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CodeGenRA.cpp
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CodeGenRA.cpp
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/*******************************************************************************
* Copyright (c) 2000, 2021 IBM Corp. and others
*
* This program and the accompanying materials are made available under
* the terms of the Eclipse Public License 2.0 which accompanies this
* distribution and is available at http://eclipse.org/legal/epl-2.0
* or the Apache License, Version 2.0 which accompanies this distribution
* and is available at https://www.apache.org/licenses/LICENSE-2.0.
*
* This Source Code may also be made available under the following Secondary
* Licenses when the conditions for such availability set forth in the
* Eclipse Public License, v. 2.0 are satisfied: GNU General Public License,
* version 2 with the GNU Classpath Exception [1] and GNU General Public
* License, version 2 with the OpenJDK Assembly Exception [2].
*
* [1] https://www.gnu.org/software/classpath/license.html
* [2] http://openjdk.java.net/legal/assembly-exception.html
*
* SPDX-License-Identifier: EPL-2.0 OR Apache-2.0 OR GPL-2.0 WITH Classpath-exception-2.0 OR LicenseRef-GPL-2.0 WITH Assembly-exception
*******************************************************************************/
#include "codegen/CodeGenerator.hpp"
#include <limits.h>
#include <stdint.h>
#include <stdlib.h>
#include <algorithm>
#include "codegen/BackingStore.hpp"
#include "codegen/CodeGenerator.hpp"
#include "codegen/CodeGenerator_inlines.hpp"
#include "env/FrontEnd.hpp"
#include "codegen/GCStackAtlas.hpp"
#include "codegen/Instruction.hpp"
#include "codegen/Linkage.hpp"
#include "codegen/Linkage_inlines.hpp"
#include "codegen/LinkageConventionsEnum.hpp"
#include "codegen/LiveReference.hpp"
#include "codegen/LiveRegister.hpp"
#include "codegen/Register.hpp"
#include "codegen/RegisterConstants.hpp"
#include "codegen/TreeEvaluator.hpp"
#include "compile/Compilation.hpp"
#include "control/Options.hpp"
#include "control/Options_inlines.hpp"
#include "env/CompilerEnv.hpp"
#include "env/IO.hpp"
#include "env/ObjectModel.hpp"
#include "env/StackMemoryRegion.hpp"
#include "env/TRMemory.hpp"
#include "il/AliasSetInterface.hpp"
#include "il/AutomaticSymbol.hpp"
#include "il/Block.hpp"
#include "il/DataTypes.hpp"
#include "il/ILOpCodes.hpp"
#include "il/ILOps.hpp"
#include "il/MethodSymbol.hpp"
#include "il/Node.hpp"
#include "il/Node_inlines.hpp"
#include "il/ParameterSymbol.hpp"
#include "il/ResolvedMethodSymbol.hpp"
#include "il/Symbol.hpp"
#include "il/SymbolReference.hpp"
#include "il/TreeTop.hpp"
#include "il/TreeTop_inlines.hpp"
#include "infra/Array.hpp"
#include "infra/Assert.hpp"
#include "infra/BitVector.hpp"
#include "infra/Cfg.hpp"
#include "infra/Flags.hpp"
#include "infra/Link.hpp"
#include "infra/List.hpp"
#include "infra/CfgEdge.hpp"
#include "infra/CfgNode.hpp"
#include "optimizer/Optimizations.hpp"
#include "optimizer/RegisterCandidate.hpp"
#include "optimizer/Structure.hpp"
#include "ras/Debug.hpp"
#define OPT_DETAILS "O^O CODE GENERATION: "
#define NUM_REGS_USED_BY_COMPLEX_OPCODES 3
namespace TR { class RealRegister; }
#if defined(DEBUG) || defined(PROD_WITH_ASSUMES)
void
OMR::CodeGenerator::checkForLiveRegisters(TR_LiveRegisters *liveRegisters)
{
TR_Debug * debug = self()->comp()->getDebug();
bool regsAreLive = false;
if (liveRegisters && liveRegisters->getFirstLiveRegister())
