xtensa: don't link with libgcc

libgcc may be absent or may have different ABI than the kernel. Don't
link with it. Drop declarations and export for helpers that are not
implemented. Use generic versions of DI mode multiplication and
comparisons. Drop register window spilling helper as it should never be
used by the compiler-generated code.
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

arch/xtensa/Kconfig

@@ -20,6 +20,9 @@ config XTENSA
 	select DMA_REMAP if MMU
 	select GENERIC_ATOMIC64
 	select GENERIC_IRQ_SHOW
+	select GENERIC_LIB_CMPDI2
+	select GENERIC_LIB_MULDI3
+	select GENERIC_LIB_UCMPDI2
 	select GENERIC_PCI_IOMAP
 	select GENERIC_SCHED_CLOCK
 	select HAVE_ARCH_AUDITSYSCALL

arch/xtensa/Makefile

@@ -51,13 +51,9 @@ KBUILD_CPPFLAGS += $(patsubst %,-I$(srctree)/%include,$(vardirs) $(plfdirs))
 
 KBUILD_DEFCONFIG := iss_defconfig
 
-# Find libgcc.a
-
-LIBGCC := $(shell $(CC) $(KBUILD_CFLAGS) -print-libgcc-file-name)
-
 head-y		:= arch/xtensa/kernel/head.o
 
-libs-y		+= arch/xtensa/lib/ $(LIBGCC)
+libs-y		+= arch/xtensa/lib/
 
 boot		:= arch/xtensa/boot
 

arch/xtensa/kernel/xtensa_ksyms.c

@@ -59,32 +59,18 @@ extern long long __ashldi3(long long, int);
 extern long long __lshrdi3(long long, int);
 extern int __divsi3(int, int);
 extern int __modsi3(int, int);
-extern long long __muldi3(long long, long long);
 extern int __mulsi3(int, int);
 extern unsigned int __udivsi3(unsigned int, unsigned int);
 extern unsigned int __umodsi3(unsigned int, unsigned int);
-extern unsigned long long __umoddi3(unsigned long long, unsigned long long);
-extern unsigned long long __udivdi3(unsigned long long, unsigned long long);
-extern int __ucmpdi2(int, int);
 
 EXPORT_SYMBOL(__ashldi3);
 EXPORT_SYMBOL(__ashrdi3);
 EXPORT_SYMBOL(__lshrdi3);
 EXPORT_SYMBOL(__divsi3);
 EXPORT_SYMBOL(__modsi3);
-EXPORT_SYMBOL(__muldi3);
 EXPORT_SYMBOL(__mulsi3);
 EXPORT_SYMBOL(__udivsi3);
 EXPORT_SYMBOL(__umodsi3);
-EXPORT_SYMBOL(__udivdi3);
-EXPORT_SYMBOL(__umoddi3);
-EXPORT_SYMBOL(__ucmpdi2);
-
-void __xtensa_libgcc_window_spill(void)
-{
-	BUG();
-}
-EXPORT_SYMBOL(__xtensa_libgcc_window_spill);
 
 unsigned int __sync_fetch_and_and_4(volatile void *p, unsigned int v)
 {