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[88.21.202.17]) by smtp.gmail.com with ESMTPSA id w15sm2823050wmi.35.2020.05.20.05.37.23 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 20 May 2020 05:37:24 -0700 (PDT) Subject: Re: [edk2-devel] [PATCH v2] ArmPkg/CompilerIntrinsicsLib: provide atomics intrinsics To: devel@edk2.groups.io, ard.biesheuvel@arm.com Cc: glin@suse.com, leif@nuviainc.com, lersek@redhat.com, liming.gao@intel.com References: <20200520114448.26104-1-ard.biesheuvel@arm.com> From: =?UTF-8?B?UGhpbGlwcGUgTWF0aGlldS1EYXVkw6k=?= Message-ID: <47f54425-df5d-17a3-e134-fe9e01fb08bd@redhat.com> Date: Wed, 20 May 2020 14:37:23 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0 MIME-Version: 1.0 In-Reply-To: <20200520114448.26104-1-ard.biesheuvel@arm.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Hi Ard, On 5/20/20 1:44 PM, Ard Biesheuvel wrote: > Gary reports the GCC 10 will emit calls to atomics intrinsics routines > unless -mno-outline-atomics is specified. This means GCC-10 introduces > new intrinsics, and even though it would be possible to work around this > by specifying the command line option, this would require a new GCC10 > toolchain profile to be created, which we prefer to avoid. > > So instead, add the new intrinsics to our library so they are provided > when necessary. > > Signed-off-by: Ard Biesheuvel > --- > v2: > - add missing .globl to export the functions from the object file > - add function end markers so the size of each is visible in the ELF metadata > - add some comments to describe what is going on Thanks, head hurts a bit less... > > ArmPkg/Library/CompilerIntrinsicsLib/CompilerIntrinsicsLib.inf | 3 + > ArmPkg/Library/CompilerIntrinsicsLib/AArch64/Atomics.S | 142 ++++++++++++++++++++ > 2 files changed, 145 insertions(+) > > diff --git a/ArmPkg/Library/CompilerIntrinsicsLib/CompilerIntrinsicsLib.inf b/ArmPkg/Library/CompilerIntrinsicsLib/CompilerIntrinsicsLib.inf > index d5bad9467758..fcf48c678119 100644 > --- a/ArmPkg/Library/CompilerIntrinsicsLib/CompilerIntrinsicsLib.inf > +++ b/ArmPkg/Library/CompilerIntrinsicsLib/CompilerIntrinsicsLib.inf > @@ -79,6 +79,9 @@ [Sources.ARM] > Arm/ldivmod.asm | MSFT > Arm/llsr.asm | MSFT > > +[Sources.AARCH64] > + AArch64/Atomics.S | GCC > + > [Packages] > MdePkg/MdePkg.dec > ArmPkg/ArmPkg.dec > diff --git a/ArmPkg/Library/CompilerIntrinsicsLib/AArch64/Atomics.S b/ArmPkg/Library/CompilerIntrinsicsLib/AArch64/Atomics.S > new file mode 100644 > index 000000000000..dc61d6bb8e52 > --- /dev/null > +++ b/ArmPkg/Library/CompilerIntrinsicsLib/AArch64/Atomics.S > @@ -0,0 +1,142 @@ > +#------------------------------------------------------------------------------ > +# > +# Copyright (c) 2020, Arm, Limited. All rights reserved.
