Index: llvm/lib/CodeGen/MIRParser/MIParser.cpp
===================================================================
--- llvm/lib/CodeGen/MIRParser/MIParser.cpp
+++ llvm/lib/CodeGen/MIRParser/MIParser.cpp
@@ -3047,18 +3047,34 @@
   if (parseOptionalAtomicOrdering(FailureOrder))
     return true;
 
+  LLT MemoryType;
   if (Token.isNot(MIToken::IntegerLiteral) &&
-      Token.isNot(MIToken::kw_unknown_size))
-    return error("expected the size integer literal or 'unknown-size' after "
+      Token.isNot(MIToken::kw_unknown_size) &&
+      Token.isNot(MIToken::lparen))
+    return error("expected memory LLT, the size integer literal or 'unknown-size' after "
                  "memory operation");
-  uint64_t Size;
+
+  uint64_t Size = MemoryLocation::UnknownSize;
   if (Token.is(MIToken::IntegerLiteral)) {
     if (getUint64(Size))
       return true;
+
+    // Convert from bytes to bits for storage.
+    MemoryType = LLT::scalar(8 * Size);
+    lex();
   } else if (Token.is(MIToken::kw_unknown_size)) {
     Size = MemoryLocation::UnknownSize;
+    lex();
+  } else {
+    if (expectAndConsume(MIToken::lparen))
+      return true;
+    if (parseLowLevelType(Token.location(), MemoryType))
+      return true;
+    if (expectAndConsume(MIToken::rparen))
+      return true;
+
+    Size = MemoryType.getSizeInBytes();
   }
-  lex();
 
   MachinePointerInfo Ptr = MachinePointerInfo();
   if (Token.is(MIToken::Identifier)) {
@@ -3074,7 +3090,8 @@
     if (parseMachinePointerInfo(Ptr))
       return true;
   }
-  unsigned BaseAlignment = (Size != MemoryLocation::UnknownSize ? Size : 1);
+  unsigned BaseAlignment =
+      (Size != MemoryLocation::UnknownSize ? PowerOf2Ceil(Size) : 1);
   AAMDNodes AAInfo;
   MDNode *Range = nullptr;
   while (consumeIfPresent(MIToken::comma)) {
@@ -3121,8 +3138,8 @@
   }
   if (expectAndConsume(MIToken::rparen))
     return true;
-  Dest = MF.getMachineMemOperand(Ptr, Flags, Size, Align(BaseAlignment), AAInfo,
-                                 Range, SSID, Order, FailureOrder);
+  Dest = MF.getMachineMemOperand(Ptr, Flags, MemoryType, Align(BaseAlignment),
+                                 AAInfo, Range, SSID, Order, FailureOrder);
   return false;
 }
 
Index: llvm/lib/CodeGen/MachineOperand.cpp
===================================================================
--- llvm/lib/CodeGen/MachineOperand.cpp
+++ llvm/lib/CodeGen/MachineOperand.cpp
@@ -1113,10 +1113,10 @@
   if (getFailureOrdering() != AtomicOrdering::NotAtomic)
     OS << toIRString(getFailureOrdering()) << ' ';
 
-  if (getSize() == MemoryLocation::UnknownSize)
-    OS << "unknown-size";
+  if (getMemoryType().isValid())
+    OS << '(' << getMemoryType() << ')';
   else
-    OS << getSize();
+    OS << "unknown-size";
 
   if (const Value *Val = getValue()) {
     OS << ((isLoad() && isStore()) ? " on " : isLoad() ? " from " : " into ");