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.

llvm-svn: 189118

llvm/include/llvm/CodeGen/ScheduleDAGInstrs.h

@@ -56,7 +56,8 @@ namespace llvm {
   /// Use a SparseMultiSet to track physical registers. Storage is only
   /// allocated once for the pass. It can be cleared in constant time and reused
   /// without any frees.
-  typedef SparseMultiSet<PhysRegSUOper, llvm::identity<unsigned>, uint16_t> Reg2SUnitsMap;
+  typedef SparseMultiSet<PhysRegSUOper, llvm::identity<unsigned>, uint16_t>
+  Reg2SUnitsMap;
 
   /// Use SparseSet as a SparseMap by relying on the fact that it never
   /// compares ValueT's, only unsigned keys. This allows the set to be cleared
@@ -64,6 +65,11 @@ namespace llvm {
   /// require a destructor.
   typedef SparseSet<VReg2SUnit, VirtReg2IndexFunctor> VReg2SUnitMap;
 
+  /// Track local uses of virtual registers. These uses are gathered by the DAG
+  /// builder and may be consulted by the scheduler to avoid iterating an entire
+  /// vreg use list.
+  typedef SparseMultiSet<VReg2SUnit, VirtReg2IndexFunctor> VReg2UseMap;
+
   /// ScheduleDAGInstrs - A ScheduleDAG subclass for scheduling lists of
   /// MachineInstrs.
   class ScheduleDAGInstrs : public ScheduleDAG {
@@ -107,6 +113,11 @@ namespace llvm {
     /// scheduling region is mapped to an SUnit.
     DenseMap<MachineInstr*, SUnit*> MISUnitMap;
 
+    /// After calling BuildSchedGraph, each vreg used in the scheduling region
+    /// is mapped to a set of SUnits. These include all local vreg uses, not
+    /// just the uses for a singly defined vreg.
+    VReg2UseMap VRegUses;
+
     /// State internal to DAG building.
     /// -------------------------------
 

llvm/lib/CodeGen/ScheduleDAGInstrs.cpp

@@ -405,6 +405,9 @@ void ScheduleDAGInstrs::addVRegUseDeps(SUnit *SU, unsigned OperIdx) {
   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 @@ void ScheduleDAGInstrs::buildSchedGraph(AliasAnalysis *AA,
   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.