The Tor Browser / file revision

 /* -*- 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/x86/Lowering-x86.h"

 #include "jit/MIR.h"

 #include "jit/x86/Assembler-x86.h"

 #include "jit/shared/Lowering-shared-inl.h"

 using namespace js;

 using namespace js::jit;

 LDefinition

 LIRGeneratorX86::tempForDispatchCache(MIRType outputType)

 {

     // x86 doesn't have a scratch register and we need one for the

     // indirect jump for dispatch-style ICs.

     //

     // Note that currently we only install dispatch-style ICs for parallel

     // execution. If this assumption changes, please change it here.

     if (gen->info().executionMode() != ParallelExecution)

         return LDefinition::BogusTemp();

     // If we don't have an output register, we need a temp.

     if (outputType == MIRType_None)

         return temp();

     // If we have a double output register, we need a temp.

     if (outputType == MIRType_Double)

         return temp();

     // Otherwise we have a non-double output register and we can reuse it.

     return LDefinition::BogusTemp();

 }

 bool

 LIRGeneratorX86::useBox(LInstruction *lir, size_t n, MDefinition *mir,

                         LUse::Policy policy, bool useAtStart)

 {

     JS_ASSERT(mir->type() == MIRType_Value);

     if (!ensureDefined(mir))

         return false;

     lir->setOperand(n, LUse(mir->virtualRegister(), policy, useAtStart));

     lir->setOperand(n + 1, LUse(VirtualRegisterOfPayload(mir), policy, useAtStart));

     return true;

 }

 bool

 LIRGeneratorX86::useBoxFixed(LInstruction *lir, size_t n, MDefinition *mir, Register reg1,

                              Register reg2)

 {

     JS_ASSERT(mir->type() == MIRType_Value);

     JS_ASSERT(reg1 != reg2);

     if (!ensureDefined(mir))

         return false;

     lir->setOperand(n, LUse(reg1, mir->virtualRegister()));

     lir->setOperand(n + 1, LUse(reg2, VirtualRegisterOfPayload(mir)));

     return true;

 }

 LAllocation

 LIRGeneratorX86::useByteOpRegister(MDefinition *mir)

 {

     return useFixed(mir, eax);

 }

 LAllocation

 LIRGeneratorX86::useByteOpRegisterOrNonDoubleConstant(MDefinition *mir)

 {

     return useFixed(mir, eax);

 }

 bool

 LIRGeneratorX86::visitBox(MBox *box)

 {

     MDefinition *inner = box->getOperand(0);

     // If the box wrapped a double, it needs a new register.

     if (IsFloatingPointType(inner->type()))

         return defineBox(new(alloc()) LBoxFloatingPoint(useRegisterAtStart(inner), tempCopy(inner, 0),

                                                         inner->type()), box);

     if (box->canEmitAtUses())

         return emitAtUses(box);

     if (inner->isConstant())

         return defineBox(new(alloc()) LValue(inner->toConstant()->value()), box);

     LBox *lir = new(alloc()) LBox(use(inner), inner->type());

     // Otherwise, we should not define a new register for the payload portion

     // of the output, so bypass defineBox().

     uint32_t vreg = getVirtualRegister();

     if (vreg >= MAX_VIRTUAL_REGISTERS)

         return false;

     // Note that because we're using PASSTHROUGH, we do not change the type of

     // the definition. We also do not define the first output as "TYPE",

     // because it has no corresponding payload at (vreg + 1). Also note that

     // although we copy the input's original type for the payload half of the

     // definition, this is only for clarity. PASSTHROUGH definitions are

     // ignored.

     lir->setDef(0, LDefinition(vreg, LDefinition::GENERAL));

     lir->setDef(1, LDefinition(inner->virtualRegister(), LDefinition::TypeFrom(inner->type()),

                                LDefinition::PASSTHROUGH));

     box->setVirtualRegister(vreg);

     return add(lir);

 }

 bool

 LIRGeneratorX86::visitUnbox(MUnbox *unbox)

 {

     // An unbox on x86 reads in a type tag (either in memory or a register) and

     // a payload. Unlike most instructions conusming a box, we ask for the type

     // second, so that the result can re-use the first input.

     MDefinition *inner = unbox->getOperand(0);

     if (!ensureDefined(inner))

         return false;

     if (IsFloatingPointType(unbox->type())) {

         LUnboxFloatingPoint *lir = new(alloc()) LUnboxFloatingPoint(unbox->type());

         if (unbox->fallible() && !assignSnapshot(lir, unbox->bailoutKind()))

             return false;

         if (!useBox(lir, LUnboxFloatingPoint::Input, inner))

             return false;

         return define(lir, unbox);

     }

     // Swap the order we use the box pieces so we can re-use the payload register.

