Sign extend correctly in disassembler

runtime/vm/disassembler_ia32.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/disassembler.h"
 
 #include "vm/globals.h"  // Needed here to get TARGET_ARCH_IA32.
 #if defined(TARGET_ARCH_IA32)
 #include "platform/utils.h"
 #include "vm/allocation.h"
@@ skipping 307 matching lines @@
     edx = 2,
     ebx = 3,
     esp = 4,
     ebp = 5,
     esi = 6,
     edi = 7
   };
 
   // Bottleneck functions to print into the out_buffer.
   void PrintInt(int value);
-  void PrintHex(int value);
+  void PrintHex(int value, bool signed_value = false);
   void Print(const char* str);
   const char* GetBranchPrefix(uint8_t** data);
 
   bool DecodeInstructionType(const InstructionDesc& idesc,
                              const char* branch_hint,
                              uint8_t** data);
 
   // Printing of common values.
   void PrintCPURegister(int reg);
   void PrintCPUByteRegister(int reg);
@@ skipping 55 matching lines @@
 
 
 void X86Decoder::PrintInt(int value) {
   char int_buffer[16];
   OS::SNPrint(int_buffer, sizeof(int_buffer), "%#x", value);
   Print(int_buffer);
 }
 
 
 // Append the int value (printed in hex) to the output buffer.
-void X86Decoder::PrintHex(int value) {
+void X86Decoder::PrintHex(int value, bool signed_value) {
   char hex_buffer[16];
-  OS::SNPrint(hex_buffer, sizeof(hex_buffer), "%#x", value);
+  if (signed_value && value < 0) {
+    OS::SNPrint(hex_buffer, sizeof(hex_buffer), "-%#x", -value);
+  } else {
+    OS::SNPrint(hex_buffer, sizeof(hex_buffer), "%#x", value);
+  }
   Print(hex_buffer);
 }
 
 
 // Append the str to the output buffer.
 void X86Decoder::Print(const char* str) {
   char cur = *str++;
   while (cur != '\0' && (buffer_pos_ < (buffer_size_ - 1))) {
     buffer_[buffer_pos_++] = cur;
     cur = *str++;
@@ skipping 261 matching lines @@
       UNIMPLEMENTED();
   }
   Print(mnem);
   Print(" ");
   int count = PrintRightOperand(data + 1);
   Print(",");
   if (size_override) {
     PrintHex(*reinterpret_cast<int16_t*>(data + 1 + count));
     return 1 + count + 2 /*int16_t*/;
   } else if (sign_extension_bit) {
-    PrintHex(*(data + 1 + count));
+    PrintHex(*reinterpret_cast<int8_t*>(data + 1 + count), sign_extension_bit);
     return 1 + count + 1 /*int8_t*/;
   } else {
     PrintHex(*reinterpret_cast<int32_t*>(data + 1 + count));
     return 1 + count + 4 /*int32_t*/;
   }
 }
 
 
 int X86Decoder::DecodeEnter(uint8_t* data) {
   uint16_t size = *reinterpret_cast<uint16_t*>(data + 1);
@@ skipping 1246 matching lines @@
       }
     }
   }
 }
 
 #endif  // !PRODUCT
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_IA32