[Hexagon] Make RDF copy propagation a bit more aggressive

Update the testcase to actually test for RDF's output.

Author: Krzysztof Parzyszek

llvm/lib/Target/Hexagon/RDFCopy.cpp

@@ -63,11 +63,46 @@ bool CopyPropagation::interpretAsCopy(const MachineInstr *MI, EqualityMap &EM) {
 void CopyPropagation::recordCopy(NodeAddr<StmtNode*> SA, EqualityMap &EM) {
   CopyMap.insert(std::make_pair(SA.Id, EM));
   Copies.push_back(SA.Id);
+
+  for (auto I : EM) {
+    auto FS = DefM.find(I.second.Reg);
+    if (FS == DefM.end() || FS->second.empty())
+      continue; // Undefined source
+    RDefMap[I.second][SA.Id] = FS->second.top()->Id;
+    // Insert DstR into the map.
+    RDefMap[I.first];
+  }
+}
+
+
+void CopyPropagation::updateMap(NodeAddr<InstrNode*> IA) {
+  RegisterSet RRs;
+  for (NodeAddr<RefNode*> RA : IA.Addr->members(DFG))
+    RRs.insert(RA.Addr->getRegRef(DFG));
+  bool Common = false;
+  for (auto &R : RDefMap) {
+    if (!RRs.count(R.first))
+      continue;
+    Common = true;
+    break;
+  }
+  if (!Common)
+    return;
+
+  for (auto &R : RDefMap) {
+    if (!RRs.count(R.first))
+      continue;
+    auto F = DefM.find(R.first.Reg);
+    if (F == DefM.end() || F->second.empty())
+      continue;
+    R.second[IA.Id] = F->second.top()->Id;
+  }
 }
 
 bool CopyPropagation::scanBlock(MachineBasicBlock *B) {
   bool Changed = false;
   NodeAddr<BlockNode*> BA = DFG.findBlock(B);
+  DFG.markBlock(BA.Id, DefM);
 
   for (NodeAddr<InstrNode*> IA : BA.Addr->members(DFG)) {
     if (DFG.IsCode<NodeAttrs::Stmt>(IA)) {
@@ -76,28 +111,19 @@ bool CopyPropagation::scanBlock(MachineBasicBlock *B) {
       if (interpretAsCopy(SA.Addr->getCode(), EM))
         recordCopy(SA, EM);
     }
+
+    updateMap(IA);
+    DFG.pushAllDefs(IA, DefM);
   }
 
   MachineDomTreeNode *N = MDT.getNode(B);
   for (auto *I : *N)
     Changed |= scanBlock(I->getBlock());
 
+  DFG.releaseBlock(BA.Id, DefM);
   return Changed;
 }
 
-NodeId CopyPropagation::getLocalReachingDef(RegisterRef RefRR,
-      NodeAddr<InstrNode*> IA) {
-  NodeAddr<RefNode*> RA = L.getNearestAliasedRef(RefRR, IA);
-  if (RA.Id != 0) {
-    if (RA.Addr->getKind() == NodeAttrs::Def)
-      return RA.Id;
-    assert(RA.Addr->getKind() == NodeAttrs::Use);
-    if (NodeId RD = RA.Addr->getReachingDef())
-      return RD;
-  }
-  return 0;
-}
-
 bool CopyPropagation::run() {
   scanBlock(&DFG.getMF().front());
 
@@ -111,6 +137,14 @@ bool CopyPropagation::run() {
                << Print<RegisterRef>(J.second, DFG);
       dbgs() << " }\n";
     }
+    dbgs() << "\nRDef map:\n";
+    for (auto R : RDefMap) {
+      dbgs() << Print<RegisterRef>(R.first, DFG) << " -> {";
+      for (auto &M : R.second)
+        dbgs() << ' ' << Print<NodeId>(M.first, DFG) << ':'
+               << Print<NodeId>(M.second, DFG);
+      dbgs() << " }\n";
+    }
   }
 
   bool Changed = false;
@@ -150,7 +184,8 @@ bool CopyPropagation::run() {
       if (DR == SR)
         continue;
 
