This is the libgcc part of the interface -- providing the functions.
Rationale is provided at the top of libgcc/config/aarch64/lse.S.
2020-04-16 Andre Vieira <andre.simoesdiasvie...@arm.com>
Backport from mainline
2019-09-19 Richard Henderson <richard.hender...@linaro.org>
* config/aarch64/lse-init.c: New file.
* config/aarch64/lse.S: New file.
* config/aarch64/t-lse: New file.
* config.host: Add t-lse to all aarch64 tuples.
diff --git a/libgcc/config.host b/libgcc/config.host
index
b12c86267dac9da8da9e1ab4123d5171c3e07f40..e436ade1a68c6cd918d2f370b14d61682cb9fd59
100644
--- a/libgcc/config.host
+++ b/libgcc/config.host
@@ -337,23 +337,27 @@ aarch64*-*-elf | aarch64*-*-rtems*)
extra_parts="$extra_parts crtbegin.o crtend.o crti.o crtn.o"
extra_parts="$extra_parts crtfastmath.o"
tmake_file="${tmake_file} ${cpu_type}/t-aarch64"
+ tmake_file="${tmake_file} ${cpu_type}/t-lse t-slibgcc-libgcc"
tmake_file="${tmake_file} ${cpu_type}/t-softfp t-softfp t-crtfm"
md_unwind_header=aarch64/aarch64-unwind.h
;;
aarch64*-*-freebsd*)
extra_parts="$extra_parts crtfastmath.o"
tmake_file="${tmake_file} ${cpu_type}/t-aarch64"
+ tmake_file="${tmake_file} ${cpu_type}/t-lse t-slibgcc-libgcc"
tmake_file="${tmake_file} ${cpu_type}/t-softfp t-softfp t-crtfm"
md_unwind_header=aarch64/freebsd-unwind.h
;;
aarch64*-*-fuchsia*)
tmake_file="${tmake_file} ${cpu_type}/t-aarch64"
+ tmake_file="${tmake_file} ${cpu_type}/t-lse t-slibgcc-libgcc"
tmake_file="${tmake_file} ${cpu_type}/t-softfp t-softfp"
;;
aarch64*-*-linux*)
extra_parts="$extra_parts crtfastmath.o"
md_unwind_header=aarch64/linux-unwind.h
tmake_file="${tmake_file} ${cpu_type}/t-aarch64"
+ tmake_file="${tmake_file} ${cpu_type}/t-lse t-slibgcc-libgcc"
tmake_file="${tmake_file} ${cpu_type}/t-softfp t-softfp t-crtfm"
;;
alpha*-*-linux*)
diff --git a/libgcc/config/aarch64/lse-init.c b/libgcc/config/aarch64/lse-init.c
new file mode 100644
index
0000000000000000000000000000000000000000..33d2914747994a1e07dcae906f0352e64045ab02
--- /dev/null
+++ b/libgcc/config/aarch64/lse-init.c
@@ -0,0 +1,45 @@
+/* Out-of-line LSE atomics for AArch64 architecture, Init.
+ Copyright (C) 2019 Free Software Foundation, Inc.
+ Contributed by Linaro Ltd.
+
+This file is part of GCC.
+
+GCC is free software; you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free
+Software Foundation; either version 3, or (at your option) any later
+version.
+
+GCC is distributed in the hope that it will be useful, but WITHOUT ANY
+WARRANTY; without even the implied warranty of MERCHANTABILITY or
+FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
+for more details.
+
+Under Section 7 of GPL version 3, you are granted additional
+permissions described in the GCC Runtime Library Exception, version
+3.1, as published by the Free Software Foundation.
+
+You should have received a copy of the GNU General Public License and
+a copy of the GCC Runtime Library Exception along with this program;
+see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
+<http://www.gnu.org/licenses/>. */
+
+/* Define the symbol gating the LSE implementations. */
+_Bool __aarch64_have_lse_atomics
+ __attribute__((visibility("hidden"), nocommon));
+
+/* Disable initialization of __aarch64_have_lse_atomics during bootstrap. */
+#ifndef inhibit_libc
+# include <sys/auxv.h>
+
+/* Disable initialization if the system headers are too old. */
+# if defined(AT_HWCAP) && defined(HWCAP_ATOMICS)
+
+static void __attribute__((constructor))
+init_have_lse_atomics (void)
+{
+ unsigned long hwcap = getauxval (AT_HWCAP);
+ __aarch64_have_lse_atomics = (hwcap & HWCAP_ATOMICS) != 0;
+}
+
+# endif /* HWCAP */
+#endif /* inhibit_libc */
diff --git a/libgcc/config/aarch64/lse.S b/libgcc/config/aarch64/lse.S
new file mode 100644
index
0000000000000000000000000000000000000000..a5f6673596c73c497156a6f128799cc43b400504
--- /dev/null
+++ b/libgcc/config/aarch64/lse.S
@@ -0,0 +1,235 @@
+/* Out-of-line LSE atomics for AArch64 architecture.
