test.asm

                  ;;; <@80,#66> -------------------- B5 (loop header) --------------------
                  ;;; <@83,#68> compare-numeric-and-branch
0x598365b8   408  3bc3           cmp eax,ebx
0x598365ba   410  0f8d6f000000   jnl 527  (0x5983662f)
                  ;;; <@88,#75> -------------------- B7 --------------------
                  ;;; <@90,#77> stack-check
0x598365c0   416  3b251c691e09   cmp esp,[0x91e691c]
0x598365c6   422  0f8282000000   jc 558  (0x5983664e)
                  ;;; <@92,#79> check-non-smi
0x598365cc   428  f6c101         test_b cl,0x1
0x598365cf   431  0f84a8000000   jz 605  (0x5983667d)
                  ;;; <@94,#80> check-maps
0x598365d5   437  8179ffc905e13b cmp [ecx+0xff],0x3be105c9    ;; object: 0x3be105c9 <Map(elements=3)>
0x598365dc   444  0f85a0000000   jnz 610  (0x59836682)
                  ;;; <@96,#81> check-prototype-maps
                  ;;; <@98,#82> constant-t
0x598365e2   450  bf8180f040     mov edi,0x40f08081          ;; object: 0x40f08081 <FixedArray[86]>
                  ;;; <@102,#91> -------------------- B8 --------------------
                  ;;; <@104,#93> constant-t
0x598365e7   455  bfb5da602a     mov edi,0x2a60dab5          ;; object: 0x2a60dab5 <String[1]: b>
                  ;;; <@106,#101> check-maps
0x598365ec   460  8179ffd904e13b cmp [ecx+0xff],0x3be104d9    ;; object: 0x3be104d9 <Map(elements=3)>
0x598365f3   467  0f840d000000   jz 486  (0x59836606)
0x598365f9   473  8179ffc905e13b cmp [ecx+0xff],0x3be105c9    ;; object: 0x3be105c9 <Map(elements=3)>
0x59836600   480  0f8581000000   jnz 615  (0x59836687)
                  ;;; <@108,#102> store-named-field
0x59836606   486  89790b         mov [ecx+0xb],edi
0x59836609   489  8d510b         lea edx,[ecx+0xb]
0x5983660c   492  81e70000f0ff   and edi,0xfff00000
0x59836612   498  f6470c04       test_b [edi+0xc],0x4
0x59836616   502  7412           jz 522  (0x5983662a)
0x59836618   504  bf0000f0ff     mov edi,0xfff00000
0x5983661d   509  23f9           and edi,ecx
0x5983661f   511  f6470c08       test_b [edi+0xc],0x8
0x59836623   515  7405           jz 522  (0x5983662a)
0x59836625   517  e8d6f6ffff     call 0x59835d00             ;; code: STUB, RecordWriteStub, minor: 1209

test.js

function test(N) {
  function A(x) {
    this.x = x;
  }

  A.prototype.get = function () { return this.x; };
  A.prototype.set = function (x) { this.x = x; };

  var o = new A('a');

  for (var i = 0; i < N; i++) {
    o.get();
    o.set('b');
  }
}

test(1);
test(100000);