stassats

5 ms·

1.
by stassats 7mo ago
I did that to write simd routines for sbcl: https://github.com/sbcl/sbcl/blob/master/src/code/arm64-simd... Probably the best way of writing assembly, can evaluate the function immediately, use
2.
by stassats 7mo ago
Still 40 years to go.
3.
by stassats 7mo ago
I have also seen some outright crashes on the new GC.
4.
by stassats 10mo ago
The tricks to avoid multiplication (and division) are probably worth a whole post. x * 6: lea eax, [rdi+rdi*2] add eax, eax x * 7: lea eax, [0+rdi*8] sub eax, edi x * 11: lea eax, [rdi+rdi*4] lea eax, [rdi+rax*2]
5.
by stassats 10mo ago
The text mentions that it can also do multiplication but doesn't expand on that. E.g. for x * 5 gcc issues lea eax, [rdi+rdi*4].
6.
by stassats 11mo ago
ABCL is really slow.
7.
by stassats 1y ago
A good strategy if you don't care about fixing bugs.
8.
by stassats 1y ago
That shouldn't mean that it doesn't return a NaN. Things are generally not optimized away because of NaNs. E.g. in GCC, abs(c) > -1.0 is not folded, unless building with -ffast-math
9.
by stassats 1y ago
That fix has limited applicability. x * x is also a non-negative float. But abs(x * x) is not optimized. Or abs(abs(x)+1). GCC, for example, does know that.
10.
by stassats 1y ago
(+ 2 (id "2")) may also produce a compile time warning. Nothing precludes from having a special rule for that. Like (+ 2 (print "2")) does warn.
11.
by stassats 1y ago
> changes in the Qt project made the technique used by the Qt4 bindings impractical for Qt5 or Qt6 - at least that was my understanding when I looked into it. It was hard to do reasonably with qt4 already. The best solution would be to s
12.
by stassats 1y ago
> Why does SBCL not use LLVM? Why doesn't GCC use LLVM? Why is Zig writing their own backend?
13.
by stassats 1y ago
> lack of tail-call elimination But lisp doesn't need TCO.
14.
by stassats 1y ago
You can turn them back into rationals, (rational (sqrt 2d0)) => 6369051672525773/4503599627370496 Or write your own operations that compute to the precision you want.
15.
by stassats 1y ago
>(safety 0) Please, don't do that!
16.
by stassats 2y ago
>any system that relies on information that was typed into a REPL three-months ago and is now only stored in the binary state of that REPL and nowhere else is totally insane as a production product. Nobody does that.
17.
by stassats 2y ago
> roadrunner is petaflops of FP32 Isn't it actually FP64?
18.
by stassats 2y ago
Using EAX is one byte shorter, so it might be doing that inadvertently.
19.
by stassats 2y ago
Common Lisp. The dynamic-extent declaration allows for stack allocation.
20.
by stassats 2y ago
> because 64-bit ARMv8.0 lacks a POPCNT instruction It does have this: https://developer.arm.com/documentation/ddi0596/2021-09/SIMD... And GCC happily uses it https://godbolt.org/z/dTW
21.
by stassats 2y ago
There's M-:
22.
by stassats 3y ago
CNT on arm64 counts 8 or 16-bit elements too.
23.
by stassats 3y ago
SYS:WITHOUT-GCING is better but is still fraught with danger (that's why I didn't mention it).
24.
by stassats 3y ago
That's not related to garbage collection.
25.
by stassats 3y ago
That's a recipe for disaster. Never do that.
26.
by stassats 4y ago
What drives people to attempt to persuade others that Lisp is not practical?
27.
by stassats 4y ago
> it's different enough than other languages it confuses people. And javascript integers (or lack thereof) don't match CL integers. So if you want to interoperate between distinct languages you do have to consider the differenc
28.
by stassats 4y ago
It's not. Reader macros don't take s-expressions, they take characters.
29.
by stassats 4y ago
Sure, what's so special about it? (get-macro-character #\() => SB-IMPL::READ-LIST (get-macro-character #\)) => SB-IMPL::READ-RIGHT-PAREN (that one just signals an error, the read-list one picks up the closing #\))
30.
by stassats 5y ago
Ok, I added the dates.

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