From a3b08d68bd281773b0300222edb4149abce4b4b8 Mon Sep 17 00:00:00 2001
From: Dan Gohman <gohman@apple.com>
Date: Mon, 13 Feb 2012 22:57:02 +0000
Subject: [PATCH] Just like in regular escape analysis, loads and stores
 through (but not of) a block pointer do not cause the block pointer to
 escape. This fixes rdar://10803830.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@150424 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Transforms/Scalar/ObjCARC.cpp            | 10 ++++
 test/Transforms/ObjCARC/retain-block-load.ll | 51 ++++++++++++++++++++
 2 files changed, 61 insertions(+)
 create mode 100644 test/Transforms/ObjCARC/retain-block-load.ll

diff --git a/lib/Transforms/Scalar/ObjCARC.cpp b/lib/Transforms/Scalar/ObjCARC.cpp
index 928440150c2..673e1a4bbb4 100644
--- a/lib/Transforms/Scalar/ObjCARC.cpp
+++ b/lib/Transforms/Scalar/ObjCARC.cpp
@@ -618,11 +618,21 @@ static bool DoesObjCBlockEscape(const Value *BlockPtr) {
       // to be an escape.
       if (isa<CallInst>(UUser) || isa<InvokeInst>(UUser))
         continue;
+      // Use by an instruction which copies the value is an escape if the
+      // result is an escape.
       if (isa<BitCastInst>(UUser) || isa<GetElementPtrInst>(UUser) ||
           isa<PHINode>(UUser) || isa<SelectInst>(UUser)) {
         Worklist.push_back(UUser);
         continue;
       }
+      // Use by a load is not an escape.
+      if (isa<LoadInst>(UUser))
+        continue;
+      // Use by a store is not an escape if the use is the address.
+      if (const StoreInst *SI = dyn_cast<StoreInst>(UUser))
+        if (V != SI->getValueOperand())
+          continue;
+      // Otherwise, conservatively assume an escape.
       return true;
     }
   } while (!Worklist.empty());
diff --git a/test/Transforms/ObjCARC/retain-block-load.ll b/test/Transforms/ObjCARC/retain-block-load.ll
new file mode 100644
index 00000000000..a5170e32365
--- /dev/null
+++ b/test/Transforms/ObjCARC/retain-block-load.ll
@@ -0,0 +1,51 @@
+; RUN: opt -objc-arc -S < %s | FileCheck %s
+
+; rdar://10803830
+; The optimizer should be able to prove that the block does not
+; "escape", so the retainBlock+release pair can be eliminated.
+
+target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
+
+%struct.__block_descriptor = type { i64, i64 }
+
+@_NSConcreteStackBlock = external global i8*
+@__block_descriptor_tmp = external global { i64, i64, i8*, i8* }
+
+; CHECK: define void @test() {
+; CHECK-NOT: @objc
+; CHECK: declare i8* @objc_retainBlock(i8*)
+; CHECK: declare void @objc_release(i8*)
+
+define void @test() {
+entry:
+  %block = alloca <{ i8*, i32, i32, i8*, %struct.__block_descriptor*, i32 }>, align 8
+  %block.isa = getelementptr inbounds <{ i8*, i32, i32, i8*, %struct.__block_descriptor*, i32 }>* %block, i64 0, i32 0
+  store i8* bitcast (i8** @_NSConcreteStackBlock to i8*), i8** %block.isa, align 8
+  %block.flags = getelementptr inbounds <{ i8*, i32, i32, i8*, %struct.__block_descriptor*, i32 }>* %block, i64 0, i32 1
+  store i32 1073741824, i32* %block.flags, align 8
+  %block.reserved = getelementptr inbounds <{ i8*, i32, i32, i8*, %struct.__block_descriptor*, i32 }>* %block, i64 0, i32 2
+  store i32 0, i32* %block.reserved, align 4
+  %block.invoke = getelementptr inbounds <{ i8*, i32, i32, i8*, %struct.__block_descriptor*, i32 }>* %block, i64 0, i32 3
+  store i8* bitcast (i32 (i8*)* @__test_block_invoke_0 to i8*), i8** %block.invoke, align 8
+  %block.descriptor = getelementptr inbounds <{ i8*, i32, i32, i8*, %struct.__block_descriptor*, i32 }>* %block, i64 0, i32 4
+  store %struct.__block_descriptor* bitcast ({ i64, i64, i8*, i8* }* @__block_descriptor_tmp to %struct.__block_descriptor*), %struct.__block_descriptor** %block.descriptor, align 8
+  %block.captured = getelementptr inbounds <{ i8*, i32, i32, i8*, %struct.__block_descriptor*, i32 }>* %block, i64 0, i32 5
+  store i32 4, i32* %block.captured, align 8
+  %tmp = bitcast <{ i8*, i32, i32, i8*, %struct.__block_descriptor*, i32 }>* %block to i8*
+  %tmp1 = call i8* @objc_retainBlock(i8* %tmp) nounwind, !clang.arc.copy_on_escape !0
+  %tmp2 = getelementptr inbounds i8* %tmp1, i64 16
+  %tmp3 = bitcast i8* %tmp2 to i8**
+  %tmp4 = load i8** %tmp3, align 8
+  %tmp5 = bitcast i8* %tmp4 to i32 (i8*)*
+  %call = call i32 %tmp5(i8* %tmp1)
+  call void @objc_release(i8* %tmp1) nounwind, !clang.imprecise_release !0
+  ret void
+}
+
+declare i32 @__test_block_invoke_0(i8* nocapture %.block_descriptor) nounwind readonly
+
+declare i8* @objc_retainBlock(i8*)
+
+declare void @objc_release(i8*)
+
+!0 = metadata !{}