Sanjay Patel 341623653d [SDAG] match rotate pattern with extra 'or' operation ...

This is another fold generalized from D111530.
We can find a common source for a rotate operation hidden inside an 'or':
https://alive2.llvm.org/ce/z/9pV8hn

Deciding when this is profitable vs. a funnel-shift is tricky, but this
does not show any regressions: if a target has a rotate but it does not
have a funnel-shift, then try to form the rotate here. That is why we
don't have x86 test diffs for the scalar tests that are duplicated from
AArch64 ( 74a65e3834 ) - shld/shrd are available. That also makes it
difficult to show vector diffs - the only case where I found a diff was
on x86 AVX512 or XOP with i64 elements.

There's an additional check for a legal type to avoid a problem seen
with x86-32 where we form a 64-bit rotate but then it gets split
inefficiently. We might avoid that by adding more rotate folds, but
I didn't check to see what is missing on that path.

This gets most of the motivating patterns for AArch64 / ARM that are in
D111530.

We still need a couple of enhancements to setcc pattern matching with
rotate/funnel-shift to get the rest.

Differential Revision: https://reviews.llvm.org/D120933

2022-03-09 13:19:00 -05:00

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