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clang-p2996/llvm/test/Transforms/InstCombine
Sanjay Patel 8fce94f916 [InstCombine] canonicalize icmp with trunc op into mask and cmp, part 2
If C is a high-bit mask:
(trunc X) u< C --> (X & C) != C (are any masked-high-bits clear?)

If C is low-bit mask:
(trunc X) u> C --> (X & ~C) != 0 (are any masked-high-bits set?)

If C is not-of-power-of-2 (one clear bit):
(trunc X) u> C --> (X & (C+1)) == C+1 (are all masked-high-bits set?)

This extends the fold added with:
acabad9ff6 (https://alive2.llvm.org/ce/z/aFr7qV)

Using decomposeBitTestICmp() to generalize this is a planned follow-up, but that requires removing an inverse fold.

Here are Alive2 generalizations for these folds:
https://alive2.llvm.org/ce/z/u-ZpC_ (ult, the previous patch)
https://alive2.llvm.org/ce/z/YsuAu2 (ult, this patch)
https://alive2.llvm.org/ce/z/ekktQP (ugt, low bitmask)
https://alive2.llvm.org/ce/z/pJY9wR (ugt, one clear bit)

Differential Revision: https://reviews.llvm.org/D112634
2021-11-16 09:27:30 -05:00
..
2021-11-15 12:29:37 -05:00
2021-08-16 09:28:06 -07:00

This directory contains test cases for the instcombine transformation.  The
dated tests are actual bug tests, whereas the named tests are used to test
for features that the this pass should be capable of performing.