[Bug target/63228] New: -m16 doesn't work if gcc is compiled for x32

[mikulas at artax dot karlin.mff.cuni.cz]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63228

            Bug ID: 63228
           Summary: -m16 doesn't work if gcc is compiled for x32
           Product: gcc
           Version: 4.9.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: mikulas at artax dot karlin.mff.cuni.cz
              Host: x86_64-linux-gnux32
            Target: x86_64-linux-gnux32
             Build: x86_64-linux-gnux32

When gcc is configured and compiled for x32 mode (x86_64-linux-gnux32 triplet),
the flag -m16 doesn't work. The bug was reproduced on gcc-4.9.1-13 from Debian
Ports x32 distribution (https://wiki.debian.org/X32Port)

Attempting to compile or assemble anything with "gcc -m16 -march=i386" results
in this error message:
error: CPU you selected does not support x86-64 instruction set
(this error causes linux kernel 3.16.2 compilation failure)

If you remove "-march=i386", the file is compiled, but it can't be assembled,
because gcc generates incorrect assembler as if it was x86_64 target. For
example, compiling a file test.c containing "int bla(void) { return 3; }" with
"gcc -c -m16 test.c", results in these error messages:
/tmp/cc89iTZG.s: Assembler messages:
/tmp/cc89iTZG.s:9: Error: bad register name `%rbp'
/tmp/cc89iTZG.s:15: Error: bad register name `%rbp'

When gcc is configured for x86_64 mode (x86_64-unknown-linux-gnu), -m16 works
correctly.