[Gnewsense-dev] binutils which works around loongson2f NOP bug by default

[Mark H Weaver]

Hello all,

I would like to propose that gNewSense should include an assembler
which works around the loongson2f NOP bug by default, without having
to explicitly pass any additional compiler flags.

The workaround does not add any significant overhead, and will work
just fine on other MIPS-based systems.  There are a great variety of
build systems out there, including simple Makefiles which would have
to be edited by hand.  It would be an enormous amount of work to
create and maintain a delta for each individual source package to
compile with the new flags.  Anyway, users should be able to use the
compiler without any special flags to produce executables which do not
cause hard lockups.

I have prepared new packages based on binutils-2.20-4~bpo50+1 from
lenny-backports, with the following changes:

* Backported workarounds for loongson2f bugs from binutils CVS.

* Added --enable-fix-loongson2f-nop option to gas/configure,
  which makes -mfix-loongson2f-nop the default for MIPS targets
  (unless overridden by -mnofix-loongson2f-nop).

* Pass --enable-fix-loongson2f-nop by default from debian/rules.

* Fixed some tests in the testsuites to take into account the new
  behavior wrt loongson2f workarounds.

I have attached a patch relative to binutils-2.20-4~bpo50+1.  Note
that I don't have previous experience modifying Debian source
packages, so I've probably done some things suboptimally.

I've also built binary packages for mipsel and placed them in
fencepost.gnu.org:~mhw/binutils-metad/

These binary packages have been bootstrapped on a Yeeloong with metad,
using an earlier build of the same binutils packages.

Ideally, I'd like to submit a patch to the upstream binutils to
support the --enable-fix-loongson2f-nop configure option, so
eventually the only delta for gNewSense would be to pass that option
from debian/rules.

What do you all think of this idea?

   Thanks,
     Mark

binutils-2.20-loongson-patch-2
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