[src/trunk]: src/sys/lib/libkern/arch/sh3 For unsignad integer division gcc u...

To: source-changes-hg%NetBSD.org@localhost
Subject: [src/trunk]: src/sys/lib/libkern/arch/sh3 For unsignad integer division gcc u...
From: uwe <uwe%NetBSD.org@localhost>
Date: Mon, 06 Apr 2020 20:55:41 +0000
details:   https://anonhg.NetBSD.org/src/rev/73b6df399c07
branches:  trunk
changeset: 767947:73b6df399c07
user:      uwe <uwe%NetBSD.org@localhost>
date:      Thu Aug 04 03:20:09 2011 +0000

description:
For unsignad integer division gcc used to emit a call to __udivsi3
"millicode" function that uses compiler-private ABI.  Newer gcc uses
heavily tuned __udivsi3_i4i that is NOT compatible with __udivsi3
because it's expected to clobber different registers.  We don't want
to link the kernel against libgcc and we don't have resources to write
heavily tuned version ourselves, so clone __udivsi3 but adjust it to
conform to the __udivsi3_i4i clobber spec.

Ditto for signed division.

You can make gcc use old routines with -mdiv=call-div1 to avoid few
extra instructions to save/restore the right registers in the signed
division funcion.

diffstat:

 sys/lib/libkern/arch/sh3/Makefile.inc  |    5 +-
 sys/lib/libkern/arch/sh3/sdivsi3_i4i.S |   85 +++++++++++++++++++++++++++
 sys/lib/libkern/arch/sh3/udivsi3_i4i.S |  102 +++++++++++++++++++++++++++++++++
 3 files changed, 191 insertions(+), 1 deletions(-)

diffs (212 lines):

diff -r 0315500b9155 -r 73b6df399c07 sys/lib/libkern/arch/sh3/Makefile.inc
--- a/sys/lib/libkern/arch/sh3/Makefile.inc     Thu Aug 04 02:38:41 2011 +0000
+++ b/sys/lib/libkern/arch/sh3/Makefile.inc     Thu Aug 04 03:20:09 2011 +0000
@@ -1,4 +1,4 @@
-#      $NetBSD: Makefile.inc,v 1.18 2009/08/14 19:23:54 dsl Exp $
+#      $NetBSD: Makefile.inc,v 1.19 2011/08/04 03:20:09 uwe Exp $
 
 SRCS+= ffs.S
 SRCS+= memset.S
@@ -6,4 +6,7 @@
 SRCS+= ashiftrt.S ashlsi3.S ashrsi3.S lshrsi3.S movstr.S movstr_i4.S
 SRCS+= movstrSI.S movstrSI12_i4.S mulsi3.S sdivsi3.S udivsi3.S
 
