[Bug target/52394] SH Target: SH2A defunct bitops

["kkojima at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52394

--- Comment #1 from Kazumoto Kojima <kkojima at gcc dot gnu.org> 2012-02-28 00:37:56 UTC ---
I guess that now these tests require -fno-strict-volatile-bitfields,
though it isn't enough to avoid failures.  It looks that something
wrong happens in expmed.c:{store, extract}_bit_field_1 and they decide
to use slow fallback {store, extract}_fixed_bit_field instead of
generating insv/extv.

Here is suspicious part of {store, extract}_bit_field_1:

      /* Now convert from counting within UNIT to counting in EXT_MODE.  */
      if (BYTES_BIG_ENDIAN && !MEM_P (xop0))
    xbitpos += GET_MODE_BITSIZE (ext_mode) - unit;

      unit = GET_MODE_BITSIZE (ext_mode);

      /* If BITS_BIG_ENDIAN is zero on a BYTES_BIG_ENDIAN machine, we count
         "backwards" from the size of the unit we are extracting from.
     Otherwise, we count bits from the most significant on a
     BYTES/BITS_BIG_ENDIAN machine.  */

      if (BITS_BIG_ENDIAN != BYTES_BIG_ENDIAN)
    xbitpos = unit - bitsize - xbitpos;

In the problematic cases, xop0 is a QImode memory and ext_mode is SImode.
The initial value of unit is 8.  When starting xbitops is 3 and bitsize is
1 for example, these lines set xbitspos to 28!  There is no insv/extv which
inserts/extracts such bit position for QImode memory and maybe_expand_insn
for CODE_FOR_{insv, extv} fails.  Perhaps, these parts should be something
like

      /* We have been counting XBITPOS within UNIT.
     Count instead within the size of the register.  */
      if (BYTES_BIG_ENDIAN && !MEM_P (xop0))
    xbitpos += GET_MODE_BITSIZE (op_mode) - unit;

      /* If BITS_BIG_ENDIAN is zero on a BYTES_BIG_ENDIAN machine, we count
         "backwards" from the size of the unit we are inserting into.
     Otherwise, we count bits from the most significant on a
     BYTES/BITS_BIG_ENDIAN machine.  */

      if (BITS_BIG_ENDIAN != BYTES_BIG_ENDIAN)
    {
      if (!MEM_P (xop0))
        xbitpos = GET_MODE_BITSIZE (op_mode) - bitsize - xbitpos;
      else
        xbitpos = unit - bitsize - xbitpos;
    }

      unit = GET_MODE_BITSIZE (op_mode);

though I don't understand these routines well.