| //===- InterferenceCache.cpp - Caching per-block interference -------------===// |
| // |
| // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| // See https://llvm.org/LICENSE.txt for license information. |
| // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // InterferenceCache remembers per-block interference in LiveIntervalUnions. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "InterferenceCache.h" |
| #include "llvm/ADT/ArrayRef.h" |
| #include "llvm/CodeGen/LiveIntervals.h" |
| #include "llvm/CodeGen/MachineBasicBlock.h" |
| #include "llvm/CodeGen/MachineFunction.h" |
| #include "llvm/CodeGen/MachineOperand.h" |
| #include "llvm/CodeGen/TargetRegisterInfo.h" |
| #include "llvm/MC/MCRegisterInfo.h" |
| #include "llvm/Support/ErrorHandling.h" |
| #include <cassert> |
| #include <cstdint> |
| #include <tuple> |
| |
| using namespace llvm; |
| |
| #define DEBUG_TYPE "regalloc" |
| |
| // Static member used for null interference cursors. |
| const InterferenceCache::BlockInterference |
| InterferenceCache::Cursor::NoInterference; |
| |
| // Initializes PhysRegEntries (instead of a SmallVector, PhysRegEntries is a |
| // buffer of size NumPhysRegs to speed up alloc/clear for targets with large |
| // reg files). Calloced memory is used for good form, and quites tools like |
| // Valgrind too, but zero initialized memory is not required by the algorithm: |
| // this is because PhysRegEntries works like a SparseSet and its entries are |
| // only valid when there is a corresponding CacheEntries assignment. There is |
| // also support for when pass managers are reused for targets with different |
| // numbers of PhysRegs: in this case PhysRegEntries is freed and reinitialized. |
| void InterferenceCache::reinitPhysRegEntries() { |
| if (PhysRegEntriesCount == TRI->getNumRegs()) return; |
| free(PhysRegEntries); |
| PhysRegEntriesCount = TRI->getNumRegs(); |
| PhysRegEntries = static_cast<unsigned char*>( |
| safe_calloc(PhysRegEntriesCount, sizeof(unsigned char))); |
| } |
| |
| void InterferenceCache::init(MachineFunction *mf, |
| LiveIntervalUnion *liuarray, |
| SlotIndexes *indexes, |
| LiveIntervals *lis, |
| const TargetRegisterInfo *tri) { |
| MF = mf; |
| LIUArray = liuarray; |
| TRI = tri; |
| reinitPhysRegEntries(); |
| for (Entry &E : Entries) |
| E.clear(mf, indexes, lis); |
| } |
| |
| InterferenceCache::Entry *InterferenceCache::get(MCRegister PhysReg) { |
| unsigned char E = PhysRegEntries[PhysReg.id()]; |
| if (E < CacheEntries && Entries[E].getPhysReg() == PhysReg) { |
| if (!Entries[E].valid(LIUArray, TRI)) |
| Entries[E].revalidate(LIUArray, TRI); |
| return &Entries[E]; |
| } |
| // No valid entry exists, pick the next round-robin entry. |
| E = RoundRobin; |
| if (++RoundRobin == CacheEntries) |
| RoundRobin = 0; |
| for (unsigned i = 0; i != CacheEntries; ++i) { |
| // Skip entries that are in use. |
| if (Entries[E].hasRefs()) { |
| if (++E == CacheEntries) |
| E = 0; |
| continue; |
| } |
| Entries[E].reset(PhysReg, LIUArray, TRI, MF); |
| PhysRegEntries[PhysReg] = E; |
| return &Entries[E]; |
| } |
| llvm_unreachable("Ran out of interference cache entries."); |
| } |
| |
| /// revalidate - LIU contents have changed, update tags. |
| void InterferenceCache::Entry::revalidate(LiveIntervalUnion *LIUArray, |
| const TargetRegisterInfo *TRI) { |
| // Invalidate all block entries. |
| ++Tag; |
| // Invalidate all iterators. |
| PrevPos = SlotIndex(); |
| unsigned i = 0; |
| for (MCRegUnitIterator Units(PhysReg, TRI); Units.isValid(); ++Units, ++i) |
| RegUnits[i].VirtTag = LIUArray[*Units].getTag(); |
| } |
| |
| void InterferenceCache::Entry::reset(MCRegister physReg, |
| LiveIntervalUnion *LIUArray, |
| const TargetRegisterInfo *TRI, |
| const MachineFunction *MF) { |
| assert(!hasRefs() && "Cannot reset cache entry with references"); |
| // LIU's changed, invalidate cache. |
| ++Tag; |
| PhysReg = physReg; |
| Blocks.resize(MF->getNumBlockIDs()); |
| |
| // Reset iterators. |
| PrevPos = SlotIndex(); |
| RegUnits.clear(); |
| for (MCRegUnitIterator Units(PhysReg, TRI); Units.isValid(); ++Units) { |
| RegUnits.push_back(LIUArray[*Units]); |
| RegUnits.back().Fixed = &LIS->getRegUnit(*Units); |
| } |
| } |
| |
| bool InterferenceCache::Entry::valid(LiveIntervalUnion *LIUArray, |
| const TargetRegisterInfo *TRI) { |
