diff --git a/llvm/include/llvm/CodeGen/MachineFunction.h b/llvm/include/llvm/CodeGen/MachineFunction.h
--- a/llvm/include/llvm/CodeGen/MachineFunction.h
+++ b/llvm/include/llvm/CodeGen/MachineFunction.h
@@ -1,5 +1,6 @@
 //===- llvm/CodeGen/MachineFunction.h ---------------------------*- C++ -*-===//
 //
+//
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
@@ -740,6 +741,12 @@
   MachineMemOperand *getMachineMemOperand(const MachineMemOperand *MMO,
                                           const AAMDNodes &AAInfo);
 
+  /// Allocate a new MachineMemOperand by copying an existing one,
+  /// replacing the flags. MachineMemOperands are owned
+  /// by the MachineFunction and need not be explicitly deallocated.
+  MachineMemOperand *getMachineMemOperand(const MachineMemOperand *MMO,
+                                          MachineMemOperand::Flags Flags);
+
   using OperandCapacity = ArrayRecycler<MachineOperand>::Capacity;
 
   /// Allocate an array of MachineOperands. This is only intended for use by
diff --git a/llvm/lib/CodeGen/MachineFunction.cpp b/llvm/lib/CodeGen/MachineFunction.cpp
--- a/llvm/lib/CodeGen/MachineFunction.cpp
+++ b/llvm/lib/CodeGen/MachineFunction.cpp
@@ -430,6 +430,15 @@
                                MMO->getOrdering(), MMO->getFailureOrdering());
 }
 
+MachineMemOperand *
+MachineFunction::getMachineMemOperand(const MachineMemOperand *MMO,
+                                      MachineMemOperand::Flags Flags) {
+  return new (Allocator) MachineMemOperand(
+      MMO->getPointerInfo(), Flags, MMO->getSize(), MMO->getBaseAlignment(),
+      MMO->getAAInfo(), MMO->getRanges(), MMO->getSyncScopeID(),
+      MMO->getOrdering(), MMO->getFailureOrdering());
+}
+
 MachineInstr::ExtraInfo *
 MachineFunction::createMIExtraInfo(ArrayRef<MachineMemOperand *> MMOs,
                                    MCSymbol *PreInstrSymbol,
diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -28669,10 +28669,18 @@
   unsigned ArgMode = MI.getOperand(7).getImm();
   unsigned Align = MI.getOperand(8).getImm();
 
+  MachineFunction *MF = MBB->getParent();
+
   // Memory Reference
   assert(MI.hasOneMemOperand() && "Expected VAARG_64 to have one memoperand");
-  SmallVector<MachineMemOperand *, 1> MMOs(MI.memoperands_begin(),
-                                           MI.memoperands_end());
+
+  MachineMemOperand *OldMMO = MI.memoperands().front();
+
+  // Clone the MMO into two separate MMOs for loading and storing
+  MachineMemOperand *LoadOnlyMMO = MF->getMachineMemOperand(
+      OldMMO, OldMMO->getFlags() & ~MachineMemOperand::MOStore);
+  MachineMemOperand *StoreOnlyMMO = MF->getMachineMemOperand(
+      OldMMO, OldMMO->getFlags() & ~MachineMemOperand::MOLoad);
 
   // Machine Information
   const TargetInstrInfo *TII = Subtarget.getInstrInfo();
@@ -28737,7 +28745,6 @@
     OverflowDestReg = MRI.createVirtualRegister(AddrRegClass);
 
     const BasicBlock *LLVM_BB = MBB->getBasicBlock();
-    MachineFunction *MF = MBB->getParent();
     overflowMBB = MF->CreateMachineBasicBlock(LLVM_BB);
     offsetMBB = MF->CreateMachineBasicBlock(LLVM_BB);
     endMBB = MF->CreateMachineBasicBlock(LLVM_BB);
@@ -28770,7 +28777,7 @@
         .add(Index)
         .addDisp(Disp, UseFPOffset ? 4 : 0)
         .add(Segment)
-        .setMemRefs(MMOs);
+        .setMemRefs(LoadOnlyMMO);
 
     // Check if there is enough room left to pull this argument.
     BuildMI(thisMBB, DL, TII->get(X86::CMP32ri))
@@ -28795,7 +28802,7 @@
         .add(Index)
         .addDisp(Disp, 16)
         .add(Segment)
-        .setMemRefs(MMOs);
+        .setMemRefs(LoadOnlyMMO);
 
     // Zero-extend the offset
     unsigned OffsetReg64 = MRI.createVirtualRegister(AddrRegClass);
@@ -28823,7 +28830,7 @@
         .addDisp(Disp, UseFPOffset ? 4 : 0)
         .add(Segment)
         .addReg(NextOffsetReg)
-        .setMemRefs(MMOs);
+        .setMemRefs(StoreOnlyMMO);
 
     // Jump to endMBB
     BuildMI(offsetMBB, DL, TII->get(X86::JMP_1))
@@ -28842,7 +28849,7 @@
       .add(Index)
       .addDisp(Disp, 8)
       .add(Segment)
-      .setMemRefs(MMOs);
+      .setMemRefs(LoadOnlyMMO);
 
   // If we need to align it, do so. Otherwise, just copy the address
   // to OverflowDestReg.
@@ -28879,7 +28886,7 @@
       .addDisp(Disp, 8)
       .add(Segment)
       .addReg(NextAddrReg)
-      .setMemRefs(MMOs);
+      .setMemRefs(StoreOnlyMMO);
 
   // If we branched, emit the PHI to the front of endMBB.
   if (offsetMBB) {
diff --git a/llvm/lib/Target/X86/X86InstrInfo.cpp b/llvm/lib/Target/X86/X86InstrInfo.cpp
--- a/llvm/lib/Target/X86/X86InstrInfo.cpp
+++ b/llvm/lib/Target/X86/X86InstrInfo.cpp
@@ -5127,10 +5127,7 @@
     } else {
       // Clone the MMO and unset the store flag.
       LoadMMOs.push_back(MF.getMachineMemOperand(
-          MMO->getPointerInfo(), MMO->getFlags() & ~MachineMemOperand::MOStore,
-          MMO->getSize(), MMO->getBaseAlignment(), MMO->getAAInfo(), nullptr,
-          MMO->getSyncScopeID(), MMO->getOrdering(),
-          MMO->getFailureOrdering()));
+          MMO, MMO->getFlags() & ~MachineMemOperand::MOStore));
     }
   }
 
@@ -5151,10 +5148,7 @@
     } else {
       // Clone the MMO and unset the load flag.
       StoreMMOs.push_back(MF.getMachineMemOperand(
-          MMO->getPointerInfo(), MMO->getFlags() & ~MachineMemOperand::MOLoad,
-          MMO->getSize(), MMO->getBaseAlignment(), MMO->getAAInfo(), nullptr,
-          MMO->getSyncScopeID(), MMO->getOrdering(),
-          MMO->getFailureOrdering()));
+          MMO, MMO->getFlags() & ~MachineMemOperand::MOLoad));
     }
   }