GlobalISel: add buildUndef method to MachineIRBuilder. NFC.

llvm-svn: 297044
diff --git a/llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp b/llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp
index c78de71..6c403a8 100644
--- a/llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp
@@ -986,7 +986,7 @@
   else if (auto CF = dyn_cast<ConstantFP>(&C))
     EntryBuilder.buildFConstant(Reg, *CF);
   else if (isa<UndefValue>(C))
-    EntryBuilder.buildInstr(TargetOpcode::IMPLICIT_DEF).addDef(Reg);
+    EntryBuilder.buildUndef(Reg);
   else if (isa<ConstantPointerNull>(C))
     EntryBuilder.buildConstant(Reg, 0);
   else if (auto GV = dyn_cast<GlobalValue>(&C))
diff --git a/llvm/lib/CodeGen/GlobalISel/MachineIRBuilder.cpp b/llvm/lib/CodeGen/GlobalISel/MachineIRBuilder.cpp
index 5eea726..08f29f4 100644
--- a/llvm/lib/CodeGen/GlobalISel/MachineIRBuilder.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/MachineIRBuilder.cpp
@@ -416,6 +416,10 @@
   return MIB;
 }
 
+MachineInstrBuilder MachineIRBuilder::buildUndef(unsigned Res) {
+  return buildInstr(TargetOpcode::IMPLICIT_DEF).addDef(Res);
+}
+
 MachineInstrBuilder MachineIRBuilder::buildMerge(unsigned Res,
                                                  ArrayRef<unsigned> Ops) {