[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.

llvm-svn: 280191

diff --git a/llvm/lib/Analysis/Loads.cpp b/llvm/lib/Analysis/Loads.cpp
index 4837ccf..af7ccb9 100644 (file)
--- a/llvm/lib/Analysis/Loads.cpp
+++ b/llvm/lib/Analysis/Loads.cpp
@@ -55,6 +55,10 @@ static bool isDereferenceableAndAlignedPointer(
     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 isDereferenceableAndAlignedPointer(
     // 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);
   }