[PATCH] libgcc: Add forward declarations for generic library routines

[Geert Uytterhoeven <geert+renesas@xxxxxxxxx>]

With W=1 on platforms that use the generic gcc library routines
(csky/loongarch/mips/riscv/sh/xtensa):

    lib/ashldi3.c:9:19: warning: no previous prototype for '__ashldi3' [-Wmissing-prototypes]
	9 | long long notrace __ashldi3(long long u, word_type b)
	  |                   ^~~~~~~~~
      CC      lib/ashrdi3.o
    lib/ashrdi3.c:9:19: warning: no previous prototype for '__ashrdi3' [-Wmissing-prototypes]
	9 | long long notrace __ashrdi3(long long u, word_type b)
	  |                   ^~~~~~~~~
      CC      lib/cmpdi2.o
    lib/cmpdi2.c:9:19: warning: no previous prototype for '__cmpdi2' [-Wmissing-prototypes]
	9 | word_type notrace __cmpdi2(long long a, long long b)
	  |                   ^~~~~~~~
      CC      lib/lshrdi3.o
    lib/lshrdi3.c:9:19: warning: no previous prototype for '__lshrdi3' [-Wmissing-prototypes]
	9 | long long notrace __lshrdi3(long long u, word_type b)
	  |                   ^~~~~~~~~
      CC      lib/muldi3.o
    lib/muldi3.c:49:19: warning: no previous prototype for '__muldi3' [-Wmissing-prototypes]
       49 | long long notrace __muldi3(long long u, long long v)
	  |                   ^~~~~~~~
      CC      lib/ucmpdi2.o
    lib/ucmpdi2.c:8:19: warning: no previous prototype for '__ucmpdi2' [-Wmissing-prototypes]
	8 | word_type notrace __ucmpdi2(unsigned long long a, unsigned long long b)
	  |                   ^~~~~~~~~

Fix this by adding forward declarations to the common libgcc header
file.

Reported-by: kernel test robot <lkp@xxxxxxxxx>
Link: https://lore.kernel.org/oe-kbuild-all/202303272214.RxzpA6bP-lkp@xxxxxxxxx/
Signed-off-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
---
 include/linux/libgcc.h | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/include/linux/libgcc.h b/include/linux/libgcc.h
index b8dc75f0c8308bd4..fc388da6a027faaf 100644
--- a/include/linux/libgcc.h
+++ b/include/linux/libgcc.h
@@ -27,4 +27,11 @@ typedef union {
 	long long ll;
 } DWunion;
 
+long long notrace __ashldi3(long long u, word_type b);
+long long notrace __ashrdi3(long long u, word_type b);
+word_type notrace __cmpdi2(long long a, long long b);
+long long notrace __lshrdi3(long long u, word_type b);
+long long notrace __muldi3(long long u, long long v);
+word_type notrace __ucmpdi2(unsigned long long a, unsigned long long b);
+
 #endif /* __ASM_LIBGCC_H */
-- 
2.34.1