MI Sched: record local vreg uses.

This will be used to compute the cyclic critical path and to
update precomputed per-node pressure differences.
In the longer term, it could also be used to speed up LiveInterval
update by avoiding visiting all global vreg users.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@189118 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/ScheduleDAGInstrs.cpp b/lib/CodeGen/ScheduleDAGInstrs.cpp
index b0245d5..2471408 100644
--- a/lib/CodeGen/ScheduleDAGInstrs.cpp
+++ b/lib/CodeGen/ScheduleDAGInstrs.cpp
@@ -405,6 +405,9 @@
   MachineInstr *MI = SU->getInstr();
   unsigned Reg = MI->getOperand(OperIdx).getReg();
 
+  // Record this local VReg use.
+  VRegUses.insert(VReg2SUnit(Reg, SU));
+
   // Lookup this operand's reaching definition.
   assert(LIS && "vreg dependencies requires LiveIntervals");
   LiveRangeQuery LRQ(LIS->getInterval(Reg), LIS->getInstructionIndex(MI));
@@ -715,10 +718,9 @@
   Uses.setUniverse(TRI->getNumRegs());
 
   assert(VRegDefs.empty() && "Only BuildSchedGraph may access VRegDefs");
-  // FIXME: Allow SparseSet to reserve space for the creation of virtual
-  // registers during scheduling. Don't artificially inflate the Universe
-  // because we want to assert that vregs are not created during DAG building.
+  VRegUses.clear();
   VRegDefs.setUniverse(MRI.getNumVirtRegs());
+  VRegUses.setUniverse(MRI.getNumVirtRegs());
 
   // Model data dependencies between instructions being scheduled and the
   // ExitSU.