[interpreter] Add support for scalable operands.

src/interpreter/bytecode-array-iterator.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/bytecode-array-iterator.h"
 
 #include "src/objects-inl.h"
 
 namespace v8 {
 namespace internal {
 namespace interpreter {
 
 BytecodeArrayIterator::BytecodeArrayIterator(
     Handle<BytecodeArray> bytecode_array)
-    : bytecode_array_(bytecode_array), bytecode_offset_(0) {}
-
+    : bytecode_array_(bytecode_array),
+      bytecode_offset_(0),
+      operand_scale_(1),
+      prefix_offset_(0) {
+  update_operand_scale();
+}
 
 void BytecodeArrayIterator::Advance() {
-  bytecode_offset_ += Bytecodes::Size(current_bytecode());
+  bytecode_offset_ += current_bytecode_size();
+  update_operand_scale();
 }
 
+void BytecodeArrayIterator::update_operand_scale() {

[rmcilroy, 2016/03/16 11:55:54]

inline into Advance if we removing set_current_offset (see below).

[oth, 2016/03/17 13:48:38]

The constructor uses it too and will break without duplicating the same code.

+  if (!done()) {
+    uint8_t current_byte = bytecode_array()->get(bytecode_offset_);
+    Bytecode current_bytecode = Bytecodes::FromByte(current_byte);
+    operand_scale_ = Bytecodes::GetPrefixBytecodeScale(current_bytecode);
+    prefix_offset_ = current_operand_scale() > 1 ? 1 : 0;
+  }
+}
 
 bool BytecodeArrayIterator::done() const {
   return bytecode_offset_ >= bytecode_array()->length();
 }
 
-
 Bytecode BytecodeArrayIterator::current_bytecode() const {
   DCHECK(!done());
-  uint8_t current_byte = bytecode_array()->get(bytecode_offset_);
-  return interpreter::Bytecodes::FromByte(current_byte);
+  uint8_t current_byte =
+      bytecode_array()->get(bytecode_offset_ + current_prefix_offset());
+  Bytecode current_bytecode = Bytecodes::FromByte(current_byte);
+  DCHECK(!Bytecodes::IsPrefixScalingBytecode(current_bytecode));
+  return current_bytecode;
 }
 
-
 int BytecodeArrayIterator::current_bytecode_size() const {
-  return Bytecodes::Size(current_bytecode());
+  return current_prefix_offset() +
+         Bytecodes::Size(current_bytecode(), current_operand_scale());
 }
 
+void BytecodeArrayIterator::set_current_offset(int offset) {

[rmcilroy, 2016/03/16 11:55:54]

I think this set_current_offset is dangerous. Could we just get rid of it for
now and always do the slow scan for now, and then we can add something back if
we decide it's causing bytecode tracing to be too slow.

[oth, 2016/03/17 13:48:38]

Done. Possibly better to put valid positions into a bitmap if a non-sequential
scan is requested. This only occurs in tracing. It's not a much work, but not
for this CL.

+  bytecode_offset_ = offset;
+  update_operand_scale();
+}
 
-uint32_t BytecodeArrayIterator::GetRawOperand(int operand_index,
-                                              OperandType operand_type) const {
+uint32_t BytecodeArrayIterator::GetUnsignedOperand(
+    int operand_index, OperandType operand_type) const {
   DCHECK_GE(operand_index, 0);
   DCHECK_LT(operand_index, Bytecodes::NumberOfOperands(current_bytecode()));
   DCHECK_EQ(operand_type,
             Bytecodes::GetOperandType(current_bytecode(), operand_index));
+  DCHECK(Bytecodes::IsUnsignedOperandType(operand_type));
   uint8_t* operand_start =
       bytecode_array()->GetFirstBytecodeAddress() + bytecode_offset_ +
-      Bytecodes::GetOperandOffset(current_bytecode(), operand_index);
-  switch (Bytecodes::SizeOfOperand(operand_type)) {
+      current_prefix_offset() +
+      Bytecodes::GetOperandOffset(current_bytecode(), operand_index,
+                                  current_operand_scale());
+  switch (Bytecodes::SizeOfOperand(operand_type, current_operand_scale())) {
     case OperandSize::kByte:
       return static_cast<uint32_t>(*operand_start);
     case OperandSize::kShort:
       return ReadUnalignedUInt16(operand_start);
+    case OperandSize::kQuad:
+      return ReadUnalignedUInt32(operand_start);
     case OperandSize::kNone:
       UNREACHABLE();
   }
   return 0;
 }
 
