[Bug ports/28872] Building glibc for MIPSel single float targets

["archicharmer at mail dot ru" <sourceware-bugzilla@sourceware.org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=28872

--- Comment #12 from Den <archicharmer at mail dot ru> ---
(In reply to Adhemerval Zanella from comment #11)
> I am not really proposing it, I am in fact trying to understand what gcc
> emits in such case.  For instance,
> [...]
> 
> So I am trying to understand how/when gcc does the double emulation that
> replaces
> s.d by a two sdc1.
I'll write the part of the additions to configures for how binutils and gcc
were built.
binutils-2.34 . --target=mipsel-unknown-linux-gnu --with-arch=r6000
--with-cpu=r6000
gcc-9.2.0 . --target=mipsel-unknown-linux-gnu --with-arch=r6000
--with-float=hard --with-fpu=single

It is not actually gcc emulates s.d as a two sdc1 (swc1 attentionly) (gcc only
"rumbles" when it meets an unsupported opcode in asm volatile), I got that
conception from this:
echo 's.d $f0,($0)' >test.s
mipsel-unknown-linux-gnu-as test.s
mipsel-unknown-linux-gnu-objdump -d a.out
00000000 <.text>:
   0:   e4000000        swc1    $f0,0(zero)
   4:   e4010004        swc1    $f1,4(zero)

> Is the segfault due the patch or is it another issue in fact?
Well, I could not determine that exactly because I can not build it without the
patch. If to build a compiler without fp then everything is working fine and
there is no such SegFaults in those places.
Actually, no one existing libc can not be built for MIPSel target when there
are the single floats only, because there are the same files with same
includings to compile. Same structure of files for FPU.

> Patch is not acceptable *as-is*
I mean the patch itself, the conception in it, is doing wrong.

> I think it still possible to fix the
> context functions to correctly work on the chip you are using.
Well, that is already behind my abilities. The patch was everything I got.

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