[CodeGen][ObjC] Don't retain captured Objective-C pointers at block

creation that are const-qualified.

When a block captures an ObjC object pointer, clang retains the pointer
to prevent prematurely destroying the object the pointer points to
before the block is called or copied.

When the captured object pointer is const-qualified, we can avoid
emitting the retain/release pair since the pointer variable cannot be
modified in the scope in which the block literal is introduced.

For example:

void test(const id x) {
    callee(^{ (void)x; });
}

This patch implements that optimization.

rdar://problem/28894510

Differential Revision: https://reviews.llvm.org/D32601

llvm-svn: 301667

2 files changed, 37 insertions, 18 deletions

diff --git a/clang/test/CodeGenObjC/arc-blocks.m b/clang/test/CodeGenObjC/arc-blocks.m
index 4bb618c3a41..69cd7bb297b 100644
--- a/clang/test/CodeGenObjC/arc-blocks.m
+++ b/clang/test/CodeGenObjC/arc-blocks.m
@@ -298,15 +298,11 @@ void test7(void) {
 // CHECK:      [[D0:%.*]] = getelementptr inbounds [[BLOCK_T]], [[BLOCK_T]]* [[BLOCK]], i32 0, i32 5
 // CHECK:      [[T0:%.*]] = getelementptr inbounds [[BLOCK_T]], [[BLOCK_T]]* [[BLOCK]], i32 0, i32 5
 // CHECK-NEXT: [[T1:%.*]] = load [[TEST8]]*, [[TEST8]]** [[SELF]],
-// CHECK-NEXT: [[T2:%.*]] = bitcast [[TEST8]]* [[T1]] to i8*
-// CHECK-NEXT: [[T3:%.*]] = call i8* @objc_retain(i8* [[T2]])
-// CHECK-NEXT: [[T4:%.*]] = bitcast i8* [[T3]] to [[TEST8]]*
-// CHECK-NEXT: store [[TEST8]]* [[T4]], [[TEST8]]** [[T0]]
+// CHECK-NEXT: store %0* [[T1]], %0** [[T0]]
 // CHECK-NEXT: bitcast [[BLOCK_T]]* [[BLOCK]] to
 // CHECK: call void @test8_helper(
-// CHECK-NEXT: [[T1:%.*]] = load [[TEST8]]*, [[TEST8]]** [[D0]]
-// CHECK-NEXT: [[T2:%.*]] = bitcast [[TEST8]]* [[T1]] to i8*
-// CHECK-NEXT: call void @objc_release(i8* [[T2]])
+// CHECK-NEXT: [[T2:%.*]] = load [[TEST8]]*, [[TEST8]]** [[D0]]
+// CHECK-NEXT: call void (...) @clang.arc.use([[TEST8]]* [[T2]])
 // CHECK: ret void
 
   extern void test8_helper(void (^)(void));
@@ -741,5 +737,31 @@ void test19(void (^b)(void)) {
 // CHECK-NEXT: ret void
 }
 
