[interpreter] Add support for scalable operands.

src/objects.cc

Index: src/objects.cc
diff --git a/src/objects.cc b/src/objects.cc
index d81b1f6b8c8bcfc1803ad3708c1df0d957c28916..907dc1e126bcdde97f63acbbf199e9a5d0dab208 100644
--- a/src/objects.cc
+++ b/src/objects.cc
@@ -15063,7 +15063,16 @@ void BytecodeArray::Disassemble(std::ostream& os) {
     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();
@@ -15077,25 +15086,36 @@ void BytecodeArray::Disassemble(std::ostream& os) {
     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();
-      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]);
+    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);
+      DCHECK_GE(i + offset, 0);
+      DCHECK_LT(i + offset, length());
       os << buf.start();
     }
-
     os << std::endl;
   }