Support dec_b instruction in ia32 and x64 disassembler.

Review URL: http://codereview.chromium.org/3412028

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@5515 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/ia32/disasm-ia32.cc

@@ -1194,12 +1194,12 @@ int DisassemblerIA32::InstructionDecode(v8::internal::Vector<char> out_buffer,
         { data++;
           int mod, regop, rm;
           get_modrm(*data, &mod, &regop, &rm);
-          if (mod == 3 && regop == ecx) {
-            AppendToBuffer("dec_b %s", NameOfCPURegister(rm));
+          if (regop == ecx) {
+            AppendToBuffer("dec_b ");
+            data += PrintRightOperand(data);
           } else {
             UnimplementedInstruction();
           }
-          data++;
         }
         break;
 

src/x64/disasm-x64.cc

@@ -1450,12 +1450,12 @@ int DisassemblerX64::InstructionDecode(v8::internal::Vector<char> out_buffer,
         data++;
         int mod, regop, rm;
         get_modrm(*data, &mod, &regop, &rm);
-        if (mod == 3 && regop == 1) {
-          AppendToBuffer("decb %s", NameOfCPURegister(rm));
+        if (regop == 1) {
+          AppendToBuffer("decb ");
+          data += PrintRightOperand(data);
         } else {
           UnimplementedInstruction();
         }
-        data++;
       }
         break;
 

test/cctest/test-disasm-ia32.cc

@@ -165,6 +165,8 @@ TEST(DisasmIa320) {
   __ mov(Operand(ebx, ecx, times_4, 10000), edx);
   __ nop();
   __ dec_b(edx);
+  __ dec_b(Operand(eax, 10));
+  __ dec_b(Operand(ebx, ecx, times_4, 10000));
   __ dec(edx);
   __ cdq();