320 lines
7.2 KiB
ArmAsm
320 lines
7.2 KiB
ArmAsm
/* Out-of-line LSE atomics for AArch64 architecture.
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Copyright (C) 2019-2021 Free Software Foundation, Inc.
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Contributed by Linaro Ltd.
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This file is part of GCC.
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GCC is free software; you can redistribute it and/or modify it under
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the terms of the GNU General Public License as published by the Free
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Software Foundation; either version 3, or (at your option) any later
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version.
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GCC is distributed in the hope that it will be useful, but WITHOUT ANY
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WARRANTY; without even the implied warranty of MERCHANTABILITY or
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FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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for more details.
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Under Section 7 of GPL version 3, you are granted additional
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permissions described in the GCC Runtime Library Exception, version
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3.1, as published by the Free Software Foundation.
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You should have received a copy of the GNU General Public License and
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a copy of the GCC Runtime Library Exception along with this program;
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see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
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<http://www.gnu.org/licenses/>. */
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/*
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* The problem that we are trying to solve is operating system deployment
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* of ARMv8.1-Atomics, also known as Large System Exensions (LSE).
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*
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* There are a number of potential solutions for this problem which have
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* been proposed and rejected for various reasons. To recap:
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*
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* (1) Multiple builds. The dynamic linker will examine /lib64/atomics/
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* if HWCAP_ATOMICS is set, allowing entire libraries to be overwritten.
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* However, not all Linux distributions are happy with multiple builds,
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* and anyway it has no effect on main applications.
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*
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* (2) IFUNC. We could put these functions into libgcc_s.so, and have
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* a single copy of each function for all DSOs. However, ARM is concerned
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* that the branch-to-indirect-branch that is implied by using a PLT,
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* as required by IFUNC, is too much overhead for smaller cpus.
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*
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* (3) Statically predicted direct branches. This is the approach that
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* is taken here. These functions are linked into every DSO that uses them.
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* All of the symbols are hidden, so that the functions are called via a
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* direct branch. The choice of LSE vs non-LSE is done via one byte load
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* followed by a well-predicted direct branch. The functions are compiled
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* separately to minimize code size.
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*/
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#include "auto-target.h"
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/* Tell the assembler to accept LSE instructions. */
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#ifdef HAVE_AS_LSE
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.arch armv8-a+lse
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#else
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.arch armv8-a
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#endif
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/* Declare the symbol gating the LSE implementations. */
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.hidden __aarch64_have_lse_atomics
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/* Turn size and memory model defines into mnemonic fragments. */
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#if SIZE == 1
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# define S b
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# define UXT uxtb
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# define B 0x00000000
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#elif SIZE == 2
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# define S h
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# define UXT uxth
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# define B 0x40000000
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#elif SIZE == 4 || SIZE == 8 || SIZE == 16
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# define S
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# define UXT mov
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# if SIZE == 4
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# define B 0x80000000
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# elif SIZE == 8
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# define B 0xc0000000
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# endif
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#else
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# error
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#endif
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#if MODEL == 1
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# define SUFF _relax
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# define A
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# define L
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# define M 0x000000
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# define N 0x000000
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#elif MODEL == 2
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# define SUFF _acq
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# define A a
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# define L
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# define M 0x400000
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# define N 0x800000
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#elif MODEL == 3
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# define SUFF _rel
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# define A
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# define L l
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# define M 0x008000
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# define N 0x400000
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#elif MODEL == 4
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# define SUFF _acq_rel
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# define A a
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# define L l
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# define M 0x408000
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# define N 0xc00000
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#else
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# error
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#endif
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/* Concatenate symbols. */
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#define glue2_(A, B) A ## B
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#define glue2(A, B) glue2_(A, B)
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#define glue3_(A, B, C) A ## B ## C
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#define glue3(A, B, C) glue3_(A, B, C)
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#define glue4_(A, B, C, D) A ## B ## C ## D
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#define glue4(A, B, C, D) glue4_(A, B, C, D)
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/* Select the size of a register, given a regno. */
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#define x(N) glue2(x, N)
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#define w(N) glue2(w, N)
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#if SIZE < 8
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# define s(N) w(N)
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#else
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# define s(N) x(N)
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#endif
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#define NAME(BASE) glue4(__aarch64_, BASE, SIZE, SUFF)
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#define LDXR glue4(ld, A, xr, S)
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#define STXR glue4(st, L, xr, S)
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/* Temporary registers used. Other than these, only the return value
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register (x0) and the flags are modified. */
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#define tmp0 16
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#define tmp1 17
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#define tmp2 15
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#define BTI_C hint 34
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/* Start and end a function. */
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.macro STARTFN name
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.text
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.balign 16
