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

src/x64/disasm-x64.cc

 // Copyright 2011 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 <assert.h>
 #include <stdarg.h>
 #include <stdio.h>
 
 #include "src/v8.h"
 
@@ skipping 1468 matching lines @@
   // need to do special processing on it.
   if (!processed) {
     switch (*data) {
       case 0xC2:
         AppendToBuffer("ret 0x%x", *reinterpret_cast<uint16_t*>(data + 1));
         data += 3;
         break;
 
       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;
       }
 
       case 0x81:  // fall through
       case 0x83:  // 0x81 with sign extension bit set
         data += PrintImmediateOp(data);
         break;
 
       case 0x0F:
         data += TwoByteOpcodeInstruction(data);
@@ skipping 395 matching lines @@
     for (int i = 6 - static_cast<int>(pc - prev_pc); i >= 0; i--) {
       fprintf(f, "  ");
     }
     fprintf(f, "  %s\n", buffer.start());
   }
 }
 
 }  // namespace disasm
 
 #endif  // V8_TARGET_ARCH_X64