[Buildroot] [PATCH v6 1/4] infra: add support for MIPS NaN

Thomas Petazzoni thomas.petazzoni at free-electrons.com
Mon Jul 17 12:11:11 UTC 2017


On Mon, 17 Jul 2017 13:03:05 +0100, Vicente Olivert Riera wrote:

> > Is it because the gcc of this external toolchain is too old ?  
> Yes, the -mnan= option was introduced in gcc 4.9.0 by this commit:
> 0bd32132d471995f3e333138363d1d928a9dde60
> The gcc of that external toolchain is 4.8.2.

OK, that explains it.

> > What can we do about this ?  
> I guess we could use an option called BR2_GCC_SUPPORTS_MNAN in order to
> avoid adding the -mnan option to the CFLAGS and to the tc-wrapper if the
> external toolchain hasn't selected that option. For internal toolchain,
> since the oldest gcc version we support is 4.9.4, then it should be
> always selected.

Sounds good to me. I guess those older gcc versions (4.8 and before)
anyway only supported the legacy NaN encoding, and therefore behave as
if -mnan=legacy is passed, correct?

You might also want to check if the same problem will happen (or not)
for the FP32 mode, and the DSP/MSA options :)


Thomas Petazzoni, CTO, Free Electrons
Embedded Linux and Kernel engineering

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