-      NodeId AtCopy = getLocalReachingDef(SR, SA);
+      auto &RDefSR = RDefMap[SR];
+      NodeId RDefSR_SA = RDefSR[SA.Id];
 
       for (NodeId N = DA.Addr->getReachedUse(), NextN; N; N = NextN) {
         auto UA = DFG.addr<UseNode*>(N);
@@ -163,8 +198,7 @@ bool CopyPropagation::run() {
 
         NodeAddr<InstrNode*> IA = UA.Addr->getOwner(DFG);
         assert(DFG.IsCode<NodeAttrs::Stmt>(IA));
-        NodeId AtUse = getLocalReachingDef(SR, IA);
-        if (AtCopy != AtUse)
+        if (RDefSR[IA.Id] != RDefSR_SA)
           continue;
 
         MachineOperand &Op = UA.Addr->getOp();
@@ -180,8 +214,8 @@ bool CopyPropagation::run() {
         Op.setReg(NewReg);
         Op.setSubReg(0);
         DFG.unlinkUse(UA, false);
-        if (AtCopy != 0) {
-          UA.Addr->linkToDef(UA.Id, DFG.addr<DefNode*>(AtCopy));
+        if (RDefSR_SA != 0) {
+          UA.Addr->linkToDef(UA.Id, DFG.addr<DefNode*>(RDefSR_SA));
         } else {
           UA.Addr->setReachingDef(0);
           UA.Addr->setSibling(0);

llvm/lib/Target/Hexagon/RDFCopy.h

@@ -25,8 +25,7 @@ class MachineInstr;
 namespace rdf {
 
   struct CopyPropagation {
-    CopyPropagation(DataFlowGraph &dfg) : MDT(dfg.getDT()), DFG(dfg),
-        L(dfg.getMF().getRegInfo(), dfg) {}
+    CopyPropagation(DataFlowGraph &dfg) : MDT(dfg.getDT()), DFG(dfg) {}
 
     virtual ~CopyPropagation() = default;
 
@@ -36,22 +35,23 @@ namespace rdf {
     DataFlowGraph &getDFG() { return DFG; }
 
     using EqualityMap = std::map<RegisterRef, RegisterRef>;
-
     virtual bool interpretAsCopy(const MachineInstr *MI, EqualityMap &EM);
 
   private:
     const MachineDominatorTree &MDT;
     DataFlowGraph &DFG;
-    Liveness L;
+    DataFlowGraph::DefStackMap DefM;
     bool Trace = false;
 
+    // map: register -> (map: stmt -> reaching def)
+    std::map<RegisterRef,std::map<NodeId,NodeId>> RDefMap;
     // map: statement -> (map: dst reg -> src reg)
     std::map<NodeId, EqualityMap> CopyMap;
     std::vector<NodeId> Copies;
 
     void recordCopy(NodeAddr<StmtNode*> SA, EqualityMap &EM);
+    void updateMap(NodeAddr<InstrNode*> IA);
     bool scanBlock(MachineBasicBlock *B);
-    NodeId getLocalReachingDef(RegisterRef RefRR, NodeAddr<InstrNode*> IA);
   };
 
 } // end namespace rdf

llvm/test/CodeGen/Hexagon/rdf-copy.ll

@@ -1,4 +1,6 @@
-; RUN: llc -march=hexagon < %s | FileCheck %s
+; RUN: llc -march=hexagon -disable-copyprop < %s | FileCheck %s
+; Disable MachineCopyPropagation to expose this opportunity to RDF copy.
+
 ;
 ; Check that
 ;     {
@@ -26,7 +28,7 @@ target triple = "hexagon"
 %struct.t = type { [12 x i8], ptr, double }
 %struct.r = type opaque
 
-define ptr @foo(ptr %chain) nounwind readonly {
+define ptr @foo(ptr %chain) nounwind readonly #0 {
 entry:
   %tobool = icmp eq ptr %chain, null
   br i1 %tobool, label %if.end, label %while.cond.preheader
@@ -48,6 +50,8 @@ if.end:                                           ; preds = %if.end.loopexit, %e
   ret ptr %chain.addr.1
 }
 
+attributes #0 = { nounwind "target-features"="-packets" }
+
 !0 = !{!"any pointer", !1}
 !1 = !{!"omnipotent char", !2}
 !2 = !{!"Simple C/C++ TBAA"}