On Wed, May 06, 2026 at 09:49:51AM +0100, Tamar Christina wrote:
> > -----Original Message-----
> > From: Alfie Richards <[email protected]>
> > Sent: 04 November 2025 13:58
> > To: [email protected]
> > Cc: Richard Earnshaw <[email protected]>; Tamar Christina
> > <[email protected]>; [email protected]; Alice Carlotti
> > <[email protected]>; Alex Coplan <[email protected]>; Wilco
> > Dijkstra <[email protected]>; [email protected]; Alfie
> > Richards <[email protected]>
> > Subject: [PATCH v1] aarch64: Add support for FEAT_SSVE_BitPerm
> >
> > Hi All,
> >
> > Requires my patch updating the AArch64 cli arch options
> > (https://gcc.gnu.org/pipermail/gcc-patches/2025-November/699488.html).
> >
> > Reg tested on AArch64.
> >
> > Okay for master after prereq lands?
> >
> > Alfie
> >
> > -- >8 --
> >
> > Adds support for the FEAT_SSVE_BitPerm AArch64 extension.
> >
> > FEAT_SSVE_BitPerm makes the FEAT_SVE2_BitPerm instructions available in
> > streaming mode.
> >
> > gcc/ChangeLog:
> >
> > * config/aarch64/aarch64-c.cc (aarch64_update_cpp_builtins): Add
> > __ARM_FEATURE_SSVE_BITPERM.
> > * config/aarch64/aarch64-sve-builtins-sve2.def:
> > Make sve-bitperm intrinsics streaming compatible.
> > * config/aarch64/aarch64-sve2.md: Change gating of sve-bitperm
> > instructions.
> > * config/aarch64/aarch64.h (TARGET_SVE_BITPERM): New macro.
> > (TARGET_SSVE_BITPERM): New macro.
> > (TARGET_STREAMING_SSVE_BITPERM): New macro.
> >
> > gcc/testsuite/ChangeLog:
...
> >
> > diff --git a/gcc/config/aarch64/aarch64-c.cc b/gcc/config/aarch64/aarch64-
> > c.cc
> > index c3957c762ef..fd940bdf733 100644
> > --- a/gcc/config/aarch64/aarch64-c.cc
> > +++ b/gcc/config/aarch64/aarch64-c.cc
> > @@ -295,6 +295,8 @@ aarch64_update_cpp_builtins (cpp_reader *pfile)
> > aarch64_def_or_undef (AARCH64_HAVE_ISA (SME2p1),
> > "__ARM_FEATURE_SME2p1", pfile);
> > aarch64_def_or_undef (TARGET_FAMINMAX,
> > "__ARM_FEATURE_FAMINMAX", pfile);
> > + aarch64_def_or_undef (TARGET_SSVE_BITPERM,
> > "__ARM_FEATURE_SSVE_BITPERM",
> > + pfile);
> >
> > // Function multi-versioning defines
> > aarch64_def_or_undef (targetm.has_ifunc_p (),
> > diff --git a/gcc/config/aarch64/aarch64-sve-builtins-sve2.def
> > b/gcc/config/aarch64/aarch64-sve-builtins-sve2.def
> > index b622fe33458..6f1601e6f22 100644
> > --- a/gcc/config/aarch64/aarch64-sve-builtins-sve2.def
> > +++ b/gcc/config/aarch64/aarch64-sve-builtins-sve2.def
> > @@ -202,8 +202,7 @@ DEF_SVE_FUNCTION (svpmullb_pair, binary_opt_n,
> > d_unsigned, none)
> > DEF_SVE_FUNCTION (svpmullt_pair, binary_opt_n, d_unsigned, none)
> > #undef REQUIRED_EXTENSIONS
> >
> > -#define REQUIRED_EXTENSIONS nonstreaming_sve (AARCH64_FL_SVE2 \
> > - | AARCH64_FL_SVE2_BITPERM)
> > +#define REQUIRED_EXTENSIONS streaming_compatible (AARCH64_FL_SVE2
> > | AARCH64_FL_SVE_BITPERM, AARCH64_FL_SSVE_BITPERM)
> > DEF_SVE_FUNCTION (svbdep, binary_opt_n, all_unsigned, none)
> > DEF_SVE_FUNCTION (svbext, binary_opt_n, all_unsigned, none)
> > DEF_SVE_FUNCTION (svbgrp, binary_opt_n, all_unsigned, none)
> > diff --git a/gcc/config/aarch64/aarch64-sve2.md
> > b/gcc/config/aarch64/aarch64-sve2.md
> > index 91091835182..7c86573d364 100644
