[ObjC] Use empty Objective-C collection literal constants when

available.

Original patch by Douglas Gregor with minor modifications.

This recommits r300389, which broke bots because there have been API
changes since the original patch was written.

rdar://problem/20689633

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@300396 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/clang/Basic/ObjCRuntime.h b/include/clang/Basic/ObjCRuntime.h
index 78fc899882456d70d6d23b742e2b0148654c2227..8dc259c7ab66f8d58b71e15f3c9d14cbf54c3241 100644 (file)
--- a/include/clang/Basic/ObjCRuntime.h
+++ b/include/clang/Basic/ObjCRuntime.h
@@ -326,6 +326,20 @@ public:
     }
   }
 
+  /// Are the empty collection symbols available?
+  bool hasEmptyCollections() const {
+    switch (getKind()) {
+    default:
+      return false;
+    case MacOSX:
+      return getVersion() >= VersionTuple(10, 11);
+    case iOS:
+      return getVersion() >= VersionTuple(9);
+    case WatchOS:
+      return getVersion() >= VersionTuple(2);
+    }
+  }
+
   /// \brief Try to parse an Objective-C runtime specification from the given
   /// string.
   ///

diff --git a/lib/CodeGen/CGObjC.cpp b/lib/CodeGen/CGObjC.cpp
index c011ab4dfc9799e53cc59513892b26e8a83f0d61..3a09a15dbc1522d7a0c80b249e54b6d1f676b89e 100644 (file)
--- a/lib/CodeGen/CGObjC.cpp
+++ b/lib/CodeGen/CGObjC.cpp
@@ -117,10 +117,22 @@ llvm::Value *CodeGenFunction::EmitObjCCollectionLiteral(const Expr *E,
   const ObjCArrayLiteral *ALE = dyn_cast<ObjCArrayLiteral>(E);
   if (!ALE)
     DLE = cast<ObjCDictionaryLiteral>(E);
-  
-  // Compute the type of the array we're initializing.
+
+  // Optimize empty collections by referencing constants, when available.
   uint64_t NumElements = 
     ALE ? ALE->getNumElements() : DLE->getNumElements();
+  if (NumElements == 0 && CGM.getLangOpts().ObjCRuntime.hasEmptyCollections()) {
+    StringRef ConstantName = ALE ? "__NSArray0__" : "__NSDictionary0__";
+    QualType IdTy(CGM.getContext().getObjCIdType());
+    llvm::Constant *Constant =
+        CGM.CreateRuntimeVariable(ConvertType(IdTy), ConstantName);
+    Address Addr(Constant, Context.getTypeAlignInChars(IdTy));
+    LValue LV = MakeAddrLValue(Addr, IdTy);
+    return Builder.CreateBitCast(EmitLoadOfScalar(LV, E->getLocStart()),
+                                 ConvertType(E->getType()));
+  }
+
+  // Compute the type of the array we're initializing.
   llvm::APInt APNumElements(Context.getTypeSize(Context.getSizeType()),
                             NumElements);
   QualType ElementType = Context.getObjCIdType().withConst();

diff --git a/lib/Sema/SemaExprCXX.cpp b/lib/Sema/SemaExprCXX.cpp
index 485d012b6e6ea652a51dba025e297595cc778178..d65570fcef766e9ae19b3e32ee2c8387a32a26e7 100644 (file)
--- a/lib/Sema/SemaExprCXX.cpp
+++ b/lib/Sema/SemaExprCXX.cpp
@@ -5980,9 +5980,21 @@ ExprResult Sema::MaybeBindToTemporary(Expr *E) {
       } else if (ObjCBoxedExpr *BoxedExpr = dyn_cast<ObjCBoxedExpr>(E)) {
         D = BoxedExpr->getBoxingMethod();
       } else if (ObjCArrayLiteral *ArrayLit = dyn_cast<ObjCArrayLiteral>(E)) {
+        // Don't do reclaims if we're using the zero-element array
+        // constant.
+        if (ArrayLit->getNumElements() == 0 &&
+            Context.getLangOpts().ObjCRuntime.hasEmptyCollections())
+          return E;
+
         D = ArrayLit->getArrayWithObjectsMethod();
       } else if (ObjCDictionaryLiteral *DictLit
                                         = dyn_cast<ObjCDictionaryLiteral>(E)) {
+        // Don't do reclaims if we're using the zero-element dictionary
+        // constant.
+        if (DictLit->getNumElements() == 0 &&
+            Context.getLangOpts().ObjCRuntime.hasEmptyCollections())
+          return E;
+
         D = DictLit->getDictWithObjectsMethod();
       }
 

