)
+  dealloc_stack %2 : $*Never
+  %12 = tuple ()
+  return %12 : $()
+} // end sil function 'testGenericClosureSpecialization'