[SYCL] Materialize shadow local variables for byval arguments before use

[againull]

Currently shadow local variables for byval arguments are used directly.
In some cases this leads to invalid casts between address spaces.
Materialize these local variables before using to fix this problem.

Signed-off-by: Artur Gainullin [email protected]

[kbobrovs]

This adds more overhead.
I wonder if the shadow->private copy can be added only where the invalid address space casts can't be fixed otherwise w/o copying.

In some cases this leads to invalid casts between address spaces.

Do you have an example of such casts?

[againull]

This adds more overhead.
I wonder if the shadow->private copy can be added only where the invalid address space casts can't be fixed otherwise w/o copying.

In some cases this leads to invalid casts between address spaces.

Do you have an example of such casts?

I have added new lit test which demonstrates such case -> illegal cast from local address space to private address space is generated without the fix.
Yes, this adds an overhead, but in all other cases (allocas, results of instructions with side effects and so on) we do materialization, I think number of byval arguments is much less than other cases (which need to be shadowed in local memory) and overhead is negligible.