[disassembler] Add more padding for printing instruction bytes

We can emit a 9-byte nop, so leave more padding, otherwise the
disassembled code looks a bit off, e.g.:

0x265ef7799a73   5b3  e902010000     jmp 0x265ef7799b7a  <+0x6ba>
0x265ef7799a78   5b8  0f1f840000000000 nop
0x265ef7799a80   5c0  83c004         addl rax,0x4

Bug: v8:11879
Change-Id: I697e97b45644e28e544705b972c88702f7f27ffc
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3054255Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Zhi An Ng <zhin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#75944}

src/diagnostics/disassembler.cc

@@ -326,7 +326,8 @@ static int DecodeIt(Isolate* isolate, ExternalReferenceEncoder* ref_encoder,
         byte* ptr =
             base::ReadUnalignedValue<byte*>(reinterpret_cast<Address>(pc));
         if (RelocInfo::IsInternalReference(it->rinfo()->rmode())) {
-          SNPrintF(decode_buffer, "%08" V8PRIxPTR "      jump table entry %4zu",
+          SNPrintF(decode_buffer,
+                   "%08" V8PRIxPTR "       jump table entry %4zu",
                    reinterpret_cast<intptr_t>(ptr),
                    static_cast<size_t>(ptr - begin));
         } else {

src/diagnostics/x64/disasm-x64.cc

@@ -2799,8 +2799,9 @@ int DisassemblerX64::InstructionDecode(v8::base::Vector<char> out_buffer,
   for (byte* bp = instr; bp < data; bp++) {
     outp += v8::base::SNPrintF(out_buffer + outp, "%02x", *bp);
   }
-  // Indent instruction, leaving space for 7 bytes, i.e. 14 characters in hex.
-  while (outp < 14) {
+  // Indent instruction, leaving space for 9 bytes, i.e. 18 characters in hex.
+  // 9-byte nop and rip-relative mov are (probably) the largest we emit.
+  while (outp < 18) {
     outp += v8::base::SNPrintF(out_buffer + outp, "  ");
   }