Merge pull request #11026 from jckarter/fix-load-from-lvalue-peephole

SILGen: Ease off +0 peepholes for load exprs.

Author: jckarter

lib/SILGen/SGFContext.h

@@ -152,9 +152,9 @@ class SGFContext {
   /// a value.  The Initialization is not okay to propagate down, but
   /// the +0/+1-ness is.
   SGFContext withFollowingProjection() const {
-    SGFContext copy;
-    copy.state.setInt(state.getInt());
-    return copy;
+    SGFContext result;
+    result.state.setInt(state.getInt());
+    return result;
   }
 };
 

lib/SILGen/SILGenExpr.cpp

@@ -1299,7 +1299,10 @@ RValue RValueEmitter::visitLoadExpr(LoadExpr *E, SGFContext C) {
   // Any writebacks here are tightly scoped.
   FormalEvaluationScope writeback(SGF);
   LValue lv = SGF.emitLValue(E->getSubExpr(), AccessKind::Read);
-  return SGF.emitLoadOfLValue(E, std::move(lv), C);
+  // We can't load at immediate +0 from the lvalue without deeper analysis,
+  // since the access will be immediately ended and might invalidate the value
+  // we loaded.
+  return SGF.emitLoadOfLValue(E, std::move(lv), C.withFollowingSideEffects());
 }
 
 SILValue SILGenFunction::emitTemporaryAllocation(SILLocation loc,
@@ -2367,7 +2370,9 @@ RValue RValueEmitter::visitMemberRefExpr(MemberRefExpr *E, SGFContext C) {
   FormalEvaluationScope scope(SGF);
 
   LValue lv = SGF.emitLValue(E, AccessKind::Read);
-  return SGF.emitLoadOfLValue(E, std::move(lv), C);
+  // We can't load at +0 without further analysis, since the formal access into
+  // the lvalue will end immediately.
+  return SGF.emitLoadOfLValue(E, std::move(lv), C.withFollowingSideEffects());
 }
 
 RValue RValueEmitter::visitDynamicMemberRefExpr(DynamicMemberRefExpr *E,
@@ -2386,7 +2391,9 @@ RValue RValueEmitter::visitSubscriptExpr(SubscriptExpr *E, SGFContext C) {
   FormalEvaluationScope scope(SGF);
 
   LValue lv = SGF.emitLValue(E, AccessKind::Read);
-  return SGF.emitLoadOfLValue(E, std::move(lv), C);
+  // We can't load at +0 without further analysis, since the formal access into
+  // the lvalue will end immediately.
+  return SGF.emitLoadOfLValue(E, std::move(lv), C.withFollowingSideEffects());
 }
 
 RValue RValueEmitter::visitDynamicSubscriptExpr(

lib/SILGen/SILGenLValue.cpp

@@ -3127,7 +3127,7 @@ RValue SILGenFunction::emitLoadOfLValue(SILLocation loc, LValue &&src,
   PathComponent &&component =
     drillToLastComponent(*this, loc, std::move(src), addr, AccessKind::Read);
 
-  // If the last component is physical, just drill down and load from it.
+  // If the last component is physical, drill down and load from it.
   if (component.isPhysical()) {
     addr = std::move(component.asPhysical())
              .offset(*this, loc, addr, AccessKind::Read);
@@ -3137,7 +3137,7 @@ RValue SILGenFunction::emitLoadOfLValue(SILLocation loc, LValue &&src,
                            isGuaranteedValid));
   }
 
-  // If the last component is logical, just emit a get.
+  // If the last component is logical, emit a get.
   return std::move(component.asLogical()).get(*this, loc, addr, C);
 }
 

test/SILGen/dynamic_lookup.swift

@@ -62,7 +62,7 @@ func direct_to_static_method(_ obj: AnyObject) {
   // CHECK: store [[ARG_COPY]] to [init] [[PBOBJ]] : $*AnyObject
   // CHECK: end_borrow [[BORROWED_ARG]] from [[ARG]]
   // CHECK: [[READ:%.*]] = begin_access [read] [unknown] [[PBOBJ]]
-  // CHECK-NEXT: [[OBJCOPY:%[0-9]+]] = load_borrow [[READ]] : $*AnyObject
+  // CHECK-NEXT: [[OBJCOPY:%[0-9]+]] = load [copy] [[READ]] : $*AnyObject
   // CHECK: end_access [[READ]]
   // CHECK-NEXT: [[OBJMETA:%[0-9]+]] = existential_metatype $@thick AnyObject.Type, [[OBJCOPY]] : $AnyObject
   // CHECK-NEXT: [[OPENMETA:%[0-9]+]] = open_existential_metatype [[OBJMETA]] : $@thick AnyObject.Type to $@thick (@opened([[UUID:".*"]]) AnyObject).Type
@@ -141,7 +141,7 @@ func opt_to_static_method(_ obj: AnyObject) {
   // CHECK:   [[OPTBOX:%[0-9]+]] = alloc_box ${ var Optional<@callee_owned () -> ()> }
   // CHECK:   [[PBO:%.*]] = project_box [[OPTBOX]]
   // CHECK:   [[READ:%.*]] = begin_access [read] [unknown] [[PBOBJ]]
-  // CHECK:   [[OBJCOPY:%[0-9]+]] = load_borrow [[READ]] : $*AnyObject
+  // CHECK:   [[OBJCOPY:%[0-9]+]] = load [copy] [[READ]] : $*AnyObject
   // CHECK:   [[OBJMETA:%[0-9]+]] = existential_metatype $@thick AnyObject.Type, [[OBJCOPY]] : $AnyObject
   // CHECK:   [[OPENMETA:%[0-9]+]] = open_existential_metatype [[OBJMETA]] : $@thick AnyObject.Type to $@thick (@opened
   // CHECK:   [[OBJCMETA:%[0-9]+]] = thick_to_objc_metatype [[OPENMETA]]

test/SILGen/functions.swift

@@ -176,7 +176,7 @@ func calls(_ i:Int, j:Int, k:Int) {
   // -- Curry the Type onto static method argument lists.
 
