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-rw-r--r--lib/CodeGen/GlobalISel/Localizer.cpp233
1 files changed, 164 insertions, 69 deletions
diff --git a/lib/CodeGen/GlobalISel/Localizer.cpp b/lib/CodeGen/GlobalISel/Localizer.cpp
index 52b340753a50..3592409710a7 100644
--- a/lib/CodeGen/GlobalISel/Localizer.cpp
+++ b/lib/CodeGen/GlobalISel/Localizer.cpp
@@ -1,9 +1,8 @@
//===- Localizer.cpp ---------------------- Localize some instrs -*- C++ -*-==//
//
-// The LLVM Compiler Infrastructure
-//
-// This file is distributed under the University of Illinois Open Source
-// License. See LICENSE.TXT for details.
+// 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
//
//===----------------------------------------------------------------------===//
/// \file
@@ -11,8 +10,8 @@
//===----------------------------------------------------------------------===//
#include "llvm/CodeGen/GlobalISel/Localizer.h"
+#include "llvm/Analysis/TargetTransformInfo.h"
#include "llvm/ADT/DenseMap.h"
-#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/Support/Debug.h"
@@ -21,17 +20,53 @@
using namespace llvm;
char Localizer::ID = 0;
-INITIALIZE_PASS(Localizer, DEBUG_TYPE,
- "Move/duplicate certain instructions close to their use", false,
- false)
+INITIALIZE_PASS_BEGIN(Localizer, DEBUG_TYPE,
+ "Move/duplicate certain instructions close to their use",
+ false, false)
+INITIALIZE_PASS_DEPENDENCY(TargetTransformInfoWrapperPass)
+INITIALIZE_PASS_END(Localizer, DEBUG_TYPE,
+ "Move/duplicate certain instructions close to their use",
+ false, false)
-Localizer::Localizer() : MachineFunctionPass(ID) {
- initializeLocalizerPass(*PassRegistry::getPassRegistry());
-}
+Localizer::Localizer() : MachineFunctionPass(ID) { }
-void Localizer::init(MachineFunction &MF) { MRI = &MF.getRegInfo(); }
+void Localizer::init(MachineFunction &MF) {
+ MRI = &MF.getRegInfo();
+ TTI = &getAnalysis<TargetTransformInfoWrapperPass>().getTTI(MF.getFunction());
+}
bool Localizer::shouldLocalize(const MachineInstr &MI) {
+ // Assuming a spill and reload of a value has a cost of 1 instruction each,
+ // this helper function computes the maximum number of uses we should consider
+ // for remat. E.g. on arm64 global addresses take 2 insts to materialize. We
+ // break even in terms of code size when the original MI has 2 users vs
+ // choosing to potentially spill. Any more than 2 users we we have a net code
+ // size increase. This doesn't take into account register pressure though.
+ auto maxUses = [](unsigned RematCost) {
+ // A cost of 1 means remats are basically free.
+ if (RematCost == 1)
+ return UINT_MAX;
+ if (RematCost == 2)
+ return 2U;
+
+ // Remat is too expensive, only sink if there's one user.
+ if (RematCost > 2)
+ return 1U;
+ llvm_unreachable("Unexpected remat cost");
+ };
+
+ // Helper to walk through uses and terminate if we've reached a limit. Saves
+ // us spending time traversing uses if all we want to know is if it's >= min.
+ auto isUsesAtMost = [&](unsigned Reg, unsigned MaxUses) {
+ unsigned NumUses = 0;
+ auto UI = MRI->use_instr_nodbg_begin(Reg), UE = MRI->use_instr_nodbg_end();
+ for (; UI != UE && NumUses < MaxUses; ++UI) {
+ NumUses++;
+ }
+ // If we haven't reached the end yet then there are more than MaxUses users.
+ return UI == UE;
+ };
+
switch (MI.getOpcode()) {
default:
return false;
@@ -40,11 +75,22 @@ bool Localizer::shouldLocalize(const MachineInstr &MI) {
case TargetOpcode::G_CONSTANT:
case TargetOpcode::G_FCONSTANT:
case TargetOpcode::G_FRAME_INDEX:
+ case TargetOpcode::G_INTTOPTR:
return true;
+ case TargetOpcode::G_GLOBAL_VALUE: {
+ unsigned RematCost = TTI->getGISelRematGlobalCost();
+ unsigned Reg = MI.getOperand(0).getReg();
+ unsigned MaxUses = maxUses(RematCost);
+ if (MaxUses == UINT_MAX)
+ return true; // Remats are "free" so always localize.
