Analysis: Add max recursison to isDereferenceableAndAlignedPointer

[arsenm]

Summary

Fixes stack overflow in test/CodeGen/X86/large-gep-chain.ll when store
lowering starts adding dereferenceable flags.

[arsenm]

ping

[arsenm]

a9af1dc34d33762751958a91aa8b82b856c2077a

llvm/lib/Analysis/Loads.cpp

static bool isAligned(const Value *Base, const APInt &Offset, Align Alignment,
   return false;
 }
 
 /// Test if V is always a pointer to allocated and suitably aligned memory for
 /// a simple load or store.
 static bool isDereferenceableAndAlignedPointer(
     const Value *V, Align Alignment, const APInt &Size, const DataLayout &DL,
     const Instruction *CtxI, const DominatorTree *DT,
-    SmallPtrSetImpl<const Value *> &Visited) {
+    SmallPtrSetImpl<const Value *> &Visited, unsigned MaxDepth) {
+
+  // Recursion limit.
+  if (MaxDepth-- == 0)
+    return false;
+
   // 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.
 
   // bitcast instructions are no-ops as far as dereferenceability is concerned.
   if (const BitCastOperator *BC = dyn_cast<BitCastOperator>(V))
     return isDereferenceableAndAlignedPointer(BC->getOperand(0), Alignment,
-                                              Size, DL, CtxI, DT, Visited);
+                                              Size, DL, CtxI, DT, Visited,
+                                              MaxDepth);
 
   bool CheckForNonNull = false;
   APInt KnownDerefBytes(Size.getBitWidth(),
                         V->getPointerDereferenceableBytes(DL, CheckForNonNull));
   if (KnownDerefBytes.getBoolValue() && KnownDerefBytes.uge(Size))
     if (!CheckForNonNull || isKnownNonZero(V, DL, 0, nullptr, CtxI, DT)) {
       // As we recursed through GEPs to get here, we've incrementally checked
       // that each step advanced by a multiple of the alignment. If our base is
if (const GEPOperator *GEP = dyn_cast<GEPOperator>(V)) {
     // pointer is aligned to Align bytes, and the Offset is divisible by Align
     // then the GEP (== Base + Offset == k_0 * Align + k_1 * Align) is also
     // aligned to Align bytes.
 
     // Offset and Size may have different bit widths if we have visited an
     // addrspacecast, so we can't do arithmetic directly on the APInt values.
     return isDereferenceableAndAlignedPointer(
         Base, Alignment, Offset + Size.sextOrTrunc(Offset.getBitWidth()), DL,
-        CtxI, DT, Visited);
+        CtxI, DT, Visited, MaxDepth);
   }
 
   // For gc.relocate, look through relocations
   if (const GCRelocateInst *RelocateInst = dyn_cast<GCRelocateInst>(V))
     return isDereferenceableAndAlignedPointer(
-        RelocateInst->getDerivedPtr(), Alignment, Size, DL, CtxI, DT, Visited);
+      RelocateInst->getDerivedPtr(), Alignment, Size, DL, CtxI, DT, Visited, MaxDepth);
 
   if (const AddrSpaceCastInst *ASC = dyn_cast<AddrSpaceCastInst>(V))
     return isDereferenceableAndAlignedPointer(ASC->getOperand(0), Alignment,
-                                              Size, DL, CtxI, DT, Visited);
+                                              Size, DL, CtxI, DT, Visited, MaxDepth);
 
   if (const auto *Call = dyn_cast<CallBase>(V))
     if (auto *RP = getArgumentAliasingToReturnedPointer(Call, true))
       return isDereferenceableAndAlignedPointer(RP, Alignment, Size, DL, CtxI,
-                                                DT, Visited);
+                                                DT, Visited, MaxDepth);
 
   // If we don't know, assume the worst.
   return false;
 }
 
 bool llvm::isDereferenceableAndAlignedPointer(const Value *V, Align Alignment,
                                               const APInt &Size,
                                               const DataLayout &DL,
                                               const Instruction *CtxI,
                                               const DominatorTree *DT) {
   // Note: At the moment, Size can be zero.  This ends up being interpreted as
   // a query of whether [Base, V] is dereferenceable and V is aligned (since
   // that's what the implementation happened to do).  It's unclear if this is
-  // the desired semantic, but at least SelectionDAG does exercise this case.  
-  
+  // the desired semantic, but at least SelectionDAG does exercise this case.
   SmallPtrSet<const Value *, 32> Visited;
   return ::isDereferenceableAndAlignedPointer(V, Alignment, Size, DL, CtxI, DT,
-                                              Visited);
+                                              Visited, 16);
 }
 
 bool llvm::isDereferenceableAndAlignedPointer(const Value *V, Type *Ty,
                                               MaybeAlign MA,
                                               const DataLayout &DL,
                                               const Instruction *CtxI,
                                               const DominatorTree *DT) {
   if (!Ty->isSized())