To me this only happens with a very rare probability. Running this script:

while (true) {
  if((Number.MAX_VALUE % 1.8111139825551001) != 0.6471300971016367) { 
    console.log("x");
  }
}

doesn't do anything for the first few seconds, before logging "x" about 10000 times in a row.

Wow, this is even weirder than my bug. At least for me the result is always the same as long as the operands stay the same, even when it is wrong.

Which build are you running?

 Issue 681524  has been merged into this issue.

sounds like optimizing compiler doing something wrong.

I'm checking if this is PGO specific or if it repro in a non-PGO Chrome build.

I doubt that this has anything to do with Chrome build. From the issue description this seems pretty clear to be a case of the optimizing compiler kicking in after a short while, and we then execute wrong code. I even suspect that the condition with the remainder operator is being constant folded.

Cannot reproduce with 56.0.2924.87, neither compiler seems to produce the wrong result for me. Maybe it's part of a bigger program that triggers the wrong behavior? Can you provide exact reproduction steps?

Ah, BTW. this is on Mac. Maybe there's a bug in fmod on Windows?

I can repro on 58.0.3012.0, both on the PGO and the non-PGO build, so it's not a PGO specific bug but it might still be a compiler bug.

I guess you're running Windows then?

Yes, I've no idea how the Dev console works so it's hard for me to debug this, do you know which part of the code is responsible for handling this type of query? I'd like to look at the generated code for it.

Since it happens on the console already w/o even being wrapped into a function that needs optimization, it's very, very likely that the bug is in the fmod library function on Windows (which is BTW known to be very buggy already). I guess it's about time that we import fdlibm's fmod instead, so that we can provide a uniform, correct implementation everywhere.

Yang, WDTY?

This issue has been Available for over a year. If it's no longer important or seems unlikely to be fixed, please consider closing it out. If it is important, please re-triage the issue.

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Someday during the last year my chrome installation got updated automatically to a version which has been compiled with clang instead of VS2015, so this issue is fixed for me. But I don't know if there are still VS2015-compiled Chrome binaries being distributed, so I can't tell if this issue has been fixed for everyone.

Good to know!

I don't think new Chrome versions are still built with Visual Studio.

Nice. This can be closed then.

\o/