Operator overloading leads to bad code optimization

[kinke]

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).

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