> > --- a/gcc/config/aarch64/aarch64-sve2.md
> > +++ b/gcc/config/aarch64/aarch64-sve2.md
> > @@ -4191,7 +4191,7 @@ (define_insn
> > "@aarch64_sve_<sve_int_op><mode>"
> > [(match_operand:SVE_FULL_I 1 "register_operand" "w")
> > (match_operand:SVE_FULL_I 2 "register_operand" "w")]
> > SVE2_INT_BITPERM))]
> > - "TARGET_SVE2_BITPERM"
> > + "TARGET_SVE_BITPERM"
> > "<sve_int_op>\t%0.<Vetype>, %1.<Vetype>, %2.<Vetype>"
> > [(set_attr "sve_type" "sve_int_bit_perm")]
> > )
> > diff --git a/gcc/config/aarch64/aarch64.h b/gcc/config/aarch64/aarch64.h
> > index 47d8fc09925..b15999b5b37 100644
> > --- a/gcc/config/aarch64/aarch64.h
> > +++ b/gcc/config/aarch64/aarch64.h
> > @@ -295,11 +295,25 @@ constexpr auto AARCH64_FL_DEFAULT_ISA_MODE
> > ATTRIBUTE_UNUSED
> > && AARCH64_HAVE_ISA (SVE_AES) \
> > && TARGET_NON_STREAMING)
> >
> > -/* SVE2 BITPERM instructions, enabled through +sve2-bitperm. */
> > +/* SVE BITPERM instructions, enabled through +sve2-bitperm or
> > + +ssve-bitperm. */
> > +#define TARGET_SVE_BITPERM (AARCH64_HAVE_ISA (SVE_BITPERM))
>
> I find this name to be very confusing (I'm aware the FEAT is FEAT_SVE_)
> but It looks like TARGET_SVE2_BITPERM isn't used anywhere else but
> the CPP defines.
I'd suggest dropping TARGET_SVE2_BITPERM entirely, and using explicit
AARCH64_HAVE_ISA calls for preprocessor defines in aarch64_update_cpp_builtins.
I also think these preprocessor defines shouldn't depend on whether we're
currently in streaming mode, although that might be a minor break with existing
behaviour.
>
> So how about instead of defining the above..
>
> > +
> > +/* Non-streaming support for SVE BITPERM instructions, enabled through
> > + +sve2-bitperm. */
> > #define TARGET_SVE2_BITPERM (AARCH64_HAVE_ISA (SVE2) \
> > && AARCH64_HAVE_ISA (SVE_BITPERM) \
> > && TARGET_NON_STREAMING)
> >
>
> ..drop TARGET_NON_STREAMING from here and change
>
> aarch64_def_or_undef (TARGET_SVE2_BITPERM,
> "__ARM_FEATURE_SVE2_BITPERM", pfile);
>
> to
>
> aarch64_def_or_undef (TARGET_SVE2_BITPERM && TARGET_NON_STREAMING,
> "__ARM_FEATURE_SVE2_BITPERM", pfile);
>
> So we avoid the really confusing macro name.
I'd instead suggesting having a single TARGET_* macro:
#define TARGET_SVE_BITPERM (AARCH64_HAVE_ISA (SVE_BITPERM) \
&& (AARCH64_HAVE_ISA (SVE2) || TARGET_STREAMING) \
&& (AARCH64_HAVE_ISA (SSVE_BITPERM) \
|| TARGET_NON_STREAMING))
The .md file would then simply check TARGET_SVE_BITPERM.
I made similar comments in my review of Sivan's FEAT_SSVE_AES patch
(https://gcc.gnu.org/pipermail/gcc-patches/2026-March/710828.html).
We should at least handle FEAT_SSVE_AES and FEAT_SSVE_BITPERM in a consistent
manner.
Alice
>
> > +/* Streaming support for SVE BITPERM instructions, enabled through
> > + +ssve-bitperm (which implies SVE2_BITPERM so that all relevant
> > instructions
> > + are streaming compatible). */
> > +#define TARGET_SSVE_BITPERM (AARCH64_HAVE_ISA (SSVE_BITPERM))
> > +
> > +#define TARGET_STREAMING_SSVE_BITPERM (AARCH64_HAVE_ISA
> > (SSVE_BITPERM) \
> > + && TARGET_STREAMING)
> > +
> > +
> > /* SVE2 SHA3 instructions, enabled through +sve2-sha3. */
> > #define TARGET_SVE2_SHA3 (AARCH64_HAVE_ISA (SVE2) \
> > && AARCH64_HAVE_ISA (SVE_SHA3) \
