[Bug target/115176] New: rbit pattern should use bitreverse rtl now

[Bug target/115176] New: rbit pattern should use bitreverse rtl now

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115176

            Bug ID: 115176
           Summary: rbit pattern should use bitreverse rtl now
           Product: gcc
           Version: 15.0
            Status: UNCONFIRMED
          Keywords: internal-improvement
          Severity: enhancement
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: pinskia at gcc dot gnu.org
  Target Milestone: ---

While looking at some code I noticed that it uses clang's __builtin_bitreverse8
builtin and looking at the aarch64 backend, I noticed the rbit patterns don't
use bitreverse but still an UNSPEC.

We should be able to change the pattern to use the rtl now.

[Bug target/115176] rbit pattern should use bitreverse rtl now

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115176

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Assignee|unassigned at gcc dot gnu.org      |pinskia at gcc dot gnu.org
     Ever confirmed|0                           |1
             Status|UNCONFIRMED                 |ASSIGNED
   Last reconfirmed|                            |2024-05-21

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
that is from aarch64-simd.md:
```
(define_insn "aarch64_rbit<mode><vczle><vczbe>"
  [(set (match_operand:VB 0 "register_operand" "=w")
        (unspec:VB [(match_operand:VB 1 "register_operand" "w")]
                   UNSPEC_RBIT))]
  "TARGET_SIMD"
  "rbit\\t%0.<Vbtype>, %1.<Vbtype>"
  [(set_attr "type" "neon_rbit")]
)
```

From aarch64.md:
```
(define_insn "@aarch64_rbit<mode>"
  [(set (match_operand:GPI 0 "register_operand" "=r")
        (unspec:GPI [(match_operand:GPI 1 "register_operand" "r")]
UNSPEC_RBIT))]
  ""
  "rbit\\t%<w>0, %<w>1"
  [(set_attr "type" "rbit")]
)
```

[Bug target/115176] rbit pattern should use bitreverse rtl now

[xry111 at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115176

Xi Ruoyao <xry111 at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |xry111 at gcc dot gnu.org

--- Comment #2 from Xi Ruoyao <xry111 at gcc dot gnu.org> ---
LoongArch currently has:

(define_insn "bitrev_4b"
  [(set (match_operand:SI 0 "register_operand" "=r")
        (unspec:SI [(match_operand:SI 1 "register_operand" "r")]
                    UNSPEC_BITREV_4B))]
  ""
  "bitrev.4b\t%0,%1"
  [(set_attr "type" "unknown")
   (set_attr "mode" "SI")])

(define_insn "bitrev_8b"
  [(set (match_operand:DI 0 "register_operand" "=r")
        (unspec:DI [(match_operand:DI 1 "register_operand" "r")]
                    UNSPEC_BITREV_8B))]
  ""
  "bitrev.8b\t%0,%1"
  [(set_attr "type" "unknown")
   (set_attr "mode" "DI")])

Maybe we can make them something like (subreg:DI (bitreverse:V8QI (subreg:QI
(match...) 0)) 0) instead.  And LoongArch also has bitrev.{w/d} instructions
but GCC doesn't know them yet.  I plan to add them after PR50481 is
implemented.

[Bug target/115176] rbit pattern should use bitreverse rtl now

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115176

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                URL|                            |https://gcc.gnu.org/piperma
                   |                            |il/gcc-patches/2024-June/65
                   |                            |4271.html
           Keywords|                            |patch

--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Patch submitted:
https://gcc.gnu.org/pipermail/gcc-patches/2024-June/654271.html

[Bug target/115176] rbit pattern should use bitreverse rtl now

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115176

--- Comment #4 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The trunk branch has been updated by Andrew Pinski <pinskia@gcc.gnu.org>:

https://gcc.gnu.org/g:c2f0aaf7539c42b024ed6b3fb6909bd2c86bb206

commit r15-1216-gc2f0aaf7539c42b024ed6b3fb6909bd2c86bb206
Author: Andrew Pinski <quic_apinski@quicinc.com>
Date:   Tue Jun 11 20:36:34 2024 +0000

    aarch64: Use bitreverse rtl code instead of unspec [PR115176]

    Bitreverse rtl code was added with r14-1586-g6160572f8d243c. So let's
    use it instead of an unspec. This is just a small cleanup but it does
    have one small fix with respect to rtx costs which didn't handle vector
modes
    correctly for the UNSPEC and now it does.
    This is part of the first step in adding __builtin_bitreverse's builtins
    but it is independent of it though.

    Bootstrapped and tested on aarch64-linux-gnu with no regressions.

    gcc/ChangeLog:

            PR target/115176
            * config/aarch64/aarch64-simd.md
(aarch64_rbit<mode><vczle><vczbe>): Use
            bitreverse instead of unspec.
            * config/aarch64/aarch64-sve-builtins-base.cc (svrbit): Convert
over to using
            rtx_code_function instead of unspec_based_function.
            * config/aarch64/aarch64-sve.md: Update comment where RBIT is
included.
            * config/aarch64/aarch64.cc (aarch64_rtx_costs): Handle BITREVERSE
like BSWAP.
            Remove UNSPEC_RBIT support.
            * config/aarch64/aarch64.md (unspec): Remove UNSPEC_RBIT.
            (aarch64_rbit<mode>): Use bitreverse instead of unspec.
            * config/aarch64/iterators.md (SVE_INT_UNARY): Add bitreverse.
            (optab): Likewise.
            (sve_int_op): Likewise.
            (SVE_INT_UNARY): Remove UNSPEC_RBIT.
            (optab): Likewise.
            (sve_int_op): Likewise.
            (min_elem_bits): Likewise.

    Signed-off-by: Andrew Pinski <quic_apinski@quicinc.com>

[Bug target/115176] rbit pattern should use bitreverse rtl now

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115176

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |15.0
         Resolution|---                         |FIXED
             Status|ASSIGNED                    |RESOLVED

--- Comment #5 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Fixed.