MIPS: Add speculation_barrier support

speculation_barrier for MIPS needs sync+jr.hb (r2+),
so we implement __speculation_barrier in libgcc, like arm32 does.

gcc/ChangeLog:
	* config/mips/mips-protos.h (mips_emit_speculation_barrier): New
	prototype.
	* config/mips/mips.cc (speculation_barrier_libfunc): New static
	variable.
	(mips_init_libfuncs): Initialize it.
	(mips_emit_speculation_barrier): New function.
	* config/mips/mips.md (speculation_barrier): Call
	mips_emit_speculation_barrier.

libgcc/ChangeLog:
	* config/mips/lib1funcs.S: New file.
	define __speculation_barrier and include mips16.S.
	* config/mips/t-mips: define LIB1ASMSRC as mips/lib1funcs.S.
	define LIB1ASMFUNCS as _speculation_barrier.
	set version info for __speculation_barrier.
	* config/mips/libgcc-mips.ver: New file.
	* config/mips/t-mips16: don't define LIB1ASMSRC as mips16.S
	included in lib1funcs.S now.

4 files changed, 94 insertions, 2 deletions

diff --git a/libgcc/config/mips/lib1funcs.S b/libgcc/config/mips/lib1funcs.S
new file mode 100644
index 0000000..97a3655
--- /dev/null
+++ b/libgcc/config/mips/lib1funcs.S
@@ -0,0 +1,65 @@
+/* Copyright (C) 2023 Free Software Foundation, Inc.
+
+This file 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.
+
+This file 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/>.  */
+
+//#include "mips16.S"
+
+#ifdef L_speculation_barrier
+
+/* MIPS16e1 has no sync/jr.hb instructions, and MIPS16e2 lacks of jr.hb.
+   So, we use normal MIPS code here, just like what we do for __sync_*.  */
+	.set nomips16
+
+	.set noreorder
+	.globl	__speculation_barrier
+	.ent	__speculation_barrier
+
+__speculation_barrier:
+	.set	push
+#if __mips >= 2
+	sync /* complementation barrier for memory.  */
+#elif defined (__linux)
+	/* MIPS1 has no sync, while Linux can trap&emu sync.  */
+	/* FIXME: Will somebody use linux/gcc for MIPS1/baremetal?  */
+	.word 0x0000000f
+#endif
+
+
+#if __mips_isa_rev >= 1
+	/* Binutils claims that JR in R1 can do same as jr.hb.
+	   R6 changes the encoding of jr.hb.  */
+	jr.hb	$ra /* Jump with instruction hazard barrier.  */
+#else
+	/* ssnop is actually available since R5500,
+	   and it will be decoded as nop on earlier processors.
+	   gas can only recognize it with -march=mips1 since 2.21.
+	   MIPS1 to MIPSr1: R10000 have 7 stage pipeline,
+	   so 8 ssnop is sufficient to block all speculation on all CPUs.  */
+	.rept 8
+	.word	0x00000040 /* The encoding of ssnop.  */
+	.endr
+	/* jr.hb will be decoded as jr on earlier processors.  */
+	.word	0x03e00408 /* The encoding of jr.hb $ra.  */
+#endif
+	.set	pop
+	.end	__speculation_barrier
+
+	.set reorder
+#endif
diff --git a/libgcc/config/mips/libgcc-mips.ver b/libgcc/config/mips/libgcc-mips.ver
new file mode 100644
index 0000000..68f8d2b
--- /dev/null
+++ b/libgcc/config/mips/libgcc-mips.ver
@@ -0,0 +1,21 @@
+# Copyright (C) 2023 Free Software Foundation, Inc.
+#
+# 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/>.
+
+GCC_14.0 {
+  __speculation_barrier
+}
diff --git a/libgcc/config/mips/t-mips b/libgcc/config/mips/t-mips
index 4fb8e13..d05ef7c 100644
--- a/libgcc/config/mips/t-mips
+++ b/libgcc/config/mips/t-mips
@@ -7,3 +7,10 @@ softfp_truncations :=
 softfp_exclude_libgcc2 := n
 
 LIB2ADD_ST += $(srcdir)/config/mips/lib2funcs.c
+
+
+LIB1ASMSRC = mips/lib1funcs.S
+LIB1ASMFUNCS = _speculation_barrier
+
+# Version these symbols if building libgcc.so.
+SHLIB_MAPFILES += $(srcdir)/config/mips/libgcc-mips.ver
diff --git a/libgcc/config/mips/t-mips16 b/libgcc/config/mips/t-mips16
index 2bad511..5fd9d60 100644
--- a/libgcc/config/mips/t-mips16
+++ b/libgcc/config/mips/t-mips16
@@ -16,8 +16,7 @@
 # along with GCC; see the file COPYING3.  If not see
 # <http://www.gnu.org/licenses/>.
 
-LIB1ASMSRC = mips/mips16.S
-LIB1ASMFUNCS = _m16addsf3 _m16subsf3 _m16mulsf3 _m16divsf3 \
+LIB1ASMFUNCS += _m16addsf3 _m16subsf3 _m16mulsf3 _m16divsf3 \
 	_m16eqsf2 _m16nesf2 _m16gtsf2 _m16gesf2 _m16lesf2 _m16ltsf2 \
 	_m16unordsf2 \
 	_m16fltsisf _m16fix_truncsfsi _m16fltunsisf \