From 26255adcaa5836fafe32e5e296d81df63a0fb9c5 Mon Sep 17 00:00:00 2001 From: Dan Gohman Date: Wed, 12 Aug 2009 01:33:27 +0000 Subject: [PATCH] Factor out the code for finding an available register for use in breaking an anti-dependence into a separate function. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@78767 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/CodeGen/PostRASchedulerList.cpp | 116 ++++++++++++++++------------ 1 file changed, 66 insertions(+), 50 deletions(-) diff --git a/lib/CodeGen/PostRASchedulerList.cpp b/lib/CodeGen/PostRASchedulerList.cpp index 944bfee8a9f..27c73a75951 100644 --- a/lib/CodeGen/PostRASchedulerList.cpp +++ b/lib/CodeGen/PostRASchedulerList.cpp @@ -158,6 +158,9 @@ namespace { void ScheduleNodeTopDown(SUnit *SU, unsigned CurCycle); void ListScheduleTopDown(); bool BreakAntiDependencies(); + unsigned findSuitableFreeRegister(unsigned AntiDepReg, + unsigned LastNewReg, + const TargetRegisterClass *); }; } @@ -510,6 +513,36 @@ void SchedulePostRATDList::ScanInstruction(MachineInstr *MI, } } +unsigned +SchedulePostRATDList::findSuitableFreeRegister(unsigned AntiDepReg, + unsigned LastNewReg, + const TargetRegisterClass *RC) { + for (TargetRegisterClass::iterator R = RC->allocation_order_begin(MF), + RE = RC->allocation_order_end(MF); R != RE; ++R) { + unsigned NewReg = *R; + // Don't replace a register with itself. + if (NewReg == AntiDepReg) continue; + // Don't replace a register with one that was recently used to repair + // an anti-dependence with this AntiDepReg, because that would + // re-introduce that anti-dependence. + if (NewReg == LastNewReg) continue; + // If NewReg is dead and NewReg's most recent def is not before + // AntiDepReg's kill, it's safe to replace AntiDepReg with NewReg. + assert(((KillIndices[AntiDepReg] == ~0u) != (DefIndices[AntiDepReg] == ~0u)) && + "Kill and Def maps aren't consistent for AntiDepReg!"); + assert(((KillIndices[NewReg] == ~0u) != (DefIndices[NewReg] == ~0u)) && + "Kill and Def maps aren't consistent for NewReg!"); + if (KillIndices[NewReg] == ~0u && + Classes[NewReg] != reinterpret_cast(-1) && + KillIndices[AntiDepReg] <= DefIndices[NewReg]) + continue; + return NewReg; + } + + // No registers are free and available! + return 0; +} + /// BreakAntiDependencies - Identifiy anti-dependencies along the critical path /// of the ScheduleDAG and break them by renaming registers. /// @@ -674,60 +707,43 @@ bool SchedulePostRATDList::BreakAntiDependencies() { // TODO: Instead of picking the first free register, consider which might // be the best. if (AntiDepReg != 0) { - for (TargetRegisterClass::iterator R = RC->allocation_order_begin(MF), - RE = RC->allocation_order_end(MF); R != RE; ++R) { - unsigned NewReg = *R; - // Don't replace a register with itself. - if (NewReg == AntiDepReg) continue; - // Don't replace a register with one that was recently used to repair - // an anti-dependence with this AntiDepReg, because that would - // re-introduce that anti-dependence. - if (NewReg == LastNewReg[AntiDepReg]) continue; - // If NewReg is dead and NewReg's most recent def is not before - // AntiDepReg's kill, it's safe to replace AntiDepReg with NewReg. - assert(((KillIndices[AntiDepReg] == ~0u) != (DefIndices[AntiDepReg] == ~0u)) && - "Kill and Def maps aren't consistent for AntiDepReg!"); - assert(((KillIndices[NewReg] == ~0u) != (DefIndices[NewReg] == ~0u)) && - "Kill and Def maps aren't consistent for NewReg!"); - if (KillIndices[NewReg] == ~0u && - Classes[NewReg] != reinterpret_cast(-1) && - KillIndices[AntiDepReg] <= DefIndices[NewReg]) { - DEBUG(errs() << "Breaking anti-dependence edge on " - << TRI->getName(AntiDepReg) - << " with " << RegRefs.count(AntiDepReg) << " references" - << " using " << TRI->getName(NewReg) << "!\n"); + if (unsigned NewReg = findSuitableFreeRegister(AntiDepReg, + LastNewReg[AntiDepReg], + RC)) { + DEBUG(errs() << "Breaking anti-dependence edge on " + << TRI->getName(AntiDepReg) + << " with " << RegRefs.count(AntiDepReg) << " references" + << " using " << TRI->getName(NewReg) << "!\n"); - // Update the references to the old register to refer to the new - // register. - std::pair::iterator, - std::multimap::iterator> - Range = RegRefs.equal_range(AntiDepReg); - for (std::multimap::iterator - Q = Range.first, QE = Range.second; Q != QE; ++Q) - Q->second->setReg(NewReg); + // Update the references to the old register to refer to the new + // register. + std::pair::iterator, + std::multimap::iterator> + Range = RegRefs.equal_range(AntiDepReg); + for (std::multimap::iterator + Q = Range.first, QE = Range.second; Q != QE; ++Q) + Q->second->setReg(NewReg); - // We just went back in time and modified history; the - // liveness information for the anti-depenence reg is now - // inconsistent. Set the state as if it were dead. - Classes[NewReg] = Classes[AntiDepReg]; - DefIndices[NewReg] = DefIndices[AntiDepReg]; - KillIndices[NewReg] = KillIndices[AntiDepReg]; - assert(((KillIndices[NewReg] == ~0u) != - (DefIndices[NewReg] == ~0u)) && - "Kill and Def maps aren't consistent for NewReg!"); + // We just went back in time and modified history; the + // liveness information for the anti-depenence reg is now + // inconsistent. Set the state as if it were dead. + Classes[NewReg] = Classes[AntiDepReg]; + DefIndices[NewReg] = DefIndices[AntiDepReg]; + KillIndices[NewReg] = KillIndices[AntiDepReg]; + assert(((KillIndices[NewReg] == ~0u) != + (DefIndices[NewReg] == ~0u)) && + "Kill and Def maps aren't consistent for NewReg!"); - Classes[AntiDepReg] = 0; - DefIndices[AntiDepReg] = KillIndices[AntiDepReg]; - KillIndices[AntiDepReg] = ~0u; - assert(((KillIndices[AntiDepReg] == ~0u) != - (DefIndices[AntiDepReg] == ~0u)) && - "Kill and Def maps aren't consistent for AntiDepReg!"); + Classes[AntiDepReg] = 0; + DefIndices[AntiDepReg] = KillIndices[AntiDepReg]; + KillIndices[AntiDepReg] = ~0u; + assert(((KillIndices[AntiDepReg] == ~0u) != + (DefIndices[AntiDepReg] == ~0u)) && + "Kill and Def maps aren't consistent for AntiDepReg!"); - RegRefs.erase(AntiDepReg); - Changed = true; - LastNewReg[AntiDepReg] = NewReg; - break; - } + RegRefs.erase(AntiDepReg); + Changed = true; + LastNewReg[AntiDepReg] = NewReg; } }