Subzero: Completely remove tracking of stack pointer live range.

src/IceLiveness.cpp

Index: src/IceLiveness.cpp
diff --git a/src/IceLiveness.cpp b/src/IceLiveness.cpp
index a1de893644c2814059079e3f856a04c6426b8389..18ef47841a063ae9f6ad8bbd4b5e0b3cffbce8e4 100644
--- a/src/IceLiveness.cpp
+++ b/src/IceLiveness.cpp
@@ -71,8 +71,12 @@ void Liveness::initInternal(NodeList::const_iterator FirstNode,
   if (IsFullInit)
     LiveToVarMap.assign(NumGlobals, nullptr);
 
-  // Sort each variable into the appropriate LiveToVarMap.  Also set
-  // VarToLiveMap.
+  // Initialize the bitmask of which variables to track.
+  RangeMask.resize(NumVars);
+  RangeMask.set(0, NumVars); // Track all variables by default.
+
+  // Sort each variable into the appropriate LiveToVarMap.  Set VarToLiveMap.
+  // Set RangeMask correctly for each variable.
   TmpNumGlobals = 0;
   for (auto I = FirstVar, E = Func->getVariables().end(); I != E; ++I) {
     Variable *Var = *I;
@@ -88,9 +92,21 @@ void Liveness::initInternal(NodeList::const_iterator FirstNode,
       LiveIndex += NumGlobals;
     }
     VarToLiveMap[VarIndex] = LiveIndex;
+    if (Var->getIgnoreLiveness() ||
+        (!IsFullInit && !Var->hasReg() && !Var->getWeight().isInf()))

[jvoung (off chromium), 2015/08/06 21:39:14]

I wasn't sure if the extra conditions here:
(!IsFullInit && !Var->hasReg && !Var->getWeight().isInf()) conflict with the
earlier change: https://codereview.chromium.org/1271923002, since this set of
vars is from FirstVar to End (could reflect new vars created from phi lowering)?

"For post phi lowering liveness analysis, all variables created from phi
lowering..., are tracked".  I thought it was just the ones before FirstVar that
had the extra conditions related to !hasReg and !isInf.

[Jim Stichnoth, 2015/08/06 22:38:50]

Yikes, thanks!  This change basically reverted that previous CL.  With the
latest patchset, the spec2k asm is identical to that in master.

+      RangeMask[VarIndex] = false;
   }
   assert(TmpNumGlobals == (IsFullInit ? NumGlobals : 0));
 
+  // Fix up RangeMask for variables before FirstVar.
+  for (auto I = Func->getVariables().begin(); I != FirstVar; ++I) {
+    Variable *Var = *I;
+    SizeT VarIndex = Var->getIndex();
+    if (Var->getIgnoreLiveness() ||
+        (!IsFullInit && !Var->hasReg() && !Var->getWeight().isInf()))
+      RangeMask[VarIndex] = false;
+  }
+
   // Process each node.
   for (auto I = FirstNode, E = Func->getNodes().end(); I != E; ++I) {
     LivenessNode &Node = Nodes[(*I)->getIndex()];
@@ -100,17 +116,6 @@ void Liveness::initInternal(NodeList::const_iterator FirstNode,
     // LiveBegin and LiveEnd are reinitialized before each pass over
     // the block.
   }
-
-  // Initialize the bitmask of which variables to track.
-  RangeMask.resize(NumVars);
-  RangeMask.set(0, NumVars);
-  if (!IsFullInit) {
-    // Reset initial variables that are not pre-colored or infinite-weight.
-    for (auto I = Func->getVariables().begin(); I != FirstVar; ++I) {
-      Variable *Var = *I;
-      RangeMask[Var->getIndex()] = (Var->hasReg() || Var->getWeight().isInf());
-    }
-  }
 }
 
 void Liveness::init() {