{
traceMsg(self()->comp(), "\n\n");
for (TR_LiveRegisterInfo *p = liveRegisters->getFirstLiveRegister(); p; p = p->getNext())
{
if (p->getNode())
traceMsg(self()->comp(), "Virtual register %s (for node [%s], ref count=%d) is live at end of method\n",
debug->getName(p->getRegister()), debug->getName(p->getNode()), p->getNode()->getReferenceCount());
else
traceMsg(self()->comp(), "Virtual register %s %p is live at end of method with node count %d\n", debug->getName(p->getRegister()), p->getRegister(), p->getNodeCount());
regsAreLive = true;
}
}
TR_ASSERT(!regsAreLive, "Virtual or real registers are live at end of method");
}
#endif
void
OMR::CodeGenerator::estimateRegisterPressure(TR::Node *node, int32_t ®isterPressure, int32_t &maxRegisterPressure, int32_t maxRegisters, TR_BitVector *valuesInGlobalRegs, bool isCold, vcount_t visitCount, TR::SymbolReference *symRef, bool &symRefIsLive, bool checkForIMuls, bool &vmThreadUsed)
{
if (node->getVisitCount() == visitCount)
{
node->setLocalIndex(node->getLocalIndex()-1);
if (node->getLocalIndex() == 0)
{
if (node->getOpCode().isLoadVar() &&
node->getSymbol()->isAutoOrParm() &&
valuesInGlobalRegs &&
valuesInGlobalRegs->get(node->getSymbolReference()->getReferenceNumber()))
{
//
// This node has already been counted in num registers live
//
}
else
{
if (!node->getOpCode().isLoadConst())
{
registerPressure--;
if ((node->getType().isInt64()) &&
self()->comp()->target().is32Bit())
registerPressure--;
}
if (node->getOpCode().isLoadVar() &&
node->getSymbolReference() == symRef)
{
symRefIsLive = false;
}
}
}
return;
}
node->setVisitCount(visitCount);
if (node->getReferenceCount() > 0)
node->setLocalIndex(node->getReferenceCount()-1);
else
node->setLocalIndex(0);
int32_t childCount;
for (childCount = node->getNumChildren()-1; childCount >= 0; childCount--)
self()->estimateRegisterPressure(node->getChild(childCount), registerPressure, maxRegisterPressure, maxRegisters, valuesInGlobalRegs, isCold, visitCount, symRef, symRefIsLive, checkForIMuls, vmThreadUsed);
bool highRegisterPressureOpCode = false;
if (node->getOpCode().isResolveCheck() ||
(node->getOpCode().isCall()) ||
node->getOpCodeValue() == TR::New ||
node->getOpCodeValue() == TR::newarray ||
node->getOpCodeValue() == TR::anewarray ||
node->getOpCodeValue() == TR::multianewarray ||
node->getOpCodeValue() == TR::monent ||
node->getOpCodeValue() == TR::monexit ||
node->getOpCodeValue() == TR::checkcast ||
node->getOpCodeValue() == TR::instanceof ||
node->getOpCodeValue() == TR::arraycopy)
highRegisterPressureOpCode = true;
if (highRegisterPressureOpCode ||
node->getOpCodeValue() == TR::asynccheck)
vmThreadUsed = true;
// Allow these call-like opcodes in cold blocks
// as we can afford to spill in cold blocks
//
if (node->getLocalIndex() > 0)
{
if (node->getOpCode().isLoadVar() &&
node->getSymbol()->isAutoOrParm() &&
valuesInGlobalRegs &&
valuesInGlobalRegs->get(node->getSymbolReference()->getReferenceNumber()))
{
//
// This node has already been counted in num registers live
//
}
else
{
if (!node->getOpCode().isLoadConst())
{
bool gprCandidate = true;
TR::DataType dtype = node->getDataType();
if (dtype == TR::Float
|| dtype == TR::Double
)
gprCandidate = false;
if (node->getDataType() == TR::Float
|| node->getDataType() == TR::Double
)
{
if (!gprCandidate)
registerPressure++;
}
else
{
if (gprCandidate)
{
registerPressure++;
if ((node->getType().isInt64()) &&
self()->comp()->target().is32Bit())
registerPressure++;
}
}
}
