[Alignment][NFC] Use llvm::Align in GISelKnownBits

[gchatelet]

Summary

This is patch is part of a series to introduce an Alignment type.
See this thread for context: http://lists.llvm.org/pipermail/llvm-dev/2019-July/133851.html
See this patch for the introduction of the type: https://reviews.llvm.org/D64790

[courbet]

llvm/lib/CodeGen/GlobalISel/GISelKnownBits.cpp

48

None

[gchatelet]

• Address comments

llvm/include/llvm/CodeGen/GlobalISel/GISelKnownBits.h

public:
   /// predicate to simplify operations downstream.
   bool signBitIsZero(Register Op);
 
   // FIXME: Is this the right place for G_FRAME_INDEX? Should it be in
   // TargetLowering?
   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,
+  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{};
   void createdInstr(MachineInstr &MI) override{};
   void changingInstr(MachineInstr &MI) override{};
   void changedInstr(MachineInstr &MI) override{};
 
 protected:

llvm/lib/CodeGen/GlobalISel/GISelKnownBits.cpp

INITIALIZE_PASS_BEGIN(GISelKnownBitsAnalysis, DEBUG_TYPE,
                       "Analysis for ComputingKnownBits", false, true)
 INITIALIZE_PASS_END(GISelKnownBitsAnalysis, DEBUG_TYPE,
                     "Analysis for ComputingKnownBits", false, true)
 
 GISelKnownBits::GISelKnownBits(MachineFunction &MF)
     : 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 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 None;
 }
 
 void GISelKnownBits::computeKnownBitsForFrameIndex(Register R, KnownBits &Known,
                                                    const APInt &DemandedElts,
                                                    unsigned Depth) {
   const MachineInstr &MI = *MRI.getVRegDef(R);
   computeKnownBitsForAlignment(Known, inferPtrAlignment(MI));
 }
 
 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) {
   return getKnownBits(MI.getOperand(0).getReg());
 }
 
 KnownBits GISelKnownBits::getKnownBits(Register R) {
   KnownBits Known;