speeding up parts of gcc by using count_leading_zero (long)

[Andrew Pinski <pinskia at physics dot uc dot edu>]

There are parts of gcc which can be sped up on PPC (and other 
architectures which have something similar)  by using the instruction 
`cntlz{w,d}' (count leading zero word, double word [PPC64 only]).

Also the parts of gcc on other architectures which do not have count 
leading zero can be sped up by instead of using a for loop, a series of 
if statements:
 register int bit_num = 0;
  if (word & 0xFFFF0000)
    word >>= 16;
  else
    bit_num += 16;
  if (word & 0xFF00)
    word >>= 8;
  else
    bit_num += 8;
  if (word & 0xF0)
    word >>= 4;
  else
    bit_num += 4;
  if (word & 0xc)
    word >>= 2;
  else
    bit_num += 2;
  if (word & 0x2)
    word >>= 1;
  else
    bit_num += 1;
  if ((word & 0x1) == 0)
    bit_num += 1;
and bit_num is the result.

The functions which could benefit from this are:
function					file
_________________________________
sbitmap_first_set_bit		sbitmap.c
sbitmap_last_set_bit		sbitmap.c
bitmap_first_set_bit		bitmap.c			(this already does a series of if 
statements)
bitmap_last_set_bit		bitmap.c			(this already does a series of if 
statements)
floor_log2_wide			toplev.c
exact_log2_wide			toplev.c
compute_inverse			ggc-page.c
build_mask64_2_operands		config/rs6000/rs6000.c

This one only effects libgcc
count_leading_zero			longlong.h

also this one from libiberty
ffs						ffs.c


There might be others but these would found by doing a grep for >> and 
looking at for a counting the bits that not set until getting one that 
is set SIZEOF_INT - cntlzw (word&-word) which is the same as ffs or 
looping until the word is zero which is the same as SIZEOF_INT - cntlzw 
(word) - 1.

Where should I put the mechanism for the cntlz for HOST_WIDE_INT, int, 
HOST_WIDEST_INT (in hwint.h?) and what should I call the functions, 
count_leading_zero_wide_int, count_leading_zero_int, and 
count_leading_zero_widest_int?

Thanks,
Andrew Pinski