ahatanak created this revision.
ahatanak added a reviewer: rjmccall.
Herald added a subscriber: dexonsmith.
Copying or disposing of a non-escaping block can be a no-op. A non-escaping
block on the stack doesn't have to be copied to the heap as we know it won't be
called after its lifetime ends.
rdar://problem/39352313
Repository:
rC Clang
https://reviews.llvm.org/D49303
Files:
docs/Block-ABI-Apple.rst
lib/CodeGen/CGBlocks.cpp
lib/CodeGen/CGBlocks.h
test/CodeGenObjC/noescape.m
Index: test/CodeGenObjC/noescape.m
===================================================================
--- test/CodeGenObjC/noescape.m
+++ test/CodeGenObjC/noescape.m
@@ -12,6 +12,12 @@
void noescapeFunc2(__attribute__((noescape)) id);
void noescapeFunc3(__attribute__((noescape)) union U);
+// Block descriptors of non-escaping blocks don't need pointers to copy/dispose
+// helper functions.
+
+// CHECK: %[[STRUCT_BLOCK_DESCRIPTOR:.*]] = type { i64, i64 }
+// CHECK: @[[BLOCK_DESCIPTOR_TMP_2:.*]] = internal constant { i64, i64, i8*, i64 } { i64 0, i64 40, i8* getelementptr inbounds ([6 x i8], [6 x i8]* @{{.*}}, i32 0, i32 0), i64 256 }, align 8
+
// CHECK-LABEL: define void @test0(
// CHECK: call void @noescapeFunc0({{.*}}, {{.*}} nocapture {{.*}})
// CHECK: declare void @noescapeFunc0(i8*, {{.*}} nocapture)
@@ -69,3 +75,26 @@
^(int *__attribute__((noescape)) p0){}(p);
b(p);
}
+
+// If the block is non-escaping, set the BLOCK_IS_NOESCAPE and BLOCK_IS_GLOBAL
+// bits of field 'flags' and set the 'isa' field to 'NSConcreteGlobalBlock'.
+
+// CHECK-LABEL: define void @test6(
+// CHECK: %[[BLOCK:.*]] = alloca <{ i8*, i32, i32, i8*, %[[STRUCT_BLOCK_DESCRIPTOR]]*, i8* }>, align 8
+// CHECK: %[[BLOCK_ISA:.*]] = getelementptr inbounds <{ i8*, i32, i32, i8*, %[[STRUCT_BLOCK_DESCRIPTOR]]*, i8* }>, <{ i8*, i32, i32, i8*, %[[STRUCT_BLOCK_DESCRIPTOR]]*, i8* }>* %[[BLOCK]], i32 0, i32 0
+// CHECK: store i8* bitcast (i8** @_NSConcreteGlobalBlock to i8*), i8** %[[BLOCK_ISA]], align 8
+// CHECK: %[[BLOCK_FLAGS:.*]] = getelementptr inbounds <{ i8*, i32, i32, i8*, %[[STRUCT_BLOCK_DESCRIPTOR]]*, i8* }>, <{ i8*, i32, i32, i8*, %[[STRUCT_BLOCK_DESCRIPTOR]]*, i8* }>* %[[BLOCK]], i32 0, i32 1
+// CHECK: store i32 -796917760, i32* %[[BLOCK_FLAGS]], align 8
+// CHECK: %[[BLOCK_DESCRIPTOR:.*]] = getelementptr inbounds <{ i8*, i32, i32, i8*, %[[STRUCT_BLOCK_DESCRIPTOR]]*, i8* }>, <{ i8*, i32, i32, i8*, %[[STRUCT_BLOCK_DESCRIPTOR]]*, i8* }>* %[[BLOCK]], i32 0, i32 4
+// CHECK: store %[[STRUCT_BLOCK_DESCRIPTOR]]* bitcast ({ i64, i64, i8*, i64 }* @[[BLOCK_DESCIPTOR_TMP_2]] to %[[STRUCT_BLOCK_DESCRIPTOR]]*), %[[STRUCT_BLOCK_DESCRIPTOR]]** %[[BLOCK_DESCRIPTOR]], align 8
+
+// Non-escaping blocks don't need copy/dispose helper functions.
+
+// CHECK-NOT: define internal void @__copy_helper_block_
+// CHECK-NOT: define internal void @__destroy_helper_block_
+
+void func(id);
+
+void test6(id a, id b) {
+ noescapeFunc0(a, ^{ func(b); });
+}
Index: lib/CodeGen/CGBlocks.h
===================================================================
--- lib/CodeGen/CGBlocks.h
+++ lib/CodeGen/CGBlocks.h
@@ -54,6 +54,7 @@
};
enum BlockLiteralFlags {
+ BLOCK_IS_NOESCAPE = (1 << 23),
BLOCK_HAS_COPY_DISPOSE = (1 << 25),
BLOCK_HAS_CXX_OBJ = (1 << 26),
BLOCK_IS_GLOBAL = (1 << 28),
Index: lib/CodeGen/CGBlocks.cpp
===================================================================
--- lib/CodeGen/CGBlocks.cpp
+++ lib/CodeGen/CGBlocks.cpp
@@ -159,6 +159,7 @@
/// These are the flags (with corresponding bit number) that the
/// compiler is actually supposed to know about.
+ /// 23. BLOCK_IS_NOESCAPE - indicates that the block is non-escaping
/// 25. BLOCK_HAS_COPY_DISPOSE - indicates that the block
/// descriptor provides copy and dispose helper functions
/// 26. BLOCK_HAS_CXX_OBJ - indicates that there's a captured
@@ -496,6 +497,9 @@
BlockLayoutChunk(align, size, lifetime, &CI, llvmType, VT));
}
+ if (info.getBlockDecl()->doesNotEscape())
+ info.NeedsCopyDispose = false;
+
// If that was everything, we're done here.
if (layout.empty()) {
info.StructureType =
@@ -778,8 +782,14 @@
llvm::Constant *descriptor;
BlockFlags flags;
if (!IsOpenCL) {
- isa = llvm::ConstantExpr::getBitCast(CGM.getNSConcreteStackBlock(),
- VoidPtrTy);
+ // If the block is non-escaping, set field 'isa 'to NSConcreteGlobalBlock
+ // and set the BLOCK_IS_GLOBAL bit of field 'flags' so that copying and
+ // disposing of blocks become no-ops.
+
+ llvm::Constant *blockISA = blockInfo.getBlockDecl()->doesNotEscape()
+ ? CGM.getNSConcreteGlobalBlock()
+ : CGM.getNSConcreteStackBlock();
+ isa = llvm::ConstantExpr::getBitCast(blockISA, VoidPtrTy);
// Build the block descriptor.
descriptor = buildBlockDescriptor(CGM, blockInfo);
@@ -794,6 +804,8 @@
flags |= BLOCK_HAS_CXX_OBJ;
if (blockInfo.UsesStret)
flags |= BLOCK_USE_STRET;
+ if (blockInfo.getBlockDecl()->doesNotEscape())
+ flags |= BLOCK_IS_NOESCAPE | BLOCK_IS_GLOBAL;
}
auto projectField =
Index: docs/Block-ABI-Apple.rst
===================================================================
--- docs/Block-ABI-Apple.rst
+++ docs/Block-ABI-Apple.rst
@@ -61,6 +61,7 @@
.. code-block:: c
enum {
+ BLOCK_IS_NOESCAPE = (1 << 23),
BLOCK_HAS_COPY_DISPOSE = (1 << 25),
BLOCK_HAS_CTOR = (1 << 26), // helpers have C++ code
BLOCK_IS_GLOBAL = (1 << 28),
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