The Tor Browser: js/src/jit/StupidAllocator.cpp@129ffea94266 (annotated)

js/src/jit/StupidAllocator.cpp@129ffea94266 (annotated)

js/src/jit/StupidAllocator.cpp

Sat, 03 Jan 2015 20:18:00 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Sat, 03 Jan 2015 20:18:00 +0100
branch: TOR_BUG_3246
changeset 7: 129ffea94266
permissions: -rw-r--r--

Conditionally enable double key logic according to:
private browsing mode or privacy.thirdparty.isolate preference and
implement in GetCookieStringCommon and FindCookie where it counts...
With some reservations of how to convince FindCookie users to test
condition and pass a nullptr when disabling double key logic.

 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
  * vim: set ts=8 sts=4 et sw=4 tw=99:
  * This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 #include "jit/StupidAllocator.h"
 #include "jstypes.h"
 using namespace js;
 using namespace js::jit;
 static inline uint32_t
 DefaultStackSlot(uint32_t vreg)
 {
     return vreg * sizeof(Value);
 }
 LAllocation *
 StupidAllocator::stackLocation(uint32_t vreg)
 {
     LDefinition *def = virtualRegisters[vreg];
     if (def->policy() == LDefinition::PRESET && def->output()->isArgument())
         return def->output();
     return new(alloc()) LStackSlot(DefaultStackSlot(vreg));
 }
 StupidAllocator::RegisterIndex
 StupidAllocator::registerIndex(AnyRegister reg)
 {
     for (size_t i = 0; i < registerCount; i++) {
         if (reg == registers[i].reg)
             return i;
     }
     MOZ_ASSUME_UNREACHABLE("Bad register");
 }
 bool
 StupidAllocator::init()
 {
     if (!RegisterAllocator::init())
         return false;
     if (!virtualRegisters.appendN((LDefinition *)nullptr, graph.numVirtualRegisters()))
         return false;
     for (size_t i = 0; i < graph.numBlocks(); i++) {
         LBlock *block = graph.getBlock(i);
         for (LInstructionIterator ins = block->begin(); ins != block->end(); ins++) {
             for (size_t j = 0; j < ins->numDefs(); j++) {
                 LDefinition *def = ins->getDef(j);
                 if (def->policy() != LDefinition::PASSTHROUGH)
                     virtualRegisters[def->virtualRegister()] = def;
             }
             for (size_t j = 0; j < ins->numTemps(); j++) {
                 LDefinition *def = ins->getTemp(j);
                 if (def->isBogusTemp())
                     continue;
                 virtualRegisters[def->virtualRegister()] = def;
             }
         }
         for (size_t j = 0; j < block->numPhis(); j++) {
             LPhi *phi = block->getPhi(j);
             LDefinition *def = phi->getDef(0);
             uint32_t vreg = def->virtualRegister();
             virtualRegisters[vreg] = def;
         }
     }
     // Assign physical registers to the tracked allocation.
     {
         registerCount = 0;
         RegisterSet remainingRegisters(allRegisters_);
         while (!remainingRegisters.empty(/* float = */ false))
             registers[registerCount++].reg = AnyRegister(remainingRegisters.takeGeneral());
         while (!remainingRegisters.empty(/* float = */ true))
             registers[registerCount++].reg = AnyRegister(remainingRegisters.takeFloat());
         JS_ASSERT(registerCount <= MAX_REGISTERS);
     }
     return true;
 }
 bool
 StupidAllocator::allocationRequiresRegister(const LAllocation *alloc, AnyRegister reg)
 {
     if (alloc->isRegister() && alloc->toRegister() == reg)
         return true;
     if (alloc->isUse()) {
         const LUse *use = alloc->toUse();
         if (use->policy() == LUse::FIXED) {
             AnyRegister usedReg = GetFixedRegister(virtualRegisters[use->virtualRegister()], use);
             if (usedReg == reg)
                 return true;
         }
     }
     return false;
 }
 bool
 StupidAllocator::registerIsReserved(LInstruction *ins, AnyRegister reg)
 {
     // Whether reg is already reserved for an input or output of ins.
     for (LInstruction::InputIterator alloc(*ins); alloc.more(); alloc.next()) {
         if (allocationRequiresRegister(*alloc, reg))
             return true;
     }
     for (size_t i = 0; i < ins->numTemps(); i++) {
         if (allocationRequiresRegister(ins->getTemp(i)->output(), reg))
             return true;
     }
     for (size_t i = 0; i < ins->numDefs(); i++) {
         if (allocationRequiresRegister(ins->getDef(i)->output(), reg))
             return true;
     }
     return false;
 }
 AnyRegister
 StupidAllocator::ensureHasRegister(LInstruction *ins, uint32_t vreg)
 {
     // Ensure that vreg is held in a register before ins.
     // Check if the virtual register is already held in a physical register.
     RegisterIndex existing = findExistingRegister(vreg);
     if (existing != UINT32_MAX) {
         if (registerIsReserved(ins, registers[existing].reg)) {
             evictRegister(ins, existing);
         } else {
             registers[existing].age = ins->id();
             return registers[existing].reg;
         }
     }
     RegisterIndex best = allocateRegister(ins, vreg);
     loadRegister(ins, vreg, best, virtualRegisters[vreg]->type());
     return registers[best].reg;
 }
 StupidAllocator::RegisterIndex