> +# > +# SPDX-License-Identifier: BSD-2-Clause-Patent > +# > +#------------------------------------------------------------------------------ > + > + /* > + * Provide the GCC intrinsics that are required when using GCC 9 or > + * later with the -moutline-atomics options (which became the default > + * in GCC 10) > + */ > + .arch armv8-a > + > + .macro reg_alias, pfx, sz > + r0_\sz .req \pfx\()0 > + r1_\sz .req \pfx\()1 > + tmp0_\sz .req \pfx\()16 > + tmp1_\sz .req \pfx\()17 > + .endm > + > + /* > + * Define register aliases of the right type for each size > + * (xN for 8 bytes, wN for everything smaller) > + */ > + reg_alias w, 1 > + reg_alias w, 2 > + reg_alias w, 4 > + reg_alias x, 8 > + > + .macro fn_start, name:req > + .section .text.\name > + .globl \name > + .type \name, %function > +\name\(): > + .endm > + > + .macro fn_end, name:req > + .size \name, . - \name > + .endm > + > + /* > + * Emit an atomic helper for \model with operands of size \sz, using > + * the operation specified by \insn (which is the LSE name), and which > + * can be implemented using the generic load-locked/store-conditional > + * (LL/SC) sequence below, using the arithmetic operation given by > + * \opc. > + */ > + .macro emit_ld_sz, sz:req, insn:req, opc:req, model:req, s, a, l > + fn_start __aarch64_\insn\()\sz\()\model > + mov tmp0_\sz, r0_\sz > +0: ld\a\()xr\s r0_\sz, [x1] > + .ifnc \insn, swp > + \opc tmp1_\sz, r0_\sz, tmp0_\sz > + .else > + \opc tmp1_\sz, tmp0_\sz > + .endif > + st\l\()xr\s w15, tmp1_\sz, [x1] > + cbnz w15, 0b I see at the end \s is in {,b,h} range. Don't you need to use x15 on 64-bit? > + ret > + fn_end __aarch64_\insn\()\sz\()\model > + .endm > + > + /* > + * Emit atomic helpers for \model for operand sizes in the > + * set {1, 2, 4, 8}, for the instruction pattern given by > + * \insn. (This is the LSE name, but this implementation uses > + * the generic LL/SC sequence using \opc as the arithmetic > + * operation on the target.) > + */ > + .macro emit_ld, insn:req, opc:req, model:req, a, l > + emit_ld_sz 1, \insn, \opc, \model, b, \a, \l > + emit_ld_sz 2, \insn, \opc, \model, h, \a, \l > + emit_ld_sz 4, \insn, \opc, \model, , \a, \l > + emit_ld_sz 8, \insn, \opc, \model, , \a, \l > + .endm > + > + /* > + * Emit the compare and swap helper for \model and size \sz > + * using LL/SC instructions. > + */ > + .macro emit_cas_sz, sz:req, model:req, uxt:req, s, a, l > + fn_start __aarch64_cas\sz\()\model > + \uxt tmp0_\sz, r0_\sz > +0: ld\a\()xr\s r0_\sz, [x2] > + cmp r0_\sz, tmp0_\sz > + bne 1f > + st\l\()xr\s w15, r1_\sz, [x2] > + cbnz w15, 0b > +1: ret > + fn_end __aarch64_cas\sz\()\model > + .endm > + > + /* > + * Emit compare-and-swap helpers for \model for operand sizes in the > + * set {1, 2, 4, 8, 16}. > + */ > + .macro emit_cas, model:req, a, l > + emit_cas_sz 1, \model, uxtb, b, \a, \l > + emit_cas_sz 2, \model, uxth, h, \a, \l > + emit_cas_sz 4, \model, mov , , \a, \l > + emit_cas_sz 8, \model, mov , , \a, \l > + > + /* > + * We cannot use the parameterized sequence for 16 byte CAS, so we > + * need to define it explicitly. > + */ > + fn_start __aarch64_cas16\model > + mov x16, x0 > + mov x17, x1 > +0: ld\a\()xp x0, x1, [x4] > + cmp x0, x16 > + ccmp x1, x17, #0, eq > + bne 1f > + st\l\()xp w15, x16, x17, [x4] > + cbnz w15, 0b > +1: ret > + fn_end __aarch64_cas16\model > + .endm > + > + /* > + * Emit the set of GCC outline atomic helper functions for > + * the memory ordering model given by \model: > + * - relax unordered loads and stores > + * - acq load-acquire, unordered store > + * - rel unordered load, store-release > + * - acq_rel load-acquire, store-release > + */ > + .macro emit_model, model:req, a, l > + emit_ld ldadd, add, \model, \a, \l > + emit_ld ldclr, bic, \model, \a, \l > + emit_ld ldeor, eor, \model, \a, \l > + emit_ld ldset, orr, \model, \a, \l > + emit_ld swp, mov, \model, \a, \l > + emit_cas \model, \a, \l > + .endm > + > + emit_model _relax > + emit_model _acq, a > + emit_model _rel,, l > + emit_model _acq_rel, a, l >