[llvm] r280191 - [Loads] Properly populate the visited set in isDereferenceableAndAlignedPointer

[David Majnemer via llvm-commits]

Author: majnemer
Date: Tue Aug 30 22:22:32 2016
New Revision: 280191

URL: http://llvm.org/viewvc/llvm-project?rev=280191&view=rev
Log:
[Loads] Properly populate the visited set in isDereferenceableAndAlignedPointer

There were paths where we wouldn't populate the visited set, causing us
to recurse forever if an SSA variable was defined in terms of itself.

This fixes PR30210.

Modified:
    llvm/trunk/lib/Analysis/Loads.cpp

Modified: llvm/trunk/lib/Analysis/Loads.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/Loads.cpp?rev=280191&r1=280190&r2=280191&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/Loads.cpp (original)
+++ llvm/trunk/lib/Analysis/Loads.cpp Tue Aug 30 22:22:32 2016
@@ -55,6 +55,10 @@ static bool isDereferenceableAndAlignedP
     const Value *V, unsigned Align, const APInt &Size, const DataLayout &DL,
     const Instruction *CtxI, const DominatorTree *DT,
     SmallPtrSetImpl<const Value *> &Visited) {
+  // Already visited?  Bail out, we've likely hit unreachable code.
+  if (!Visited.insert(V).second)
+    return false;
+
   // Note that it is not safe to speculate into a malloc'd region because
   // malloc may return null.
 
@@ -87,8 +91,7 @@ static bool isDereferenceableAndAlignedP
     // then the GEP (== Base + Offset == k_0 * Align + k_1 * Align) is also
     // aligned to Align bytes.
 
-    return Visited.insert(Base).second &&
-           isDereferenceableAndAlignedPointer(Base, Align, Offset + Size, DL,
+    return isDereferenceableAndAlignedPointer(Base, Align, Offset + Size, DL,
                                               CtxI, DT, Visited);
   }