Reason of deoptimization

[Ignacio Queralt]

Hi everybody,

I'm running a program on the d8, and I get the following reason of deoptimization of a function:

[deoptimizing (DEOPT soft): begin 0x8e9fc0357b9 <JS Function bnpDivRemTo (SharedFunctionInfo 0x8e9fc030571)> (opt #4) @62, FP to SP delta: 208]

            ;;; deoptimize at 9761: Insufficient type feedback for generic named access

  reading input frame bnpDivRemTo => node=4, args=778, height=20; inputs:

I understand the explanation is "Insufficient type feedback for generic named access", but what does this mean? I'm not sure I understand why the deoptimization takes place in the program. I know is hard to tell by just looking at this log, but does anybody know what could it be?

Thanks for your help,

Ignacio.

[Ben Noordhuis]

I believe that happens when you reach a named property lookup that
hasn't been exercised in the unoptimized code, e.g.:

if (Math.random() > 1e-6) {
v = o.x; // common path
} else {
v = o.y; // uncommon path
}