You cannot add a loop skew optimization to compiler before compiler needs a loop skew optimization. Which it would not need at all because it is loop skew optimization (it requires matrix operations) that need a loop skew optimization.
In short, compiler is not an ideal representation of the user programs it needs to optimize.
Perhaps Wirth would say that compilers are _close enough_ to user programs to be a decent enough representation in most cases. And of course he was sensible enough to also recognize that there are special cases, like matrix operations, where it might be wirthwhile.
EDIT: typo in the last word but I'm leaving it in for obvious reasons.
Wirth ran an OS research lab. For that, the compiler likely is a fairly typical workload.
But yes, it wouldn’t work well in a general context. For example, auto-vectorization likely doesn’t speed up a compiler much at all, while adding the code to detect where it’s possible will slow it down.
So, that feature never can be added.
On the other hand, may lead to better designs. If, instead, you add language features that make it easier for programmers to write vectorized code, that might end up being easier for programmers. They would have to write more code, but they also would have to guess less whether their code would end up being vectorized.
perhaps you could write the compiler using the data structures used by co-dfns (which i still don't understand) so that vectorization would speed it up, auto- or otherwise
In short, compiler is not an ideal representation of the user programs it needs to optimize.