Some flags only make sense for particular target platforms.
(iX86 machines) GHC tries to “steal” four registers from GCC, for performance reasons; it almost always works. However, when GCC is compiling some modules with four stolen registers, it will crash, probably saying:
Foo.hc:533: fixed or forbidden register was spilled. This may be due to a compiler bug or to impossible asm statements or clauses.
Just give some registers back with
-monly-N-regs. Try `3' first, then `2'.
If `2' doesn't work, please report the bug to us.