[Alignment][NFC] Update MachineMemOperand implementation to use MaybeAlign

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

Reviewers: courbet

Reviewed By: courbet

Subscribers: hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D76625

Author: gchatelet

llvm/include/llvm/CodeGen/MachineMemOperand.h

@@ -169,7 +169,7 @@ class MachineMemOperand {
   MachinePointerInfo PtrInfo;
   uint64_t Size;
   Flags FlagVals;
-  uint16_t BaseAlignLog2; // log_2(base_alignment) + 1
+  Align BaseAlign;
   MachineAtomicInfo AtomicInfo;
   AAMDNodes AAInfo;
   const MDNode *Ranges;
@@ -229,7 +229,7 @@ class MachineMemOperand {
 
   /// Return the minimum known alignment in bytes of the base address, without
   /// the offset.
-  uint64_t getBaseAlignment() const { return (1ull << BaseAlignLog2) >> 1; }
+  uint64_t getBaseAlignment() const { return BaseAlign.value(); }
 
   /// Return the AA tags for the memory reference.
   AAMDNodes getAAInfo() const { return AAInfo; }

llvm/lib/CodeGen/MachineOperand.cpp

@@ -1009,8 +1009,8 @@ MachineMemOperand::MachineMemOperand(MachinePointerInfo ptrinfo, Flags f,
                                      const MDNode *Ranges, SyncScope::ID SSID,
                                      AtomicOrdering Ordering,
                                      AtomicOrdering FailureOrdering)
-    : PtrInfo(ptrinfo), Size(s), FlagVals(f), BaseAlignLog2(Log2_32(a) + 1),
-      AAInfo(AAInfo), Ranges(Ranges) {
+    : PtrInfo(ptrinfo), Size(s), FlagVals(f), BaseAlign(a), AAInfo(AAInfo),
+      Ranges(Ranges) {
   assert((PtrInfo.V.isNull() || PtrInfo.V.is<const PseudoSourceValue *>() ||
           isa<PointerType>(PtrInfo.V.get<const Value *>()->getType())) &&
          "invalid pointer value");
@@ -1043,7 +1043,7 @@ void MachineMemOperand::refineAlignment(const MachineMemOperand *MMO) {
 
   if (MMO->getBaseAlignment() >= getBaseAlignment()) {
     // Update the alignment value.
-    BaseAlignLog2 = Log2_32(MMO->getBaseAlignment()) + 1;
+    BaseAlign = Align(MMO->getBaseAlignment());
     // Also update the base and offset, because the new alignment may
     // not be applicable with the old ones.
     PtrInfo = MMO->PtrInfo;