Index: llvm/include/llvm/CodeGen/SelectionDAGISel.h
===================================================================
--- llvm/include/llvm/CodeGen/SelectionDAGISel.h
+++ llvm/include/llvm/CodeGen/SelectionDAGISel.h
@@ -21,6 +21,7 @@
 
 namespace llvm {
 class AAResults;
+class AssumptionCache;
 class TargetInstrInfo;
 class TargetMachine;
 class SelectionDAGBuilder;
@@ -48,6 +49,7 @@
   SelectionDAG *CurDAG;
   std::unique_ptr<SelectionDAGBuilder> SDB;
   AAResults *AA = nullptr;
+  AssumptionCache *AC = nullptr;
   GCFunctionInfo *GFI = nullptr;
   CodeGenOpt::Level OptLevel;
   const TargetInstrInfo *TII;
Index: llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h
===================================================================
--- llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h
+++ llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h
@@ -42,6 +42,7 @@
 class AllocaInst;
 class AtomicCmpXchgInst;
 class AtomicRMWInst;
+class AssumptionCache;
 class BasicBlock;
 class BranchInst;
 class CallInst;
@@ -191,6 +192,7 @@
 
   SelectionDAG &DAG;
   AAResults *AA = nullptr;
+  AssumptionCache *AC = nullptr;
   const TargetLibraryInfo *LibInfo;
 
   class SDAGSwitchLowering : public SwitchCG::SwitchLowering {
@@ -244,7 +246,7 @@
         SL(std::make_unique<SDAGSwitchLowering>(this, funcinfo)), FuncInfo(funcinfo),
         SwiftError(swifterror) {}
 
-  void init(GCFunctionInfo *gfi, AAResults *AA,
+  void init(GCFunctionInfo *gfi, AAResults *AA, AssumptionCache *AC,
             const TargetLibraryInfo *li);
 
   /// Clear out the current SelectionDAG and the associated state and prepare
Index: llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
===================================================================
--- llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -1026,8 +1026,10 @@
 }
 
 void SelectionDAGBuilder::init(GCFunctionInfo *gfi, AliasAnalysis *aa,
+                               AssumptionCache *ac,
                                const TargetLibraryInfo *li) {
   AA = aa;
+  AC = ac;
   GFI = gfi;
   LibInfo = li;
   Context = DAG.getContext();
@@ -4139,7 +4141,7 @@
   }
 
   if (isDereferenceableAndAlignedPointer(SV, Ty, Alignment, DAG.getDataLayout(),
-                                         &I, nullptr, nullptr, LibInfo))
+                                         &I, AC, nullptr, LibInfo))
     MMOFlags |= MachineMemOperand::MODereferenceable;
 
   SDLoc dl = getCurSDLoc();
Index: llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
===================================================================
--- llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
+++ llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
@@ -22,6 +22,7 @@
 #include "llvm/ADT/Statistic.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/Analysis/AliasAnalysis.h"
+#include "llvm/Analysis/AssumptionCache.h"
 #include "llvm/Analysis/BranchProbabilityInfo.h"
 #include "llvm/Analysis/CFG.h"
 #include "llvm/Analysis/EHPersonalities.h"
@@ -336,6 +337,7 @@
   AU.addPreserved<GCModuleInfo>();
   AU.addRequired<TargetLibraryInfoWrapperPass>();
   AU.addRequired<TargetTransformInfoWrapperPass>();
+  AU.addRequired<AssumptionCacheTracker>();
   if (UseMBPI && OptLevel != CodeGenOpt::None)
     AU.addRequired<BranchProbabilityInfoWrapperPass>();
   AU.addRequired<ProfileSummaryInfoWrapperPass>();
@@ -403,6 +405,7 @@
   LibInfo = &getAnalysis<TargetLibraryInfoWrapperPass>().getTLI(Fn);
   GFI = Fn.hasGC() ? &getAnalysis<GCModuleInfo>().getFunctionInfo(Fn) : nullptr;
   ORE = std::make_unique<OptimizationRemarkEmitter>(&Fn);
+  AC = &getAnalysis<AssumptionCacheTracker>().getAssumptionCache(mf.getFunction());
   auto *PSI = &getAnalysis<ProfileSummaryInfoWrapperPass>().getPSI();
   BlockFrequencyInfo *BFI = nullptr;
   if (PSI && PSI->hasProfileSummary() && OptLevel != CodeGenOpt::None)
@@ -430,7 +433,7 @@
   else
     AA = nullptr;
 
-  SDB->init(GFI, AA, LibInfo);
+  SDB->init(GFI, AA, AC, LibInfo);
 
   MF->setHasInlineAsm(false);