I guess people are just going to keep discovering that you can't really make a C compiler do constant time

@rygorous sure, and the right answer is to figure out real solutions (as seems to be happening in LLVM, for constant time), not complaining about the optimizer

@rygorous don't worry the LLMs will do this asm rewriting for us

@rygorous @regehr Regarding diffing, the thread I had with John the other day got me thinking about using FileCheck for that kind of thing and I want to try it out, but I suspect the problem is that it's either too loose or too strict in terms of the matching depending on how many matches you specify, across compilers. Either way, too much work on maintain.

@regehr What about fractions?

@dabeaz

@rygorous @regehr And ABI-related bugs can be much more insidious than I once thought, since they're not guaranteed to actually crash as one might expect. They can just lurk there as vulnerabilities, potentially causing crashes in totally unrelated code:

https://randomascii.wordpress.com/2022/11/21/please-restore-our-registers-when-youre-done-with-them/

@regehr even the best programmers in the world struggle with this kind of stuff, ffs...

@rygorous @regehr Petition to rename to -fun-math.

@rygorous @regehr -fhonor-yahweh -fhonor-buddha -fhonor-brahma just to be safe. You need all the help you can get with -ffast-math.

@rygorous

well, if the problems are important enough, something like this:

https://discourse.llvm.org/t/rfc-constant-time-coding-support/87781

@regehr all I will say to that is eyup

@rygorous @pervognsen aw, look at all the little nans and infs flying and being free!!!

@kaoudis I've not been paying too much attention to the LLVM effort-- anything interesting going on there? or should I just dig into the discourse?

@regehr @rygorous My first thought was, if this is meant for the far future, assuming they retain our current warning symbol for radiation seems a bit hopeful.

@regehr I think* @wizardengineer landed the first bits of that work!

*I left trail of bits voluntarily (and for reasons unrelated) a bit before this happened though

@rygorous @regehr
Rename to -ffast-bad-math perhaps?

@kaoudis @wizardengineer ah! I don't think I knew that. where are you at right now?

@rygorous @regehr
-flooks-like-math-if-you-squint

@regehr Maybe it's time to write new assemblers that complement NASM*.

* Or MASM; I wish NASM had an invoke keyword, like MASM, to abstract away calling conventions. Rather than writing a macro for it.

@rygorous @regehr We've had a hell of a time with our macos ARM64 ASM. Last ~3 ld64 updates have all had reloc problems