fix imul(reg, op, imm) emission on x64

src/x64/disasm-x64.cc

Index: src/x64/disasm-x64.cc
diff --git a/src/x64/disasm-x64.cc b/src/x64/disasm-x64.cc
index 9b558839780186abdd55081c41fcd731bb466eb8..dcbba9fc81af7c96060c77bc4c294adbfe1ed960 100644
--- a/src/x64/disasm-x64.cc
+++ b/src/x64/disasm-x64.cc
@@ -1486,15 +1486,15 @@ int DisassemblerX64::InstructionDecode(v8::internal::Vector<char> out_buffer,
 
       case 0x69:  // fall through
       case 0x6B: {
-        int mod, regop, rm;
-        get_modrm(*(data + 1), &mod, &regop, &rm);
-        int32_t imm = *data == 0x6B ? *(data + 2)
-            : *reinterpret_cast<int32_t*>(data + 2);
-        AppendToBuffer("imul%c %s,%s,0x%x",
-                       operand_size_code(),
-                       NameOfCPURegister(regop),
-                       NameOfCPURegister(rm), imm);
-        data += 2 + (*data == 0x6B ? 1 : 4);
+        int count = 1;
+        count += PrintOperands("imul", REG_OPER_OP_ORDER, data + count);
+        AppendToBuffer(",0x");
+        if (*data == 0x69) {
+          count += PrintImmediate(data + count, operand_size());
+        } else {
+          count += PrintImmediate(data + count, OPERAND_BYTE_SIZE);
+        }
+        data += count;
         break;
       }