Subzero: Improve performance of liveness analysis and live range construction.

src/IceCfg.cpp

Index: src/IceCfg.cpp
diff --git a/src/IceCfg.cpp b/src/IceCfg.cpp
index 83d8e2664cd70cc9b4cea2fcc69e12af943a0a6f..6ef85b2c9c96821f980ca656920df82ebd0b6719 100644
--- a/src/IceCfg.cpp
+++ b/src/IceCfg.cpp
@@ -205,9 +205,9 @@ void Cfg::liveness(LivenessMode Mode) {
   // Collect timing for just the portion that constructs the live
   // range intervals based on the end-of-live-range computation, for a
   // finer breakdown of the cost.
+  TimerMarker T1(TimerStack::TT_liveRange, this);
   // Make a final pass over instructions to delete dead instructions
   // and build each Variable's live range.
-  TimerMarker T1(TimerStack::TT_liveRange, this);
   for (CfgNode *Node : Nodes)
     Node->livenessPostprocess(Mode, getLiveness());
   if (Mode == Liveness_Intervals) {
@@ -246,7 +246,6 @@ void Cfg::liveness(LivenessMode Mode) {
       if (Var->getWeight().isInf())
         Var->setLiveRangeInfiniteWeight();
     }
-    dump();
   }
 }
 
@@ -263,14 +262,14 @@ bool Cfg::validateLiveness() const {
       if (llvm::isa<InstFakeKill>(Inst))
         continue;
       InstNumberT InstNumber = Inst->getNumber();
-      Variable *Dest = Inst->getDest();
-      if (Dest) {
+      if (Variable *Dest = Inst->getDest()) {
         // TODO: This instruction should actually begin Dest's live
         // range, so we could probably test that this instruction is
         // the beginning of some segment of Dest's live range.  But
         // this wouldn't work with non-SSA temporaries during

[jvoung (off chromium), 2014/10/13 20:50:50]

with the new flag for non-SSA temporaries, could the containsValue() be stricter
(if I'm reading the TODO comment correctly)?

[Jim Stichnoth, 2014/10/13 23:15:22]

Cool, done.  There's a minor problem when a phi temporary is assigned in the
first instruction of the block, but is also live at the end of the previous
block, so we just avoid testing the first instruction of the block.

[jvoung (off chromium), 2014/10/13 23:38:29]

Thanks! Can the TODO be removed then?

[Jim Stichnoth, 2014/10/14 00:15:01]

Oops, done.

         // lowering.
-        if (!Dest->getLiveRange().containsValue(InstNumber)) {
+        if (!Dest->getIgnoreLiveness() &&
+            !Dest->getLiveRange().containsValue(InstNumber)) {
           Valid = false;
           Str << "Liveness error: inst " << Inst->getNumber() << " dest ";
           Dest->dump(this);
@@ -282,7 +281,8 @@ bool Cfg::validateLiveness() const {
         SizeT NumVars = Src->getNumVars();
         for (SizeT J = 0; J < NumVars; ++J) {
           const Variable *Var = Src->getVar(J);
-          if (!Var->getLiveRange().containsValue(InstNumber)) {
+          if (!Var->getIgnoreLiveness() &&
+              !Var->getLiveRange().containsValue(InstNumber)) {
             Valid = false;
             Str << "Liveness error: inst " << Inst->getNumber() << " var ";
             Var->dump(this);