[Beignet] [PATCH] GBE: Fixed one bug in scalarize pass

[Yang, Rong R]

Yes, the second loop check is insufficiency, LGTM. Thanks.

-----Original Message-----
From: beignet-bounces+rong.r.yang=intel.com at lists.freedesktop.org [mailto:beignet-bounces+rong.r.yang=intel.com at lists.freedesktop.org] On Behalf Of Zhigang Gong
Sent: Wednesday, June 19, 2013 6:37 PM
To: beignet at lists.freedesktop.org
Cc: Zhigang Gong
Subject: [Beignet] [PATCH] GBE: Fixed one bug in scalarize pass

I met segfault at void Scalarize::dce() randomly when I integrate a openCL kernel to the chromium's GPU process. After discuss with Yang Rong, I found one bug in this function. As it use two loops to erase the dead instructions, but it doesn't set the pointer to NULL at the first loop when it already erased the instruction. Thus at the second loop, when it call (*i)->getParent, the (*i) may already be deleted then it may refer a freed region and may cause segfault.

Signed-off-by: Zhigang Gong <zhigang.gong at linux.intel.com>
---
 backend/src/llvm/llvm_scalarize.cpp | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/backend/src/llvm/llvm_scalarize.cpp b/backend/src/llvm/llvm_scalarize.cpp
index 3c0d6a4..bab2236 100644
--- a/backend/src/llvm/llvm_scalarize.cpp
+++ b/backend/src/llvm/llvm_scalarize.cpp
@@ -825,11 +825,13 @@ namespace gbe {
     //two passes delete for some phinode
     for (std::vector<Instruction*>::reverse_iterator i = deadList.rbegin(), e = deadList.rend(); i != e; ++i) {
       (*i)->dropAllReferences();
-      if((*i)->use_empty())
+      if((*i)->use_empty()) {
         (*i)->eraseFromParent();
+        (*i) = NULL;
+      }
     }
     for (std::vector<Instruction*>::reverse_iterator i = deadList.rbegin(), e = deadList.rend(); i != e; ++i) {
-      if((*i)->getParent())
+      if((*i) && (*i)->getParent())
         (*i)->eraseFromParent();
     }
     deadList.clear();
--
1.7.11.7

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