[linuxsh-dev] Re: FPU in kernel (SH-4)

[NIIBE Y. <gn...@m1...>]

Masahiro Abe wrote:
 > Please don't force to use -m4-nofpu option for compiling kernel. We've
 > had a discussion in Japanese ML that "-m4-nofpu" and "-m4" are not
 > compatible in terms of passing arguments to functions. "-m4-nofpu" does
 > that in SH3 way, while "-m4" does that in SH4 way, which is different. 
 > (I can't show you details now, but Kojima-san may remember this
 > discussion.) RTLinux core module and other Realtime task module must use
 > "-m4" to be able to use FPU. "-m4-nofpu" kernel and "-m4" module can't
 > work properly together.
 > 
 > So, please consider introducing "-fno-fpudiv" or "-fidiv" for "-m4", as
 > Niibe-san proposed, and make "-m4 -fno-fpudiv" kernel and "-m4" module
 > work properly.

Exactly.  That's the point to switch use of "-m4 and -fno-fpudiv".

In short, The flag "-m4-nofpu" is not for SH-4, it's SH-3 variant
(Though I think that the name is misnomer).
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