+ bool B = isUsesAtMost(Reg, MaxUses);
+ return B;
+ }
}
}
void Localizer::getAnalysisUsage(AnalysisUsage &AU) const {
+ AU.addRequired<TargetTransformInfoWrapperPass>();
getSelectionDAGFallbackAnalysisUsage(AU);
MachineFunctionPass::getAnalysisUsage(AU);
}
@@ -58,6 +104,107 @@ bool Localizer::isLocalUse(MachineOperand &MOUse, const MachineInstr &Def,
return InsertMBB == Def.getParent();
}
+bool Localizer::localizeInterBlock(MachineFunction &MF,
+ LocalizedSetVecT &LocalizedInstrs) {
+ bool Changed = false;
+ DenseMap<std::pair<MachineBasicBlock *, unsigned>, unsigned> MBBWithLocalDef;
+
+ // Since the IRTranslator only emits constants into the entry block, and the
+ // rest of the GISel pipeline generally emits constants close to their users,
+ // we only localize instructions in the entry block here. This might change if
+ // we start doing CSE across blocks.
+ auto &MBB = MF.front();
+ for (auto RI = MBB.rbegin(), RE = MBB.rend(); RI != RE; ++RI) {
+ MachineInstr &MI = *RI;
+ if (!shouldLocalize(MI))
+ continue;
+ LLVM_DEBUG(dbgs() << "Should localize: " << MI);
+ assert(MI.getDesc().getNumDefs() == 1 &&
+ "More than one definition not supported yet");
+ unsigned Reg = MI.getOperand(0).getReg();
+ // Check if all the users of MI are local.
+ // We are going to invalidation the list of use operands, so we
+ // can't use range iterator.
+ for (auto MOIt = MRI->use_begin(Reg), MOItEnd = MRI->use_end();
+ MOIt != MOItEnd;) {
+ MachineOperand &MOUse = *MOIt++;
+ // Check if the use is already local.
+ MachineBasicBlock *InsertMBB;
+ LLVM_DEBUG(MachineInstr &MIUse = *MOUse.getParent();
+ dbgs() << "Checking use: " << MIUse
+ << " #Opd: " << MIUse.getOperandNo(&MOUse) << '\n');
+ if (isLocalUse(MOUse, MI, InsertMBB))
+ continue;
+ LLVM_DEBUG(dbgs() << "Fixing non-local use\n");
+ Changed = true;
+ auto MBBAndReg = std::make_pair(InsertMBB, Reg);
+ auto NewVRegIt = MBBWithLocalDef.find(MBBAndReg);
+ if (NewVRegIt == MBBWithLocalDef.end()) {
+ // Create the localized instruction.
+ MachineInstr *LocalizedMI = MF.CloneMachineInstr(&MI);
+ LocalizedInstrs.insert(LocalizedMI);
+ MachineInstr &UseMI = *MOUse.getParent();
+ if (MRI->hasOneUse(Reg) && !UseMI.isPHI())
+ InsertMBB->insert(InsertMBB->SkipPHIsAndLabels(UseMI), LocalizedMI);
+ else
+ InsertMBB->insert(InsertMBB->SkipPHIsAndLabels(InsertMBB->begin()),
+ LocalizedMI);
+
+ // Set a new register for the definition.
+ unsigned NewReg = MRI->createGenericVirtualRegister(MRI->getType(Reg));
+ MRI->setRegClassOrRegBank(NewReg, MRI->getRegClassOrRegBank(Reg));
+ LocalizedMI->getOperand(0).setReg(NewReg);
+ NewVRegIt =
+ MBBWithLocalDef.insert(std::make_pair(MBBAndReg, NewReg)).first;
+ LLVM_DEBUG(dbgs() << "Inserted: " << *LocalizedMI);
+ }
+ LLVM_DEBUG(dbgs() << "Update use with: " << printReg(NewVRegIt->second)
+ << '\n');
+ // Update the user reg.
+ MOUse.setReg(NewVRegIt->second);
+ }
+ }
+ return Changed;
+}
+
+bool Localizer::localizeIntraBlock(LocalizedSetVecT &LocalizedInstrs) {
+ bool Changed = false;
+
+ // For each already-localized instruction which has multiple users, then we
+ // scan the block top down from the current position until we hit one of them.
+
+ // FIXME: Consider doing inst duplication if live ranges are very long due to
+ // many users, but this case may be better served by regalloc improvements.
+
+ for (MachineInstr *MI : LocalizedInstrs) {
+ unsigned Reg = MI->getOperand(0).getReg();
+ MachineBasicBlock &MBB = *MI->getParent();
+ // All of the user MIs of this reg.