if (node->getOpCode().isLoadVar() &&
node->getSymbolReference() == symRef)
{
symRefIsLive = true;
}
if (!symRefIsLive)
{
//These opcodes result in high register usage
//
if (highRegisterPressureOpCode ||
((node->getType().isInt64()) &&
self()->comp()->target().is32Bit() &&
(node->getOpCode().isMul() ||
node->getOpCode().isDiv() ||
node->getOpCode().isRem() ||
node->getOpCode().isLeftShift() ||
node->getOpCode().isRightShift() ||
node->getOpCode().isBooleanCompare())))
{
if (!isCold)
{
if (registerPressure >= (maxRegisters - NUM_REGS_USED_BY_COMPLEX_OPCODES -1)) // Only allow if register pressure is known to be very low
{
maxRegisterPressure = maxRegisters;
}
}
}
else if (checkForIMuls &&
(node->getOpCode().isMul() ||
node->getOpCode().isDiv()))
{
if (!isCold)
{
maxRegisterPressure = maxRegisters;
}
}
else
{
if (registerPressure > maxRegisterPressure)
{
if (!isCold)
maxRegisterPressure = registerPressure;
}
}
}
}
}
}
int32_t
OMR::CodeGenerator::estimateRegisterPressure(TR::Block *block, vcount_t visitCount, int32_t maxStaticFrequency, int32_t maxFrequency, bool &vmThreadUsed, int32_t numGlobalRegs, TR_BitVector *valuesInGlobalRegs, TR::SymbolReference * symRef, bool checkForIMuls)
{
int32_t maxRegisterPressure = numGlobalRegs;
int32_t currRegisterPressure = numGlobalRegs;
block = block->startOfExtendedBlock();
TR::TreeTop *treeTop = block->getEntry()->getNextTreeTop();
bool isCold = false;
if (maxFrequency < 0)
{
maxFrequency = 0;
for (TR::CFGNode *node = self()->comp()->getFlowGraph()->getFirstNode(); node; node = node->getNext())
{
if (node->getFrequency() > maxFrequency)
maxFrequency = node->getFrequency();
}
}
//
// Use some measure for coldness
//
if (block->isCold() ||
((maxFrequency > 0) &&
(block->getFrequency()*100/maxFrequency < 20)))
isCold = true;
if (!isCold)
{
TR_BlockStructure *blockStructure = block->getStructureOf();
int32_t blockWeight = 1;
if (blockStructure &&
!block->isCold())
{
blockStructure->calculateFrequencyOfExecution(&blockWeight);
}
if ((maxStaticFrequency > 0) &&
(blockWeight*100/maxStaticFrequency < 20))
isCold = true;
}
bool symRefIsLive = false;
while (treeTop)
{
TR::Node *node = treeTop->getNode();
self()->estimateRegisterPressure(node, currRegisterPressure, maxRegisterPressure, self()->getMaximumNumbersOfAssignableGPRs(), valuesInGlobalRegs, isCold, visitCount, symRef, symRefIsLive, checkForIMuls, vmThreadUsed);
if (vmThreadUsed &&
(maxRegisterPressure >= self()->getMaximumNumbersOfAssignableGPRs()))
{
//dumpOptDetails("For global register candidate %d reg pressure reached limit %d at block_%d isCold %d maxFreq %d\n", rc->getSymbolReference()->getReferenceNumber(), maxRegisterPressure, liveBlockNum, isCold, maxFrequency);
break;
}
if (node->getOpCodeValue() == TR::BBStart)
{
if (!node->getBlock()->isExtensionOfPreviousBlock())
break;
//
// Use some measure for coldness
//
if (node->getBlock()->isCold() ||
((maxFrequency > 0) &&
(node->getBlock()->getFrequency()*100/maxFrequency < 20)))
isCold = true;
else
{
TR_BlockStructure *blockStructure = block->getStructureOf();
int32_t blockWeight = 1;
if (blockStructure &&
!block->isCold())
{
blockStructure->calculateFrequencyOfExecution(&blockWeight);
}
if ((maxStaticFrequency > 0) &&
(blockWeight*100/maxStaticFrequency < 20))
isCold = true;
else
isCold = false;
}
}
treeTop = treeTop->getNextTreeTop();
}
return maxRegisterPressure;
}
// Set the future use count on all registers, and keep track of what kind of registers
// need to be assigned.
