Build issue "Error: operands mismatch -- statement `movec %d2,%caar' ignored" on m68k

[Thomas Petazzoni <thomas.petazzoni@xxxxxxxxxxx>]

Hello,

While trying to build the multi_defconfig, from Linux 6.12.5, for a
68040 system, the build fails with:

{standard input}: Assembler messages:
{standard input}:104: Error: operands mismatch -- statement `movec %d2,%caar' ignored
make[5]: *** [scripts/Makefile.build:229: arch/m68k/kernel/sys_m68k.o] Error 1

It seems like the 68020/68030 code:

        if (CPU_IS_020_OR_030) {
                if (scope == FLUSH_SCOPE_LINE && len < 256) {
                        unsigned long cacr;
                        __asm__ ("movec %%cacr, %0" : "=r" (cacr));
                        if (cache & FLUSH_CACHE_INSN)
                                cacr |= 4;
                        if (cache & FLUSH_CACHE_DATA)
                                cacr |= 0x400;
                        len >>= 2;
                        while (len--) {
                                __asm__ __volatile__ ("movec %1, %%caar\n\t"
                                                      "movec %0, %%cacr"
                                                      : /* no outputs */
                                                      : "r" (cacr), "r" (addr));
                                addr += 4;
                        }
                } else {
                        /* Flush the whole cache, even if page granularity requested. */
                        unsigned long cacr;
                        __asm__ ("movec %%cacr, %0" : "=r" (cacr));
                        if (cache & FLUSH_CACHE_INSN)
                                cacr |= 8;
                        if (cache & FLUSH_CACHE_DATA)
                                cacr |= 0x800;
                        __asm__ __volatile__ ("movec %0, %%cacr" : : "r" (cacr));
                }
                ret = 0;
                goto out_unlock;

gets compiled in, and binutils isn't happy about it.

The issue can trivially be reproduced by building the following
Buildroot configuration:

BR2_m68k=y
BR2_LINUX_KERNEL=y
BR2_LINUX_KERNEL_USE_ARCH_DEFAULT_CONFIG=y

Quick recipe:

$ git clone https://gitlab.com/buildroot.org/buildroot.git
$ cd buildroot/
$ cat >.config <<EOF
BR2_m68k=y
BR2_LINUX_KERNEL=y
BR2_LINUX_KERNEL_USE_ARCH_DEFAULT_CONFIG=y
EOF
$ make olddefconfig
$ make

Is this expected?

Best regards,

Thomas
-- 
Thomas Petazzoni, co-owner and CEO, Bootlin
Embedded Linux and Kernel engineering and training
https://bootlin.com