diff --git a/llvm/include/llvm/CodeGen/GlobalISel/MachineIRBuilder.h b/llvm/include/llvm/CodeGen/GlobalISel/MachineIRBuilder.h
--- a/llvm/include/llvm/CodeGen/GlobalISel/MachineIRBuilder.h
+++ b/llvm/include/llvm/CodeGen/GlobalISel/MachineIRBuilder.h
@@ -379,7 +379,14 @@
   ///
   /// \return a MachineInstrBuilder for the newly created instruction.
   MachineInstrBuilder buildDynStackAlloc(const DstOp &Res, const SrcOp &Size,
-                                         unsigned Align);
+                                         MaybeAlign Align);
+
+  LLVM_ATTRIBUTE_DEPRECATED(inline MachineInstrBuilder buildDynStackAlloc(
+                                const DstOp &Res, const SrcOp &Size,
+                                unsigned Align),
+                            "Use the version that takes MaybeAlign instead") {
+    return buildDynStackAlloc(Res, Size, MaybeAlign(Align));
+  }
 
   /// Build and insert \p Res = G_FRAME_INDEX \p Idx
   ///
diff --git a/llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp b/llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp
--- a/llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp
@@ -1858,12 +1858,7 @@
     return false;
 
   // Now we're in the harder dynamic case.
-  Type *Ty = AI.getAllocatedType();
-  unsigned Align =
-      std::max((unsigned)DL->getPrefTypeAlignment(Ty), AI.getAlignment());
-
   Register NumElts = getOrCreateVReg(*AI.getArraySize());
-
   Type *IntPtrIRTy = DL->getIntPtrType(AI.getType());
   LLT IntPtrTy = getLLTForType(*IntPtrIRTy, *DL);
   if (MRI->getType(NumElts) != IntPtrTy) {
@@ -1872,29 +1867,32 @@
     NumElts = ExtElts;
   }
 
+  Type *Ty = AI.getAllocatedType();
+
   Register AllocSize = MRI->createGenericVirtualRegister(IntPtrTy);
   Register TySize =
       getOrCreateVReg(*ConstantInt::get(IntPtrIRTy, DL->getTypeAllocSize(Ty)));
   MIRBuilder.buildMul(AllocSize, NumElts, TySize);
 
-  unsigned StackAlign =
-      MF->getSubtarget().getFrameLowering()->getStackAlignment();
-  if (Align <= StackAlign)
-    Align = 0;
-
   // Round the size of the allocation up to the stack alignment size
   // by add SA-1 to the size. This doesn't overflow because we're computing
   // an address inside an alloca.
-  auto SAMinusOne = MIRBuilder.buildConstant(IntPtrTy, StackAlign - 1);
+  Align StackAlign = MF->getSubtarget().getFrameLowering()->getStackAlign();
+  auto SAMinusOne = MIRBuilder.buildConstant(IntPtrTy, StackAlign.value() - 1);
   auto AllocAdd = MIRBuilder.buildAdd(IntPtrTy, AllocSize, SAMinusOne,
                                       MachineInstr::NoUWrap);
   auto AlignCst =
-      MIRBuilder.buildConstant(IntPtrTy, ~(uint64_t)(StackAlign - 1));
+      MIRBuilder.buildConstant(IntPtrTy, ~(uint64_t)(StackAlign.value() - 1));
   auto AlignedAlloc = MIRBuilder.buildAnd(IntPtrTy, AllocAdd, AlignCst);
 
-  MIRBuilder.buildDynStackAlloc(getOrCreateVReg(AI), AlignedAlloc, Align);
+  Align Alignment = max(AI.getAlign(), DL->getPrefTypeAlign(Ty));
+  MaybeAlign DynStackAllocAlign = Alignment;
+  if (Alignment <= StackAlign)
+    DynStackAllocAlign = None;
+  MIRBuilder.buildDynStackAlloc(getOrCreateVReg(AI), AlignedAlloc,
+                                DynStackAllocAlign);
 
-  MF->getFrameInfo().CreateVariableSizedObject(Align ? Align : 1, &AI);
+  MF->getFrameInfo().CreateVariableSizedObject(Alignment, &AI);
   assert(MF->getFrameInfo().hasVarSizedObjects());
   return true;
 }
diff --git a/llvm/lib/CodeGen/GlobalISel/MachineIRBuilder.cpp b/llvm/lib/CodeGen/GlobalISel/MachineIRBuilder.cpp
--- a/llvm/lib/CodeGen/GlobalISel/MachineIRBuilder.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/MachineIRBuilder.cpp
@@ -162,12 +162,12 @@
 
 MachineInstrBuilder MachineIRBuilder::buildDynStackAlloc(const DstOp &Res,
                                                          const SrcOp &Size,
-                                                         unsigned Align) {
+                                                         MaybeAlign Align) {
   assert(Res.getLLTTy(*getMRI()).isPointer() && "expected ptr dst type");
   auto MIB = buildInstr(TargetOpcode::G_DYN_STACKALLOC);
   Res.addDefToMIB(*getMRI(), MIB);
   Size.addSrcToMIB(MIB);
-  MIB.addImm(Align);
+  MIB.addImm(Align ? Align->value() : 0);
   return MIB;
 }