1 files changed, 306 insertions, 0 deletions
diff --git a/js/src/jit/shared/Lowering-shared.cpp b/js/src/jit/shared/Lowering-shared.cpp
new file mode 100644
index 0000000000..4d313491d7
--- /dev/null
+++ b/js/src/jit/shared/Lowering-shared.cpp
@@ -0,0 +1,306 @@
+/* -*- 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/shared/Lowering-shared-inl.h"
+
+#include "jit/LIR.h"
+#include "jit/MIR.h"
+
+#include "vm/Symbol.h"
+
+using namespace js;
+using namespace jit;
+
+bool
+LIRGeneratorShared::ShouldReorderCommutative(MDefinition* lhs, MDefinition* rhs, MInstruction* ins)
+{
+    // lhs and rhs are used by the commutative operator.
+    MOZ_ASSERT(lhs->hasDefUses());
+    MOZ_ASSERT(rhs->hasDefUses());
+
+    // Ensure that if there is a constant, then it is in rhs.
+    if (rhs->isConstant())
+        return false;
+    if (lhs->isConstant())
+        return true;
+
+    // Since clobbering binary operations clobber the left operand, prefer a
+    // non-constant lhs operand with no further uses. To be fully precise, we
+    // should check whether this is the *last* use, but checking hasOneDefUse()
+    // is a decent approximation which doesn't require any extra analysis.
+    bool rhsSingleUse = rhs->hasOneDefUse();
+    bool lhsSingleUse = lhs->hasOneDefUse();
+    if (rhsSingleUse) {
+        if (!lhsSingleUse)
+            return true;
+    } else {
+        if (lhsSingleUse)
+            return false;
+    }
+
+    // If this is a reduction-style computation, such as
+    //
+    //   sum = 0;
+    //   for (...)
+    //      sum += ...;
+    //
+    // put the phi on the left to promote coalescing. This is fairly specific.
+    if (rhsSingleUse &&
+        rhs->isPhi() &&
+        rhs->block()->isLoopHeader() &&
+        ins == rhs->toPhi()->getLoopBackedgeOperand())
+    {
+        return true;
+    }
+
+    return false;
+}
+
+void
+LIRGeneratorShared::ReorderCommutative(MDefinition** lhsp, MDefinition** rhsp, MInstruction* ins)
+{
+    MDefinition* lhs = *lhsp;
+    MDefinition* rhs = *rhsp;
+
+    if (ShouldReorderCommutative(lhs, rhs, ins)) {
+        *rhsp = lhs;
+        *lhsp = rhs;
+    }
+}
+
+void
+LIRGeneratorShared::visitConstant(MConstant* ins)
+{
+    if (!IsFloatingPointType(ins->type()) && ins->canEmitAtUses()) {
+        emitAtUses(ins);
+        return;
+    }
+
+    switch (ins->type()) {
+      case MIRType::Double:
+        define(new(alloc()) LDouble(ins->toRawF64()), ins);
+        break;
+      case MIRType::Float32:
+        define(new(alloc()) LFloat32(ins->toRawF32()), ins);
+        break;
+      case MIRType::Boolean:
+        define(new(alloc()) LInteger(ins->toBoolean()), ins);
+        break;
+      case MIRType::Int32:
+        define(new(alloc()) LInteger(ins->toInt32()), ins);
+        break;
+      case MIRType::Int64:
+        defineInt64(new(alloc()) LInteger64(ins->toInt64()), ins);
+        break;
+      case MIRType::String:
+        define(new(alloc()) LPointer(ins->toString()), ins);
+        break;
+      case MIRType::Symbol:
+        define(new(alloc()) LPointer(ins->toSymbol()), ins);
+        break;
+      case MIRType::Object:
+        define(new(alloc()) LPointer(&ins->toObject()), ins);
+        break;
+      default:
+        // Constants of special types (undefined, null) should never flow into
+        // here directly. Operations blindly consuming them require a Box.
+        MOZ_CRASH("unexpected constant type");
+    }
+}
+
+void
+LIRGeneratorShared::defineTypedPhi(MPhi* phi, size_t lirIndex)
+{
+    LPhi* lir = current->getPhi(lirIndex);
+
+    uint32_t vreg = getVirtualRegister();
+
+    phi->setVirtualRegister(vreg);
+    lir->setDef(0, LDefinition(vreg, LDefinition::TypeFrom(phi->type())));
+    annotate(lir);
+}
+
+void
+LIRGeneratorShared::lowerTypedPhiInput(MPhi* phi, uint32_t inputPosition, LBlock* block, size_t lirIndex)
+{
+    MDefinition* operand = phi->getOperand(inputPosition);
+    LPhi* lir = block->getPhi(lirIndex);
+    lir->setOperand(inputPosition, LUse(operand->virtualRegister(), LUse::ANY));
+}
+
+LRecoverInfo*
+LIRGeneratorShared::getRecoverInfo(MResumePoint* rp)
+{
+    if (cachedRecoverInfo_ && cachedRecoverInfo_->mir() == rp)
+        return cachedRecoverInfo_;
+
+    LRecoverInfo* recoverInfo = LRecoverInfo::New(gen, rp);
+    if (!recoverInfo)
+        return nullptr;
+
+    cachedRecoverInfo_ = recoverInfo;
+    return recoverInfo;
+}
+
+#ifdef DEBUG
+bool
+LRecoverInfo::OperandIter::canOptimizeOutIfUnused()
+{
+    MDefinition* ins = **this;
+
+    // We check ins->type() in addition to ins->isUnused() because
+    // EliminateDeadResumePointOperands may replace nodes with the constant
+    // MagicValue(JS_OPTIMIZED_OUT).
