How to generate fpu code (not emulated) with ia16-elf-g++ compiler?

Question

I've downloaded Sourcery IA16 compiler, which is a GNU C++ compiler for 16-bit targets, and it works (although, it does not support far pointers, and have some glitches with inline asm register allocation, whatever).

But when I declare a float variable in C, the compiler says:

/tmp/ccBB3kEN.o: In function `foo()':
(.text+0x38): undefined reference to `__floatsisf'
/tmp/ccBB3kEN.o: In function `foo()':
(.text+0x44): undefined reference to `__mulsf3'
/tmp/ccBB3kEN.o: In function `foo()':
(.text+0x4c): undefined reference to `__fixsfsi'

As figure shows, by default, it wants to use soft-fpu, so I tought, I should add some compiler options to generate native FPU code. But I've failed.

Now I'm using compiler option -march=i80186, and the help says that I should add some postfix to it:

-march=CPU[,+EXTENSION...]
  Igenerate code for CPU and EXTENSION, CPU is one of:
  generic32, generic64, i386, i486, i586, i686,
  pentium, pentiumpro, pentiumii, pentiumiii, pentium4,
  prescott, nocona, core, core2, corei7, l1om, k1om,
  iamcu, k6, k6_2, athlon, opteron, k8, amdfam10,
  bdver1, bdver2, bdver3, bdver4, znver1, btver1,
  btver2
EXTENSION is combination of:
  8087, 287, 387, no87, mmx, nommx, sse, sse2, sse3,
  (etc.)

It looks like help text is not for IA16, as it does not contains 16-bit CPUs (but contains 32/64-bit ones), and also extensions do not work, I've been tried with -march=i8086,8087:

ia16-elf-g++: error: unrecognized command line option '-march=i8086,8087

Other options, like -mhard-float also does not work.

ia16-elf-g++: error: unrecognized command line option '-mhard-float'

My question is: how can I set 8086 + 8087 target for this compiler? If it does not support it, is there any other C/C++ compiler which can produce MS-DOS .com output with FPU code (on Linux or MacOS platforms)?

Answer 1

Docs are at path/to/share/doc/sourceryg++-ia16-elf/man/man1/ia16-elf-g++.1

If the target emulator or device isn't a 80{{,1}8{6,8},286} : -mfpmath=80387

Note that ia16-elf-g{++,cc} produce tiny model .COM files by default.

You can also try -march=i8086+8087, but this might only work with as.