//
TR_RegisterKinds
OMR::CodeGenerator::prepareRegistersForAssignment()
{
TR_Array<TR::Register *>& regArray=self()->getRegisterArray();
TR::Register *registerCursor;
TR_RegisterMask km, foundKindsMask = 0;
int i;
for (i=0; i < regArray.size(); i++)
{
registerCursor = regArray[i];
if (registerCursor->getKind() != TR_SSR)
registerCursor->setFutureUseCount(registerCursor->getTotalUseCount());
km = registerCursor->getKindAsMask();
if (!(foundKindsMask & km))
foundKindsMask |= km;
}
return TR_RegisterKinds(foundKindsMask);
}
TR_BackingStore *
OMR::CodeGenerator::allocateInternalPointerSpill(TR::AutomaticSymbol *pinningArrayPointer)
{
// Search for an existing free spill slot for this pinningArrayPointer
//
TR_BackingStore *spill = NULL;
for(auto i = self()->getInternalPointerSpillFreeList().begin(); i != self()->getInternalPointerSpillFreeList().end(); ++i)
{
if ((*i)->getSymbolReference()->getSymbol()->getAutoSymbol()->castToInternalPointerAutoSymbol()->getPinningArrayPointer() == pinningArrayPointer)
{
spill = *i;
_internalPointerSpillFreeList.remove(spill);
break;
}
}
// If there isn't an existing one, make a new one
//
if (!spill)
{
int32_t slot;
TR::AutomaticSymbol *spillSymbol =
TR::AutomaticSymbol::createInternalPointer(self()->trHeapMemory(),
TR::Address,
TR::Compiler->om.sizeofReferenceAddress(),
self()->fe());
spillSymbol->setSpillTempAuto();
spillSymbol->setPinningArrayPointer(pinningArrayPointer);
self()->comp()->getMethodSymbol()->addAutomatic(spillSymbol);
spill = new (self()->trHeapMemory()) TR_BackingStore(self()->comp()->getSymRefTab(), spillSymbol, 0);
slot = spill->getSymbolReference()->getCPIndex();
slot = (slot < 0) ? (-slot - 1) : slot;
self()->comp()->getJittedMethodSymbol()->getAutoSymRefs(slot).add(spill->getSymbolReference());
_allSpillList.push_front(spill);
}
spill->setIsOccupied();
return spill;
}
TR_BackingStore *
OMR::CodeGenerator::allocateSpill(bool containsCollectedReference, int32_t *offset, bool reuse)
{
return self()->allocateSpill((int32_t)(TR::Compiler->om.sizeofReferenceAddress()), containsCollectedReference, offset, reuse); // cast parameter explicitly
}
TR_BackingStore *
OMR::CodeGenerator::allocateSpill(int32_t dataSize, bool containsCollectedReference, int32_t *offset, bool reuse)
{
TR_ASSERT_FATAL(dataSize <= 16, "assertion failure");
TR_ASSERT_FATAL(!containsCollectedReference || (dataSize == TR::Compiler->om.sizeofReferenceAddress()), "assertion failure");
if (self()->comp()->getOption(TR_TraceRA))
traceMsg(self()->comp(), "\nallocateSpill(%d, %s, %s)", dataSize, containsCollectedReference? "collected":"uncollected", offset? "offset":"NULL");
if (offset && self()->comp()->getOption(TR_DisableHalfSlotSpills))
{
// Pretend the caller can't handle half-slot spills
*offset = 0;
offset = NULL;
}
TR_BackingStore *spill = NULL;
// mapStack will get confused if we put a 4-byte collected reference in an
// 8-byte spill temp. It will map the temp according to its GC map index
// multiplied by the size of a Java pointer, and that will only give it 4 bytes.
//
// TODO: Make mapStack smarter and support this in the GC maps.
//
bool try8ByteSpills = (dataSize < 16) && ((TR::Compiler->om.sizeofReferenceAddress() == 8) || !containsCollectedReference);
bool try16ByteSpills = (dataSize == 16);
if(reuse)
{
if (dataSize <= 4 && !self()->getSpill4FreeList().empty())
{
spill = self()->getSpill4FreeList().front();
self()->getSpill4FreeList().pop_front();
}
if (!spill && try8ByteSpills && !self()->getSpill8FreeList().empty())
{
spill = self()->getSpill8FreeList().front();
self()->getSpill8FreeList().pop_front();
}
if (!spill && try16ByteSpills && !self()->getSpill16FreeList().empty())
{
spill = self()->getSpill16FreeList().front();
self()->getSpill16FreeList().pop_front();
}
if (
(spill && self()->comp()->getOption(TR_TraceRA) && !performTransformation(self()->comp(), "O^O SPILL TEMPS: Reuse spill temp %s\n", self()->getDebug()->getName(spill->getSymbolReference()))))
{
// Discard the spill temp we popped and never use it again; allocate a
// new one instead, and later, where we would have returned this spill
// temp to the free list, we return the new one instead and continue
// using that one for future allocations.
//
// This approach was chosen because it tends to make lastOptTransformationIndex
// produce a smaller delta than if we had left the spill in the lists.
// TODO: Use the same size for the new spill temp so that it will be freed to
// the same list, thereby further reducing the delta.