+ SmallPtrSet<MachineInstr *, 32> Users;
+ for (MachineInstr &UseMI : MRI->use_nodbg_instructions(Reg)) {
+ if (!UseMI.isPHI())
+ Users.insert(&UseMI);
+ }
+ // If all the users were PHIs then they're not going to be in our block,
+ // don't try to move this instruction.
+ if (Users.empty())
+ continue;
+
+ MachineBasicBlock::iterator II(MI);
+ ++II;
+ while (II != MBB.end() && !Users.count(&*II))
+ ++II;
+
+ LLVM_DEBUG(dbgs() << "Intra-block: moving " << *MI << " before " << *&*II
+ << "\n");
+ assert(II != MBB.end() && "Didn't find the user in the MBB");
+ MI->removeFromParent();
+ MBB.insert(II, MI);
+ Changed = true;
+ }
+ return Changed;
+}
+
bool Localizer::runOnMachineFunction(MachineFunction &MF) {
// If the ISel pipeline failed, do not bother running that pass.
if (MF.getProperties().hasProperty(
@@ -68,62 +215,10 @@ bool Localizer::runOnMachineFunction(MachineFunction &MF) {
init(MF);
- bool Changed = false;
- // Keep track of the instructions we localized.
- // We won't need to process them if we see them later in the CFG.
- SmallPtrSet<MachineInstr *, 16> LocalizedInstrs;
- DenseMap<std::pair<MachineBasicBlock *, unsigned>, unsigned> MBBWithLocalDef;
- // TODO: Do bottom up traversal.
- for (MachineBasicBlock &MBB : MF) {
- for (MachineInstr &MI : MBB) {
- if (LocalizedInstrs.count(&MI) || !shouldLocalize(MI))
- continue;
- LLVM_DEBUG(dbgs() << "Should localize: " << MI);
- assert(MI.getDesc().getNumDefs() == 1 &&
- "More than one definition not supported yet");
- unsigned Reg = MI.getOperand(0).getReg();
- // Check if all the users of MI are local.
- // We are going to invalidation the list of use operands, so we
- // can't use range iterator.
- for (auto MOIt = MRI->use_begin(Reg), MOItEnd = MRI->use_end();
- MOIt != MOItEnd;) {
- MachineOperand &MOUse = *MOIt++;
- // Check if the use is already local.
- MachineBasicBlock *InsertMBB;
- LLVM_DEBUG(MachineInstr &MIUse = *MOUse.getParent();
- dbgs() << "Checking use: " << MIUse
- << " #Opd: " << MIUse.getOperandNo(&MOUse) << '\n');
- if (isLocalUse(MOUse, MI, InsertMBB))
- continue;
- LLVM_DEBUG(dbgs() << "Fixing non-local use\n");
- Changed = true;
- auto MBBAndReg = std::make_pair(InsertMBB, Reg);
- auto NewVRegIt = MBBWithLocalDef.find(MBBAndReg);
- if (NewVRegIt == MBBWithLocalDef.end()) {
- // Create the localized instruction.
- MachineInstr *LocalizedMI = MF.CloneMachineInstr(&MI);
- LocalizedInstrs.insert(LocalizedMI);
- // Don't try to be smart for the insertion point.
- // There is no guarantee that the first seen use is the first
- // use in the block.
- InsertMBB->insert(InsertMBB->SkipPHIsAndLabels(InsertMBB->begin()),
- LocalizedMI);
+ // Keep track of the instructions we localized. We'll do a second pass of
+ // intra-block localization to further reduce live ranges.
+ LocalizedSetVecT LocalizedInstrs;
- // Set a new register for the definition.
- unsigned NewReg =
- MRI->createGenericVirtualRegister(MRI->getType(Reg));
- MRI->setRegClassOrRegBank(NewReg, MRI->getRegClassOrRegBank(Reg));
- LocalizedMI->getOperand(0).setReg(NewReg);
- NewVRegIt =
- MBBWithLocalDef.insert(std::make_pair(MBBAndReg, NewReg)).first;
- LLVM_DEBUG(dbgs() << "Inserted: " << *LocalizedMI);
- }
- LLVM_DEBUG(dbgs() << "Update use with: " << printReg(NewVRegIt->second)
- << '\n');
- // Update the user reg.
- MOUse.setReg(NewVRegIt->second);
- }
- }
- }
- return Changed;
+ bool Changed = localizeInterBlock(MF, LocalizedInstrs);
+ return Changed |= localizeIntraBlock(LocalizedInstrs);
}
generated by cgit v1.2.3 (git 2.25.1) at 2025-02-22 13:21:06 +0000