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.globl \name
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.hidden \name
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.type \name, %function
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.cfi_startproc
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\name:
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BTI_C
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.endm
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.macro ENDFN name
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.cfi_endproc
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.size \name, . - \name
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.endm
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/* Branch to LABEL if LSE is disabled. */
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.macro JUMP_IF_NOT_LSE label
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adrp x(tmp0), __aarch64_have_lse_atomics
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ldrb w(tmp0), [x(tmp0), :lo12:__aarch64_have_lse_atomics]
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cbz w(tmp0), \label
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.endm
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#ifdef L_cas
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STARTFN NAME(cas)
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JUMP_IF_NOT_LSE 8f
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#if SIZE < 16
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#ifdef HAVE_AS_LSE
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# define CAS glue4(cas, A, L, S) s(0), s(1), [x2]
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#else
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# define CAS .inst 0x08a07c41 + B + M
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#endif
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CAS /* s(0), s(1), [x2] */
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ret
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8: UXT s(tmp0), s(0)
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0: LDXR s(0), [x2]
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cmp s(0), s(tmp0)
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bne 1f
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STXR w(tmp1), s(1), [x2]
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cbnz w(tmp1), 0b
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1: ret
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#else
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#define LDXP glue3(ld, A, xp)
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#define STXP glue3(st, L, xp)
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#ifdef HAVE_AS_LSE
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# define CASP glue3(casp, A, L) x0, x1, x2, x3, [x4]
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#else
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# define CASP .inst 0x48207c82 + M
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#endif
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CASP /* x0, x1, x2, x3, [x4] */
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ret
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8: mov x(tmp0), x0
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mov x(tmp1), x1
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0: LDXP x0, x1, [x4]
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cmp x0, x(tmp0)
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ccmp x1, x(tmp1), #0, eq
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bne 1f
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STXP w(tmp2), x2, x3, [x4]
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cbnz w(tmp2), 0b
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1: ret
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#endif
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ENDFN NAME(cas)
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#endif
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#ifdef L_swp
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#ifdef HAVE_AS_LSE
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# define SWP glue4(swp, A, L, S) s(0), s(0), [x1]
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#else
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# define SWP .inst 0x38208020 + B + N
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#endif
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STARTFN NAME(swp)
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JUMP_IF_NOT_LSE 8f
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SWP /* s(0), s(0), [x1] */
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ret
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8: mov s(tmp0), s(0)
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0: LDXR s(0), [x1]
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STXR w(tmp1), s(tmp0), [x1]
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cbnz w(tmp1), 0b
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ret
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ENDFN NAME(swp)
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#endif
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#if defined(L_ldadd) || defined(L_ldclr) \
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|| defined(L_ldeor) || defined(L_ldset)
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#ifdef L_ldadd
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#define LDNM ldadd
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#define OP add
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#define OPN 0x0000
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#elif defined(L_ldclr)
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#define LDNM ldclr
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#define OP bic
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#define OPN 0x1000
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#elif defined(L_ldeor)
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#define LDNM ldeor
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#define OP eor
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#define OPN 0x2000
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#elif defined(L_ldset)
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#define LDNM ldset
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#define OP orr
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#define OPN 0x3000
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#else
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#error
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#endif
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#ifdef HAVE_AS_LSE
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# define LDOP glue4(LDNM, A, L, S) s(0), s(0), [x1]
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#else
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# define LDOP .inst 0x38200020 + OPN + B + N
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#endif
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STARTFN NAME(LDNM)
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JUMP_IF_NOT_LSE 8f
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LDOP /* s(0), s(0), [x1] */
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ret
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8: mov s(tmp0), s(0)
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0: LDXR s(0), [x1]
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OP s(tmp1), s(0), s(tmp0)
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STXR w(tmp2), s(tmp1), [x1]
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cbnz w(tmp2), 0b
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ret
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ENDFN NAME(LDNM)
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#endif
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/* GNU_PROPERTY_AARCH64_* macros from elf.h for use in asm code. */
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#define FEATURE_1_AND 0xc0000000
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#define FEATURE_1_BTI 1
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#define FEATURE_1_PAC 2
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/* Supported features based on the code generation options. */
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#if defined(__ARM_FEATURE_BTI_DEFAULT)
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# define BTI_FLAG FEATURE_1_BTI
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#else
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# define BTI_FLAG 0
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#endif
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#if __ARM_FEATURE_PAC_DEFAULT & 3
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# define PAC_FLAG FEATURE_1_PAC
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#else
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# define PAC_FLAG 0
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#endif
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/* Add a NT_GNU_PROPERTY_TYPE_0 note. */
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#define GNU_PROPERTY(type, value) \
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.section .note.gnu.property, "a"; \
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.p2align 3; \
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.word 4; \
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.word 16; \
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.word 5; \
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.asciz "GNU"; \
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.word type; \
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.word 4; \
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.word value; \
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.word 0;
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#if defined(__linux__) || defined(__FreeBSD__)
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.section .note.GNU-stack, "", %progbits
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/* Add GNU property note if built with branch protection. */
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# if (BTI_FLAG|PAC_FLAG) != 0
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GNU_PROPERTY (FEATURE_1_AND, BTI_FLAG|PAC_FLAG)
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# endif
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#endif
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