     LUnbox *lir = new(alloc()) LUnbox;

     lir->setOperand(0, usePayloadInRegisterAtStart(inner));

     lir->setOperand(1, useType(inner, LUse::ANY));

     if (unbox->fallible() && !assignSnapshot(lir, unbox->bailoutKind()))

         return false;

     // Note that PASSTHROUGH here is illegal, since types and payloads form two

     // separate intervals. If the type becomes dead before the payload, it

     // could be used as a Value without the type being recoverable. Unbox's

     // purpose is to eagerly kill the definition of a type tag, so keeping both

     // alive (for the purpose of gcmaps) is unappealing. Instead, we create a

     // new virtual register.

     return defineReuseInput(lir, unbox, 0);

 }

 bool

 LIRGeneratorX86::visitReturn(MReturn *ret)

 {

     MDefinition *opd = ret->getOperand(0);

     JS_ASSERT(opd->type() == MIRType_Value);

     LReturn *ins = new(alloc()) LReturn;

     ins->setOperand(0, LUse(JSReturnReg_Type));

     ins->setOperand(1, LUse(JSReturnReg_Data));

     return fillBoxUses(ins, 0, opd) && add(ins);

 }

 bool

 LIRGeneratorX86::defineUntypedPhi(MPhi *phi, size_t lirIndex)

 {

     LPhi *type = current->getPhi(lirIndex + VREG_TYPE_OFFSET);

     LPhi *payload = current->getPhi(lirIndex + VREG_DATA_OFFSET);

     uint32_t typeVreg = getVirtualRegister();

     if (typeVreg >= MAX_VIRTUAL_REGISTERS)

         return false;

     phi->setVirtualRegister(typeVreg);

     uint32_t payloadVreg = getVirtualRegister();

     if (payloadVreg >= MAX_VIRTUAL_REGISTERS)

         return false;

     JS_ASSERT(typeVreg + 1 == payloadVreg);

     type->setDef(0, LDefinition(typeVreg, LDefinition::TYPE));

     payload->setDef(0, LDefinition(payloadVreg, LDefinition::PAYLOAD));

     annotate(type);

     annotate(payload);

     return true;

 }

 void

 LIRGeneratorX86::lowerUntypedPhiInput(MPhi *phi, uint32_t inputPosition, LBlock *block, size_t lirIndex)

 {

     MDefinition *operand = phi->getOperand(inputPosition);

     LPhi *type = block->getPhi(lirIndex + VREG_TYPE_OFFSET);

     LPhi *payload = block->getPhi(lirIndex + VREG_DATA_OFFSET);

     type->setOperand(inputPosition, LUse(operand->virtualRegister() + VREG_TYPE_OFFSET, LUse::ANY));

     payload->setOperand(inputPosition, LUse(VirtualRegisterOfPayload(operand), LUse::ANY));

 }

 bool

 LIRGeneratorX86::visitAsmJSUnsignedToDouble(MAsmJSUnsignedToDouble *ins)

 {

     JS_ASSERT(ins->input()->type() == MIRType_Int32);

     LAsmJSUInt32ToDouble *lir = new(alloc()) LAsmJSUInt32ToDouble(useRegisterAtStart(ins->input()), temp());

     return define(lir, ins);

 }

 bool

 LIRGeneratorX86::visitAsmJSUnsignedToFloat32(MAsmJSUnsignedToFloat32 *ins)

 {

     JS_ASSERT(ins->input()->type() == MIRType_Int32);

     LAsmJSUInt32ToFloat32 *lir = new(alloc()) LAsmJSUInt32ToFloat32(useRegisterAtStart(ins->input()), temp());

     return define(lir, ins);

 }

 bool

 LIRGeneratorX86::visitAsmJSLoadHeap(MAsmJSLoadHeap *ins)

 {

     MDefinition *ptr = ins->ptr();

     LAllocation ptrAlloc;

     JS_ASSERT(ptr->type() == MIRType_Int32);

     // For the x86 it is best to keep the 'ptr' in a register if a bounds check is needed.

     if (ptr->isConstant() && ins->skipBoundsCheck()) {

         int32_t ptrValue = ptr->toConstant()->value().toInt32();

         // A bounds check is only skipped for a positive index.

