[RFC] Fix unwind info for sparc -mflat

Richard Henderson rth@twiddle.net
Tue Jun 21 01:00:00 GMT 2011


The current code generation for -mflat uses 3 insn patterns
which emit up two three insns (sort of) emulating the save
instruction.

The problem is that the unwind info is only produced at the
end of any pattern, leaving a 1 or 2 insn hole for which the
unwind info is not correct.

I tried to figure out why things had been done in this
slightly convoluted manner and failed.  It seems to me that
this is easily represented with the individual instructions.
A comment indicated that there had been problems with the
copy to %o7 being deleted.  Elsewhere we have successfully
used a naked USE pattern to keep such things from being
deleted.

Unfortunately, I can't seem to get -mflat to bootstrap on
gcc62 (as sparc-linux, not sparc64) either before or after
this patch, so I'm not sure what sort of pre-requisite I'm
missing in order to be able to test it...

Comments?


r~
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