[interpreter] Wide register support.

src/interpreter/register-translator.cc

+// Copyright 2015 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "src/interpreter/register-translator.h"
+
+#include "src/interpreter/bytecode-array-builder.h"
+
+namespace v8 {
+namespace internal {
+namespace interpreter {
+
+RegisterTranslator::RegisterTranslator(RegisterMover* mover)
+    : mover_(mover), emitting_moves_(false), window_registers_count_(0) {}
+
+
+void RegisterTranslator::TranslateRegisters(Bytecode bytecode,
+                                            uint32_t* raw_operands,
+                                            int raw_operand_count) {
+  DCHECK_EQ(Bytecodes::NumberOfOperands(bytecode), raw_operand_count);
+  if (!emitting_moves_) {
+    emitting_moves_ = true;
+    DCHECK_EQ(window_registers_count_, 0);
+    int register_bitmap = Bytecodes::GetRegisterOperandBitmap(bytecode);
+    for (int i = 0; i < raw_operand_count; i++) {
+      if ((register_bitmap & (1 << i)) == 0) {
+        DCHECK(NonRegisterOperandIsValid(bytecode, i));
+        continue;
+      }
+      Register in_reg = Register::FromRawOperand(raw_operands[i]);
+      Register out_reg = TranslateAndMove(bytecode, i, in_reg);
+      raw_operands[i] = out_reg.ToRawOperand();
+    }
+    emitting_moves_ = false;
+  } else {
+    // When the register translator is translating registers, it will
+    // cause the bytecode generator to emit moves on it's behalf. This
+    // path is reached by these moves.
+    DCHECK(bytecode == Bytecode::kMovWide && raw_operand_count == 2 &&
+           Register::FromRawOperand(raw_operands[0]).is_valid() &&
+           Register::FromRawOperand(raw_operands[1]).is_valid());
+  }
+}
+
+
+Register RegisterTranslator::TranslateAndMove(Bytecode bytecode,
+                                              int operand_index, Register reg) {
+  OperandType operand_type = Bytecodes::GetOperandType(bytecode, operand_index);
+  Register translated_reg = Translate(reg);
+  Register addressable_reg = MakeAddressable(translated_reg, operand_type);
+  if (addressable_reg != translated_reg) {
+    if (operand_type == OperandType::kReg8 &&
+        OperandIsMoveable(bytecode, operand_index)) {
+      mover()->MoveRegisterUntranslated(translated_reg, addressable_reg);
+    } else {
+      Register invalid_reg;
+      mover()->MoveRegisterUntranslated(invalid_reg, invalid_reg);

[rmcilroy, 2016/01/25 12:12:05]

Maybe we can make this a Death test instead? 

If we can't do a death test then personally I would prefer that there was a
"test mode" on this class and we CHECK failed if this was false, and did
something exposable to tests if it was true, rather than relying on the layer
above having a CHECK for invalid_reg. Whatever the decision, please make it
explicit with a comment here.

[oth, 2016/01/25 16:51:57]

Didn't appreciate death test was an option. Have not added test mode, but have
put a CHECK in and the RegisterTranslator tests for bad ranges look for this.

+    }
+  }
+  return addressable_reg;
+}
+
+
+void RegisterTranslator::UntranslateRegisters() {
+  if (!emitting_moves_) {
+    emitting_moves_ = true;
+    while (window_registers_count_ > 0) {
+      window_registers_count_ -= 1;
+      Register source(kTranslationWindowStart + window_registers_count_);
+      Register destination = window_registers_[window_registers_count_];
+      mover()->MoveRegisterUntranslated(source, destination);
+    }
+    emitting_moves_ = false;
+  }
+}
+
+
+Register RegisterTranslator::MakeAddressable(Register reg,
+                                             OperandType reg_type) {
+  DCHECK(!InTranslationWindow(reg));
+  OperandSize reg_size = Bytecodes::SizeOfOperand(reg_type);
+  if (reg_size == OperandSize::kByte && !FitsInReg8Operand(reg)) {
+    // TODO(oth): Moves into and out from translation window could be
+    // decoupled if there were metadata to say whether the register
+    // operand was an input, output, or input-and-output for a given
+    // bytecode.
+    Register destination(kTranslationWindowStart + window_registers_count_);
+    window_registers_[window_registers_count_] = reg;
+    window_registers_count_ += 1;
+    DCHECK_LE(window_registers_count_, kTranslationWindowLength);
+    return destination;
+  } else {
+    return reg;
+  }
+}
+
+
+// static
+bool RegisterTranslator::NonRegisterOperandIsValid(Bytecode bytecode,
+                                                   int operand_index) {
+  OperandType operand_type = Bytecodes::GetOperandType(bytecode, operand_index);
+  if (operand_type == OperandType::kRegCount8 ||
+      operand_type == OperandType::kRegCount16) {

[rmcilroy, 2016/01/25 12:12:05]

Should this not be checked in OperandIsValid in bytecode array builder instead
of here? It seems a bit strange to split this up between here and bytecode array
builder

[oth, 2016/01/25 16:51:57]

Done.

