ClosureLifetimeFixup; emit mark_dependence [nonescaping].

It is safe to do so because the on_stack transformation already checks that the closure has a single known apply use.

Author: atrick

lib/SILOptimizer/Mandatory/ClosureLifetimeFixup.cpp

@@ -406,7 +406,7 @@ static SILValue insertMarkDependenceForCapturedArguments(PartialApplyInst *pai,
       if (m->hasGuaranteedInitialKind())
         continue;
     curr = b.createMarkDependence(pai->getLoc(), curr, arg.get(),
-                                  MarkDependenceKind::Escaping);
+                                  MarkDependenceKind::NonEscaping);
   }
 
   return curr;

lib/SILOptimizer/Utils/LoopUtils.cpp

@@ -260,7 +260,12 @@ bool swift::canDuplicateLoopInstruction(SILLoop *L, SILInstruction *I) {
       return false;
     }
   }
-
+  // Like partial_apply [onstack], mark_dependence [nonescaping] creates a
+  // borrow scope. We currently assume that a set of dominated scope-ending uses
+  // can be found.
+  if (auto *MD = dyn_cast<MarkDependenceInst>(I)) {
+    return !MD->isNonEscaping();
+  }
   // CodeGen can't build ssa for objc methods.
   if (auto *Method = dyn_cast<MethodInst>(I)) {
     if (Method->getMember().isForeign) {

test/SILOptimizer/closure-lifetime-fixup.sil

@@ -272,7 +272,7 @@ bb3:
 // CHECK:       [[SUCCESS_1]]
 // CHECK:         copy_addr [[INSTANCE]] to [init] [[STACK]] : $*Self, {{.*}} scope [[STACK_SCOPE:[0-9]+]]
 // CHECK:         [[CLOSURE:%[^,]+]] = partial_apply [callee_guaranteed] [on_stack] undef<Self>([[STACK]])
-// CHECK:         [[DEPENDENCY:%[^,]+]] = mark_dependence [[CLOSURE]] {{.*}} on [[STACK]]
+// CHECK:         [[DEPENDENCY:%[^,]+]] = mark_dependence [nonescaping] [[CLOSURE]] {{.*}} on [[STACK]]
 // CHECK:         try_apply undef([[DEPENDENCY]]) {{.*}}, normal [[SUCCESS_2:bb[0-9]+]], error [[FAILURE_2:bb[0-9]+]]
 // CHECK:       [[SUCCESS_2]]
 // CHECK:         destroy_value [[DEPENDENCY]]

test/SILOptimizer/opaque_values_Onone.swift

@@ -73,7 +73,7 @@ func doit<T>(_ f: () -> T) -> T {
 // CHECK:         [[DUPLICATE_CLOSURE:%[^,]+]] = function_ref @$s19opaque_values_Onone10duplicate15valuex_xtx_tlFx_xtyXEfU_
 // CHECK:         copy_addr [[INSTANCE_ADDR_IN]] to [init] [[INSTANCE_ADDR]]
 // CHECK:         [[DUPLICATE_INSTANCE_CLOSURE:%[^,]+]] = partial_apply [callee_guaranteed] [on_stack] [[DUPLICATE_CLOSURE]]<Value>([[INSTANCE_ADDR]])
-// CHECK:         [[DEPENDENDENCY:%[^,]+]] = mark_dependence [[DUPLICATE_INSTANCE_CLOSURE]] : $@noescape @callee_guaranteed () -> @out (Value, Value) on [[INSTANCE_ADDR]] : $*Value
+// CHECK:         [[DEPENDENDENCY:%[^,]+]] = mark_dependence [nonescaping] [[DUPLICATE_INSTANCE_CLOSURE]] : $@noescape @callee_guaranteed () -> @out (Value, Value) on [[INSTANCE_ADDR]] : $*Value
 // CHECK:         [[CONVERTED:%[^,]+]] = convert_function [[DEPENDENDENCY]]
 // CHECK:         apply {{%[^,]+}}<(Value, Value)>([[OUTPUT_TUPLE_ADDR]], [[CONVERTED]])
 // CHECK-LABEL: } // end sil function 'duplicate1'
@@ -97,7 +97,7 @@ func duplicate1<Value>(value: Value) -> (Value, Value) {
 // CHECK:         [[DUPLICATE_CLOSURE:%[^,]+]] = function_ref @$s19opaque_values_Onone10duplicate25valuex3one_x3twotx_tlFxAD_xAEtyXEfU_
 // CHECK:         copy_addr [[INSTANCE_ADDR_IN]] to [init] [[INSTANCE_ADDR]]
 // CHECK:         [[DUPLICATE_INSTANCE_CLOSURE:%[^,]+]] = partial_apply [callee_guaranteed] [on_stack] [[DUPLICATE_CLOSURE]]<Value>([[INSTANCE_ADDR]])
-// CHECK:         [[DEPENDENDENCY:%[^,]+]] = mark_dependence [[DUPLICATE_INSTANCE_CLOSURE]] : $@noescape @callee_guaranteed () -> @out (one: Value, two: Value) on [[INSTANCE_ADDR]] : $*Value
+// CHECK:         [[DEPENDENDENCY:%[^,]+]] = mark_dependence [nonescaping] [[DUPLICATE_INSTANCE_CLOSURE]] : $@noescape @callee_guaranteed () -> @out (one: Value, two: Value) on [[INSTANCE_ADDR]] : $*Value
 // CHECK:         [[CONVERTED:%[^,]+]] = convert_function [[DEPENDENDENCY]]
 // CHECK:         apply {{%[^,]+}}<(one: Value, two: Value)>([[OUTPUT_TUPLE_ADDR]], [[CONVERTED]])
 // CHECK-LABEL: } // end sil function 'duplicate2'
@@ -133,7 +133,7 @@ func duplicate_with_int2<Value>(value: Value) -> ((Value, Value), Int) {
 // CHECK:         [[CLOSURE:%[^,]+]] = function_ref @$s19opaque_values_Onone19duplicate_with_int35valueSi_x_x_x_SitxttSitx_tlFSi_x_x_x_SitxttSityXEfU_
 // CHECK:         copy_addr [[INSTANCE_ADDR_IN]] to [init] [[INSTANCE_ADDR]]
 // CHECK:         [[INSTANCE_CLOSURE:%[^,]+]] = partial_apply [callee_guaranteed] [on_stack] [[CLOSURE]]<Value>([[INSTANCE_ADDR]])
-// CHECK:         [[DEPENDENCY:%[^,]+]] = mark_dependence [[INSTANCE_CLOSURE]]
+// CHECK:         [[DEPENDENCY:%[^,]+]] = mark_dependence [nonescaping] [[INSTANCE_CLOSURE]]
 // CHECK:         [[CONVERTED:%[^,]+]] = convert_function [[DEPENDENCY]]
 // CHECK:         apply {{%[^,]+}}<(Int, (Value, (Value, (Value, Int), Value)), Int)>({{%[^,]+}}, [[CONVERTED]])
 // CHECK-LABEL: } // end sil function 'duplicate_with_int3'