Subzero: Optimize a common live range overlap calculation.

src/IceOperand.cpp

 //===- subzero/src/IceOperand.cpp - High-level operand implementation -----===//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // This file implements the Operand class and its target-independent
@@ skipping 19 matching lines @@
 
 bool operator<(const RegWeight &A, const RegWeight &B) {
   return A.getWeight() < B.getWeight();
 }
 bool operator<=(const RegWeight &A, const RegWeight &B) { return !(B < A); }
 bool operator==(const RegWeight &A, const RegWeight &B) {
   return !(B < A) && !(A < B);
 }
 
 void LiveRange::addSegment(InstNumberT Start, InstNumberT End) {
+  if (End > Start)
+    IsNonpoints = true;
 #ifdef USE_SET
   RangeElementType Element(Start, End);
   RangeType::iterator Next = Range.lower_bound(Element);
   assert(Next == Range.upper_bound(Element)); // Element not already present
 
   // Beginning of code that merges contiguous segments.  TODO: change
   // "if(true)" to "if(false)" to see if this extra optimization code
   // gives any performance gain, or is just destabilizing.
   if (true) {
     RangeType::iterator FirstDelete = Next;
@@ skipping 65 matching lines @@
     if (I2->second <= I1->first) {
       ++I2;
       continue;
     }
     return true;
   }
   return false;
 }
 
 bool LiveRange::overlaps(InstNumberT OtherBegin) const {
+  if (!IsNonpoints)
+    return false;
   bool Result = false;
   for (const RangeElementType &I : Range) {
     if (OtherBegin < I.first) {
       Result = false;
       break;
     }
     if (OtherBegin < I.second) {
       Result = true;
       break;
     }
@@ skipping 313 matching lines @@
 
 Ostream &operator<<(Ostream &Str, const RegWeight &W) {
   if (W.getWeight() == RegWeight::Inf)
     Str << "Inf";
   else
     Str << W.getWeight();
   return Str;
 }
 
 } // end of namespace Ice