+# newer gcc uses different integer division millicode by default
+SRCS+=  sdivsi3_i4i.S udivsi3_i4i.S
+
 NO_SRCS+= bswap64.c
diff -r 0315500b9155 -r 73b6df399c07 sys/lib/libkern/arch/sh3/sdivsi3_i4i.S
--- /dev/null   Thu Jan 01 00:00:00 1970 +0000
+++ b/sys/lib/libkern/arch/sh3/sdivsi3_i4i.S    Thu Aug 04 03:20:09 2011 +0000
@@ -0,0 +1,85 @@
+/*     $NetBSD: sdivsi3_i4i.S,v 1.1 2011/08/04 03:20:09 uwe Exp $      */
+
+/*-
+ * Copyright (c) 1990 The Regents of the University of California.
+ * All rights reserved.
+ *
+ * This code is derived from software contributed to Berkeley by
+ * William Jolitz.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the University nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ *     from: @(#)udivsi3.s     5.1 (Berkeley) 5/15/90
+ */
+
+#include <machine/asm.h>
+#if defined(LIBC_SCCS)
+       RCSID("$NetBSD: sdivsi3_i4i.S,v 1.1 2011/08/04 03:20:09 uwe Exp $")
+#endif
+
+/* See comments in udivsi3_i4i.S */
+
+#ifdef __ELF__
+       .hidden __sdivsi3_i4i
+#endif
+
+
+/* r0 <= r4 / r5 */
+NENTRY(__sdivsi3_i4i)
+       mov     r4, r0
+       mov     r5, r1
+
+       tst     r1, r1
+       bt      .L_div_by_zero
+
+       !! this version cannot clobber r2 and r3, but can clobber macl/mach
+       lds     r2, macl
+       lds     r3, mach
+
+       mov     #0, r2
+       div0s   r2, r0
+       subc    r3, r3
+       subc    r2, r0
+       div0s   r1, r3
+#define DIVSTEP        rotcl r0; div1 r1, r3
+       /* repeat 32 times */
+       DIVSTEP; DIVSTEP; DIVSTEP; DIVSTEP; DIVSTEP; DIVSTEP; DIVSTEP; DIVSTEP;
+       DIVSTEP; DIVSTEP; DIVSTEP; DIVSTEP; DIVSTEP; DIVSTEP; DIVSTEP; DIVSTEP;
+       DIVSTEP; DIVSTEP; DIVSTEP; DIVSTEP; DIVSTEP; DIVSTEP; DIVSTEP; DIVSTEP;
+       DIVSTEP; DIVSTEP; DIVSTEP; DIVSTEP; DIVSTEP; DIVSTEP; DIVSTEP; DIVSTEP;
+#undef DIVSTEP
+       rotcl   r0
+
+       addc    r2, r0
+
+       sts     mach, r3
+       sts     macl, r2
+
+       rts
+        nop
+
+.L_div_by_zero:
+       rts
+        mov    #0, r0
diff -r 0315500b9155 -r 73b6df399c07 sys/lib/libkern/arch/sh3/udivsi3_i4i.S
--- /dev/null   Thu Jan 01 00:00:00 1970 +0000
+++ b/sys/lib/libkern/arch/sh3/udivsi3_i4i.S    Thu Aug 04 03:20:09 2011 +0000
@@ -0,0 +1,102 @@
+/*     $NetBSD: udivsi3_i4i.S,v 1.1 2011/08/04 03:20:09 uwe Exp $      */
+
+/*-
+ * Copyright (c) 1990 The Regents of the University of California.
+ * All rights reserved.
+ *
+ * This code is derived from software contributed to Berkeley by
+ * William Jolitz.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the University nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ *     from: @(#)udivsi3.s     5.1 (Berkeley) 5/15/90
+ */
+
+#include <machine/asm.h>
+#if defined(LIBC_SCCS)
+       RCSID("$NetBSD: udivsi3_i4i.S,v 1.1 2011/08/04 03:20:09 uwe Exp $")
+#endif
+
+/*
+ * XXX: uwe: this is a kludge...
+ *
+ * For unsigned integer division gcc used to emit a call to __udivsi3
+ * "millicode" function that uses compiler-private ABI.  Newer gcc
+ * uses heavily tuned __udivsi3_i4i that is NOT compatible with
+ * __udivsi3 because it's expected to clobber different registers.  We
+ * don't want to link the kernel against libgcc and we don't have
+ * resources to write heavily tuned version ourselves, so clone
+ * __udivsi3 but adjust it to conform to the __udivsi3_i4i clobber
+ * spec.
+ */
+
+/*
+ * IMPOTANT: This function is special.
+ *
+ * This function is an auxiliary function that is referenced by the
+ * code generated by gcc for integer division.  But gcc does NOT treat
+ * a call to this function as an ordinary function call w.r.t. the set
+ * of register this call clobbers.  See the definition of "udivsi3_i1"
+ * in gcc/config/sh/sh.md.
+ *
+ * Any call to this function MUST NOT clobber any registers besides r4
+ * and r0, where the result is returned.  At the time of the call the
+ * r4 contains the first argument, so we are only left with r0, and we
+ * cannot do anything meaningful using only one register.  The
+ * consequences are:
+ *
+ * . this function cannot have _PROF_PROLOGUE
+ * . this function cannot be called via PLT
+ */
+
+
+#ifdef __ELF__
+       .hidden __udivsi3_i4i
+#endif
+
+
+/* r0 <= r4 / r5 */
+NENTRY(__udivsi3_i4i)
+       tst     r5, r5
+       bt      .L_div_by_zero
+
+       mov     r4, r1          ! cannot clobber r4 in this version
+       mov     #0, r0
+       div0u
+#define DIVSTEP        rotcl r1; div1 r5, r0
+       /* repeat 32 times */
+       DIVSTEP; DIVSTEP; DIVSTEP; DIVSTEP; DIVSTEP; DIVSTEP; DIVSTEP; DIVSTEP;
+       DIVSTEP; DIVSTEP; DIVSTEP; DIVSTEP; DIVSTEP; DIVSTEP; DIVSTEP; DIVSTEP;
+       DIVSTEP; DIVSTEP; DIVSTEP; DIVSTEP; DIVSTEP; DIVSTEP; DIVSTEP; DIVSTEP;
+       DIVSTEP; DIVSTEP; DIVSTEP; DIVSTEP; DIVSTEP; DIVSTEP; DIVSTEP; DIVSTEP;
+#undef DIVSTEP
+       rotcl   r1
+
+       rts
+        mov    r1, r0
+
+.L_div_by_zero:
+       rts
+        mov    #0, r0
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