         JS_ASSERT(ptrValue >= 0);

         ptrAlloc = LAllocation(ptr->toConstant()->vp());

     } else {

         ptrAlloc = useRegisterAtStart(ptr);

     }

     LAsmJSLoadHeap *lir = new(alloc()) LAsmJSLoadHeap(ptrAlloc);

     return define(lir, ins);

 }

 bool

 LIRGeneratorX86::visitAsmJSStoreHeap(MAsmJSStoreHeap *ins)

 {

     MDefinition *ptr = ins->ptr();

     LAsmJSStoreHeap *lir;

     JS_ASSERT(ptr->type() == MIRType_Int32);

     if (ptr->isConstant() && ins->skipBoundsCheck()) {

         int32_t ptrValue = ptr->toConstant()->value().toInt32();

         JS_ASSERT(ptrValue >= 0);

         LAllocation ptrAlloc = LAllocation(ptr->toConstant()->vp());

         switch (ins->viewType()) {

           case ArrayBufferView::TYPE_INT8: case ArrayBufferView::TYPE_UINT8:

             // See comment below.

             lir = new(alloc()) LAsmJSStoreHeap(ptrAlloc, useFixed(ins->value(), eax));

             break;

           case ArrayBufferView::TYPE_INT16: case ArrayBufferView::TYPE_UINT16:

           case ArrayBufferView::TYPE_INT32: case ArrayBufferView::TYPE_UINT32:

           case ArrayBufferView::TYPE_FLOAT32: case ArrayBufferView::TYPE_FLOAT64:

             // See comment below.

             lir = new(alloc()) LAsmJSStoreHeap(ptrAlloc, useRegisterAtStart(ins->value()));

             break;

           default: MOZ_ASSUME_UNREACHABLE("unexpected array type");

         }

         return add(lir, ins);

     }

     switch (ins->viewType()) {

       case ArrayBufferView::TYPE_INT8: case ArrayBufferView::TYPE_UINT8:

         // See comment for LIRGeneratorX86::useByteOpRegister.

         lir = new(alloc()) LAsmJSStoreHeap(useRegister(ins->ptr()), useFixed(ins->value(), eax));

         break;

       case ArrayBufferView::TYPE_INT16: case ArrayBufferView::TYPE_UINT16:

       case ArrayBufferView::TYPE_INT32: case ArrayBufferView::TYPE_UINT32:

       case ArrayBufferView::TYPE_FLOAT32: case ArrayBufferView::TYPE_FLOAT64:

         // For now, don't allow constant values. The immediate operand

         // affects instruction layout which affects patching.

         lir = new(alloc()) LAsmJSStoreHeap(useRegisterAtStart(ptr), useRegisterAtStart(ins->value()));

         break;

       default: MOZ_ASSUME_UNREACHABLE("unexpected array type");

     }

     return add(lir, ins);

 }

 bool

 LIRGeneratorX86::visitStoreTypedArrayElementStatic(MStoreTypedArrayElementStatic *ins)

 {

     // The code generated for StoreTypedArrayElementStatic is identical to that

     // for AsmJSStoreHeap, and the same concerns apply.

     LStoreTypedArrayElementStatic *lir;

     switch (ins->viewType()) {

       case ArrayBufferView::TYPE_INT8: case ArrayBufferView::TYPE_UINT8:

       case ArrayBufferView::TYPE_UINT8_CLAMPED:

         lir = new(alloc()) LStoreTypedArrayElementStatic(useRegister(ins->ptr()),

                                                          useFixed(ins->value(), eax));

         break;

       case ArrayBufferView::TYPE_INT16: case ArrayBufferView::TYPE_UINT16:

       case ArrayBufferView::TYPE_INT32: case ArrayBufferView::TYPE_UINT32:

       case ArrayBufferView::TYPE_FLOAT32: case ArrayBufferView::TYPE_FLOAT64:

         lir = new(alloc()) LStoreTypedArrayElementStatic(useRegisterAtStart(ins->ptr()),

                                                          useRegisterAtStart(ins->value()));

         break;

       default: MOZ_ASSUME_UNREACHABLE("unexpected array type");

     }

     return add(lir, ins);

 }

 bool

 LIRGeneratorX86::visitAsmJSLoadFuncPtr(MAsmJSLoadFuncPtr *ins)

 {

     return define(new(alloc()) LAsmJSLoadFuncPtr(useRegisterAtStart(ins->index())), ins);

 }