Operator overloading leads to bad code optimization

[ClapTrap]

On Sunday, 5 December 2021 at 23:36:21 UTC, kinke wrote:
> On Sunday, 5 December 2021 at 21:38:55 UTC, max haughton wrote:
>> On Friday, 3 December 2021 at 21:24:07 UTC, claptrap wrote:
>>> Just a simple function to split a bezier in two.
>>>
>>> Using "-O3"
>>>
>>> LDC the operator version is 84 instructions
>>> LDC the hand expanded math is 49 instructions.
>>>
>>> It seems something as simple as this should be better 
>>> optimised? Or am I missing something?
>>>
>>> https://godbolt.org/z/4h9vob3Yo
>>> [...]
>>
>> [...]
>> Seems like GCC does not have this issue.
>
> With gdc v11.1, I count 69 instructions for split and 51 for 
> split2 (59 with -O3). So I guess there's a semantic difference 
> here with the slightly changed evaluation order (2D addition 
> before scaling).

gdc v11.1 doesn't inline the operator calls when I try it, if you 
try an earlier version 10.2 it does which reduces it to 48 
instructions

> With `alias Point = __vector(float[2])`, split is reduced to 28 
> instructions: https://godbolt.org/z/7ffebjaz8

Wow, that's awesome!