+/// This is not accurate because two overlapping register sets may have some
+/// nonoverlapping reserved registers. However, computing the allocation order
+/// for all register classes would be too expensive.
+unsigned RegisterClassInfo::computePSetLimit(unsigned Idx) const {
+ const TargetRegisterClass *RC = 0;
+ unsigned NumRCUnits = 0;
+ for (TargetRegisterInfo::regclass_iterator
+ RI = TRI->regclass_begin(), RE = TRI->regclass_end(); RI != RE; ++RI) {
+ const int *PSetID = TRI->getRegClassPressureSets(*RI);
+ for (; *PSetID != -1; ++PSetID) {
+ if ((unsigned)*PSetID == Idx)
+ break;
+ }
+ if (*PSetID == -1)
+ continue;
+
+ // Found a register class that counts against this pressure set.
+ // For efficiency, only compute the set order for the largest set.
+ unsigned NUnits = TRI->getRegClassWeight(*RI).WeightLimit;
+ if (!RC || NUnits > NumRCUnits) {
+ RC = *RI;
+ NumRCUnits = NUnits;
+ }
+ }
+ compute(RC);
+ unsigned NReserved = RC->getNumRegs() - getNumAllocatableRegs(RC);
+ return TRI->getRegPressureSetLimit(Idx)
+ - TRI->getRegClassWeight(RC).RegWeight * NReserved;
+}