+ Copyright (C) 2019 Free Software Foundation, Inc.
+ Contributed by Linaro Ltd.
+
+This file is part of GCC.
+
+GCC is free software; you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free
+Software Foundation; either version 3, or (at your option) any later
+version.
+
+GCC is distributed in the hope that it will be useful, but WITHOUT ANY
+WARRANTY; without even the implied warranty of MERCHANTABILITY or
+FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
+for more details.
+
+Under Section 7 of GPL version 3, you are granted additional
+permissions described in the GCC Runtime Library Exception, version
+3.1, as published by the Free Software Foundation.
+
+You should have received a copy of the GNU General Public License and
+a copy of the GCC Runtime Library Exception along with this program;
+see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
+<http://www.gnu.org/licenses/>. */
+
+/*
+ * The problem that we are trying to solve is operating system deployment
+ * of ARMv8.1-Atomics, also known as Large System Exensions (LSE).
+ *
+ * There are a number of potential solutions for this problem which have
+ * been proposed and rejected for various reasons. To recap:
+ *
+ * (1) Multiple builds. The dynamic linker will examine /lib64/atomics/
+ * if HWCAP_ATOMICS is set, allowing entire libraries to be overwritten.
+ * However, not all Linux distributions are happy with multiple builds,
+ * and anyway it has no effect on main applications.
+ *
+ * (2) IFUNC. We could put these functions into libgcc_s.so, and have
+ * a single copy of each function for all DSOs. However, ARM is concerned
+ * that the branch-to-indirect-branch that is implied by using a PLT,
+ * as required by IFUNC, is too much overhead for smaller cpus.
+ *
+ * (3) Statically predicted direct branches. This is the approach that
+ * is taken here. These functions are linked into every DSO that uses them.
+ * All of the symbols are hidden, so that the functions are called via a
+ * direct branch. The choice of LSE vs non-LSE is done via one byte load
+ * followed by a well-predicted direct branch. The functions are compiled
+ * separately to minimize code size.
+ */
+
+/* Tell the assembler to accept LSE instructions. */
+ .arch armv8-a+lse
+
+/* Declare the symbol gating the LSE implementations. */
+ .hidden __aarch64_have_lse_atomics
+
+/* Turn size and memory model defines into mnemonic fragments. */
+#if SIZE == 1
+# define S b
+# define UXT uxtb
+#elif SIZE == 2
+# define S h
+# define UXT uxth
+#elif SIZE == 4 || SIZE == 8 || SIZE == 16
+# define S
+# define UXT mov
+#else
+# error
+#endif
+
+#if MODEL == 1
+# define SUFF _relax
+# define A
+# define L
+#elif MODEL == 2
+# define SUFF _acq
+# define A a
+# define L
+#elif MODEL == 3
+# define SUFF _rel
+# define A
+# define L l
+#elif MODEL == 4
+# define SUFF _acq_rel
+# define A a
+# define L l
+#else
+# error
+#endif
+
+/* Concatenate symbols. */
+#define glue2_(A, B) A ## B
+#define glue2(A, B) glue2_(A, B)
+#define glue3_(A, B, C) A ## B ## C
+#define glue3(A, B, C) glue3_(A, B, C)
+#define glue4_(A, B, C, D) A ## B ## C ## D
+#define glue4(A, B, C, D) glue4_(A, B, C, D)
+
+/* Select the size of a register, given a regno. */
+#define x(N) glue2(x, N)
+#define w(N) glue2(w, N)
+#if SIZE < 8
+# define s(N) w(N)
+#else
+# define s(N) x(N)
+#endif
+
+#define NAME(BASE) glue4(__aarch64_, BASE, SIZE, SUFF)
+#define LDXR glue4(ld, A, xr, S)
+#define STXR glue4(st, L, xr, S)
+
+/* Temporary registers used. Other than these, only the return value
+ register (x0) and the flags are modified. */
