[PATCH] [MachineLICM] Use newer model of register pressure sets.

[Daniel Jasper]

Hi qcolombet,

TargetRegisterInfo::getRegPressureLimit has a note that it is an old model that relies on manually entered classes. Using the newer model of register pressure sets seems more appropriate. We might eventually even switch to lib/CodeGen/RegisterPressure.cpp, but we should probably do incremental changes here.

Using the newer model also makes it easier to take regmasks into account which is necessary to fix llvm.org/PR23143. I am currently also preparing a patch for that, but would like to do this switch independently.

http://reviews.llvm.org/D8986

Files:
  lib/CodeGen/MachineLICM.cpp

Index: lib/CodeGen/MachineLICM.cpp
===================================================================
--- lib/CodeGen/MachineLICM.cpp
+++ lib/CodeGen/MachineLICM.cpp
@@ -251,11 +251,6 @@
     /// if there is little to no overhead moving instructions into loops.
     void SinkIntoLoop();
 
-    /// getRegisterClassIDAndCost - For a given register return the ID and cost
-    /// of its representative register class by reference.
-    void getRegisterClassIDAndCost(unsigned Reg, unsigned &RCId,
-                                   unsigned &RCCost) const;
-
     /// InitRegPressure - Find all virtual register references that are liveout
     /// of the preheader to initialize the starting "register pressure". Note
     /// this does not count live through (livein but not used) registers.
@@ -360,13 +355,12 @@
 
   if (PreRegAlloc) {
     // Estimate register pressure during pre-regalloc pass.
-    unsigned NumRC = TRI->getNumRegClasses();
+    unsigned NumRC = TRI->getNumRegPressureSets();
     RegPressure.resize(NumRC);
     std::fill(RegPressure.begin(), RegPressure.end(), 0);
     RegLimit.resize(NumRC);
-    for (TargetRegisterInfo::regclass_iterator I = TRI->regclass_begin(),
-           E = TRI->regclass_end(); I != E; ++I)
-      RegLimit[(*I)->getID()] = TRI->getRegPressureLimit(*I, MF);
+    for (unsigned i = 0, e = NumRC; i != e; ++i)
+      RegLimit[i] = TRI->getRegPressureSetLimit(MF, i);
   }
 
   // Get our Loop information...
@@ -842,19 +836,6 @@
   return MO.isKill() || MRI->hasOneNonDBGUse(MO.getReg());
 }
 
-void MachineLICM::getRegisterClassIDAndCost(unsigned Reg, unsigned &RCId,
-                                            unsigned &RCCost) const {
-  const TargetRegisterClass *RC = MRI->getRegClass(Reg);
-  MVT VT = *RC->vt_begin();
-  if (VT == MVT::Untyped) {
-    RCId = RC->getID();
-    RCCost = 1;
-  } else {
-    RCId = TLI->getRepRegClassFor(VT)->getID();
-    RCCost = TLI->getRepRegClassCostFor(VT);
-  }
-}
-
 /// InitRegPressure - Find all virtual register references that are liveout of
 /// the preheader to initialize the starting "register pressure". Note this
 /// does not count live through (livein but not used) registers.
@@ -906,20 +887,26 @@
 
     // FIXME: It seems bad to use RegSeen only for some of these calculations.
     bool isNew = ConsiderSeen ? RegSeen.insert(Reg).second : false;
-    unsigned RCId, RCCost;
-    getRegisterClassIDAndCost(Reg, RCId, RCCost);
-    int PriorCost = 0;
-    if (Cost.find(RCId) != Cost.end())
-      PriorCost = Cost[RCId];
+    const TargetRegisterClass *RC = MRI->getRegClass(Reg);
+
+    RegClassWeight W = TRI->getRegClassWeight(RC);
+    int RCCost = 0;
     if (MO.isDef())
-      Cost[RCId] = PriorCost + RCCost;
+      RCCost = W.RegWeight;
     else {
       bool isKill = isOperandKill(MO, MRI);
       if (isNew && !isKill && ConsiderUnseenAsDef)
         // Haven't seen this, it must be a livein.
-        Cost[RCId] = PriorCost + RCCost;
+        RCCost = W.RegWeight;
       else if (!isNew && isKill)
-        Cost[RCId] = PriorCost - RCCost;
+        RCCost = -W.RegWeight;
+    }
+    const int *PS = TRI->getRegClassPressureSets(RC);
+    for (; *PS != -1; ++PS) {
+      if (Cost.find(*PS) != Cost.end())
+        Cost[*PS] = RCCost;
+      else
+        Cost[*PS] += RCCost;
     }
   }
   return Cost;

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