Fix PR3241: Currently EmitCopyFromReg emits a copy from the physical register to a virtual register unless it requires an expensive cross class copy. That means we are only treating "expensive to copy" register dependency as physical register dependency.

Also future proof the scheduler to handle "normal" physical register dependencies. The code is not exercised yet.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@62074 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 24 insertions, 22 deletions

diff --git a/lib/CodeGen/SelectionDAG/ScheduleDAGFast.cpp b/lib/CodeGen/SelectionDAG/ScheduleDAGFast.cpp
index 113dfb1751..b86492992c 100644
--- a/lib/CodeGen/SelectionDAG/ScheduleDAGFast.cpp
+++ b/lib/CodeGen/SelectionDAG/ScheduleDAGFast.cpp
@@ -28,7 +28,7 @@ using namespace llvm;
 
 STATISTIC(NumUnfolds,    "Number of nodes unfolded");
 STATISTIC(NumDups,       "Number of duplicated nodes");
-STATISTIC(NumCCCopies,   "Number of cross class copies");
+STATISTIC(NumPRCopies,   "Number of physical copies");
 
 static RegisterScheduler
   fastDAGScheduler("fast", "Fast suboptimal list scheduling",
@@ -93,10 +93,10 @@ private:
   void ReleasePred(SUnit *SU, SDep *PredEdge);
   void ScheduleNodeBottomUp(SUnit*, unsigned);
   SUnit *CopyAndMoveSuccessors(SUnit*);
-  void InsertCCCopiesAndMoveSuccs(SUnit*, unsigned,
-                                  const TargetRegisterClass*,
-                                  const TargetRegisterClass*,
-                                  SmallVector<SUnit*, 2>&);
+  void InsertCopiesAndMoveSuccs(SUnit*, unsigned,
+                                const TargetRegisterClass*,
+                                const TargetRegisterClass*,
+                                SmallVector<SUnit*, 2>&);
   bool DelayForLiveRegsBottomUp(SUnit*, SmallVector<unsigned, 4>&);
   void ListScheduleBottomUp();
 
@@ -361,17 +361,16 @@ SUnit *ScheduleDAGFast::CopyAndMoveSuccessors(SUnit *SU) {
       DelDeps.push_back(std::make_pair(SuccSU, D));
     }
   }
-  for (unsigned i = 0, e = DelDeps.size(); i != e; ++i) {
+  for (unsigned i = 0, e = DelDeps.size(); i != e; ++i)
     RemovePred(DelDeps[i].first, DelDeps[i].second);
-  }
 
   ++NumDups;
   return NewSU;
 }
 
-/// InsertCCCopiesAndMoveSuccs - Insert expensive cross register class copies
-/// and move all scheduled successors of the given SUnit to the last copy.
-void ScheduleDAGFast::InsertCCCopiesAndMoveSuccs(SUnit *SU, unsigned Reg,
+/// InsertCopiesAndMoveSuccs - Insert register copies and move all
+/// scheduled successors of the given SUnit to the last copy.
+void ScheduleDAGFast::InsertCopiesAndMoveSuccs(SUnit *SU, unsigned Reg,
                                               const TargetRegisterClass *DestRC,
                                               const TargetRegisterClass *SrcRC,
                                                SmallVector<SUnit*, 2> &Copies) {
@@ -408,7 +407,7 @@ void ScheduleDAGFast::InsertCCCopiesAndMoveSuccs(SUnit *SU, unsigned Reg,
   Copies.push_back(CopyFromSU);
   Copies.push_back(CopyToSU);
 
-  ++NumCCCopies;
+  ++NumPRCopies;
 }
 
 /// getPhysicalRegisterVT - Returns the ValueType of the physical register
@@ -524,19 +523,22 @@ void ScheduleDAGFast::ListScheduleBottomUp() {
         assert(LRegs.size() == 1 && "Can't handle this yet!");
         unsigned Reg = LRegs[0];
         SUnit *LRDef = LiveRegDefs[Reg];
-        SUnit *NewDef = CopyAndMoveSuccessors(LRDef);
+        MVT VT = getPhysicalRegisterVT(LRDef->getNode(), Reg, TII);
+        const TargetRegisterClass *RC =
+          TRI->getPhysicalRegisterRegClass(Reg, VT);
+        const TargetRegisterClass *DestRC = TRI->getCrossCopyRegClass(RC);
+
+        // If cross copy register class is null, then it must be possible copy
+        // the value directly. Do not try duplicate the def.
+        SUnit *NewDef = 0;
+        if (DestRC)
+          NewDef = CopyAndMoveSuccessors(LRDef);
+        else
+          DestRC = RC;
         if (!NewDef) {
-          // Issue expensive cross register class copies.
-          MVT VT = getPhysicalRegisterVT(LRDef->getNode(), Reg, TII);
-          const TargetRegisterClass *RC =
-            TRI->getPhysicalRegisterRegClass(Reg, VT);
-          const TargetRegisterClass *DestRC = TRI->getCrossCopyRegClass(RC);
-          if (!DestRC) {
-            assert(false && "Don't know how to copy this physical register!");
-            abort();
-          }
+          // Issue copies, these can be expensive cross register class copies.
           SmallVector<SUnit*, 2> Copies;
-          InsertCCCopiesAndMoveSuccs(LRDef, Reg, DestRC, RC, Copies);
+          InsertCopiesAndMoveSuccs(LRDef, Reg, DestRC, RC, Copies);
           DOUT << "Adding an edge from SU # " << TrySU->NodeNum
                << " to SU #" << Copies.front()->NodeNum << "\n";
           AddPred(TrySU, SDep(Copies.front(), SDep::Order, /*Latency=*/1,