inserting instructions into prologue/epilogue

[Gunther Nikl]

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.

Then I used TARGET_ASM_FUNCTION_END_PROLOGUE to emit additional assembly
code. However this hook is _only_ called if prologue/epilogue instructions
are scheduled. Is that the expected behaviour? tm.texi doesn't mention this.
I tried to get rid of TARGET_ASM_FUNCTION_END_PROLOGUE by emitting the
loads as RTL, but then I also get flow.c aborts if prologue and epilogue
are scheduled. It works when not scheduling. This is the load code:

     ref = gen_rtx_SYMBOL_REF (Pmode, "symbol");
     emit_insn (gen_elf_high (reg, ref));
     emit_insn (gen_elf_low (reg, reg, ref));

How do I prevent the aborts from flow? Any help appreciated.

Gunther Nikl