Hi!

Building for for bpf-unknown-none target, recent GCCs will issue an unused
variable warning as the REGNO_REG_CLASS macro doesn't actually use its
argument. Reference the argument as (void) to silence the warning.

.../gcc/configure --prefix=... --enable-werror-always --enable-languages=all --disable-gcov --disable-shared --disable-threads --target=bpf-unknown-none --without-headers
[...]
make V=1 all-gcc
[...]

/usr/lib/gcc-snapshot/bin/g++  -fno-PIE -c   -g -O2   -DIN_GCC  -DCROSS_DIRECTORY_STRUCTURE   -fno-exceptions -fno-rtti -fasynchronous-unwind-tables -W -Wall -Wno-narrowing -Wwrite-strings -Wcast-qual -Wmissing-format-attribute -Woverloaded-virtual -pedantic -Wno-long-long -Wno-variadic-macros -Wno-overlength-strings -Werror -fno-common  -DHAVE_CONFIG_H -I. -I. -I../../gcc/gcc -I../../gcc/gcc/. -I../../gcc/gcc/../include -I../../gcc/gcc/../libcpp/include -I../../gcc/gcc/../libcody  -I../../gcc/gcc/../libdecnumber -I../../gcc/gcc/../libdecnumber/dpd -I../libdecnumber -I../../gcc/gcc/../libbacktrace   -o regcprop.o -MT regcprop.o -MMD -MP -MF ./.deps/regcprop.TPo ../../gcc/gcc/regcprop.cc
../../gcc/gcc/regcprop.cc: In function 'bool copyprop_hardreg_forward_1(basic_block, value_data*)':
../../gcc/gcc/regcprop.cc:794:24: error: unused variable 'regno' [-Werror=unused-variable]
  794 |           unsigned int regno = REGNO (SET_SRC (set));
      |                        ^~~~~
cc1plus: all warnings being treated as errors
make[1]: *** [Makefile:1146: regcprop.o] Error 1
make[1]: Leaving directory '/var/lib/laminar/run/gcc-bpf-unknown-none/1/toolchain-build/gcc'
make: *** [Makefile:4565: all-gcc] Error 2


Ok for HEAD?

Thanks,
  Jan-Benedict

gcc/
	* config/bpf/bpf.h (REGNO_REG_CLASS): Reference arguments as (void).

diff --git a/gcc/config/bpf/bpf.h b/gcc/config/bpf/bpf.h
index 5b3f4a58763..57903477a4a 100644
--- a/gcc/config/bpf/bpf.h
+++ b/gcc/config/bpf/bpf.h
@@ -209,7 +209,7 @@ enum reg_class
    register REGNO.  In general there is more that one such class;
    choose a class which is "minimal", meaning that no smaller class
    also contains the register.  */
-#define REGNO_REG_CLASS(REGNO) GENERAL_REGS
+#define REGNO_REG_CLASS(REGNO) ((void)(REGNO), GENERAL_REGS)
 
 /* A macro whose definition is the name of the class to which a
    valid base register must belong.  A base register is one used in
--