| unsigned i = 0, e = RegUnits.size(); |
| for (MCRegUnitIterator Units(PhysReg, TRI); Units.isValid(); ++Units, ++i) { |
| if (i == e) |
| return false; |
| if (LIUArray[*Units].changedSince(RegUnits[i].VirtTag)) |
| return false; |
| } |
| return i == e; |
| } |
| |
| void InterferenceCache::Entry::update(unsigned MBBNum) { |
| SlotIndex Start, Stop; |
| std::tie(Start, Stop) = Indexes->getMBBRange(MBBNum); |
| |
| // Use advanceTo only when possible. |
| if (PrevPos != Start) { |
| if (!PrevPos.isValid() || Start < PrevPos) { |
| for (unsigned i = 0, e = RegUnits.size(); i != e; ++i) { |
| RegUnitInfo &RUI = RegUnits[i]; |
| RUI.VirtI.find(Start); |
| RUI.FixedI = RUI.Fixed->find(Start); |
| } |
| } else { |
| for (unsigned i = 0, e = RegUnits.size(); i != e; ++i) { |
| RegUnitInfo &RUI = RegUnits[i]; |
| RUI.VirtI.advanceTo(Start); |
| if (RUI.FixedI != RUI.Fixed->end()) |
| RUI.FixedI = RUI.Fixed->advanceTo(RUI.FixedI, Start); |
| } |
| } |
| PrevPos = Start; |
| } |
| |
| MachineFunction::const_iterator MFI = |
| MF->getBlockNumbered(MBBNum)->getIterator(); |
| BlockInterference *BI = &Blocks[MBBNum]; |
| ArrayRef<SlotIndex> RegMaskSlots; |
| ArrayRef<const uint32_t*> RegMaskBits; |
| while (true) { |
| BI->Tag = Tag; |
| BI->First = BI->Last = SlotIndex(); |
| |
| // Check for first interference from virtregs. |
| for (unsigned i = 0, e = RegUnits.size(); i != e; ++i) { |
| LiveIntervalUnion::SegmentIter &I = RegUnits[i].VirtI; |
| if (!I.valid()) |
| continue; |
| SlotIndex StartI = I.start(); |
| if (StartI >= Stop) |
| continue; |
| if (!BI->First.isValid() || StartI < BI->First) |
| BI->First = StartI; |
| } |
| |
| // Same thing for fixed interference. |
| for (unsigned i = 0, e = RegUnits.size(); i != e; ++i) { |
| LiveInterval::const_iterator I = RegUnits[i].FixedI; |
| LiveInterval::const_iterator E = RegUnits[i].Fixed->end(); |
| if (I == E) |
| continue; |
| SlotIndex StartI = I->start; |
| if (StartI >= Stop) |
| continue; |
| if (!BI->First.isValid() || StartI < BI->First) |
| BI->First = StartI; |
| } |
| |
| // Also check for register mask interference. |
| RegMaskSlots = LIS->getRegMaskSlotsInBlock(MBBNum); |
| RegMaskBits = LIS->getRegMaskBitsInBlock(MBBNum); |
| SlotIndex Limit = BI->First.isValid() ? BI->First : Stop; |
| for (unsigned i = 0, e = RegMaskSlots.size(); |
| i != e && RegMaskSlots[i] < Limit; ++i) |
| if (MachineOperand::clobbersPhysReg(RegMaskBits[i], PhysReg)) { |
| // Register mask i clobbers PhysReg before the LIU interference. |
| BI->First = RegMaskSlots[i]; |
| break; |
| } |
| |
| PrevPos = Stop; |
| if (BI->First.isValid()) |
| break; |
| |
| // No interference in this block? Go ahead and precompute the next block. |
| if (++MFI == MF->end()) |
| return; |
| MBBNum = MFI->getNumber(); |
| BI = &Blocks[MBBNum]; |
| if (BI->Tag == Tag) |
| return; |
| std::tie(Start, Stop) = Indexes->getMBBRange(MBBNum); |
| } |
| |
| // Check for last interference in block. |
| for (unsigned i = 0, e = RegUnits.size(); i != e; ++i) { |
| LiveIntervalUnion::SegmentIter &I = RegUnits[i].VirtI; |
| if (!I.valid() || I.start() >= Stop) |
| continue; |
| I.advanceTo(Stop); |
| bool Backup = !I.valid() || I.start() >= Stop; |
| if (Backup) |
| --I; |
| SlotIndex StopI = I.stop(); |
| if (!BI->Last.isValid() || StopI > BI->Last) |
| BI->Last = StopI; |
| if (Backup) |
| ++I; |
| } |
| |
| // Fixed interference. |
| for (unsigned i = 0, e = RegUnits.size(); i != e; ++i) { |
| LiveInterval::iterator &I = RegUnits[i].FixedI; |
| LiveRange *LR = RegUnits[i].Fixed; |
| if (I == LR->end() || I->start >= Stop) |
| continue; |
| I = LR->advanceTo(I, Stop); |
| bool Backup = I == LR->end() || I->start >= Stop; |
| if (Backup) |
| --I; |
| SlotIndex StopI = I->end; |
| if (!BI->Last.isValid() || StopI > BI->Last) |
| BI->Last = StopI; |
| if (Backup) |
| ++I; |
| } |
| |
| // Also check for register mask interference. |
| SlotIndex Limit = BI->Last.isValid() ? BI->Last : Start; |
| for (unsigned i = RegMaskSlots.size(); |
| i && RegMaskSlots[i-1].getDeadSlot() > Limit; --i) |
| if (MachineOperand::clobbersPhysReg(RegMaskBits[i-1], PhysReg)) { |
| // Register mask i-1 clobbers PhysReg after the LIU interference. |
| // Model the regmask clobber as a dead def. |
| BI->Last = RegMaskSlots[i-1].getDeadSlot(); |
| break; |
| } |
| } |