//
spill = NULL;
}
}
TR::AutomaticSymbol *spillSymbol;
if (spill)
{
spillSymbol = spill->getSymbolReference()->getSymbol()->getAutoSymbol();
}
else
{
// Must allocate a new one
//
int spillSize = std::max(dataSize, static_cast<int32_t>(TR::Compiler->om.sizeofReferenceAddress()));
TR_ASSERT(4 <= spillSize && spillSize <= 16, "Spill temps should be between 4 and 16 bytes");
spillSymbol = TR::AutomaticSymbol::create(self()->trHeapMemory(),TR::NoType,spillSize);
spillSymbol->setSpillTempAuto();
self()->comp()->getMethodSymbol()->addAutomatic(spillSymbol);
spill = new (self()->trHeapMemory()) TR_BackingStore(self()->comp()->getSymRefTab(), spillSymbol, 0);
int32_t slot = spill->getSymbolReference()->getCPIndex();
slot = (slot < 0) ? (-slot - 1) : slot;
self()->comp()->getJittedMethodSymbol()->getAutoSymRefs(slot).add(spill->getSymbolReference());
_allSpillList.push_front(spill);
}
if (dataSize <= 4 && spillSymbol->getSize() == 8)
{
// We must only set the backing store half-occupied flags so that
// freeSpill will do the right thing.
//
if ( offset == NULL
|| spill->secondHalfIsOccupied()
|| !performTransformation(self()->comp(), "O^O HALF-SLOT SPILLS: Use second half of %s\n", self()->getDebug()->getName(spill->getSymbolReference())))
{
spill->setFirstHalfIsOccupied();
}
else
{
*offset = 4;
spill->setSecondHalfIsOccupied();
self()->getSpill4FreeList().push_front(spill);
}
}
else
{
spill->setIsOccupied();
}
if (containsCollectedReference && spillSymbol->getGCMapIndex() < 0)
{
spillSymbol->setGCMapIndex(self()->getStackAtlas()->assignGCIndex());
_collectedSpillList.push_front(spill);
if (self()->comp()->getOption(TR_TraceRA))
traceMsg(self()->comp(), "\n -> added to collectedSpillList");
}
spill->setContainsCollectedReference(containsCollectedReference);
TR_ASSERT(spill->isOccupied(), "assertion failure");
if (self()->comp()->getOption(TR_TraceRA))
traceMsg(self()->comp(), "\nallocateSpill returning (%s(%d%d), %d) ", self()->getDebug()->getName(spill->getSymbolReference()->getSymbol()), spill->firstHalfIsOccupied()?1:0, spill->secondHalfIsOccupied()?1:0, offset? *offset : 0);
return spill;
}
void
OMR::CodeGenerator::freeSpill(TR_BackingStore *spill, int32_t dataSize, int32_t offset)
{
TR_ASSERT(1 <= dataSize && dataSize <= 16, "assertion failure");
TR_ASSERT(offset == 0 || offset == 4, "assertion failure");
TR_ASSERT(dataSize + offset <= 16, "assertion failure");
if (self()->comp()->getOption(TR_TraceRA))
{
traceMsg(self()->comp(), "\nfreeSpill(%s(%d%d), %d, %d, isLocked=%d)",
self()->getDebug()->getName(spill->getSymbolReference()->getSymbol()),
spill->firstHalfIsOccupied()?1:0,
spill->secondHalfIsOccupied()?1:0,
dataSize, offset, self()->isFreeSpillListLocked());
}
// Do not add a freed spill slot back onto the free list if the list is locked.
// This is to enforce re-use of the same spill slot for a virtual register
// while assigning non-linear control flow regions.
//
// However, we must still clear the occupied status of the temp.
//
bool updateFreeList = self()->isFreeSpillListLocked() ? false : true;
if (spill->getSymbolReference()->getSymbol()->getAutoSymbol()->isInternalPointer())
{
spill->setIsEmpty();
if (updateFreeList)
{
_internalPointerSpillFreeList.push_front(spill);
if (self()->comp()->getOption(TR_TraceRA))
traceMsg(self()->comp(), "\n -> Added to internalPointerSpillFreeList");
}
}
else if (dataSize <= 4 && spill->getSymbolReference()->getSymbol()->getSize() == 8)
{
if (offset == 0)
{
spill->setFirstHalfIsEmpty();
if (self()->comp()->getOption(TR_TraceRA))
traceMsg(self()->comp(), "\n -> setFirstHalfIsEmpty");
}
else
{
TR_ASSERT(offset == 4, "assertion failure");
spill->setSecondHalfIsEmpty();
if (self()->comp()->getOption(TR_TraceRA))
traceMsg(self()->comp(), "\n -> setSecondHalfIsEmpty");
}
if (spill->isEmpty())
{
TR_ASSERT(spill->isEmpty(), "assertion failure");
if (updateFreeList)
{
_spill4FreeList.remove(spill); // It may have been half-full before
_spill8FreeList.push_front(spill);
if (self()->comp()->getOption(TR_TraceRA))
traceMsg(self()->comp(), "\n -> moved to spill8FreeList");
}
}
else if (spill->firstHalfIsOccupied())
{
// TODO: Once every caller can cope with nonzero offsets, we should add first-half-occupied symbols into _spill4FreeList.
