address feedback

Author: boomanaiden154

llvm/lib/CodeGen/MLRegAllocEvictAdvisor.cpp

@@ -366,6 +366,9 @@ class MLEvictAdvisor : public RegAllocEvictionAdvisor {
   mutable DenseMap<RegID, LIFeatureComponents> CachedFeatures;
 
   mutable std::unordered_map<unsigned, unsigned> VirtRegEvictionCounts;
+  void incrementEvictionCount(const CandidateRegList &Regs,
+                              const LiveInterval &VirtReg,
+                              size_t CandidatePosition) const;
 };
 
 #define _DECL_FEATURES(type, name, shape, _)                                   \
@@ -658,7 +661,10 @@ bool MLEvictAdvisor::loadInterferenceFeatures(
       // large amount of compile time being spent in regalloc. If we hit the
       // threshold, prevent the range from being evicted. We still let the
       // range through if it is urgent as we are required to produce an
-      // eviction if the candidate is not spillable.
+      // eviction if the candidate is not spillable. If we cannot find the
+      // virtual register in the map, we just assume it has not been evicted
+      // before and thus has a value of zero (which is what the subscript
+      // operator returns by default).
       if (VirtRegEvictionCounts[Intf->reg().id()] > MaxEvictionCount && !Urgent)
         return false;
 
@@ -680,6 +686,22 @@ bool MLEvictAdvisor::loadInterferenceFeatures(
   return true;
 }
 
+void MLEvictAdvisor::incrementEvictionCount(const CandidateRegList &Regs,
+                                            const LiveInterval &VirtReg,
+                                            size_t CandidatePosition) const {
+  if (CandidatePosition == CandidateVirtRegPos) {
+    VirtRegEvictionCounts[VirtReg.reg()] += 1;
+  } else {
+    for (MCRegUnit Unit : TRI->regunits(Regs[CandidatePosition].first)) {
+      LiveIntervalUnion::Query &Q = Matrix->query(VirtReg, Unit);
+      const auto &IFIntervals = Q.interferingVRegs(EvictInterferenceCutoff);
+      for (const LiveInterval *Intf : reverse(IFIntervals)) {
+        VirtRegEvictionCounts[Intf->reg()] += 1;
+      }
+    }
+  }
+}
+
 MCRegister MLEvictAdvisor::tryFindEvictionCandidate(
     const LiveInterval &VirtReg, const AllocationOrder &Order,
     uint8_t CostPerUseLimit, const SmallVirtRegSet &FixedRegisters) const {
@@ -807,18 +829,9 @@ MCRegister MLEvictAdvisor::tryFindEvictionCandidate(
   (void)ValidPosLimit;
 
   // Update information about how many times the virtual registers being
-  // evicted have been evicted.
-  if (CandidatePos == CandidateVirtRegPos) {
-    VirtRegEvictionCounts[VirtReg.reg()] += 1;
-  } else {
-    for (MCRegUnit Unit : TRI->regunits(Regs[CandidatePos].first)) {
-      LiveIntervalUnion::Query &Q = Matrix->query(VirtReg, Unit);
-      const auto &IFIntervals = Q.interferingVRegs(EvictInterferenceCutoff);
-      for (const LiveInterval *Intf : reverse(IFIntervals)) {
-        VirtRegEvictionCounts[Intf->reg()] += 1;
-      }
-    }
-  }
+  // evicted have been evicted so that we can prevent the model from evicting
+  // the same ranges continually and eating compile time.
+  incrementEvictionCount(Regs, VirtReg, CandidatePos);
 
   return Regs[CandidatePos].first;
 }