Re: PATCH: remove more if (0) code

["Richard Guenther" <richard dot guenther at gmail dot com>]

On undefined, Dominique Dhumieres <dominiq@lps.ens.fr> wrote:
> Revision 133848 gives:
>
>  /opt/gcc/i686-darwin/./prev-gcc/xgcc -B/opt/gcc/i686-darwin/./prev-gcc/ -B/opt/gcc/gcc4.4w/i686-apple-darwin9/bin/ -c  -g -O2 -fomit-frame-pointer -DIN_GCC   -W -Wall -Wwrite-strings -Wstrict-prototypes -Wmissing-prototypes -Wold-style-definition -Wmissing-format-attribute -pedantic -Wno-long-long -Wno-variadic-macros                                      -Wno-overlength-strings -Werror -fno-common  -DHAVE_CONFIG_H -I. -I. -I../../gcc-4.4-work/gcc -I../../gcc-4.4-work/gcc/. -I../../gcc-4.4-work/gcc/../include -I./../intl -I../../gcc-4.4-work/gcc/../libcpp/include -I/sw/include  -I../../gcc-4.4-work/gcc/../libdecnumber -I../../gcc-4.4-work/gcc/../libdecnumber/dpd -I../libdecnumber  ../../gcc-4.4-work/gcc/tree-ssa-structalias.c -o tree-ssa-structalias.o
>  cc1: warnings being treated as errors
>  ../../gcc-4.4-work/gcc/expmed.c:1849: error: 'extract_force_align_mem_bit_field' defined but not used
>  make[3]: *** [expmed.o] Error 1
>  make[3]: *** Waiting for unfinished jobs....
>  make[2]: *** [all-stage2-gcc] Error 2
>  make[1]: *** [stage2-bubble] Error 2
>  make: *** [all] Error 2
>
>  It seems that the following patch is also needed.

This is ok (and counts as obvious) with a proper ChangeLog entry.

Richard.