if (self()->comp()->getOption(TR_TraceRA))
traceMsg(self()->comp(), "\n -> first half is still occupied; conservatively keeping out of spill4FreeList");
}
else
{
TR_ASSERT(spill->secondHalfIsOccupied(), "assertion failure");
if (updateFreeList)
{
// Half-free
_spill4FreeList.push_front(spill);
if (self()->comp()->getOption(TR_TraceRA))
traceMsg(self()->comp(), "\n -> moved to spill4FreeList");
}
}
}
else
{
spill->setIsEmpty();
if (updateFreeList)
{
if (spill->getSymbolReference()->getSymbol()->getSize() <= 4)
{
_spill4FreeList.push_front(spill);
if (self()->comp()->getOption(TR_TraceRA))
traceMsg(self()->comp(), "\n -> added to spill4FreeList");
}
else if (spill->getSymbolReference()->getSymbol()->getSize() == 8)
{
_spill8FreeList.push_front(spill);
if (self()->comp()->getOption(TR_TraceRA))
traceMsg(self()->comp(), "\n -> added to spill8FreeList");
}
else if (spill->getSymbolReference()->getSymbol()->getSize() == 16)
{
_spill16FreeList.push_front(spill);
if (self()->comp()->getOption(TR_TraceRA))
traceMsg(self()->comp(), "\n -> added to spill16FreeList");
}
}
}
}
void
OMR::CodeGenerator::jettisonAllSpills()
{
if (self()->comp()->getOption(TR_TraceRA))
traceMsg(self()->comp(), "jettisonAllSpills: Clearing spill-temp freelists\n");
_spill4FreeList.clear();
_spill8FreeList.clear();
_spill16FreeList.clear();
_internalPointerSpillFreeList.clear();
}
TR::Register * OMR::CodeGenerator::allocateRegister(TR_RegisterKinds rk)
{
TR_ASSERT(rk != TR_SSR,"use allocatePseudoRegister for TR_SSR registers\n");
TR::Register * temp = new (self()->trHeapMemory()) TR::Register(rk);
self()->addAllocatedRegister(temp);
if (self()->getDebug())
self()->getDebug()->newRegister(temp);
return temp;
}
void
OMR::CodeGenerator::findAndFixCommonedReferences()
{
//
// TODO : Required to re-assess the feasibility of the spill
// strategy currently adopted at calls (potential GC points) where
// live references are stored in memory and restored when they need
// to be used. With register maps in place, the number of spills
// because of a call might possibly be reduced.
//
// When the above adjustment is made, it might be feasible for
// nodes to linked together across calls without necessarily incurring
// the cost of spilling the value (corresponding to the node)
// before a call. Might need to increase the strength of Local
// Dead Load Elimination in that case to perform linking of loads across
// calls.
//
//
if (debug("traceSpill"))
{
diagnostic("Start spilling at GC safe points\n");
self()->comp()->dumpMethodTrees("Trees before spilling");
}
self()->comp()->incVisitCount();
for (TR::TreeTop *tt = self()->comp()->getStartTree(); tt; tt = tt->getNextTreeTop())
{
TR::Node *node = tt->getNode();
bool isSafePoint = node->canGCandReturn();
if (isSafePoint)
{
TR::Node *safePointNode;
if (node->getOpCodeValue() == TR::treetop ||
node->getOpCode().isResolveOrNullCheck())
{
safePointNode = node->getFirstChild();
}
else
{
safePointNode = node;
}
if (safePointNode->getVisitCount() != self()->comp()->getVisitCount())
{
// Remember the first available spill temp. Temps added to the available
// spill temp list by children of this node shouldn't be used to spill
// around this node, since the temp will have a new value stored before
// this treetop.
//
auto firstAvailableSpillTemp = _availableSpillTemps.begin();
// Find commoned references in the children of the safe point node.
