Subzero : Live Range Splitting after initial Register Allocation

src/IceCfgNode.cpp

Index: src/IceCfgNode.cpp
diff --git a/src/IceCfgNode.cpp b/src/IceCfgNode.cpp
index c92c9eb49af6f43dedd41739cde1cee4f83db4b0..eb0bcfc8aa6e1c5764a8938695336b51c28397f6 100644
--- a/src/IceCfgNode.cpp
+++ b/src/IceCfgNode.cpp
@@ -459,8 +459,10 @@ void CfgNode::advancedPhiLowering() {
       // Undo the effect of the phi instruction on this node's live-in set by
       // marking the phi dest variable as live on entry.
       SizeT VarNum = Func->getLiveness()->getLiveIndex(Dest->getIndex());
-      assert(!Func->getLiveness()->getLiveIn(this)[VarNum]);
-      Func->getLiveness()->getLiveIn(this)[VarNum] = true;
+      if (Func->getLiveness()->getLiveIn(this).size() >= VarNum) {

[Jim Stichnoth, 2016/07/29 17:04:06]

Shouldn't the '>=' be '>' ?

In any case, I think a more standard bounds-check idiom is:

  if (VarNum < Func->getLiveness()->getLiveIn(this).size()) {

Also, with repeated getLiveIn() calls, it might be clearer and more efficient to
do this:

  auto blah = Func->getLiveness()->getLiveIn(this);
  if (VarNum < blah.size()) {
    assert(!blah[VarNum]);
    blah[VarNum] = true;
  }

[manasijm, 2016/08/01 22:20:03]

Done.

+        assert(!Func->getLiveness()->getLiveIn(this)[VarNum]);
+        Func->getLiveness()->getLiveIn(this)[VarNum] = true;
+      }
       Phi->setDeleted();
     }
   }
@@ -867,15 +869,15 @@ void CfgNode::livenessAddIntervals(Liveness *Liveness, InstNumberT FirstInstNum,
 
     Variable *Var = Liveness->getVariable(i, this);
     if (LB > LE) {
-      Var->addLiveRange(FirstInstNum, LE);
-      Var->addLiveRange(LB, LastInstNum + 1);
+      Var->addLiveRange(FirstInstNum, LE, this);
+      Var->addLiveRange(LB, LastInstNum + 1, this);
       // Assert that Var is a global variable by checking that its liveness
       // index is less than the number of globals. This ensures that the
       // LiveInAndOut[] access is valid.
       assert(i < Liveness->getNumGlobalVars());
       LiveInAndOut[i] = false;
     } else {
-      Var->addLiveRange(LB, LE);
+      Var->addLiveRange(LB, LE, this);
     }
     if (i == i1)
       ++IBB;
@@ -887,7 +889,7 @@ void CfgNode::livenessAddIntervals(Liveness *Liveness, InstNumberT FirstInstNum,
        i = LiveInAndOut.find_next(i)) {
     Variable *Var = Liveness->getVariable(i, this);
     if (Liveness->getRangeMask(Var->getIndex()))
-      Var->addLiveRange(FirstInstNum, LastInstNum + 1);
+      Var->addLiveRange(FirstInstNum, LastInstNum + 1, this);
   }
 }