ARM first & default LDC
Max Haughton
maxhaton at gmail.com
Wed Dec 30 17:49:43 UTC 2020
On Wednesday, 30 December 2020 at 16:22:27 UTC, Ola Fosheim
Grøstad wrote:
> On Wednesday, 30 December 2020 at 16:18:34 UTC, Max Haughton
> wrote:
>> Space optimizing still requires quite a lot of time
>> eliminating work, although LLVM is still pretty bad at it
>> specifically - if you give a recursive factorial
>> implementation to LLVM, it can't see the overflow's going to
>> happen to so it will (at O3) give you about 100 SIMD
>> instructions rather than a simple loop.
>
> :-D I wasn't aware of that.
>
> Yes, but I guess one could start with a non-optimizing SSA
> based backend with the intent of improving it later, but a
> focus on space optimization. At least it could be competitive
> in a niche rather than a lesser version of llvm...
SSA basically gets you a lot of optimisations for "free"
(amortized) if you maintain the property but other than that a
simple backend is hugely faster than LLVM as evidenced by
languages moving away from LLVM for debug builds.
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