-
-int8_t BytecodeArrayIterator::GetImmediateOperand(int operand_index) const {
-  uint32_t operand = GetRawOperand(operand_index, OperandType::kImm8);
-  return static_cast<int8_t>(operand);
+int32_t BytecodeArrayIterator::GetSignedOperand(
+    int operand_index, OperandType operand_type) const {
+  DCHECK_GE(operand_index, 0);
+  DCHECK_LT(operand_index, Bytecodes::NumberOfOperands(current_bytecode()));
+  DCHECK_EQ(operand_type,
+            Bytecodes::GetOperandType(current_bytecode(), operand_index));
+  DCHECK(!Bytecodes::IsUnsignedOperandType(operand_type));
+  uint8_t* operand_start =
+      bytecode_array()->GetFirstBytecodeAddress() + bytecode_offset_ +
+      current_prefix_offset() +
+      Bytecodes::GetOperandOffset(current_bytecode(), operand_index,
+                                  current_operand_scale());
+  switch (Bytecodes::SizeOfOperand(operand_type, current_operand_scale())) {
+    case OperandSize::kByte:
+      return static_cast<int8_t>(*operand_start);
+    case OperandSize::kShort:
+      return static_cast<int16_t>(ReadUnalignedUInt16(operand_start));
+    case OperandSize::kQuad:
+      return static_cast<int32_t>(ReadUnalignedUInt32(operand_start));
+    case OperandSize::kNone:
+      UNREACHABLE();
+  }
+  return 0;
 }
 
-int BytecodeArrayIterator::GetRegisterCountOperand(int operand_index) const {
-  OperandSize size =
-      Bytecodes::GetOperandSize(current_bytecode(), operand_index);
-  OperandType type = (size == OperandSize::kByte) ? OperandType::kRegCount8
-                                                  : OperandType::kRegCount16;
-  uint32_t operand = GetRawOperand(operand_index, type);
-  return static_cast<int>(operand);
+uint32_t BytecodeArrayIterator::GetFlagOperand(int operand_index) const {
+  DCHECK(Bytecodes::GetOperandType(current_bytecode(), operand_index) ==
+         OperandType::kFlag8);
+  return GetUnsignedOperand(operand_index, OperandType::kFlag8);
 }
 
+int32_t BytecodeArrayIterator::GetImmediateOperand(int operand_index) const {
+  DCHECK(Bytecodes::GetOperandType(current_bytecode(), operand_index) ==
+         OperandType::kImm);
+  return GetSignedOperand(operand_index, OperandType::kImm);
+}
 
-int BytecodeArrayIterator::GetIndexOperand(int operand_index) const {
+uint32_t BytecodeArrayIterator::GetRegisterCountOperand(
+    int operand_index) const {
+  DCHECK(Bytecodes::GetOperandType(current_bytecode(), operand_index) ==
+         OperandType::kRegCount);
+  return GetUnsignedOperand(operand_index, OperandType::kRegCount);
+}
+
+uint32_t BytecodeArrayIterator::GetIndexOperand(int operand_index) const {
   OperandType operand_type =
       Bytecodes::GetOperandType(current_bytecode(), operand_index);
-  DCHECK(operand_type == OperandType::kIdx8 ||
-         operand_type == OperandType::kIdx16);
-  uint32_t operand = GetRawOperand(operand_index, operand_type);
-  return static_cast<int>(operand);
+  DCHECK(operand_type == OperandType::kIdx);
+  return GetUnsignedOperand(operand_index, operand_type);
 }
 
