Fetch associated types abstractly when fetching an associated conformance.

By default, emitTypeMetadataRef does a blocking request for complete
metadata, which is the right thing to do for most purposes in IRGen.
Unfortunately, it's actively dangerous in code that can be called
during metadata completion, like an associated conformance accessor,
because it can cause artificial dependency cycles that the runtime
isn't equipped to detect, much less solve.

This is a partial fix for rdar://69901318, which also exposes a bad
metadata access path that seems to be causing an artificial problem.

Author: rjmccall

lib/IRGen/GenProto.cpp

@@ -2567,8 +2567,10 @@ MetadataResponse MetadataPath::followComponent(IRGenFunction &IGF,
 
     if (!source) return MetadataResponse();
 
-    auto sourceMetadata = IGF.emitTypeMetadataRef(sourceType);
-    auto associatedMetadata = IGF.emitTypeMetadataRef(sourceKey.Type);
+    auto sourceMetadata =
+      IGF.emitAbstractTypeMetadataRef(sourceType);
+    auto associatedMetadata =
+      IGF.emitAbstractTypeMetadataRef(sourceKey.Type);
     auto sourceWTable = source.getMetadata();
 
     AssociatedConformance associatedConformanceRef(sourceProtocol,

test/IRGen/associated_types.swift

@@ -75,8 +75,9 @@ func testFastRuncible<T: Runcible, U: FastRuncible>(_ t: T, u: U)
 //   1. Get the type metadata for U.RuncerType.Runcee.
 //     1a. Get the type metadata for U.RuncerType.
 //         Note that we actually look things up in T, which is going to prove unfortunate.
-// CHECK: [[T2:%.*]] = call swiftcc %swift.metadata_response @swift_getAssociatedTypeWitness([[INT]] 0, i8** %T.Runcible, %swift.type* %T, %swift.protocol_requirement* getelementptr{{.*}}i32 12), i32 -1), %swift.protocol_requirement* getelementptr inbounds (<{{.*}}>, <{{.*}}>* @"$s16associated_types8RuncibleMp", i32 0, i32 14)) [[NOUNWIND_READNONE:#.*]]
+// CHECK: [[T2:%.*]] = call swiftcc %swift.metadata_response @swift_getAssociatedTypeWitness([[INT]] 255, i8** %T.Runcible, %swift.type* %T, %swift.protocol_requirement* getelementptr{{.*}}i32 12), i32 -1), %swift.protocol_requirement* getelementptr inbounds (<{{.*}}>, <{{.*}}>* @"$s16associated_types8RuncibleMp", i32 0, i32 14)) [[NOUNWIND_READNONE:#.*]]
 // CHECK-NEXT: %T.RuncerType = extractvalue %swift.metadata_response [[T2]], 0
+// CHECK-NEXT: extractvalue %swift.metadata_response [[T2]], 1
 //   2. Get the witness table for U.RuncerType.Runcee : Speedy
 //     2a. Get the protocol witness table for U.RuncerType : FastRuncer.
 // CHECK-NEXT: %T.RuncerType.FastRuncer = call swiftcc i8** @swift_getAssociatedConformanceWitness(i8** %U.FastRuncible, %swift.type* %U, %swift.type* %T.RuncerType

test/IRGen/generic_structs.sil

@@ -246,9 +246,6 @@ struct GenericLayoutWithAssocType<T: ParentHasAssociatedType> {
 
 // CHECK-LABEL: define internal swiftcc %swift.metadata_response @"$s15generic_structs26GenericLayoutWithAssocTypeVMr"(
 
-// CHECK: [[T0:%.*]] = call{{( tail)?}} swiftcc %swift.metadata_response @swift_checkMetadataState(i64 0, %swift.type* %T)
-// CHECK: [[T_CHECKED:%.*]] = extractvalue %swift.metadata_response [[T0]], 0
-
 // CHECK: [[T0_GEP:%.*]] = getelementptr inbounds i8*, i8** %T.ParentHasAssociatedType, i32 1
 // CHECK: [[T0:%.*]] = load i8*, i8** [[T0_GEP]]
 // CHECK: [[T1:%.*]] = bitcast i8* [[T0]] to i8**

test/IRGen/generic_structs_future.sil

@@ -247,9 +247,6 @@ struct GenericLayoutWithAssocType<T: ParentHasAssociatedType> {
 
 // CHECK-LABEL: define internal swiftcc %swift.metadata_response @"$s22generic_structs_future26GenericLayoutWithAssocTypeVMr"(
 
-// CHECK: [[T0:%.*]] = call{{( tail)?}} swiftcc %swift.metadata_response @swift_checkMetadataState(i64 0, %swift.type* %T)
-// CHECK: [[T_CHECKED:%.*]] = extractvalue %swift.metadata_response [[T0]], 0
-
 // CHECK: [[T0_GEP:%.*]] = getelementptr inbounds i8*, i8** %T.ParentHasAssociatedType, i32 1
 // CHECK: [[T0:%.*]] = load i8*, i8** [[T0_GEP]]
 // CHECK: [[T1:%.*]] = bitcast i8* [[T0]] to i8**

test/IRGen/same_type_constraints.swift

@@ -67,7 +67,7 @@ where Self : CodingType,
   print(Self.ValueType.self)
 }
 
-// OSIZE: define internal swiftcc i8** @"$s21same_type_constraints12GenericKlazzCyxq_GAA1EAA4Data_AA0F4TypePWT"(%swift.type* %"GenericKlazz<T, R>.Data", %swift.type* nocapture readonly %"GenericKlazz<T, R>", i8** nocapture readnone %"GenericKlazz<T, R>.E") [[ATTRS:#[0-9]+]] {
+// OSIZE: define internal swiftcc i8** @"$s21same_type_constraints12GenericKlazzCyxq_GAA1EAA4Data_AA0F4TypePWT"(%swift.type* readnone %"GenericKlazz<T, R>.Data", %swift.type* nocapture readonly %"GenericKlazz<T, R>", i8** nocapture readnone %"GenericKlazz<T, R>.E") [[ATTRS:#[0-9]+]] {
 // OSIZE: [[ATTRS]] = {{{.*}}noinline
 
 // Check that same-typing two generic parameters together lowers correctly.