Index: utils/TableGen/GlobalISelEmitter.cpp
===================================================================
--- utils/TableGen/GlobalISelEmitter.cpp
+++ utils/TableGen/GlobalISelEmitter.cpp
@@ -33,6 +33,7 @@
 #include "CodeGenDAGPatterns.h"
 #include "llvm/ADT/Optional.h"
 #include "llvm/ADT/Statistic.h"
+#include "llvm/CodeGen/LowLevelType.h"
 #include "llvm/CodeGen/MachineValueType.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Error.h"
@@ -57,22 +58,38 @@
 
 //===- Helper functions ---------------------------------------------------===//
 
+/// This class stands in for LLT wherever we want to tablegen-erate an
+/// equivalent at compiler run-time.
+class LLTCodeGen {
+private:
+  LLT Ty;
+
+public:
+  LLTCodeGen(const LLT &Ty) : Ty(Ty) {}
+
+  void emitCxxConstructorCall(raw_ostream &OS) const {
+    if (Ty.isScalar()) {
+      OS << "LLT::scalar(" << Ty.getSizeInBits() << ")";
+      return;
+    }
+    if (Ty.isVector()) {
+      OS << "LLT:vector(" << Ty.getNumElements() << ", " << Ty.getSizeInBits()
+         << ")";
+      return;
+    }
+    llvm_unreachable("Unhandled LLT");
+  }
+};
+
 /// Convert an MVT to an equivalent LLT if possible, or the invalid LLT() for
 /// MVTs that don't map cleanly to an LLT (e.g., iPTR, *any, ...).
-static Optional<std::string> MVTToLLT(MVT::SimpleValueType SVT) {
-  std::string TyStr;
-  raw_string_ostream OS(TyStr);
+static Optional<LLTCodeGen> MVTToLLT(MVT::SimpleValueType SVT) {
   MVT VT(SVT);
-  if (VT.isVector() && VT.getVectorNumElements() != 1) {
-    OS << "LLT::vector(" << VT.getVectorNumElements() << ", "
-       << VT.getScalarSizeInBits() << ")";
-  } else if (VT.isInteger() || VT.isFloatingPoint()) {
-    OS << "LLT::scalar(" << VT.getSizeInBits() << ")";
-  } else {
-    return None;
-  }
-  OS.flush();
-  return TyStr;
+  if (VT.isVector() && VT.getVectorNumElements() != 1)
+    return LLTCodeGen(LLT::vector(VT.getVectorNumElements(), VT.getScalarSizeInBits()));
+  if (VT.isInteger() || VT.isFloatingPoint())
+    return LLTCodeGen(LLT::scalar(VT.getSizeInBits()));
+  return None;
 }
 
 static bool isTrivialOperatorNode(const TreePatternNode *N) {
@@ -166,10 +183,10 @@
 /// Generates code to check that an operand is a particular LLT.
 class LLTOperandMatcher : public OperandPredicateMatcher {
 protected:
-  std::string Ty;
+  LLTCodeGen Ty;
 
 public:
-  LLTOperandMatcher(std::string Ty)
+  LLTOperandMatcher(const LLTCodeGen &Ty)
       : OperandPredicateMatcher(OPM_LLT), Ty(Ty) {}
 
   static bool classof(const OperandPredicateMatcher *P) {
@@ -178,7 +195,9 @@
 
   void emitCxxPredicateExpr(raw_ostream &OS,
                             StringRef OperandExpr) const override {
-    OS << "MRI.getType(" << OperandExpr << ".getReg()) == (" << Ty << ")";
+    OS << "MRI.getType(" << OperandExpr << ".getReg()) == (";
+    Ty.emitCxxConstructorCall(OS);
+    OS << ")";
   }
 };