assigned to @rotateright

Same is true for lshr:
https://alive2.llvm.org/ce/z/NFowLr

Err, submitted too soon

Same is true for lshr:
https://alive2.llvm.org/ce/z/NFowLr
https://c.godbolt.org/z/7q545n

I think we could use ComputeNumSignBits() here.
I'll try to take a look..

Same for zext, but we get that already: https://c.godbolt.org/z/6GqxTM
https://alive2.llvm.org/ce/z/289tfg
https://alive2.llvm.org/ce/z/GWh-uX

@​lebedev.ri Are you still looking at this?

@​lebedev.ri Are you still looking at this?

Not really. If someone wants to pick this up, feel free to.
There is a number of patches needed here:

• general computenumsignbits fold
• fold for that specific IR, to handle non-splat vectors
• fold for the case where the first op is lshr
• ???
• do we need something similar for zero-extension?

Looking at the ComputeNumSignBits pattern - tests:
https://reviews.llvm.org/rG337854270023

https://reviews.llvm.org/D103617

Filed the 'lshr' pattern as bug 50575.
The example pasted in the description is transformed into that (ashr->lshr).

But the bug title and the example in the godbolt link in the description are different and should be fixed with:
https://reviews.llvm.org/rGb865eead7657

So I think it's ok to close this one, but feel free to reopen or file new bugs to track other items.

Cheers Sanjay!