+#define tmp0 16
+#define tmp1 17
+#define tmp2 15
+
+/* Start and end a function. */
+.macro STARTFN name
+ .text
+ .balign 16
+ .globl \name
+ .hidden \name
+ .type \name, %function
+ .cfi_startproc
+\name:
+.endm
+
+.macro ENDFN name
+ .cfi_endproc
+ .size \name, . - \name
+.endm
+
+/* Branch to LABEL if LSE is disabled. */
+.macro JUMP_IF_NOT_LSE label
+ adrp x(tmp0), __aarch64_have_lse_atomics
+ ldrb w(tmp0), [x(tmp0), :lo12:__aarch64_have_lse_atomics]
+ cbz w(tmp0), \label
+.endm
+
+#ifdef L_cas
+
+STARTFN NAME(cas)
+ JUMP_IF_NOT_LSE 8f
+
+#if SIZE < 16
+#define CAS glue4(cas, A, L, S)
+
+ CAS s(0), s(1), [x2]
+ ret
+
+8: UXT s(tmp0), s(0)
+0: LDXR s(0), [x2]
+ cmp s(0), s(tmp0)
+ bne 1f
+ STXR w(tmp1), s(1), [x2]
+ cbnz w(tmp1), 0b
+1: ret
+
+#else
+#define LDXP glue3(ld, A, xp)
+#define STXP glue3(st, L, xp)
+#define CASP glue3(casp, A, L)
+
+ CASP x0, x1, x2, x3, [x4]
+ ret
+
+8: mov x(tmp0), x0
+ mov x(tmp1), x1
+0: LDXP x0, x1, [x4]
+ cmp x0, x(tmp0)
+ ccmp x1, x(tmp1), #0, eq
+ bne 1f
+ STXP w(tmp2), x(tmp0), x(tmp1), [x4]
+ cbnz w(tmp2), 0b
+1: ret
+
+#endif
+
+ENDFN NAME(cas)
+#endif
+
+#ifdef L_swp
+#define SWP glue4(swp, A, L, S)
+
+STARTFN NAME(swp)
+ JUMP_IF_NOT_LSE 8f
+
+ SWP s(0), s(0), [x1]
+ ret
+
+8: mov s(tmp0), s(0)
+0: LDXR s(0), [x1]
+ STXR w(tmp1), s(tmp0), [x1]
+ cbnz w(tmp1), 0b
+ ret
+
+ENDFN NAME(swp)
+#endif
+
+#if defined(L_ldadd) || defined(L_ldclr) \
+ || defined(L_ldeor) || defined(L_ldset)
+
+#ifdef L_ldadd
+#define LDNM ldadd
+#define OP add
+#elif defined(L_ldclr)
+#define LDNM ldclr
+#define OP bic
+#elif defined(L_ldeor)
+#define LDNM ldeor
+#define OP eor
+#elif defined(L_ldset)
+#define LDNM ldset
+#define OP orr
+#else
+#error
+#endif
+#define LDOP glue4(LDNM, A, L, S)
+
+STARTFN NAME(LDNM)
+ JUMP_IF_NOT_LSE 8f
+
+ LDOP s(0), s(0), [x1]
+ ret
+
+8: mov s(tmp0), s(0)
+0: LDXR s(0), [x1]
+ OP s(tmp1), s(0), s(tmp0)
+ STXR w(tmp1), s(tmp1), [x1]
+ cbnz w(tmp1), 0b
+ ret
+
+ENDFN NAME(LDNM)
+#endif
diff --git a/libgcc/config/aarch64/t-lse b/libgcc/config/aarch64/t-lse
new file mode 100644
index
0000000000000000000000000000000000000000..fe3868dacbf5582146aa5824c0ce11aa5b931d52
--- /dev/null
+++ b/libgcc/config/aarch64/t-lse
@@ -0,0 +1,44 @@
+# Out-of-line LSE atomics for AArch64 architecture.
+# Copyright (C) 2019 Free Software Foundation, Inc.
+# Contributed by Linaro Ltd.
+#
+# This file is part of GCC.
+#
+# GCC is free software; you can redistribute it and/or modify it
+# under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3, or (at your option)
+# any later version.
+#
+# GCC is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+# General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with GCC; see the file COPYING3. If not see
+# <http://www.gnu.org/licenses/>.
+
+# Compare-and-swap has 5 sizes and 4 memory models.
+S0 := $(foreach s, 1 2 4 8 16, $(addsuffix _$(s), cas))
+O0 := $(foreach m, 1 2 3 4, $(addsuffix _$(m)$(objext), $(S0)))
+
+# Swap, Load-and-operate have 4 sizes and 4 memory models
+S1 := $(foreach s, 1 2 4 8, $(addsuffix _$(s), swp ldadd ldclr ldeor ldset))
+O1 := $(foreach m, 1 2 3 4, $(addsuffix _$(m)$(objext), $(S1)))
+
+LSE_OBJS := $(O0) $(O1)
+
+libgcc-objects += $(LSE_OBJS) lse-init$(objext)
+
+empty =
+space = $(empty) $(empty)
+PAT_SPLIT = $(subst _,$(space),$(*F))
+PAT_BASE = $(word 1,$(PAT_SPLIT))
+PAT_N = $(word 2,$(PAT_SPLIT))
+PAT_M = $(word 3,$(PAT_SPLIT))
+
+lse-init$(objext): $(srcdir)/config/aarch64/lse-init.c
+ $(gcc_compile) -c $<
+
+$(LSE_OBJS): $(srcdir)/config/aarch64/lse.S
+ $(gcc_compile) -DL_$(PAT_BASE) -DSIZE=$(PAT_N) -DMODEL=$(PAT_M) -c $<
