[polly] r336350 - [CodeGen] Fix potential null pointer dereference. NFC.

[Michael Kruse via llvm-commits]

Author: meinersbur
Date: Thu Jul  5 06:44:50 2018
New Revision: 336350

URL: http://llvm.org/viewvc/llvm-project?rev=336350&view=rev
Log:
[CodeGen] Fix potential null pointer dereference. NFC.

ScalarEvolution::getSCEV dereferences its argument, s.t. passing nullptr
leads to undefined behaviour.

Check for nullptr before calling it instead of checking its argument
afterwards.

Modified:
    polly/trunk/lib/CodeGen/IRBuilder.cpp

Modified: polly/trunk/lib/CodeGen/IRBuilder.cpp
URL: http://llvm.org/viewvc/llvm-project/polly/trunk/lib/CodeGen/IRBuilder.cpp?rev=336350&r1=336349&r2=336350&view=diff
==============================================================================
--- polly/trunk/lib/CodeGen/IRBuilder.cpp (original)
+++ polly/trunk/lib/CodeGen/IRBuilder.cpp Thu Jul  5 06:44:50 2018
@@ -160,11 +160,13 @@ static llvm::Value *getMemAccInstPointer
 
 void ScopAnnotator::annotateSecondLevel(llvm::Instruction *Inst,
                                         llvm::Value *BasePtr) {
-  auto *PtrSCEV = SE->getSCEV(getMemAccInstPointerOperand(Inst));
+  Value *Ptr = getMemAccInstPointerOperand(Inst);
+  if (!Ptr)
+    return;
+
+  auto *PtrSCEV = SE->getSCEV(Ptr);
   auto *BasePtrSCEV = SE->getPointerBase(PtrSCEV);
 
-  if (!PtrSCEV)
-    return;
   auto SecondLevelAliasScope = SecondLevelAliasScopeMap.lookup(PtrSCEV);
   auto SecondLevelOtherAliasScopeList =
       SecondLevelOtherAliasScopeListMap.lookup(PtrSCEV);