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: 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 ++++++++++
 1 file changed, 10 insertions(+)

(limited to 'lib/Transforms')

diff --git a/lib/Transforms/Scalar/ObjCARC.cpp b/lib/Transforms/Scalar/ObjCARC.cpp
index 9284401..673e1a4 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());
-- 
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