+
+ // Speculatively check to see if we can get a register right now. If not,
+ // we know we won't be able to by adding more constraints. If so, we can
+ // check to see if it is valid. Doing an exhaustive search of the fixed_ list
+ // is very bad (it contains all callee clobbered registers for any functions
+ // with a call), so we want to avoid doing that if possible.
+ unsigned physReg = getFreePhysReg(cur);
+ if (physReg) {
+ // We got a register. However, if it's in the fixed_ list, we might
+ // conflict with it. Check to see if we conflict with it or any of its
+ // aliases.
+ SmallSet<unsigned, 8> RegAliases;
+ for (const unsigned *AS = tri_->getAliasSet(physReg); *AS; ++AS)
+ RegAliases.insert(*AS);
+
+ bool ConflictsWithFixed = false;
+ for (unsigned i = 0, e = fixed_.size(); i != e; ++i) {
+ IntervalPtr &IP = fixed_[i];
+ if (physReg == IP.first->reg || RegAliases.count(IP.first->reg)) {
+ // Okay, this reg is on the fixed list. Check to see if we actually
+ // conflict.
+ LiveInterval *I = IP.first;
+ if (I->endNumber() > StartPosition) {
+ LiveInterval::iterator II = I->advanceTo(IP.second, StartPosition);
+ IP.second = II;
+ if (II != I->begin() && II->start > StartPosition)
+ --II;
+ if (cur->overlapsFrom(*I, II)) {
+ ConflictsWithFixed = true;
+ break;
+ }
+ }
+ }
+ }
+
+ // Okay, the register picked by our speculative getFreePhysReg call turned
+ // out to be in use. Actually add all of the conflicting fixed registers to
+ // prt so we can do an accurate query.
+ if (ConflictsWithFixed) {
+ // For every interval in fixed we overlap with, mark the register as not
+ // free and update spill weights.
+ for (unsigned i = 0, e = fixed_.size(); i != e; ++i) {
+ IntervalPtr &IP = fixed_[i];
+ LiveInterval *I = IP.first;
+
+ const TargetRegisterClass *RegRC = OneClassForEachPhysReg[I->reg];
+ if (RelatedRegClasses.getLeaderValue(RegRC) == RCLeader &&
+ I->endNumber() > StartPosition) {
+ LiveInterval::iterator II = I->advanceTo(IP.second, StartPosition);
+ IP.second = II;
+ if (II != I->begin() && II->start > StartPosition)
+ --II;
+ if (cur->overlapsFrom(*I, II)) {
+ unsigned reg = I->reg;
+ prt_->addRegUse(reg);
+ SpillWeightsToAdd.push_back(std::make_pair(reg, I->weight));
+ }
+ }
+ }