This reverts commit e9de32fd159d30cfd6fcc861b57b7e99ec2742ab due to
multiple performance regressions observed across downstream Numba
benchmarks (https://github.com/llvm/llvm-project/issues/138509#issuecomment-3193855772).
While avoiding non-trivial unswitches on newly-cloned loops helps
mitigate the pathological case reported in https://github.com/llvm/llvm-project/issues/138509,
it may as well make the IR less friendly to vectorization / loop-
canonicalization (in the test reported, previously no select with
loop-carried dependence existed in the new specialized loops),
leading the abovementioned approach to be reconsidered.
Track newly-cloned loops coming from unswitching non-trivial invariant
conditions, so as to prevent conditions in such cloned blocks from
being unswitched again.
Fixes: https://github.com/llvm/llvm-project/issues/138509.
With the addition of #84628, truncs to i1 are being emitted as
conditions to branch instructions. This caused significant regressions
in cases which were previously improved by loop unswitch. Adding truncs
to i1 restore the previous performance seen.
It is confusing to have two ways of specifying the same pass
('simple-loop-unswitch' and 'unswitch'). This patch replaces
'unswitch' by 'simple-loop-unswitch' to get a unique identifier.
Using 'simple-loop-unswitch' instead of 'unswitch' also has the
advantage of matching how the pass is named in DEBUG_TYPE etc. So
this makes it a bit more consistent how we refer to the pass in
options such as -passes, -print-after and -debug-only.
Reviewed By: aeubanks
Differential Revision: https://reviews.llvm.org/D105628
There was a bug from cost calculation for partially invariant unswitch.
The costs of non-duplicated blocks are substracted from the total LoopCost, so
anything that is duplicated should not be counted.
Differential Revision: https://reviews.llvm.org/D103816