 StupidAllocator::allocateRegister(LInstruction *ins, uint32_t vreg)
 {
     // Pick a register for vreg, evicting an existing register if necessary.
     // Spill code will be placed before ins, and no existing allocated input
     // for ins will be touched.
     JS_ASSERT(ins);
     LDefinition *def = virtualRegisters[vreg];
     JS_ASSERT(def);
     RegisterIndex best = UINT32_MAX;
     for (size_t i = 0; i < registerCount; i++) {
         AnyRegister reg = registers[i].reg;
         if (reg.isFloat() != def->isFloatReg())
             continue;
         // Skip the register if it is in use for an allocated input or output.
         if (registerIsReserved(ins, reg))
             continue;
         if (registers[i].vreg == MISSING_ALLOCATION ||
             best == UINT32_MAX ||
             registers[best].age > registers[i].age)
         {
             best = i;
         }
     }
     evictRegister(ins, best);
     return best;
 }
 void
 StupidAllocator::syncRegister(LInstruction *ins, RegisterIndex index)
 {
     if (registers[index].dirty) {
         LMoveGroup *input = getInputMoveGroup(ins->id());
         LAllocation *source = new(alloc()) LAllocation(registers[index].reg);
         uint32_t existing = registers[index].vreg;
         LAllocation *dest = stackLocation(existing);
         input->addAfter(source, dest, registers[index].type);
         registers[index].dirty = false;
     }
 }
 void
 StupidAllocator::evictRegister(LInstruction *ins, RegisterIndex index)
 {
     syncRegister(ins, index);
     registers[index].set(MISSING_ALLOCATION);
 }
 void
 StupidAllocator::loadRegister(LInstruction *ins, uint32_t vreg, RegisterIndex index, LDefinition::Type type)
 {
     // Load a vreg from its stack location to a register.
     LMoveGroup *input = getInputMoveGroup(ins->id());
     LAllocation *source = stackLocation(vreg);
     LAllocation *dest = new(alloc()) LAllocation(registers[index].reg);
     input->addAfter(source, dest, type);
     registers[index].set(vreg, ins);
     registers[index].type = type;
 }
 StupidAllocator::RegisterIndex
 StupidAllocator::findExistingRegister(uint32_t vreg)
 {
     for (size_t i = 0; i < registerCount; i++) {
         if (registers[i].vreg == vreg)
             return i;
     }
     return UINT32_MAX;
 }
 bool
 StupidAllocator::go()
 {
     // This register allocator is intended to be as simple as possible, while
     // still being complicated enough to share properties with more complicated
     // allocators. Namely, physical registers may be used to carry virtual
     // registers across LIR instructions, but not across basic blocks.
     //
     // This algorithm does not pay any attention to liveness. It is performed
     // as a single forward pass through the basic blocks in the program. As
     // virtual registers and temporaries are defined they are assigned physical
     // registers, evicting existing allocations in an LRU fashion.
     // For virtual registers not carried in a register, a canonical spill
     // location is used. Each vreg has a different spill location; since we do
     // not track liveness we cannot determine that two vregs have disjoint
     // lifetimes. Thus, the maximum stack height is the number of vregs (scaled
     // by two on 32 bit platforms to allow storing double values).
     graph.setLocalSlotCount(DefaultStackSlot(graph.numVirtualRegisters()));
     if (!init())
         return false;
     for (size_t blockIndex = 0; blockIndex < graph.numBlocks(); blockIndex++) {
         LBlock *block = graph.getBlock(blockIndex);
         JS_ASSERT(block->mir()->id() == blockIndex);
         for (size_t i = 0; i < registerCount; i++)
             registers[i].set(MISSING_ALLOCATION);
         for (LInstructionIterator iter = block->begin(); iter != block->end(); iter++) {
             LInstruction *ins = *iter;
             if (ins == *block->rbegin())
                 syncForBlockEnd(block, ins);
             allocateForInstruction(ins);
         }
     }
     return true;
 }
 void
 StupidAllocator::syncForBlockEnd(LBlock *block, LInstruction *ins)
 {
     // Sync any dirty registers, and update the synced state for phi nodes at
     // each successor of a block. We cannot conflate the storage for phis with
     // that of their inputs, as we cannot prove the live ranges of the phi and
     // its input do not overlap. The values for the two may additionally be
     // different, as the phi could be for the value of the input in a previous
     // loop iteration.
     for (size_t i = 0; i < registerCount; i++)
         syncRegister(ins, i);
     LMoveGroup *group = nullptr;
     MBasicBlock *successor = block->mir()->successorWithPhis();
     if (successor) {
         uint32_t position = block->mir()->positionInPhiSuccessor();
         LBlock *lirsuccessor = graph.getBlock(successor->id());
         for (size_t i = 0; i < lirsuccessor->numPhis(); i++) {
             LPhi *phi = lirsuccessor->getPhi(i);
             uint32_t sourcevreg = phi->getOperand(position)->toUse()->virtualRegister();
             uint32_t destvreg = phi->getDef(0)->virtualRegister();
             if (sourcevreg == destvreg)
