Index: lib/CodeGen/MIRParser/MILexer.h
===================================================================
--- lib/CodeGen/MIRParser/MILexer.h
+++ lib/CodeGen/MIRParser/MILexer.h
@@ -123,13 +123,10 @@
 
     // Identifier tokens
     Identifier,
-    IntegerType,
     NamedRegister,
     NamedVirtualRegister,
     MachineBasicBlockLabel,
     MachineBasicBlock,
-    PointerType,
-    ScalarType,
     StackObject,
     FixedStackObject,
     NamedGlobalValue,
Index: lib/CodeGen/MIRParser/MILexer.cpp
===================================================================
--- lib/CodeGen/MIRParser/MILexer.cpp
+++ lib/CodeGen/MIRParser/MILexer.cpp
@@ -179,23 +179,6 @@
   return C;
 }
 
-static Cursor maybeLexIntegerOrScalarType(Cursor C, MIToken &Token) {
-  if ((C.peek() != 'i' && C.peek() != 's' && C.peek() != 'p') ||
-      !isdigit(C.peek(1)))
-    return None;
-  char Kind = C.peek();
-  auto Range = C;
-  C.advance(); // Skip 'i', 's', or 'p'
-  while (isdigit(C.peek()))
-    C.advance();
-
-  Token.reset(Kind == 'i'
-                  ? MIToken::IntegerType
-                  : (Kind == 's' ? MIToken::ScalarType : MIToken::PointerType),
-              Range.upto(C));
-  return C;
-}
-
 static MIToken::TokenKind getIdentifierKind(StringRef Identifier) {
   return StringSwitch<MIToken::TokenKind>(Identifier)
       .Case("_", MIToken::underscore)
@@ -650,8 +633,6 @@
     return C.remaining();
   }
 
-  if (Cursor R = maybeLexIntegerOrScalarType(C, Token))
-    return R.remaining();
   if (Cursor R = maybeLexMachineBasicBlock(C, Token, ErrorCallback))
     return R.remaining();
   if (Cursor R = maybeLexIdentifier(C, Token))
Index: lib/CodeGen/MIRParser/MIParser.cpp
===================================================================
--- lib/CodeGen/MIRParser/MIParser.cpp
+++ lib/CodeGen/MIRParser/MIParser.cpp
@@ -1303,11 +1303,16 @@
 }
 
 bool MIParser::parseLowLevelType(StringRef::iterator Loc, LLT &Ty) {
-  if (Token.is(MIToken::ScalarType)) {
+  if (Token.range().front() == 's' || Token.range().front() == 'p')
+    for (auto C : Token.range().drop_front())
+      if (!isdigit(C))
+        return error("Expected integers after 's'/'p' type character");
+
+  if (Token.range().front() == 's') {
     Ty = LLT::scalar(APSInt(Token.range().drop_front()).getZExtValue());
     lex();
     return false;
-  } else if (Token.is(MIToken::PointerType)) {
+  } else if (Token.range().front() == 'p') {
     const DataLayout &DL = MF.getDataLayout();
     unsigned AS = APSInt(Token.range().drop_front()).getZExtValue();
     Ty = LLT::pointer(AS, DL.getPointerSizeInBits(AS));
@@ -1331,8 +1336,11 @@
     return error(Loc, "expected '<N x sM>' for vector type");
   lex();
 
-  if (Token.isNot(MIToken::ScalarType))
+  if (Token.range().front() != 's')
     return error(Loc, "expected '<N x sM>' for vector type");
+  for (auto C : Token.range().drop_front())
+    if (!isdigit(C))
+      return error("Expected integers after 's' type character");
   uint64_t ScalarSize = APSInt(Token.range().drop_front()).getZExtValue();
   lex();
 
@@ -1345,7 +1353,11 @@
 }
 
 bool MIParser::parseTypedImmediateOperand(MachineOperand &Dest) {
-  assert(Token.is(MIToken::IntegerType));
+  assert(Token.is(MIToken::Identifier));
+  for (auto C : Token.range().drop_front())
+    if (!isdigit(C))
+      return error("Expected integers after 'i'/'s'/'p' type character");
+
   auto Loc = Token.location();
   lex();
   if (Token.isNot(MIToken::IntegerLiteral))
@@ -2004,8 +2016,6 @@
     return parseRegisterOperand(Dest, TiedDefIdx);
   case MIToken::IntegerLiteral:
     return parseImmediateOperand(Dest);
-  case MIToken::IntegerType:
-    return parseTypedImmediateOperand(Dest);
   case MIToken::kw_half:
   case MIToken::kw_float:
   case MIToken::kw_double:
@@ -2066,8 +2076,10 @@
       Dest = MachineOperand::CreateRegMask(RegMask);
       lex();
       break;
-    } else
+    } else if (Token.stringValue() == "CustomRegMask") {
       return parseCustomRegisterMaskOperand(Dest);
+    } else
+      return parseTypedImmediateOperand(Dest);
   default:
     // FIXME: Parse the MCSymbol machine operand.
     return error("expected a machine operand");
Index: test/CodeGen/MIR/WebAssembly/int-type-register-class-name.mir
===================================================================
--- /dev/null
+++ test/CodeGen/MIR/WebAssembly/int-type-register-class-name.mir
@@ -0,0 +1,13 @@
+# RUN: llc -mtriple=wasm32-unknown-unknown -run-pass none -o - %s | FileCheck %s
+# When a register class has a name of an integer type (i32)
+---
+name: regclass_name_test
+liveins:
+  - { reg: '$arguments' }
+body: |
+  bb.0:
+    liveins: $arguments
+    %0:i32 = CONST_I32 0, implicit-def dead $arguments
+    ; CHECK: %0:i32 = CONST_I32 0, implicit-def dead $arguments
+    RETURN_VOID implicit-def dead $arguments
+...
Index: test/CodeGen/MIR/WebAssembly/lit.local.cfg
===================================================================
--- /dev/null
+++ test/CodeGen/MIR/WebAssembly/lit.local.cfg
@@ -0,0 +1,2 @@
+if not 'WebAssembly' in config.root.targets:
+    config.unsupported = True