remove unneeded allocations

[extrawurst]

all Matrix.invert():
currently the mixin AFAIK creates a dynamic array even though the matrix already contains one, just assignments would be enough.
for example: https://github.com/Dav1dde/gl3n/blob/master/gl3n/linalg.d#L1036

Matrix.perspective() with FOV:
https://github.com/Dav1dde/gl3n/blob/master/gl3n/linalg.d#L1179

[Dav1dde]

I agree, but if you look at https://github.com/Dav1dde/gl3n/blob/master/gl3n/linalg.d#L1127-L1158 - It's simply not feasable to do. You would need to store half of the content in local variables and access the other half on the fly (matrix[x][y]). That just generates a huge blob of unreadable code. My hope is/was that the generator somehow can optimize that to a static array (so you don't have the runtime allocation + memcpy).

[extrawurst]

i am not sure about this, i always thought a multidimensional array literal is constructed using gc allocations. i could be wrong.

[Dav1dde]

Tbh, I have no idea, I was simply assuming the optimizer has gotten good enough ... Then again, it's D/dmd. But we wont know for sure until someone runs it through a debugger/looks at the asm.

If you wanna go for it and create the ugly code required for replacing it, I will merge it. But please add unittests beforehand (the code required will be really ugly, I assume, easy to make mistakes).

[extrawurst]

a simple test with array literals on http://d.godbolt.org/ reveil that these create a call to _d_arrayLiteralTX that actually uses a gc_allocation:
https://github.com/D-Programming-Language/druntime/blob/e47a00bff935c3f079bb567a6ec97663ba384487/src/rt/lifetime.d#L2135

so at least we now know that literals create heap traffic :(

[Dav1dde]

Yeah that sucks ... if even gcc doesn't optimize it.
(To answer your question from IRC this morning, yes I am dav1d on freenode)