RF16: Unable to build test program with -Os

[VVIsaev]

Faced an issue with -mcpu=em_mini while testing #231. Without -Os or with -mcpu=em program builds fine.

$ module load arc_gnu/2020.09-elf32
$ arc-elf32-gcc --version
arc-elf32-gcc (ARCompact/ARCv2 ISA elf32 toolchain 2020.09) 10.2.0
Copyright (C) 2020 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

$ cat bug.c
#include <stddef.h>
#include <string.h>

int test_newlib_argv(int argc, char **argv)
{
        int i;

        const char *test_argv[] = {"a", "b", NULL};
        const int test_argc = sizeof(test_argv) / sizeof(char *);

        for (i = 0; i < argc; i++) {
                if (strcmp(argv[i], test_argv[i]) == 0)
                        return 1;
        }

        return 0;
}


int main()
{
        char *argv[] = {"a", "b", NULL};
        int argc = sizeof(argv) / sizeof(char *);

        return test_newlib_argv(argc, argv);
}
$ arc-elf32-gcc -mcpu=em_mini -Os bug.c  -o bug
/global/freeware/Linux/2.X/arc_gnu_2020.09-elf32/bin/../lib/gcc/arc-elf32/10.2.0/../../../../arc-elf32/bin/ld: /tmp/ccl8riw1.o: in function `test_newlib_argv':
bug.c:(.text+0x4): undefined reference to `__st_r13_to_r15'
/global/freeware/Linux/2.X/arc_gnu_2020.09-elf32/bin/../lib/gcc/arc-elf32/10.2.0/../../../../arc-elf32/bin/ld: bug.c:(.text+0x4): undefined reference to `__st_r13_to_r15'
/global/freeware/Linux/2.X/arc_gnu_2020.09-elf32/bin/../lib/gcc/arc-elf32/10.2.0/../../../../arc-elf32/bin/ld: bug.c:(.text+0x32): undefined reference to `__ld_r13_to_r15_ret'
/global/freeware/Linux/2.X/arc_gnu_2020.09-elf32/bin/../lib/gcc/arc-elf32/10.2.0/../../../../arc-elf32/bin/ld: bug.c:(.text+0x32): undefined reference to `__ld_r13_to_r15_ret'
collect2: error: ld returned 1 exit status
$ ls bug
ls: cannot access bug: No such file or directory
$ arc-elf32-gcc -mcpu=em -Os bug.c  -o bug
$ ls bug
bug
$ rm bug
$ arc-elf32-gcc -mcpu=em_mini bug.c -o bug
$ ls bug
bug

[claziss]

Fixed with foss-for-synopsys-dwc-arc-processors/gcc@2c3a3e1 "arc: Don't allow millicode thunks with reduced register set CPUs."