Avoid needlessly copying a block to the heap when a block literal

initializes a local auto variable or is assigned to a local auto
variable that is declared in the scope that introduced the block
literal.

rdar://problem/13289333

https://reviews.llvm.org/D58514

llvm-svn: 355012

1 files changed, 18 insertions, 1 deletions

diff --git a/clang/lib/CodeGen/CGObjC.cpp b/clang/lib/CodeGen/CGObjC.cpp
index fba1a531a2a..7063517efc3 100644
--- a/clang/lib/CodeGen/CGObjC.cpp
+++ b/clang/lib/CodeGen/CGObjC.cpp
@@ -2871,6 +2871,7 @@ public:
   Result visit(const Expr *e);
   Result visitCastExpr(const CastExpr *e);
   Result visitPseudoObjectExpr(const PseudoObjectExpr *e);
+  Result visitBlockExpr(const BlockExpr *e);
   Result visitBinaryOperator(const BinaryOperator *e);
   Result visitBinAssign(const BinaryOperator *e);
   Result visitBinAssignUnsafeUnretained(const BinaryOperator *e);
@@ -2947,6 +2948,12 @@ ARCExprEmitter<Impl,Result>::visitPseudoObjectExpr(const PseudoObjectExpr *E) {
 }
 
 template <typename Impl, typename Result>
+Result ARCExprEmitter<Impl, Result>::visitBlockExpr(const BlockExpr *e) {
+  // The default implementation just forwards the expression to visitExpr.
+  return asImpl().visitExpr(e);
+}
+
+template <typename Impl, typename Result>
 Result ARCExprEmitter<Impl,Result>::visitCastExpr(const CastExpr *e) {
   switch (e->getCastKind()) {
 
@@ -3089,7 +3096,8 @@ Result ARCExprEmitter<Impl,Result>::visit(const Expr *e) {
   // Look through pseudo-object expressions.
   } else if (const PseudoObjectExpr *pseudo = dyn_cast<PseudoObjectExpr>(e)) {
     return asImpl().visitPseudoObjectExpr(pseudo);
-  }
+  } else if (auto *be = dyn_cast<BlockExpr>(e))
+    return asImpl().visitBlockExpr(be);
 
   return asImpl().visitExpr(e);
 }
@@ -3124,6 +3132,15 @@ struct ARCRetainExprEmitter :
     return TryEmitResult(result, true);
   }
 
+  TryEmitResult visitBlockExpr(const BlockExpr *e) {
+    TryEmitResult result = visitExpr(e);
+    // Avoid the block-retain if this is a block literal that doesn't need to be
+    // copied to the heap.
+    if (e->getBlockDecl()->canAvoidCopyToHeap())
+      result.setInt(true);
+    return result;
+  }
+
   /// Block extends are net +0.  Naively, we could just recurse on
   /// the subexpression, but actually we need to ensure that the
   /// value is copied as a block, so there's a little filter here.