Subzero: Reduce copying of Liveness bitvectors.

src/IceCfg.cpp

 //===- subzero/src/IceCfg.cpp - Control flow graph implementation ---------===//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 ///
 /// \file
@@ skipping 316 matching lines @@
   for (SizeT I = 0; I < NumNodes; ++I)
     Nodes[I]->advancedPhiLowering();
 
   TimerMarker TT(TimerStack::TT_lowerPhiAssignments, this);
   if (true) {
     // The following code does an in-place update of liveness and live ranges
     // as a result of adding the new phi edge split nodes.
     getLiveness()->initPhiEdgeSplits(Nodes.begin() + NumNodes,
                                      Variables.begin() + NumVars);
     TimerMarker TTT(TimerStack::TT_liveness, this);
+    LivenessBV ScratchBV;
     // Iterate over the newly added nodes to add their liveness info.
     for (auto I = Nodes.begin() + NumNodes, E = Nodes.end(); I != E; ++I) {
       InstNumberT FirstInstNum = getNextInstNumber();
       (*I)->renumberInstructions();
       InstNumberT LastInstNum = getNextInstNumber() - 1;
-      (*I)->liveness(getLiveness());
+      (*I)->liveness(getLiveness(), &ScratchBV);

[John, 2016/02/29 15:12:31]

make scratchbv a member of Liveness?

[Jim Stichnoth, 2016/02/29 22:58:26]

Done.

       (*I)->livenessAddIntervals(getLiveness(), FirstInstNum, LastInstNum);
     }
   } else {
     // The following code does a brute-force recalculation of live ranges as a
     // result of adding the new phi edge split nodes. The liveness calculation
     // is particularly expensive because the new nodes are not yet in a proper
     // topological order and so convergence is slower.
     //
     // This code is kept here for reference and can be temporarily enabled in
     // case the incremental code is under suspicion.
@@ skipping 460 matching lines @@
     Node->livenessLightweight();
 }
 
 void Cfg::liveness(LivenessMode Mode) {
   TimerMarker T(TimerStack::TT_liveness, this);
   Live.reset(new Liveness(this, Mode));
   getVMetadata()->init(VMK_Uses);
   Live->init();
   // Initialize with all nodes needing to be processed.
   BitVector NeedToProcess(Nodes.size(), true);
+  LivenessBV ScratchBV;
   while (NeedToProcess.any()) {
     // Iterate in reverse topological order to speed up convergence.
     for (CfgNode *Node : reverse_range(Nodes)) {
       if (NeedToProcess[Node->getIndex()]) {
         NeedToProcess[Node->getIndex()] = false;
-        bool Changed = Node->liveness(getLiveness());
+        bool Changed = Node->liveness(getLiveness(), &ScratchBV);
         if (Changed) {
           // If the beginning-of-block liveness changed since the last
           // iteration, mark all in-edges as needing to be processed.
           for (CfgNode *Pred : Node->getInEdges())
             NeedToProcess[Pred->getIndex()] = true;
         }
       }
     }
   }
   if (Mode == Liveness_Intervals) {
@@ skipping 230 matching lines @@
   deleteJumpTableInsts();
   const bool NeedSandboxing = Ctx->getFlags().getUseSandboxing();
   for (CfgNode *Node : Nodes) {
     if (NeedSandboxing && Node->needsAlignment())
       getAssembler()->alignCfgNode();
     Node->emitIAS(this);
   }
   emitJumpTables();
 }
 
+size_t Cfg::getTotalMemoryMB() {
+  constexpr size_t OneMB = 1024 * 1024;
+  return (CfgLocalAllocator<int>().current()->getTotalMemory() / OneMB);

[John, 2016/02/29 15:12:30]

Add a comment explaining why int and not something else.

[Jim Stichnoth, 2016/02/29 22:58:26]

Done.

+}
+
 // Dumps the IR with an optional introductory message.
 void Cfg::dump(const IceString &Message) {
   if (!BuildDefs::dump())
     return;
   if (!isVerbose())
     return;
   OstreamLocker L(Ctx);
   Ostream &Str = Ctx->getStrDump();
   if (!Message.empty())
     Str << "================ " << Message << " ================\n";
   if (isVerbose(IceV_Mem)) {
-    constexpr size_t OneMB = 1024 * 1024;
-    Str << "Memory size = "
-        << (CfgLocalAllocator<int>().current()->getTotalMemory() / OneMB)
-        << " MB\n";
+    Str << "Memory size = " << getTotalMemoryMB() << " MB\n";
   }
   setCurrentNode(getEntryNode());
   // Print function name+args
   if (isVerbose(IceV_Instructions)) {
     Str << "define ";
     if (getInternal() && !Ctx->getFlags().getDisableInternal())
       Str << "internal ";
     Str << ReturnType << " @" << Ctx->mangleName(getFunctionName()) << "(";
     for (SizeT i = 0; i < Args.size(); ++i) {
       if (i > 0)
@@ skipping 36 matching lines @@
     }
   }
   // Print each basic block
   for (CfgNode *Node : Nodes)
     Node->dump(this);
   if (isVerbose(IceV_Instructions))
     Str << "}\n";
 }
 
 } // end of namespace Ice