>  Dominique
>
>  --------------------------
>
>  --- ../_gcc_clean/gcc/expmed.c  2008-04-02 22:25:26.000000000 +0200
>  +++ ../gcc-4.4-work/gcc/expmed.c        2008-04-02 23:15:44.000000000 +0200
>  @@ -1835,151 +1835,6 @@
>    return immed_double_const (low, high, mode);
>   }
>
>
>  -/* Extract a bit field from a memory by forcing the alignment of the
>  -   memory.  This efficient only if the field spans at least 4 boundaries.
>  -
>  -   OP0 is the MEM.
>  -   BITSIZE is the field width; BITPOS is the position of the first bit.
>  -   UNSIGNEDP is true if the result should be zero-extended.  */
>  -
>  -static rtx
>  -extract_force_align_mem_bit_field (rtx op0, unsigned HOST_WIDE_INT bitsize,
>  -                                  unsigned HOST_WIDE_INT bitpos,
>  -                                  int unsignedp)
>  -{
>  -  enum machine_mode mode, dmode;
>  -  unsigned int m_bitsize, m_size;
>  -  unsigned int sign_shift_up, sign_shift_dn;
>  -  rtx base, a1, a2, v1, v2, comb, shift, result, start;
>  -
>  -  /* Choose a mode that will fit BITSIZE.  */
>  -  mode = smallest_mode_for_size (bitsize, MODE_INT);
>  -  m_size = GET_MODE_SIZE (mode);
>  -  m_bitsize = GET_MODE_BITSIZE (mode);
>  -
>  -  /* Choose a mode twice as wide.  Fail if no such mode exists.  */
>  -  dmode = mode_for_size (m_bitsize * 2, MODE_INT, false);
>  -  if (dmode == BLKmode)
>  -    return NULL;
>  -
>  -  do_pending_stack_adjust ();
>  -  start = get_last_insn ();
>  -
>  -  /* At the end, we'll need an additional shift to deal with sign/zero
>  -     extension.  By default this will be a left+right shift of the
>  -     appropriate size.  But we may be able to eliminate one of them.  */
>  -  sign_shift_up = sign_shift_dn = m_bitsize - bitsize;
>  -
>  -  if (STRICT_ALIGNMENT)
>  -    {
>  -      base = plus_constant (XEXP (op0, 0), bitpos / BITS_PER_UNIT);
>  -      bitpos %= BITS_PER_UNIT;
>  -
>  -      /* We load two values to be concatenate.  There's an edge condition
>  -        that bears notice -- an aligned value at the end of a page can
>  -        only load one value lest we segfault.  So the two values we load
>  -        are at "base & -size" and "(base + size - 1) & -size".  If base
>  -        is unaligned, the addresses will be aligned and sequential; if
>  -        base is aligned, the addresses will both be equal to base.  */
>  -
>  -      a1 = expand_simple_binop (Pmode, AND, force_operand (base, NULL),
>  -                               GEN_INT (-(HOST_WIDE_INT)m_size),
>  -                               NULL, true, OPTAB_LIB_WIDEN);
>  -      mark_reg_pointer (a1, m_bitsize);
>  -      v1 = gen_rtx_MEM (mode, a1);
>  -      set_mem_align (v1, m_bitsize);
>  -      v1 = force_reg (mode, validize_mem (v1));
>  -
>  -      a2 = plus_constant (base, GET_MODE_SIZE (mode) - 1);
>  -      a2 = expand_simple_binop (Pmode, AND, force_operand (a2, NULL),
>  -                               GEN_INT (-(HOST_WIDE_INT)m_size),
>  -                               NULL, true, OPTAB_LIB_WIDEN);
>  -      v2 = gen_rtx_MEM (mode, a2);
>  -      set_mem_align (v2, m_bitsize);
>  -      v2 = force_reg (mode, validize_mem (v2));
>  -
>  -      /* Combine these two values into a double-word value.  */
>  -      if (m_bitsize == BITS_PER_WORD)
>  -       {
>  -         comb = gen_reg_rtx (dmode);
>  -         emit_insn (gen_rtx_CLOBBER (VOIDmode, comb));
>  -         emit_move_insn (gen_rtx_SUBREG (mode, comb, 0), v1);
>  -         emit_move_insn (gen_rtx_SUBREG (mode, comb, m_size), v2);
>  -       }
>  -      else
>  -       {
>  -         if (BYTES_BIG_ENDIAN)
>  -           comb = v1, v1 = v2, v2 = comb;
>  -         v1 = convert_modes (dmode, mode, v1, true);
>  -         if (v1 == NULL)
>  -           goto fail;
>  -         v2 = convert_modes (dmode, mode, v2, true);
>  -         v2 = expand_simple_binop (dmode, ASHIFT, v2, GEN_INT (m_bitsize),
>  -                                   NULL, true, OPTAB_LIB_WIDEN);
>  -         if (v2 == NULL)
>  -           goto fail;
>  -         comb = expand_simple_binop (dmode, IOR, v1, v2, NULL,
>  -                                     true, OPTAB_LIB_WIDEN);
>  -         if (comb == NULL)
>  -           goto fail;
>  -       }
>  -
>  -      shift = expand_simple_binop (Pmode, AND, base, GEN_INT (m_size - 1),
>  -                                  NULL, true, OPTAB_LIB_WIDEN);
>  -      shift = expand_mult (Pmode, shift, GEN_INT (BITS_PER_UNIT), NULL, 1);
>  -
>  -      if (bitpos != 0)
>  -       {
>  -         if (sign_shift_up <= bitpos)
>  -           bitpos -= sign_shift_up, sign_shift_up = 0;
>  -         shift = expand_simple_binop (Pmode, PLUS, shift, GEN_INT (bitpos),
>  -                                      NULL, true, OPTAB_LIB_WIDEN);
>  -       }
>  -    }
>  -  else
>  -    {
>  -      unsigned HOST_WIDE_INT offset = bitpos / BITS_PER_UNIT;
>  -      bitpos %= BITS_PER_UNIT;
>  -
>  -      /* When strict alignment is not required, we can just load directly
>  -        from memory without masking.  If the remaining BITPOS offset is
>  -        small enough, we may be able to do all operations in MODE as
>  -        opposed to DMODE.  */
>  -      if (bitpos + bitsize <= m_bitsize)
>  -       dmode = mode;
>  -      comb = adjust_address (op0, dmode, offset);
>  -
>  -      if (sign_shift_up <= bitpos)
>  -       bitpos -= sign_shift_up, sign_shift_up = 0;
>  -      shift = GEN_INT (bitpos);
>  -    }
>  -
>  -  /* Shift down the double-word such that the requested value is at bit 0.  */
>  -  if (shift != const0_rtx)
>  -    comb = expand_simple_binop (dmode, unsignedp ? LSHIFTRT : ASHIFTRT,
>  -                               comb, shift, NULL, unsignedp, OPTAB_LIB_WIDEN);
>  -  if (comb == NULL)
>  -    goto fail;
>  -
>  -  /* If the field exactly matches MODE, then all we need to do is return the
>  -     lowpart.  Otherwise, shift to get the sign bits set properly.  */
>  -  result = force_reg (mode, gen_lowpart (mode, comb));
>  -
>  -  if (sign_shift_up)
>  -    result = expand_simple_binop (mode, ASHIFT, result,
>  -                                 GEN_INT (sign_shift_up),
>  -                                 NULL_RTX, 0, OPTAB_LIB_WIDEN);
>  -  if (sign_shift_dn)
>  -    result = expand_simple_binop (mode, unsignedp ? LSHIFTRT : ASHIFTRT,
>  -                                 result, GEN_INT (sign_shift_dn),
>  -                                 NULL_RTX, 0, OPTAB_LIB_WIDEN);
>  -
>  -  return result;
>  -
>  - fail:
>  -  delete_insns_since (start);
>  -  return NULL;
>  -}
>
>   /* Extract a bit field that is split across two words
>     and return an RTX for the result.
>