+// CHECK-LABEL: define void @test20(
+// CHECK: [[XADDR:%.*]] = alloca i8*
+// CHECK-NEXT: [[BLOCK:%.*]] = alloca <[[BLOCKTY:.*]]>
+// CHECK-NEXT: [[RETAINEDX:%.*]] = call i8* @objc_retain(i8* %{{.*}})
+// CHECK-NEXT: store i8* [[RETAINEDX]], i8** [[XADDR]]
+// CHECK-NEXT: [[CAPTUREFIELD:%.*]] = getelementptr inbounds <[[BLOCKTY]]>, <[[BLOCKTY]]>* [[BLOCK]], i32 0, i32 5
+// CHECK: [[BLOCKCAPTURED:%.*]] = getelementptr inbounds <[[BLOCKTY]]>, <[[BLOCKTY]]>* [[BLOCK]], i32 0, i32 5
+// CHECK: [[CAPTURED:%.*]] = load i8*, i8** [[XADDR]]
+// CHECK: store i8* [[CAPTURED]], i8** [[BLOCKCAPTURED]]
+// CHECK: [[CAPTURE:%.*]] = load i8*, i8** [[CAPTUREFIELD]]
+// CHECK-NEXT: call void (...) @clang.arc.use(i8* [[CAPTURE]])
+// CHECK-NEXT: [[X:%.*]] = load i8*, i8** [[XADDR]]
+// CHECK-NEXT: call void @objc_release(i8* [[X]])
+// CHECK-NEXT: ret void
+
+// CHECK-LABEL: define internal void @__copy_helper_block
+// CHECK: [[BLOCKSOURCE:%.*]] = bitcast i8* %{{.*}} to <[[BLOCKTY]]>*
+// CHECK: [[CAPTUREFIELD:%.*]] = getelementptr inbounds <[[BLOCKTY]]>, <[[BLOCKTY]]>* [[BLOCKSOURCE]], i32 0, i32 5
+// CHECK: [[BLOCKCOPYSRC:%.*]] = load i8*, i8** [[CAPTUREFIELD]]
+// CHECK: call i8* @objc_retain(i8* [[BLOCKCOPYSRC]])
+
+void test20_callee(void (^)());
+void test20(const id x) {
+  test20_callee(^{ (void)x; });
+}
+
 // CHECK: attributes [[NUW]] = { nounwind }
 // CHECK-UNOPT: attributes [[NUW]] = { nounwind }
diff --git a/clang/test/CodeGenObjC/arc-foreach.m b/clang/test/CodeGenObjC/arc-foreach.m
index db150e88a59..e34445704e3 100644
--- a/clang/test/CodeGenObjC/arc-foreach.m
+++ b/clang/test/CodeGenObjC/arc-foreach.m
@@ -63,11 +63,11 @@ void test0(NSArray *array) {
 // CHECK-LP64:      [[D0:%.*]] = getelementptr inbounds [[BLOCK_T]], [[BLOCK_T]]* [[BLOCK]], i32 0, i32 5
 // CHECK-LP64:      [[T0:%.*]] = getelementptr inbounds [[BLOCK_T]], [[BLOCK_T]]* [[BLOCK]], i32 0, i32 5
 // CHECK-LP64-NEXT: [[T1:%.*]] = load i8*, i8** [[X]]
-// CHECK-LP64-NEXT: [[T2:%.*]] = call i8* @objc_retain(i8* [[T1]])
-// CHECK-LP64-NEXT: store i8* [[T2]], i8** [[T0]]
-// CHECK-LP64-NEXT: [[T1:%.*]] = bitcast [[BLOCK_T]]* [[BLOCK]] 
-// CHECK-LP64: call void @use_block(
-// CHECK-LP64-NEXT: call void @objc_storeStrong(i8** [[D0]], i8* null)
+// CHECK-LP64-NEXT: store i8* [[T1]], i8** [[T0]]
+// CHECK-LP64-NEXT: [[BLOCK1:%.*]] = bitcast [[BLOCK_T]]* [[BLOCK]]
+// CHECK-LP64-NEXT: call void @use_block(void ()* [[BLOCK1]])
+// CHECK-LP64-NEXT: [[CAPTURE:%.*]] = load i8*, i8** [[D0]]
+// CHECK-LP64: call void (...) @clang.arc.use(i8* [[CAPTURE]])
 
 // CHECK-LP64:      [[T0:%.*]] = load i8*, i8** @OBJC_SELECTOR_REFERENCES_
 // CHECK-LP64-NEXT: [[T1:%.*]] = bitcast [[ARRAY_T]]* [[SAVED_ARRAY]] to i8*
@@ -200,13 +200,10 @@ NSArray *array4;
 // CHECK-LP64:         [[T0:%.*]] = getelementptr inbounds <{ i8*, i32, i32, i8*, %struct.__block_descriptor*, [[TY]]* }>, <{ i8*, i32, i32, i8*, %struct.__block_descriptor*, [[TY]]* }>* [[BLOCK]], i32 0, i32 5
 // CHECK-LP64:         [[BC:%.*]] = getelementptr inbounds <{ i8*, i32, i32, i8*, %struct.__block_descriptor*, [[TY]]* }>, <{ i8*, i32, i32, i8*, %struct.__block_descriptor*, [[TY]]* }>* [[BLOCK]], i32 0, i32 5
 // CHECK-LP64:         [[T1:%.*]] = load [[TY]]*, [[TY]]** [[SELF_ADDR]]
-// CHECK-LP64:         [[T2:%.*]] = bitcast [[TY]]* [[T1]] to i8*
-// CHECK-LP64:         [[T3:%.*]] = call i8* @objc_retain(i8* [[T2]])
-// CHECK-LP64:         [[T4:%.*]] = bitcast i8* [[T3]] to [[TY]]*
-// CHECK-LP64:         store [[TY]]* [[T4]], [[TY]]** [[BC]]
+// CHECK-LP64:         store [[TY]]* [[T1]], [[TY]]** [[BC]]
 
-// CHECK-LP64:         [[T5:%.*]] = bitcast [[TY]]** [[T0]] to i8**
-// CHECK-LP64:         call void @objc_storeStrong(i8** [[T5]], i8* null)
+// CHECK-LP64:         [[T5:%.*]] = load [[TY]]*, [[TY]]** [[T0]]
+// CHECK-LP64:         call void (...) @clang.arc.use([[TY]]* [[T5]])
 // CHECK-LP64:         switch i32 {{%.*}}, label %[[UNREACHABLE:.*]] [
 // CHECK-LP64-NEXT:      i32 0, label %[[CLEANUP_CONT:.*]]
 // CHECK-LP64-NEXT:      i32 2, label %[[FORCOLL_END:.*]]