                 continue;
             LAllocation *source = stackLocation(sourcevreg);
             LAllocation *dest = stackLocation(destvreg);
             if (!group) {
                 // The moves we insert here need to happen simultaneously with
                 // each other, yet after any existing moves before the instruction.
                 LMoveGroup *input = getInputMoveGroup(ins->id());
                 if (input->numMoves() == 0) {
                     group = input;
                 } else {
                     group = LMoveGroup::New(alloc());
                     block->insertAfter(input, group);
                 }
             }
             group->add(source, dest, phi->getDef(0)->type());
         }
     }
 }
 void
 StupidAllocator::allocateForInstruction(LInstruction *ins)
 {
     // Sync all registers before making a call.
     if (ins->isCall()) {
         for (size_t i = 0; i < registerCount; i++)
             syncRegister(ins, i);
     }
     // Allocate for inputs which are required to be in registers.
     for (LInstruction::InputIterator alloc(*ins); alloc.more(); alloc.next()) {
         if (!alloc->isUse())
             continue;
         LUse *use = alloc->toUse();
         uint32_t vreg = use->virtualRegister();
         if (use->policy() == LUse::REGISTER) {
             AnyRegister reg = ensureHasRegister(ins, vreg);
             alloc.replace(LAllocation(reg));
         } else if (use->policy() == LUse::FIXED) {
             AnyRegister reg = GetFixedRegister(virtualRegisters[vreg], use);
             RegisterIndex index = registerIndex(reg);
             if (registers[index].vreg != vreg) {
                 evictRegister(ins, index);
                 RegisterIndex existing = findExistingRegister(vreg);
                 if (existing != UINT32_MAX)
                     evictRegister(ins, existing);
                 loadRegister(ins, vreg, index, virtualRegisters[vreg]->type());
             }
             alloc.replace(LAllocation(reg));
         } else {
             // Inputs which are not required to be in a register are not
             // allocated until after temps/definitions, as the latter may need
             // to evict registers which hold these inputs.
         }
     }
     // Find registers to hold all temporaries and outputs of the instruction.
     for (size_t i = 0; i < ins->numTemps(); i++) {
         LDefinition *def = ins->getTemp(i);
         if (!def->isBogusTemp())
             allocateForDefinition(ins, def);
     }
     for (size_t i = 0; i < ins->numDefs(); i++) {
         LDefinition *def = ins->getDef(i);
         if (def->policy() != LDefinition::PASSTHROUGH)
             allocateForDefinition(ins, def);
     }
     // Allocate for remaining inputs which do not need to be in registers.
     for (LInstruction::InputIterator alloc(*ins); alloc.more(); alloc.next()) {
         if (!alloc->isUse())
             continue;
         LUse *use = alloc->toUse();
         uint32_t vreg = use->virtualRegister();
         JS_ASSERT(use->policy() != LUse::REGISTER && use->policy() != LUse::FIXED);
         RegisterIndex index = findExistingRegister(vreg);
         if (index == UINT32_MAX) {
             LAllocation *stack = stackLocation(use->virtualRegister());
             alloc.replace(*stack);
         } else {
             registers[index].age = ins->id();
             alloc.replace(LAllocation(registers[index].reg));
         }
     }
     // If this is a call, evict all registers except for those holding outputs.
     if (ins->isCall()) {
         for (size_t i = 0; i < registerCount; i++) {
             if (!registers[i].dirty)
                 registers[i].set(MISSING_ALLOCATION);
         }
     }
 }
 void
 StupidAllocator::allocateForDefinition(LInstruction *ins, LDefinition *def)
 {
     uint32_t vreg = def->virtualRegister();
     CodePosition from;
     if ((def->output()->isRegister() && def->policy() == LDefinition::PRESET) ||
         def->policy() == LDefinition::MUST_REUSE_INPUT)
     {
         // Result will be in a specific register, spill any vreg held in
         // that register before the instruction.
         RegisterIndex index =
             registerIndex(def->policy() == LDefinition::PRESET
                           ? def->output()->toRegister()
                           : ins->getOperand(def->getReusedInput())->toRegister());
         evictRegister(ins, index);
         registers[index].set(vreg, ins, true);
         registers[index].type = virtualRegisters[vreg]->type();
         def->setOutput(LAllocation(registers[index].reg));
     } else if (def->policy() == LDefinition::PRESET) {
         // The result must be a stack location.
         def->setOutput(*stackLocation(vreg));
     } else {
         // Find a register to hold the result of the instruction.
         RegisterIndex best = allocateRegister(ins, vreg);
         registers[best].set(vreg, ins, true);
         registers[best].type = virtualRegisters[vreg]->type();
         def->setOutput(LAllocation(registers[best].reg));
     }
 }

The Tor Browser / annotate

js/src/jit/StupidAllocator.cpp@129ffea94266 (annotated)

js/src/jit/StupidAllocator.cpp