inserting instructions into prologue/epilogue

[Nathan Sidwell]

Gunther Nikl wrote:
> Hello!
> 
> I am trying to add instructions into function prologue/epilogue. These
> instructions shall save and load "fixed" registers to avoid assembly.
> 
> Register saving in the prologue appears to work. The restore code in the
> epilogue aborts in flow.c/propagate_one_insn with
> 
>   "Attempt to delete prologue/epilogue insn"
> 
> unless the stackslot was marked with MEM_VOLATILE_P. I don't think thats
> the proper fix.

you can add a (USE reg) after the restore in the prologue.  Then flow considers 
the register, and the preceding load, to be live at that point.

nathan
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