commit ba0367a70862eb820c77501e750d7e30b8cdb52a
author Akira Hatanaka <ahatanaka@apple.com> Fri Sep 22 21:32:06 2017 +0000
committer Akira Hatanaka <ahatanaka@apple.com> Fri Sep 22 21:32:06 2017 +0000
tree 059db4394cf42d77109c409ef21f9903ab13d458
parent a423c738b1e20374b9c2da405e6be1cfeaa2ca31

[CodeGen][ObjC] Build the global block structure before emitting the
body of global block invoke functions.

This commit fixes an infinite loop in IRGen that occurs when compiling
the following code:

void FUNC2() {
  static void (^const block1)(int) = ^(int a){
    if (a--)
      block1(a);
  };
}

This is how IRGen gets stuck in the infinite loop:

1. GenerateBlockFunction is called to emit the body of "block1".

2. GetAddrOfGlobalBlock is called to get the address of "block1". The
   function calls getAddrOfGlobalBlockIfEmitted to check whether the
   global block has been emitted. If it hasn't been emitted, it then
   tries to emit the body of the block function by calling
   GenerateBlockFunction, which goes back to step 1.

This commit prevents the inifinite loop by building the global block in
GenerateBlockFunction before emitting the body of the block function.

rdar://problem/34541684

Differential Revision: https://reviews.llvm.org/D38118

llvm-svn: 314029

clang/lib/CodeGen/CGBlocks.cpp

diff --git a/clang/lib/CodeGen/CGBlocks.cpp b/clang/lib/CodeGen/CGBlocks.cpp
index 8d82898..6cf7f71 100644
--- a/clang/lib/CodeGen/CGBlocks.cpp
+++ b/clang/lib/CodeGen/CGBlocks.cpp
@@ -725,12 +725,13 @@
   llvm::Constant *blockFn
     = CodeGenFunction(CGM, true).GenerateBlockFunction(CurGD, blockInfo,
                                                        LocalDeclMap,
-                                                       isLambdaConv);
+                                                       isLambdaConv,
+                                                       blockInfo.CanBeGlobal);
   blockFn = llvm::ConstantExpr::getBitCast(blockFn, VoidPtrTy);
 
   // If there is nothing to capture, we can emit this as a global block.
   if (blockInfo.CanBeGlobal)
-    return buildGlobalBlock(CGM, blockInfo, blockFn);
+    return CGM.getAddrOfGlobalBlockIfEmitted(blockInfo.BlockExpression);
 
   // Otherwise, we have to emit this as a local block.
 
@@ -1114,17 +1115,14 @@
   computeBlockInfo(*this, nullptr, blockInfo);
 
   // Using that metadata, generate the actual block function.
-  llvm::Constant *blockFn;
   {
     CodeGenFunction::DeclMapTy LocalDeclMap;
-    blockFn = CodeGenFunction(*this).GenerateBlockFunction(GlobalDecl(),
-                                                           blockInfo,
-                                                           LocalDeclMap,
-                                                           false);
+    CodeGenFunction(*this).GenerateBlockFunction(
+        GlobalDecl(), blockInfo, LocalDeclMap,
+        /*IsLambdaConversionToBlock*/ false, /*BuildGlobalBlock*/ true);
   }
-  blockFn = llvm::ConstantExpr::getBitCast(blockFn, VoidPtrTy);
 
-  return buildGlobalBlock(*this, blockInfo, blockFn);
+  return getAddrOfGlobalBlockIfEmitted(BE);
 }
 
 static llvm::Constant *buildGlobalBlock(CodeGenModule &CGM,
@@ -1226,7 +1224,8 @@
 CodeGenFunction::GenerateBlockFunction(GlobalDecl GD,
                                        const CGBlockInfo &blockInfo,
                                        const DeclMapTy &ldm,
-                                       bool IsLambdaConversionToBlock) {
+                                       bool IsLambdaConversionToBlock,
+                                       bool BuildGlobalBlock) {
   const BlockDecl *blockDecl = blockInfo.getBlockDecl();
 
   CurGD = GD;
@@ -1285,6 +1284,10 @@
       fnLLVMType, llvm::GlobalValue::InternalLinkage, name, &CGM.getModule());
   CGM.SetInternalFunctionAttributes(blockDecl, fn, fnInfo);
 
+  if (BuildGlobalBlock)
+    buildGlobalBlock(CGM, blockInfo,
+                     llvm::ConstantExpr::getBitCast(fn, VoidPtrTy));
+
   // Begin generating the function.
   StartFunction(blockDecl, fnType->getReturnType(), fn, fnInfo, args,
                 blockDecl->getLocation(),