diff --git a/llvm/include/llvm/CodeGen/GlobalISel/GISelKnownBits.h b/llvm/include/llvm/CodeGen/GlobalISel/GISelKnownBits.h
--- a/llvm/include/llvm/CodeGen/GlobalISel/GISelKnownBits.h
+++ b/llvm/include/llvm/CodeGen/GlobalISel/GISelKnownBits.h
@@ -63,12 +63,13 @@
   void computeKnownBitsForFrameIndex(Register R, KnownBits &Known,
                                      const APInt &DemandedElts,
                                      unsigned Depth = 0);
-  static unsigned inferAlignmentForFrameIdx(int FrameIdx, int Offset,
-                                            const MachineFunction &MF);
-  static void computeKnownBitsForAlignment(KnownBits &Known, unsigned Align);
+  static Align inferAlignmentForFrameIdx(int FrameIdx, int Offset,
+                                         const MachineFunction &MF);
+  static void computeKnownBitsForAlignment(KnownBits &Known,
+                                           MaybeAlign Alignment);
 
   // Try to infer alignment for MI.
-  static unsigned inferPtrAlignment(const MachineInstr &MI);
+  static MaybeAlign inferPtrAlignment(const MachineInstr &MI);
 
   // Observer API. No-op for non-caching implementation.
   void erasingInstr(MachineInstr &MI) override{};
diff --git a/llvm/lib/CodeGen/GlobalISel/GISelKnownBits.cpp b/llvm/lib/CodeGen/GlobalISel/GISelKnownBits.cpp
--- a/llvm/lib/CodeGen/GlobalISel/GISelKnownBits.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/GISelKnownBits.cpp
@@ -33,19 +33,19 @@
     : MF(MF), MRI(MF.getRegInfo()), TL(*MF.getSubtarget().getTargetLowering()),
       DL(MF.getFunction().getParent()->getDataLayout()) {}
 
-unsigned GISelKnownBits::inferAlignmentForFrameIdx(int FrameIdx, int Offset,
-                                                   const MachineFunction &MF) {
+Align GISelKnownBits::inferAlignmentForFrameIdx(int FrameIdx, int Offset,
+                                                const MachineFunction &MF) {
   const MachineFrameInfo &MFI = MF.getFrameInfo();
-  return MinAlign(Offset, MFI.getObjectAlignment(FrameIdx));
+  return commonAlignment(Align(MFI.getObjectAlignment(FrameIdx)), Offset);
   // TODO: How to handle cases with Base + Offset?
 }
 
-unsigned GISelKnownBits::inferPtrAlignment(const MachineInstr &MI) {
+MaybeAlign GISelKnownBits::inferPtrAlignment(const MachineInstr &MI) {
   if (MI.getOpcode() == TargetOpcode::G_FRAME_INDEX) {
     int FrameIdx = MI.getOperand(1).getIndex();
     return inferAlignmentForFrameIdx(FrameIdx, 0, *MI.getMF());
   }
-  return 0;
+  return llvm::None;
 }
 
 void GISelKnownBits::computeKnownBitsForFrameIndex(Register R, KnownBits &Known,
@@ -56,10 +56,10 @@
 }
 
 void GISelKnownBits::computeKnownBitsForAlignment(KnownBits &Known,
-                                                  unsigned Align) {
-  if (Align)
+                                                  MaybeAlign Alignment) {
+  if (Alignment)
     // The low bits are known zero if the pointer is aligned.
-    Known.Zero.setLowBits(Log2_32(Align));
+    Known.Zero.setLowBits(Log2(Alignment));
 }
 
 KnownBits GISelKnownBits::getKnownBits(MachineInstr &MI) {