-
 Register BytecodeArrayIterator::GetRegisterOperand(int operand_index) const {
   OperandType operand_type =
       Bytecodes::GetOperandType(current_bytecode(), operand_index);
   DCHECK(Bytecodes::IsRegisterOperandType(operand_type));
-  uint32_t operand = GetRawOperand(operand_index, operand_type);
-  Register reg;
-  switch (Bytecodes::GetOperandSize(current_bytecode(), operand_index)) {
-    case OperandSize::kByte:
-      reg = Register::FromOperand(static_cast<uint8_t>(operand));
-      break;
-    case OperandSize::kShort:
-      reg = Register::FromWideOperand(static_cast<uint16_t>(operand));
-      break;
-    case OperandSize::kNone:
-      UNREACHABLE();
-      reg = Register::invalid_value();
-      break;
-  }
+  int32_t operand = GetSignedOperand(operand_index, operand_type);
+  Register reg = Register::FromOperand(operand);
   DCHECK_GE(reg.index(),
             Register::FromParameterIndex(0, bytecode_array()->parameter_count())
                 .index());
   DCHECK(reg.index() < bytecode_array()->register_count() ||
          (reg.index() == 0 &&
           Bytecodes::IsMaybeRegisterOperandType(
               Bytecodes::GetOperandType(current_bytecode(), operand_index))));
   return reg;
 }
 
 int BytecodeArrayIterator::GetRegisterOperandRange(int operand_index) const {
   interpreter::OperandType operand_type =
       Bytecodes::GetOperandType(current_bytecode(), operand_index);
   DCHECK(Bytecodes::IsRegisterOperandType(operand_type));
   switch (operand_type) {
-    case OperandType::kRegPair8:
-    case OperandType::kRegPair16:
-    case OperandType::kRegOutPair8:
-    case OperandType::kRegOutPair16:
+    case OperandType::kRegPair:
+    case OperandType::kRegOutPair:
       return 2;
-    case OperandType::kRegOutTriple8:
-    case OperandType::kRegOutTriple16:
+    case OperandType::kRegOutTriple:
       return 3;
     default: {
       if (operand_index + 1 !=
           Bytecodes::NumberOfOperands(current_bytecode())) {
         OperandType next_operand_type =
             Bytecodes::GetOperandType(current_bytecode(), operand_index + 1);
-        if (Bytecodes::IsRegisterCountOperandType(next_operand_type)) {
+        if (OperandType::kRegCount == next_operand_type) {
           return GetRegisterCountOperand(operand_index + 1);
         }
       }
       return 1;
     }
   }
 }
 
+uint32_t BytecodeArrayIterator::GetRuntimeIdOperand(int operand_index) const {
+  OperandType operand_type =
+      Bytecodes::GetOperandType(current_bytecode(), operand_index);
+  DCHECK(operand_type == OperandType::kRuntimeId);
+  return GetUnsignedOperand(operand_index, operand_type);
+}
+
 Handle<Object> BytecodeArrayIterator::GetConstantForIndexOperand(
     int operand_index) const {
   return FixedArray::get(bytecode_array()->constant_pool(),
                          GetIndexOperand(operand_index),
                          bytecode_array()->GetIsolate());
 }
 
 
 int BytecodeArrayIterator::GetJumpTargetOffset() const {
   Bytecode bytecode = current_bytecode();
   if (interpreter::Bytecodes::IsJumpImmediate(bytecode)) {
     int relative_offset = GetImmediateOperand(0);
-    return current_offset() + relative_offset;
-  } else if (interpreter::Bytecodes::IsJumpConstant(bytecode) ||
-             interpreter::Bytecodes::IsJumpConstantWide(bytecode)) {
+    return current_offset() + relative_offset + current_prefix_offset();
+  } else if (interpreter::Bytecodes::IsJumpConstant(bytecode)) {
     Smi* smi = Smi::cast(*GetConstantForIndexOperand(0));
-    return current_offset() + smi->value();
+    return current_offset() + smi->value() + current_prefix_offset();
   } else {
     UNREACHABLE();
     return kMinInt;
   }
 }
 
 }  // namespace interpreter
 }  // namespace internal
 }  // namespace v8