   // CHECK: [[READC:%.*]] = begin_access [read] [unknown] [[CADDR]]
-  // CHECK: [[C:%[0-9]+]] = load_borrow [[READC]]
+  // CHECK: [[C:%[0-9]+]] = load [copy] [[READC]]
   // CHECK: [[META:%.*]] = value_metatype $@thick SomeClass.Type, [[C]]
   // CHECK: [[METHOD:%[0-9]+]] = class_method [[META]] : {{.*}}, #SomeClass.static_method!1
   // CHECK: [[READI:%.*]] = begin_access [read] [unknown] [[IADDR]]

test/SILGen/load_from_lvalue_in_plus_zero_context.swift

@@ -0,0 +1,32 @@
+// RUN: %target-swift-frontend -emit-silgen %s | %FileCheck %s
+
+class A {
+  lazy var b: B = B()
+}
+
+final class B {
+  var c: C? {
+    get { return nil }
+    set {}
+  }
+}
+
+struct C {
+  let d: String
+}
+
+// CHECK-LABEL: sil hidden @{{.*}}test
+func test(a: A) {
+  let s: String?
+  // CHECK:   [[C_TEMP:%.*]] = alloc_stack $Optional<C>
+  // CHECK:   [[TAG:%.*]] = select_enum_addr [[C_TEMP]]
+  // CHECK:   cond_br [[TAG]], [[SOME:bb[0-9]+]], [[NONE:bb[0-9]+]]
+  // CHECK: [[SOME]]:
+  // CHECK:   [[C_PAYLOAD:%.*]] = unchecked_take_enum_data_addr [[C_TEMP]]
+  // -- This must be a copy, since we'll immediately destroy the value in the
+  //    temp buffer
+  // CHECK:   [[LOAD:%.*]] = load [copy] [[C_PAYLOAD]]
+  // CHECK:   destroy_addr [[C_TEMP]]
+  s = a.b.c?.d
+  print(s)
+}

test/SILGen/opaque_values_silgen.swift

@@ -1022,20 +1022,21 @@ func s480_________getError(someError: Error) -> Any {
 // CHECK-LABEL: sil private @_T020opaque_values_silgen21s490_______loadBorrowyyF3FooL_V3foo7ElementQzSg5IndexQz3pos_tF : $@convention(method) <Elements where Elements : Collection> (@in Elements.Index, @inout Foo<Elements>) -> @out Optional<Elements.Element> {
 // CHECK: bb0(%0 : $Elements.Index, %1 : $*Foo<Elements>):
 // CHECK: [[READ:%.*]] = begin_access [read] [unknown] %1 : $*Foo<Elements>
-// CHECK: [[LOAD:%.*]] = load_borrow [[READ]] : $*Foo<Elements>
+// CHECK: [[LOAD:%.*]] = load [copy] [[READ]] : $*Foo<Elements>
 // CHECK: end_access [[READ]] : $*Foo<Elements>
-// CHECK: [[EXTRACT:%.*]] = struct_extract [[LOAD]] : $Foo<Elements>, #<abstract function>Foo._elements
+// CHECK: [[BORROW_LOAD:%.*]] = begin_borrow [[LOAD]]
+// CHECK: [[EXTRACT:%.*]] = struct_extract [[BORROW_LOAD]] : $Foo<Elements>, #<abstract function>Foo._elements
 // CHECK: [[COPYELT:%.*]] = copy_value [[EXTRACT]] : $Elements
 // CHECK: [[BORROW:%.*]] = begin_borrow %0 : $Elements.Index
 // CHECK: [[COPYIDX:%.*]] = copy_value [[BORROW]] : $Elements.Index
 // CHECK: [[WT:%.*]] = witness_method $Elements, #Collection.subscript!getter.1 : <Self where Self : Collection> (Self) -> (Self.Index) -> Self.Element : $@convention(witness_method) <τ_0_0 where τ_0_0 : Collection> (@in τ_0_0.Index, @in_guaranteed τ_0_0) -> @out τ_0_0.Element
 // CHECK: %{{.*}} = apply [[WT]]<Elements>([[COPYIDX]], [[COPYELT]]) : $@convention(witness_method) <τ_0_0 where τ_0_0 : Collection> (@in τ_0_0.Index, @in_guaranteed τ_0_0) -> @out τ_0_0.Element
 // CHECK: destroy_value [[COPYELT]] : $Elements
-// CHECK: [[ENUM:%.*]] = enum $Optional<Elements.Element>, #Optional.some!enumelt.1, %12 : $Elements.Element
+// CHECK: [[ENUM:%.*]] = enum $Optional<Elements.Element>, #Optional.some!enumelt.1, %13 : $Elements.Element
 // CHECK: end_borrow [[BORROW]] from %0 : $Elements.Index, $Elements.Index
-// CHECK: end_borrow [[LOAD]] from [[READ]] : $Foo<Elements>, $*Foo<Elements>
+// CHECK: destroy_value [[LOAD]]
 // CHECK: destroy_value %0 : $Elements.Index
-// CHECK: return %14 : $Optional<Elements.Element>
+// CHECK: return %15 : $Optional<Elements.Element>
 // CHECK-LABEL: } // end sil function '_T020opaque_values_silgen21s490_______loadBorrowyyF3FooL_V3foo7ElementQzSg5IndexQz3pos_tF'
 
 func s490_______loadBorrow() {