diff --git a/test/CodeGenObjC/empty-collection-literals.m b/test/CodeGenObjC/empty-collection-literals.m
new file mode 100644 (file)
index 0000000..0f9715f
--- /dev/null
+++ b/test/CodeGenObjC/empty-collection-literals.m
@@ -0,0 +1,51 @@
+// RUN: %clang_cc1 -I %S/Inputs -triple x86_64-apple-macosx10.10.0 -fobjc-runtime=macosx-10.10.0 -emit-llvm -fblocks -fobjc-arc -fobjc-runtime-has-weak -o - %s | FileCheck -check-prefix=CHECK-WITHOUT-EMPTY-COLLECTIONS %s
+// RUN: %clang_cc1 -I %S/Inputs -triple x86_64-apple-macosx10.11.0 -fobjc-runtime=macosx-10.11.0 -emit-llvm -fblocks -fobjc-arc -fobjc-runtime-has-weak -o - %s | FileCheck -check-prefix=CHECK-WITH-EMPTY-COLLECTIONS %s
+
+// RUN: %clang_cc1 -I %S/Inputs -triple arm64-apple-ios8.0 -fobjc-runtime=ios-8.0 -emit-llvm -fblocks -fobjc-arc -fobjc-runtime-has-weak -o - %s | FileCheck -check-prefix=CHECK-WITHOUT-EMPTY-COLLECTIONS %s
+// RUN: %clang_cc1 -I %S/Inputs -triple arm64-apple-ios9.0 -fobjc-runtime=ios-9.0 -emit-llvm -fblocks -fobjc-arc -fobjc-runtime-has-weak -o - %s | FileCheck -check-prefix=CHECK-WITH-EMPTY-COLLECTIONS %s
+
+// RUN: %clang_cc1 -I %S/Inputs -triple armv7k-apple-watchos2.0 -fobjc-runtime=watchos-1.0 -emit-llvm -fblocks -fobjc-arc -fobjc-runtime-has-weak -o - %s | FileCheck -check-prefix=CHECK-WITHOUT-EMPTY-COLLECTIONS %s
+// RUN: %clang_cc1 -I %S/Inputs -triple armv7k-apple-watchos2.0 -fobjc-runtime=watchos-2.0 -emit-llvm -fblocks -fobjc-arc -fobjc-runtime-has-weak -o - %s | FileCheck -check-prefix=CHECK-WITH-EMPTY-COLLECTIONS %s
+
+// RUN: %clang_cc1 -I %S/Inputs -triple arm64-apple-tvos8.0 -fobjc-runtime=ios-8.0 -emit-llvm -fblocks -fobjc-arc -fobjc-runtime-has-weak -o - %s | FileCheck -check-prefix=CHECK-WITHOUT-EMPTY-COLLECTIONS %s
+// RUN: %clang_cc1 -I %S/Inputs -triple arm64-apple-tvos9.0 -fobjc-runtime=ios-9.0 -emit-llvm -fblocks -fobjc-arc -fobjc-runtime-has-weak -o - %s | FileCheck -check-prefix=CHECK-WITH-EMPTY-COLLECTIONS %s
+
+#include "literal-support.h"
+
+void test_empty_array() {
+  // CHECK-WITHOUT-EMPTY-COLLECTIONS-LABEL: define void @test_empty_array
+  // CHECK-WITHOUT-EMPTY-COLLECTIONS-NOT: ret void
+  // CHECK-WITHOUT-EMPTY-COLLECTIONS: {{call.*objc_msgSend}}
+  // CHECK-WITHOUT-EMPTY-COLLECTIONS-NOT: ret void
+  // CHECK-WITHOUT-EMPTY-COLLECTIONS: {{call.*objc_retainAutoreleasedReturnValue}}
+  // CHECK-WITHOUT-EMPTY-COLLECTIONS: ret void
+
+  // CHECK-WITH-EMPTY-COLLECTIONS-LABEL: define void @test_empty_array
+  // CHECK-WITH-EMPTY-COLLECTIONS-NOT: ret void
+  // CHECK-WITH-EMPTY-COLLECTIONS: load {{.*}} @__NSArray0__
+  // CHECK-WITH-EMPTY-COLLECTIONS-NOT: ret void
+  // CHECK-WITH-EMPTY-COLLECTIONS: {{call.*objc_retain\(}}
+  // CHECK-WITH-EMPTY-COLLECTIONS-NOT: ret void
+  // CHECK-WITH-EMPTY-COLLECTIONS: call void @objc_storeStrong
+  // CHECK-WITH-EMPTY-COLLECTIONS-NEXT: ret void
+  NSArray *arr = @[];
+}
+
+void test_empty_dictionary() {
+  // CHECK-WITHOUT-EMPTY-COLLECTIONS-LABEL: define void @test_empty_dictionary
+  // CHECK-WITHOUT-EMPTY-COLLECTIONS-NOT: ret void
+  // CHECK-WITHOUT-EMPTY-COLLECTIONS: {{call.*objc_msgSend}}
+  // CHECK-WITHOUT-EMPTY-COLLECTIONS-NOT: ret void
+  // CHECK-WITHOUT-EMPTY-COLLECTIONS: {{call.*objc_retainAutoreleasedReturnValue}}
+  // CHECK-WITHOUT-EMPTY-COLLECTIONS: ret void
+
+  // CHECK-WITH-EMPTY-COLLECTIONS-LABEL: define void @test_empty_dictionary
+  // CHECK-WITH-EMPTY-COLLECTIONS-NOT: ret void
+  // CHECK-WITH-EMPTY-COLLECTIONS: load {{.*}} @__NSDictionary0__
+  // CHECK-WITH-EMPTY-COLLECTIONS-NOT: ret void
+  // CHECK-WITH-EMPTY-COLLECTIONS: {{call.*objc_retain\(}}
+  // CHECK-WITH-EMPTY-COLLECTIONS-NOT: ret void
+  // CHECK-WITH-EMPTY-COLLECTIONS: call void @objc_storeStrong
+  // CHECK-WITH-EMPTY-COLLECTIONS-NEXT: ret void
+  NSDictionary *dict = @{};
+}