+    if (operand_index > 0) {
+      switch (Bytecodes::GetOperandType(bytecode, operand_index - 1)) {
+        case OperandType::kMaybeReg8:
+        case OperandType::kMaybeReg16:
+        case OperandType::kReg8:
+        case OperandType::kReg16:
+          return true;
+        case OperandType::kNone:
+          UNREACHABLE();
+        case OperandType::kIdx8:
+        case OperandType::kIdx16:
+        case OperandType::kImm8:
+        case OperandType::kRegCount8:
+        case OperandType::kRegCount16:
+        case OperandType::kRegPair8:
+        case OperandType::kRegPair16:
+        case OperandType::kRegTriple8:
+        case OperandType::kRegTriple16:
+          break;
+      }
+    }
+    return false;
+  } else {
+    return true;
+  }
+}
+
+
+// static
+bool RegisterTranslator::OperandIsMoveable(Bytecode bytecode,

[rmcilroy, 2016/01/25 12:12:05]

This could be exposed as part of the RegisterMover delegate to keep the logic of
which bytecodes are moveable and whether a reg operand followed by a regcount
operand means a reg range in there.

[oth, 2016/01/25 16:51:56]

Done.

+                                           int operand_index) {
+  // By design, the translator does not copy any register ranges into
+  // the translation window. There should be wide variants of such
+  // bytecodes instead to avoid the need for a large translation
+  // window.
+  OperandType operand_type = Bytecodes::GetOperandType(bytecode, operand_index);
+  if (operand_type == OperandType::kReg8 ||
+      operand_type == OperandType::kReg16) {
+    if (operand_index == Bytecodes::NumberOfOperands(bytecode) - 1) {
+      return true;
+    }
+    OperandType next_operand_type =
+        Bytecodes::GetOperandType(bytecode, operand_index + 1);
+    return (next_operand_type != OperandType::kRegCount8 &&
+            next_operand_type != OperandType::kRegCount16);
+  } else {
+    return false;
+  }
+}
+
+
+// static
+Register RegisterTranslator::Translate(Register reg) {
+  if (reg.index() >= kTranslationWindowStart) {
+    return Register(reg.index() + kTranslationWindowLength);
+  } else {
+    return reg;
+  }
+}
+
+
+// static
+bool RegisterTranslator::InTranslationWindow(Register reg) {
+  return (reg.index() >= kTranslationWindowStart &&
+          reg.index() <= kTranslationWindowLimit);
+}
+
+
+// static
+int RegisterTranslator::DistanceToTranslationWindow(Register reg) {
+  return kTranslationWindowStart - reg.index();
+}
+
+
+// static
+bool RegisterTranslator::FitsInReg8Operand(Register reg) {
+  return reg.is_byte_operand() && reg.index() < kTranslationWindowStart;
+}
+
+
+// static
+bool RegisterTranslator::FitsInReg16Operand(Register reg) {
+  int max_index = Register::MaxRegisterIndex() - kTranslationWindowLength + 1;
+  return reg.is_short_operand() && reg.index() < max_index;
+}
+
+
+// static
+int RegisterTranslator::RegisterCountAdjustment(int register_count,
+                                                int parameter_count) {
+  if (register_count > kTranslationWindowStart) {
+    return kTranslationWindowLength;
+  } else if (parameter_count > 0) {
+    Register param0 = Register::FromParameterIndex(0, parameter_count);
+    if (!param0.is_byte_operand()) {
+      // TODO(oth): Move translation window in this scenario.

[rmcilroy, 2016/01/25 12:12:05]

Explain why (i.e., the translation window causes a large frame size).

[oth, 2016/01/25 16:51:56]

Done.

+      return kTranslationWindowLimit + 1 - register_count;
+    }
+  }
+  return 0;
+}
+
+}  // namespace interpreter
+}  // namespace internal
+}  // namespace v8