[RFA] pretty-ipa merge 7: bitmap_last_set_bit

[Jan Hubicka <hubicka at ucw dot cz>]

Hi,
bootstrapped/regtested x86_64-linux together with the EHcleanup patches
using the function. OK?
	* bitmap.c (bitmap_last_set_bit): New function.
	* bitmap.h (bitmap_last_set_bit): Declare.
Index: bitmap.c
===================================================================
*** bitmap.c	(revision 145204)
--- bitmap.c	(working copy)
*************** bitmap_first_set_bit (const_bitmap a)
*** 806,811 ****
--- 806,859 ----
  #endif
   return bit_no;
  }
+ 
+ /* Return the bit number of the first set bit in the bitmap.  The
+    bitmap must be non-empty.  */
+ 
+ unsigned
+ bitmap_last_set_bit (const_bitmap a)
+ {
+   const bitmap_element *elt = a->current ? a->current : a->first;
+   unsigned bit_no;
+   BITMAP_WORD word;
+   int ix;
+ 
+   gcc_assert (elt);
+   while (elt->next)
+     elt = elt->next;
+   bit_no = elt->indx * BITMAP_ELEMENT_ALL_BITS;
+   for (ix = BITMAP_ELEMENT_WORDS - 1; ix >= 0; ix--)
+     {
+       word = elt->bits[ix];
+       if (word)
+ 	goto found_bit;
+     }
+   gcc_unreachable ();
+  found_bit:
+   bit_no += ix * BITMAP_WORD_BITS;
+ 
+   /* Binary search for the last set bit.  */
+ #if BITMAP_WORD_BITS > 64
+ #error "Fill out the table."
+ #endif
+ #if BITMAP_WORD_BITS > 32
+   if ((word & 0xffffffff00000000))
+     word >>= 32, bit_no += 32;
+ #endif
+   if (word & 0xffff0000)
+     word >>= 16, bit_no += 16;
+   if (!(word & 0xff00))
+     word >>= 8, bit_no += 8;
+   if (!(word & 0xf0))
+     word >>= 4, bit_no += 4;
+   if (!(word & 12))
+     word >>= 2, bit_no += 2;
+   if (!(word & 2))
+     word >>= 1, bit_no += 1;
+ 
+  gcc_assert (word & 1);
+  return bit_no;
+ }
  
  
  /* DST = A & B.  */
Index: bitmap.h
===================================================================
*** bitmap.h	(revision 145204)
--- bitmap.h	(working copy)
*************** extern void bitmap_obstack_free (bitmap)
*** 183,188 ****
--- 183,189 ----
  #define dump_bitmap(file, bitmap) bitmap_print (file, bitmap, "", "\n")
  #define bitmap_zero(a) bitmap_clear (a)
  extern unsigned bitmap_first_set_bit (const_bitmap);
+ extern unsigned bitmap_last_set_bit (const_bitmap);
  
  /* Compute bitmap hash (for purposes of hashing etc.)  */
  extern hashval_t bitmap_hash(const_bitmap);