[4.2] IRGen: Fix type of a global with tail allocated storage

Cast the result to the expected type rather than a special
'..._tailelemsN' type.

Scope: Usage of a global array if involved in a phi node (control-flow)
could cause a compiler assert.
Risk: Low.
Testing: Swift CI
Reviewed: Erik Eckstein

rdar://44563038

Author: aschwaighofer

lib/IRGen/GenDecl.cpp

@@ -2118,6 +2118,7 @@ Address IRGenModule::getAddrOfSILGlobalVariable(SILGlobalVariable *var,
   ResilienceExpansion expansion = getResilienceExpansionForLayout(var);
 
   llvm::Type *storageType;
+  llvm::Type *castStorageToType = nullptr;
   Size fixedSize;
   Alignment fixedAlignment;
   bool inFixedBuffer = false;
@@ -2147,6 +2148,7 @@ Address IRGenModule::getAddrOfSILGlobalVariable(SILGlobalVariable *var,
     storageType = Layout->getType();
     fixedSize = Layout->getSize();
     fixedAlignment = Layout->getAlignment();
+    castStorageToType = cast<FixedTypeInfo>(ti).getStorageType();
     assert(fixedAlignment >= TargetInfo.HeapObjectAlignment);
   } else if (isREPLVar || ti.isFixedSize(expansion)) {
     // Allocate static storage.
@@ -2242,7 +2244,9 @@ Address IRGenModule::getAddrOfSILGlobalVariable(SILGlobalVariable *var,
     // to a reference to it).
     addr = llvm::ConstantExpr::getGetElementPtr(nullptr, gvar, Indices);
   }
-  addr = llvm::ConstantExpr::getBitCast(addr, storageType->getPointerTo());
+  addr = llvm::ConstantExpr::getBitCast(
+      addr,
+      castStorageToType ? castStorageToType : storageType->getPointerTo());
   return Address(addr, Alignment(gvar->getAlignment()));
 }
 

test/IRGen/static_initializer.sil

@@ -152,11 +152,31 @@ bb0:
   // CHECK: [[TMP:%.*]] = call swiftcc %swift.metadata_response @"$S18static_initializer16TestArrayStorageCMa"(i64 0)
   // CHECK: [[MD:%[0-9]+]] = extractvalue %swift.metadata_response [[TMP]], 0
   // CHECK: [[O:%[0-9a-z]+]] = call %swift.refcounted* @swift_initStaticObject(%swift.type* [[MD]], %swift.refcounted* getelementptr inbounds (%T18static_initializer16TestArrayStorageC_tailelems0c, %T18static_initializer16TestArrayStorageC_tailelems0c* @static_array, i32 0, i32 1, i32 0))
-  // CHECK: [[R:%[0-9]+]] = bitcast %swift.refcounted* [[O]] to %T18static_initializer16TestArrayStorageC_tailelems0*
-  // CHECK: [[R2:%[0-9]+]] = bitcast %T18static_initializer16TestArrayStorageC_tailelems0* [[R]] to %T18static_initializer16TestArrayStorageC*
-  // CHECK: ret %T18static_initializer16TestArrayStorageC* [[R2]]
+  // CHECK: [[R:%[0-9]+]] = bitcast %swift.refcounted* [[O]] to %T18static_initializer16TestArrayStorageC*
+  // CHECK: ret %T18static_initializer16TestArrayStorageC* [[R]]
   %0 = global_value @static_array : $TestArrayStorage
   %1 = struct $TestArray (%0 : $TestArrayStorage)
   return %1 : $TestArray
 }
 
+// CHECK-LABEL: define{{( dllexport)?}}{{( protected)?}} swiftcc %T18static_initializer16TestArrayStorageC* @phi_nodes(i1, %T18static_initializer16TestArrayStorageC*)
+// CHECK: [[T0:%.*]] = call %swift.refcounted* @swift_initStaticObject
+// CHECK: [[T1:%.*]] = bitcast %swift.refcounted* [[T0]] to %T18static_initializer16TestArrayStorageC*
+// CHECK: br
+// CHECK: br
+// CHECK: [[T3:%.*]] = phi %T18static_initializer16TestArrayStorageC* [ %1, {{.*}} ], [ [[T1]], {{.*}} ]
+// CHECK: ret %T18static_initializer16TestArrayStorageC* [[T3]]
+sil @phi_nodes : $@convention(thin) (Builtin.Int1, TestArrayStorage) -> TestArrayStorage {
+bb0(%0 : $Builtin.Int1, %1 : $TestArrayStorage):
+ cond_br %0, bb1, bb2
+
+bb1:
+  %2 = global_value @static_array : $TestArrayStorage
+  br bb3(%2 : $TestArrayStorage)
+
+bb2:
+  br bb3(%1 : $TestArrayStorage)
+
+bb3(%3 : $TestArrayStorage):
+  return %3 : $TestArrayStorage
+}