m68k: Use kernel's generic muldi3 libgcc function

Use the kernels own generic lib/muldi3.c implementation of muldi3 for
68K machines. Some 68K CPUs support 64bit multiplies so move the arch
specific umul_ppmm() macro into a header file that is included by
lib/muldi3.c. That way it can take advantage of the single instruction
when available.

There does not appear to be any existing mechanism for the generic
lib/muldi3.c code to pick up an external arch definition of umul_ppmm().
Create an arch specific libgcc.h that can optionally be included by
the system include/linux/libgcc.h to allow for this.

Somewhat oddly there is also a similar definition of umul_ppmm() in
the non-architecture code in lib/crypto/mpi/longlong.h for a wide range
or machines. Its presence ends up complicating the include setup and
means not being able to use something like compiler.h instead. Actually
there is a few other defines of umul_ppmm() macros spread around in
various architectures, but not directly usable for the m68k case.

Signed-off-by: Greg Ungerer <[e-mail]>
Link: https://lore.kernel.org/[e-mail]
Reviewed-by: Geert Uytterhoeven <[e-mail]>
Reviewed-by: Arnd Bergmann <[e-mail]>
Signed-off-by: Geert Uytterhoeven <[e-mail]>

arch/Kconfig

···
 	  linux/compiler-*.h in order to override macro definitions that those
 	  headers generally provide.
 
+config HAVE_ARCH_LIBGCC_H
+	bool
+	help
+	  An architecture can select this if it provides an
+	  asm/libgcc.h header that should be included after
+	  linux/libgcc.h in order to override macro definitions that
+	  header generally provides.
+
 config HAVE_ARCH_PREL32_RELOCATIONS
 	bool
 	help

arch/m68k/Kconfig

···
 	select GENERIC_LIB_ASHLDI3
 	select GENERIC_LIB_ASHRDI3
 	select GENERIC_LIB_LSHRDI3
+	select GENERIC_LIB_MULDI3
 	select HAS_IOPORT if PCI || ISA || ATARI_ROM_ISA
+	select HAVE_ARCH_LIBGCC_H
 	select HAVE_ARCH_SECCOMP
 	select HAVE_ARCH_SECCOMP_FILTER
 	select HAVE_ASM_MODVERSIONS

arch/m68k/include/asm/libgcc.h

···
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __ASM_M68K_LIBGCC_H
+#define __ASM_M68K_LIBGCC_H
+
+#ifndef CONFIG_CPU_HAS_NO_MULDIV64
+/*
+ * For those 68K CPUs that support 64bit multiply define umul_ppm()
+ * for the common muldi3 libgcc helper function (in lib/muldi3.c).
+ * CPUs that don't have it (like the original 68000 and ColdFire)
+ * will fallback to using the C-coded version of umul_ppmm().
+ */
+#define umul_ppmm(w1, w0, u, v)				\
+	__asm__ ("mulu%.l %3,%1:%0"			\
+		 : "=d" ((unsigned long)(w0)),		\
+		   "=d" ((unsigned long)(w1))		\
+		 : "%0" ((unsigned long)(u)),		\
+		   "dmi" ((unsigned long)(v)))
+#endif /* !CONFIG_CPU_HAS_NO_MULDIV64 */
+
+#endif /* __ASM_M68K_LIBGCC_H */

arch/m68k/lib/Makefile

···
 # Makefile for m68k-specific library files..
 #
 
-lib-y	:= muldi3.o memcpy.o memset.o memmove.o
+lib-y	:= memcpy.o memset.o memmove.o
 
 lib-$(CONFIG_MMU) += uaccess.o
 lib-$(CONFIG_CPU_HAS_NO_MULDIV64) += mulsi3.o divsi3.o udivsi3.o

arch/m68k/lib/muldi3.c

···
-/* muldi3.c extracted from gcc-2.7.2.3/libgcc2.c and 
-			   gcc-2.7.2.3/longlong.h which is: */
-/* Copyright (C) 1989, 1992, 1993, 1994, 1995 Free Software Foundation, Inc.
-
-This file is part of GNU CC.
-
-GNU CC 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 2, or (at your option)
-any later version.
-
-GNU CC 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. */
-
-#include <linux/compiler.h>
-#include <linux/export.h>
-#include <linux/libgcc.h>
-
-#ifdef CONFIG_CPU_HAS_NO_MULDIV64
-
-#define SI_TYPE_SIZE 32
-#define __BITS4 (SI_TYPE_SIZE / 4)
-#define __ll_B (1L << (SI_TYPE_SIZE / 2))
-#define __ll_lowpart(t) ((USItype) (t) % __ll_B)
-#define __ll_highpart(t) ((USItype) (t) / __ll_B)
-
-#define umul_ppmm(w1, w0, u, v)						\
-  do {									\
-    USItype __x0, __x1, __x2, __x3;					\
-    USItype __ul, __vl, __uh, __vh;					\
-									\
-    __ul = __ll_lowpart (u);						\
-    __uh = __ll_highpart (u);						\
-    __vl = __ll_lowpart (v);						\
-    __vh = __ll_highpart (v);						\
-									\
-    __x0 = (USItype) __ul * __vl;					\
-    __x1 = (USItype) __ul * __vh;					\
-    __x2 = (USItype) __uh * __vl;					\
-    __x3 = (USItype) __uh * __vh;					\
-									\
-    __x1 += __ll_highpart (__x0);/* this can't give carry */		\
-    __x1 += __x2;		/* but this indeed can */		\
-    if (__x1 < __x2)		/* did we get it? */			\
-      __x3 += __ll_B;		/* yes, add it in the proper pos. */	\
-									\
-    (w1) = __x3 + __ll_highpart (__x1);					\
-    (w0) = __ll_lowpart (__x1) * __ll_B + __ll_lowpart (__x0);		\
-  } while (0)
-
-#else
-
-#define umul_ppmm(w1, w0, u, v) \
-  __asm__ ("mulu%.l %3,%1:%0"						\
-           : "=d" ((USItype)(w0)),					\
-             "=d" ((USItype)(w1))					\
-           : "%0" ((USItype)(u)),					\
-             "dmi" ((USItype)(v)))
-
-#endif
-
-#define __umulsidi3(u, v) \
-  ({DIunion __w;							\
-    umul_ppmm (__w.s.high, __w.s.low, u, v);				\
-    __w.ll; })
-
-typedef 	 int SItype	__mode(SI);
-typedef unsigned int USItype	__mode(SI);
-typedef		 int DItype	__mode(DI);
-typedef int word_type           __mode(__word__);
-
-struct DIstruct {SItype high, low;};
-
-typedef union
-{
-  struct DIstruct s;
-  DItype ll;
-} DIunion;
-
-DItype
-__muldi3 (DItype u, DItype v)
-{
-  DIunion w;
-  DIunion uu, vv;
-
-  uu.ll = u;
-  vv.ll = v;
-
-  w.ll = __umulsidi3 (uu.s.low, vv.s.low);
-  w.s.high += ((USItype) uu.s.low * (USItype) vv.s.high
-	       + (USItype) uu.s.high * (USItype) vv.s.low);
-
-  return w.ll;
-}
-EXPORT_SYMBOL(__muldi3);

include/linux/libgcc.h

···
 long long notrace __muldi3(long long u, long long v);
 word_type notrace __ucmpdi2(unsigned long long a, unsigned long long b);
 
+#ifdef CONFIG_HAVE_ARCH_LIBGCC_H
+#include <asm/libgcc.h>
+#endif
+
 #endif /* __ASM_LIBGCC_H */