test.asm

--- Optimized code ---
kind = OPTIMIZED_FUNCTION
name = foo
stack_slots = 1
Instructions (size = 90)
0x48634f60     0  55             push ebp
0x48634f61     1  89e5           mov ebp,esp
0x48634f63     3  56             push esi
0x48634f64     4  57             push edi
0x48634f65     5  6a00           push 0x0
                  ;;; <@0,#0> -------------------- B0 --------------------
                  ;;; <@2,#1> context
0x48634f67     7  8b75fc         mov esi,[ebp+0xfc]
                  ;;; <@10,#8> -------------------- B1 --------------------
                  ;;; <@12,#10> stack-check
0x48634f6a    10  3b25c4062d01   cmp esp,[0x12d06c4]
0x48634f70    16  7305           jnc 23  (0x48634f77)
0x48634f72    18  e869abfdff     call 0x4860fae0             ;; code: STUB, StackCheckStub, minor: 0
                  ;;; <@13,#10> gap
0x48634f77    23  8b4508         mov eax,[ebp+0x8]
                  ;;; <@14,#12> check-non-smi
0x48634f7a    26  a801           test al,0x1
0x48634f7c    28  0f8415000000   jz 55  (0x48634f97)
                  ;;; --------------
                  ;;; Here we are checking receiver's hidden class. Notice that hidden class of the prototype is not 
                  ;;; checked because the check is elided. This code will instead be deoptimized if somebody changes
                  ;;; hidden class of the A.prototype.
                  ;;; --------------
                  ;;; <@16,#13> check-maps
0x48634f82    34  8178ff8904a152 cmp [eax+0xff],0x52a10489    ;; object: 0x52a10489 <Map(elements=3)>
0x48634f89    41  0f850d000000   jnz 60  (0x48634f9c)
                  ;;; <@20,#21> -------------------- B2 --------------------
                  ;;; <@22,#25> constant-t
0x48634f8f    47  33c0           xor eax,eax
                  ;;; <@24,#23> return
0x48634f91    49  89ec           mov esp,ebp
0x48634f93    51  5d             pop ebp
0x48634f94    52  c20800         ret 0x8
                  ;;; -------------------- Jump table --------------------
                  ;;; jump table entry 0: deoptimization bailout 1.
0x48634f97    55  e86e507dfb     call 0x43e0a00a             ;; deoptimization bailout 1
                  ;;; jump table entry 1: deoptimization bailout 2.
0x48634f9c    60  e873507dfb     call 0x43e0a014             ;; deoptimization bailout 2
0x48634fa1    65  90             nop
0x48634fa2    66  90             nop
0x48634fa3    67  90             nop
0x48634fa4    68  90             nop
0x48634fa5    69  90             nop
0x48634fa6    70  66             nop
0x48634fa7    71  90             nop

test.js

function A() { }
A.prototype.foo = function () { return 0; };

function foo(a) { return a.foo(); }

foo(new A);
foo(new A);
foo(new A);
%OptimizeFunctionOnNextCall(foo);
foo(new A);