// They must be spilled to temps to prepare for this possible GC.
//
self()->findCommonedReferences(safePointNode, tt);
// Now spill the live references to temps
//
if (!_liveReferenceList.empty())
{
self()->spillLiveReferencesToTemps(tt->getPrevTreeTop(), firstAvailableSpillTemp);
}
}
// Finally see if the safe point node itself is a commoned reference.
// If so, it will become a live reference for the next GC point.
//
if (node != safePointNode)
{
self()->findCommonedReferences(node, tt);
}
}
else
{
// Find commoned references in this tree.
//
self()->findCommonedReferences(node, tt);
}
}
if (debug("traceSpill"))
diagnostic("End spilling at GC safe points\n");
}
void
OMR::CodeGenerator::findCommonedReferences(TR::Node *node, TR::TreeTop *treeTop)
{
if (node->getVisitCount() == self()->comp()->getVisitCount())
return;
node->setVisitCount(self()->comp()->getVisitCount());
for (int32_t childCount = node->getNumChildren() - 1; childCount >= 0; childCount--)
{
TR::Node *child = node->getChild(childCount);
// Visit the children and add their children's references before adding
// them to the live reference list. This makes sure that the live reference
// list is kept in the order in which references must be processed.
//
if (child->getVisitCount() != self()->comp()->getVisitCount())
{
self()->findCommonedReferences(child, treeTop);
}
if (child->getDataType() == TR::Address &&
!child->getOpCode().isLoadConst() &&
child->getOpCodeValue() != TR::loadaddr)
{
TR::Symbol * sym = child->getOpCode().hasSymbolReference() ? child->getSymbol() : 0;
if (child->getReferenceCount() > 1)
{
// This is a reference that may be live across a possible GC
//
if (!sym || !sym->isNotCollected())
self()->processReference(child, node, treeTop);
}
else if (sym && sym->isSpillTempAuto())
{
// This is the only (and hence last) use of a spill temp so it can
// be released.
//
_availableSpillTemps.push_front(child->getSymbolReference());
if (debug("traceSpill"))
diagnostic("Release spill temp [%p] at node [%p]\n",child->getSymbolReference(),child);
}
}
}
}
void
OMR::CodeGenerator::processReference(TR::Node *reference, TR::Node *parent, TR::TreeTop *treeTop)
{
// The live reference list appender is used to add and remove elements from the
// live reference list, so that the list is maintained in the order in which
// elements are inserted.
//
// The list must be maintained in this order so that if both a parent and a
// child are in the live reference list, when it comes time to spill the
// original parent will be updated to reference the new copy of the child
// before a new copy of the parent is created.
//
auto iterator = _liveReferenceList.begin();
TR_LiveReference *cursor;
while (iterator != _liveReferenceList.end())
{
if ((*iterator)->getReferenceNode() == reference)
{
// if this is the last parent, then we have found all the parents of the
// reference and must remove this reference from the list because it can not
// be alive across any future calls that may be encountered.
if (reference->getReferenceCount() == (*iterator)->getNumberOfParents() + 1)
{
_liveReferenceList.erase(iterator);
// If this reference was to a spill temp, that temp can be freed
// up to be re-used
//
if (reference->getOpCode().hasSymbolReference())
{
TR::SymbolReference * symRef = reference->getSymbolReference();
if (symRef->getSymbol()->isSpillTempAuto())
{
_availableSpillTemps.push_front(symRef);
if (debug("traceSpill"))
diagnostic("Release spill temp [%p] at node [%p]\n",symRef,reference);
}
}
}
// otherwise we add it to the list so that we will be able to find it
// if it turns out to be alive across a GC safe point and we have to introduce
// a temp and fix up all the parents.
else
{
(*iterator)->addParentToList(parent);
self()->needSpillTemp(*iterator, parent, treeTop);
}
return;
}
++iterator;
}
cursor = new (self()->trHeapMemory()) TR_LiveReference(reference, parent, self()->trMemory());
_liveReferenceList.push_back(cursor);
self()->needSpillTemp(cursor, parent, treeTop);
}
void
OMR::CodeGenerator::spillLiveReferencesToTemps(TR::TreeTop *insertionTree, std::list<TR::SymbolReference*, TR::typed_allocator<TR::SymbolReference*, TR::Allocator> >::iterator firstAvailableSpillTemp)
{
if (debug("traceSpill") && !_liveReferenceList.empty())
diagnostic("Spill at GC safe node [%p]\n",insertionTree->getNextTreeTop()->getNode());
auto referenceIterator = _liveReferenceList.begin();
while (referenceIterator != _liveReferenceList.end())
{
TR::Node *originalReference = (*referenceIterator)->getReferenceNode();
// Find or allocate a spill temp.
