Subzero: Reduce copying of Liveness bitvectors.

src/IceCfg.cpp

Index: src/IceCfg.cpp
diff --git a/src/IceCfg.cpp b/src/IceCfg.cpp
index 5c51ae6d3893316efe28aff8793de937b902931b..7df55f523f5c919fd8257845928c4c3b57387262 100644
--- a/src/IceCfg.cpp
+++ b/src/IceCfg.cpp
@@ -334,12 +334,13 @@ void Cfg::advancedPhiLowering() {
     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 {
@@ -820,12 +821,13 @@ void Cfg::liveness(LivenessMode Mode) {
   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.
@@ -1076,6 +1078,11 @@ void Cfg::emitIAS() {
   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())
@@ -1087,10 +1094,7 @@ void Cfg::dump(const IceString &Message) {
   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