Make NumMicroOps a variable in the subtarget's instruction itinerary.

The TargetInstrInfo::getNumMicroOps API does not change, but soon it
will be used by MachineScheduler. Now each subtarget can specify the
number of micro-ops per itinerary class. For ARM, this is currently
always dynamic (-1), because it is used for load/store multiple which
depends on the number of register operands.

Zero is now a valid number of micro-ops. This can be used for
nop pseudo-instructions or instructions that the hardware can squash
during dispatch.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@159406 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/TargetInstrInfoImpl.cpp b/lib/CodeGen/TargetInstrInfoImpl.cpp
index 7af08f5..54be88a 100644
--- a/lib/CodeGen/TargetInstrInfoImpl.cpp
+++ b/lib/CodeGen/TargetInstrInfoImpl.cpp
@@ -560,8 +560,8 @@
     return 1;
 
   unsigned Class = MI->getDesc().getSchedClass();
-  unsigned UOps = ItinData->Itineraries[Class].NumMicroOps;
-  if (UOps)
+  int UOps = ItinData->Itineraries[Class].NumMicroOps;
+  if (UOps >= 0)
     return UOps;
 
   // The # of u-ops is dynamically determined. The specific target should