// If the reference is to an existing spill temp there is no need to
// generate another store, we can just create another load after the
// GC point.
//
// If the reference is a simple load and the load is not killed before the
// first use after this GC point, there is no need for a spill temp, the
// original load can just be duplicated at the first use after this point.
//
// Otherwise pick up an available spill temp from the free list or create
// a new one.
bool storeSpillTemp = false;
TR::SymbolReference *tempSymRef = NULL;
if (originalReference->getOpCode().hasSymbolReference() &&
originalReference->getSymbol()->isSpillTempAuto())
{
tempSymRef = originalReference->getSymbolReference();
if (debug("traceSpill"))
diagnostic(" Re-use spill temp [%p] for reference [%p] without storing\n",tempSymRef,originalReference);
}
else if ((*referenceIterator)->needSpillTemp())
{
if (!_availableSpillTemps.empty())
{
tempSymRef = *firstAvailableSpillTemp;
firstAvailableSpillTemp = _availableSpillTemps.erase(firstAvailableSpillTemp);
if (debug("traceSpill"))
diagnostic(" Re-use available spill temp [%p] for reference [%p]\n",tempSymRef,originalReference);
}
else
{
int32_t slot;
TR::AutomaticSymbol *tempSym = TR::AutomaticSymbol::create(self()->trHeapMemory());
tempSym->setSize(TR::DataType::getSize(TR::Address));
tempSym->setSpillTempAuto();
tempSymRef = new (self()->trHeapMemory()) TR::SymbolReference(self()->comp()->getSymRefTab(), tempSym);
slot = tempSymRef->getCPIndex();
slot = (slot < 0) ? (-slot - 1) : slot;
self()->comp()->getJittedMethodSymbol()->getAutoSymRefs(slot).add(tempSymRef);
self()->comp()->getMethodSymbol()->addAutomatic(tempSym);
if (debug("traceSpill"))
diagnostic(" Create new spill temp [%p] for reference [%p]\n",tempSymRef,originalReference);
}
storeSpillTemp = true;
}
else
{
tempSymRef = NULL;
if (debug("traceSpill"))
diagnostic(" No need to spill live reference [%p]\n",originalReference);
}
// Create a copy of the reference for use by parents before the GC point.
// Reference count will be number of parents before the GC safe point; if
// there is a store to a spill temp the reference count will be incremented
// to take account of this extra reference.
//
TR::Node *newReference = TR::Node::copy(originalReference);
newReference->setReferenceCount((*referenceIterator)->getNumberOfParents());
// Go through the parent list changing them to point to the new reference
// node wherever they pointed to the original node
//
ListIterator<TR::Node> nodeIterator(&(*referenceIterator)->getParentList());
TR::Node *nodeCursor = nodeIterator.getFirst();
while (nodeCursor)
{
for (int32_t childCount = 0;
childCount < nodeCursor->getNumChildren();
++childCount)
{
if (nodeCursor->getChild(childCount) == originalReference)
{
nodeCursor->setChild(childCount, newReference);
}
}
nodeCursor = nodeIterator.getNext();
}
if (tempSymRef)
{
// There is a spill temp
// Store it before the GC point if necessary
//
if (storeSpillTemp)
{
// insert new TR::astore node into tree top list before the call
TR::TreeTop::create(self()->comp(), insertionTree, TR::Node::createWithSymRef(TR::astore, 1, 1, newReference, tempSymRef));
}
// Rewrite the original reference as an aload of the temp.
TR::Node::recreate(originalReference, TR::aload);
originalReference->setNumChildren(0);
originalReference->setSymbolReference(tempSymRef);
}
// The original reference is now only used by parents subsequent to the
// GC safe point. Adjust its reference count.
//
originalReference->setReferenceCount(originalReference->getReferenceCount() - (*referenceIterator)->getNumberOfParents());
// Reset its visit count so that it is processed again for live
// references.
//
originalReference->setVisitCount(0);
++referenceIterator;
}
_liveReferenceList.clear();
}
void
OMR::CodeGenerator::needSpillTemp(TR_LiveReference * cursor, TR::Node *parent, TR::TreeTop *treeTop)
{
// If the reference is a simple load and the load is not killed before the