[MIR-Canon] Don't do vreg skip for independent instructions if there are none.

We don't want to create vregs if there is nothing to use them for. That causes
verifier errors.

Differential Revision: https://reviews.llvm.org/D62740

llvm-svn: 362247
diff --git a/llvm/lib/CodeGen/MIRCanonicalizerPass.cpp b/llvm/lib/CodeGen/MIRCanonicalizerPass.cpp
index a409723..c7d1131 100644
--- a/llvm/lib/CodeGen/MIRCanonicalizerPass.cpp
+++ b/llvm/lib/CodeGen/MIRCanonicalizerPass.cpp
@@ -743,7 +743,8 @@
   // of the MachineBasicBlock so that they are named in the order that we sorted
   // them alphabetically. Eventually we wont need SkipVRegs because we will use
   // named vregs instead.
-  NVC.SkipVRegs();
+  if (IdempotentInstCount)
+    NVC.SkipVRegs();
 
   auto MII = MBB->begin();
   for (unsigned i = 0; i < IdempotentInstCount && MII != MBB->end(); ++i) {