[interpreter] Add support for scalable operands.

src/objects.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/objects.h"
 
 #include <cmath>
 #include <iomanip>
 #include <sstream>
 
@@ skipping 15045 matching lines @@
   const uint8_t* first_bytecode_address = GetFirstBytecodeAddress();
   int bytecode_size = 0;
 
   interpreter::SourcePositionTableIterator source_positions(
       source_position_table());
 
   for (int i = 0; i < this->length(); i += bytecode_size) {
     const uint8_t* bytecode_start = &first_bytecode_address[i];
     interpreter::Bytecode bytecode =
         interpreter::Bytecodes::FromByte(bytecode_start[0]);
-    bytecode_size = interpreter::Bytecodes::Size(bytecode);
+    int prefix_offset = 0;

[rmcilroy, 2016/03/10 16:45:38]

It might be time to rework this so that it uses the BytecodeIterator somehow - I
think it could be much simpler just using that, WDYT? This could maybe be a
seperate (preceeding) CL to do this and hopefully after that's happened nothing
much would need to change in this CL.

[oth, 2016/03/11 16:26:13]

Ack.

+    int operand_scale =
+        interpreter::Bytecodes::GetPrefixBytecodeScale(bytecode);
+    if (operand_scale > 1) {
+      // Bytecode is a prefix for wider operands in the next bytecode.
+      prefix_offset += 1;
+      bytecode = interpreter::Bytecodes::FromByte(bytecode_start[1]);
+    }
+    bytecode_size =
+        prefix_offset + interpreter::Bytecodes::Size(bytecode, operand_scale);
 
     if (!source_positions.done() && i == source_positions.bytecode_offset()) {
       os << std::setw(5) << source_positions.source_position();
       os << (source_positions.is_statement() ? " S> " : " E> ");
       source_positions.Advance();
     } else {
       os << "         ";
     }
 
     SNPrintF(buf, "%p", bytecode_start);
     os << buf.start() << " : ";
     interpreter::Bytecodes::Decode(os, bytecode_start, parameter_count());
 
-    if (interpreter::Bytecodes::IsJumpConstantWide(bytecode)) {
-      DCHECK_EQ(bytecode_size, 3);
-      int index = static_cast<int>(ReadUnalignedUInt16(bytecode_start + 1));
-      int offset = Smi::cast(constant_pool()->get(index))->value();
+    if (interpreter::Bytecodes::IsJump(bytecode)) {
+      static const int operand_offset = 1;
+      int operand;
+      switch (operand_scale) {
+        case 1:
+          operand = static_cast<int8_t>(bytecode_start[operand_offset]);
+          break;
+        case 2:
+          operand = static_cast<int16_t>(ReadUnalignedUInt16(
+              bytecode_start + prefix_offset + operand_offset));
+          break;
+        case 4:
+          operand = static_cast<int>(ReadUnalignedUInt32(
+              bytecode_start + prefix_offset + operand_offset));
+          break;
+        default:
+          UNREACHABLE();
+      }
+      int offset;
+      if (interpreter::Bytecodes::IsJumpConstant(bytecode)) {
+        offset = Smi::cast(constant_pool()->get(operand))->value();
+      } else {
+        offset = operand;
+      }
+      offset += prefix_offset;
       SNPrintF(buf, " (%p)", bytecode_start + offset);
-      os << buf.start();
-    } else if (interpreter::Bytecodes::IsJumpConstant(bytecode)) {
-      DCHECK_EQ(bytecode_size, 2);
-      int index = static_cast<int>(bytecode_start[1]);
-      int offset = Smi::cast(constant_pool()->get(index))->value();
-      SNPrintF(buf, " (%p)", bytecode_start + offset);
-      os << buf.start();
-    } else if (interpreter::Bytecodes::IsJump(bytecode)) {
-      DCHECK_EQ(bytecode_size, 2);
-      int offset = static_cast<int8_t>(bytecode_start[1]);
-      SNPrintF(buf, " (%p)", bytecode_start + offset);
+      DCHECK_GE(i + offset, 0);
+      DCHECK_LT(i + offset, length());
       os << buf.start();
     }
-
     os << std::endl;
   }
 
   if (constant_pool()->length() > 0) {
     os << "Constant pool (size = " << constant_pool()->length() << ")\n";
     constant_pool()->Print();
   }
 
 #ifdef ENABLE_DISASSEMBLER
   if (handler_table()->length() > 0) {
@@ skipping 4727 matching lines @@
   if (cell->value() != *new_value) {
     cell->set_value(*new_value);
     Isolate* isolate = cell->GetIsolate();
     cell->dependent_code()->DeoptimizeDependentCodeGroup(
         isolate, DependentCode::kPropertyCellChangedGroup);
   }
 }
 
 }  // namespace internal
 }  // namespace v8