+    if ((ins->isUnused() || ins->type() == MIRType::MagicOptimizedOut) &&
+        (*it_)->isResumePoint())
+    {
+        return !(*it_)->toResumePoint()->isObservableOperand(op_);
+    }
+
+    return true;
+}
+#endif
+
+#ifdef JS_NUNBOX32
+LSnapshot*
+LIRGeneratorShared::buildSnapshot(LInstruction* ins, MResumePoint* rp, BailoutKind kind)
+{
+    LRecoverInfo* recoverInfo = getRecoverInfo(rp);
+    if (!recoverInfo)
+        return nullptr;
+
+    LSnapshot* snapshot = LSnapshot::New(gen, recoverInfo, kind);
+    if (!snapshot)
+        return nullptr;
+
+    size_t index = 0;
+    for (LRecoverInfo::OperandIter it(recoverInfo); !it; ++it) {
+        // Check that optimized out operands are in eliminable slots.
+        MOZ_ASSERT(it.canOptimizeOutIfUnused());
+
+        MDefinition* ins = *it;
+
+        if (ins->isRecoveredOnBailout())
+            continue;
+
+        LAllocation* type = snapshot->typeOfSlot(index);
+        LAllocation* payload = snapshot->payloadOfSlot(index);
+        ++index;
+
+        if (ins->isBox())
+            ins = ins->toBox()->getOperand(0);
+
+        // Guards should never be eliminated.
+        MOZ_ASSERT_IF(ins->isUnused(), !ins->isGuard());
+
+        // Snapshot operands other than constants should never be
+        // emitted-at-uses. Try-catch support depends on there being no
+        // code between an instruction and the LOsiPoint that follows it.
+        MOZ_ASSERT_IF(!ins->isConstant(), !ins->isEmittedAtUses());
+
+        // The register allocation will fill these fields in with actual
+        // register/stack assignments. During code generation, we can restore
+        // interpreter state with the given information. Note that for
+        // constants, including known types, we record a dummy placeholder,
+        // since we can recover the same information, much cleaner, from MIR.
+        if (ins->isConstant() || ins->isUnused()) {
+            *type = LAllocation();
+            *payload = LAllocation();
+        } else if (ins->type() != MIRType::Value) {
+            *type = LAllocation();
+            *payload = use(ins, LUse(LUse::KEEPALIVE));
+        } else {
+            *type = useType(ins, LUse::KEEPALIVE);
+            *payload = usePayload(ins, LUse::KEEPALIVE);
+        }
+    }
+
+    return snapshot;
+}
+
+#elif JS_PUNBOX64
+
+LSnapshot*
+LIRGeneratorShared::buildSnapshot(LInstruction* ins, MResumePoint* rp, BailoutKind kind)
+{
+    LRecoverInfo* recoverInfo = getRecoverInfo(rp);
+    if (!recoverInfo)
+        return nullptr;
+
+    LSnapshot* snapshot = LSnapshot::New(gen, recoverInfo, kind);
+    if (!snapshot)
+        return nullptr;
+
+    size_t index = 0;
+    for (LRecoverInfo::OperandIter it(recoverInfo); !it; ++it) {
+        // Check that optimized out operands are in eliminable slots.
+        MOZ_ASSERT(it.canOptimizeOutIfUnused());
+
+        MDefinition* def = *it;
+
+        if (def->isRecoveredOnBailout())
+            continue;
+
+        if (def->isBox())
+            def = def->toBox()->getOperand(0);
+
+        // Guards should never be eliminated.
+        MOZ_ASSERT_IF(def->isUnused(), !def->isGuard());
+
+        // Snapshot operands other than constants should never be
+        // emitted-at-uses. Try-catch support depends on there being no
+        // code between an instruction and the LOsiPoint that follows it.
+        MOZ_ASSERT_IF(!def->isConstant(), !def->isEmittedAtUses());
+
+        LAllocation* a = snapshot->getEntry(index++);
+
+        if (def->isUnused()) {
+            *a = LAllocation();
+            continue;
+        }
+
+        *a = useKeepaliveOrConstant(def);
+    }
+
+    return snapshot;
+}
+#endif
+
+void
+LIRGeneratorShared::assignSnapshot(LInstruction* ins, BailoutKind kind)
+{
+    // assignSnapshot must be called before define/add, since
+    // it may add new instructions for emitted-at-use operands.
+    MOZ_ASSERT(ins->id() == 0);
+
+    LSnapshot* snapshot = buildSnapshot(ins, lastResumePoint_, kind);
+    if (snapshot)
+        ins->assignSnapshot(snapshot);
+    else
+        gen->abort("buildSnapshot failed");
+}
+
+void
+LIRGeneratorShared::assignSafepoint(LInstruction* ins, MInstruction* mir, BailoutKind kind)
+{
+    MOZ_ASSERT(!osiPoint_);
+    MOZ_ASSERT(!ins->safepoint());
+
+    ins->initSafepoint(alloc());
+
+    MResumePoint* mrp = mir->resumePoint() ? mir->resumePoint() : lastResumePoint_;
+    LSnapshot* postSnapshot = buildSnapshot(ins, mrp, kind);
+    if (!postSnapshot) {
+        gen->abort("buildSnapshot failed");
+        return;
+    }
+
+    osiPoint_ = new(alloc()) LOsiPoint(ins->safepoint(), postSnapshot);
+
+    if (!lirGraph_.noteNeedsSafepoint(ins))
+        gen->abort("noteNeedsSafepoint failed");
+}
+