[PATCH] Strict volatile bit-fields clean-up, Take 2

[Bernd Edlinger <bernd dot edlinger at hotmail dot de>]

Hi,

This is my proposal for ulimately getting rid of the nasty store_fixed_bit_field recursion.

IMHO, the root of the recursion trouble is here:

@@ -1007,12 +1013,8 @@ store_fixed_bit_field (rtx op0, unsigned

   if (MEM_P (op0))
     {
      mode = GET_MODE (op0);
      if (GET_MODE_BITSIZE (mode) == 0
         || GET_MODE_BITSIZE (mode)> GET_MODE_BITSIZE (word_mode))
       mode = word_mode;
       mode = get_best_mode (bitsize, bitnum, bitregion_start, bitregion_end,
                           MEM_ALIGN (op0), mode, MEM_VOLATILE_P (op0));


But, because now we always have bitregion_start and bitregion_end to limit
the access size, it is no longer necessary to restrict the largest mode, that
get_best_mode may return.

This patch is very similar to the previous patch, which split up the extract_fixed_bit_field,

This time, I just split up store_fixed_bit_field and use store_fixed_bit_field_1 to force the
strict-volatile-bitfield mode it necessary, and let get_best_mode find a mode, that is
can be used to access the field, which is no longer impacted by the memory context's selected
mode in this case.

I tried this patch with an ARM-Cross compiler and a large eCos application, to see if anything
changes in the generated code with this patch, but 2 MB of code stays binary the same,
that's a good sign.

I added the new Ada test case, and the test case from PR59134, which does no longer re-produce
after my previous C++ memory model patch, but this "fix" was more or less by chance.


Boot-Strap on X86_64-pc-linux-gnu (languages=all,ada,go) and regression-tests
still running.


Ok for trunk (when the tests succeed)?


Thanks
Bernd.

Attachment: changelog-bitfields-update-2.txt
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