On 8/30/26 8:53 AM, Hans-Peter Nilsson wrote:
Date: Sat, 29 Aug 2026 00:43:27 -0600
Cc: [email protected]
From: Jeff Law <[email protected]>
On 8/27/26 3:13 PM, Hans-Peter Nilsson wrote:
Let's harmonize canonicalization for NOT-on-ROTATE and NOT-on-ROTATERT
with that of BSWAP and BITREVERSE, and document the canonical
form. Tested cross to cris-elf, native on x86_64-pc-linux-gnu.
Ok to commit?
brgds, H-P
-- >8 --
Before this patch, the combine pass would match (bitreverse:SI (not:SI
reg)) but not (rotate:SI (not:SI reg (const_int 16)))), instead
requiring (not:SI (rotate:SI reg (const_int 16))) for the compound
operation to be recognized. That looked inconsistent considering that
both are bit-rearrangement operations commutative with bitwise negation.
I was about to write "operations with which bitwise negation is
commutative", but thought better list the operations explicitly.
* doc/md.texi (Insn Canonicalizations): Document BITREVERSE,
BSWAP, ROTATE, and ROTATERT as having the canonical form of
NOT moved inside the first operand.
* simplify-rtx.cc (simplify_context::simplify_unary_operation_1):
Move a NOT to the inside of ROTATE and ROTATERT, like for BITREVERSE
and BSWAP.
* config/cris/cris.md (*rotsi2_16_not<setcc><setnz><setnzvc>): Adjust
accordingly.
OK
Thanks! Unfortunately, there's fallout on aarch64-unknown-linux-gnu,
as "[email protected]" informed me, so there'll be a v2, but just
with an added aarch64 MD patch with a similar correction as with
cris.md.
Yea, but I consider this kind of fallout minor and not unexpected given
the nature of the change. We fix and move on.
brgds, H-P
PS. there's a flaky test or set of tests in gcov they should filter out.
Yea, Daniel mentioned one of the newer gcov tests that has bouncing
around. The linaro tester has some ability to identify flakey tests and
temporarily disable them.
jeff
