calculateRegisterUsage adds end points for each user of an instruction
to Ends and ignores instructions not added to it, i.e. instructions with
no users.
This means things like stores aren't included, which in turn means
values that are only used in stores are also not included for
consideration. This means we underestimate the register usage in cases
where the only users are things like stores.
Update the code to don't skip instructions without users (i.e. not in
Ends) if they have side-effects.
PR: https://github.com/llvm/llvm-project/pull/126415
Previously, while calculating register usage due to invariants, it was assumed that invariant would always be part of widening
instructions. This resulted in calculating vector register types for vectors which cant be legalized(check the newly added test for more details).
An invariant might not always need a vector register. For e.g., invariant might just be used for iteration check.
This patch checks if the invariant is part of any widening instruction and considers register usage accordingly. Fixes issue 60493
Differential Revision: https://reviews.llvm.org/D143422
Previously, while calculating register usage due to invariants, it was assumed that invariant would always be part of widening
instructions. This resulted in calculating vector register types for vectors which cant be legalized(check the newly added test for more details).
An invariant might not always need a vector register. For e.g., invariant might just be used for iteration check.
This patch checks if the invariant is part of any widening instruction and considers register usage accordingly. Fixes issue 60493
Differential Revision: https://reviews.llvm.org/D143422
