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Re: [PATCH] Improve PR91257, specialize bitmap_ior_and_compl_into


On Tue, 30 Jul 2019, Jakub Jelinek wrote:

> On Tue, Jul 30, 2019 at 12:20:00PM +0200, Richard Biener wrote:
> > +      if (compl_p)
> > +	for (ix = 0; ix < BITMAP_ELEMENT_WORDS; ix++)
> > +	  {
> > +	    and_elt.bits[ix] = b_elt->bits[ix] & ~c_elt->bits[ix];
> > +	    overall |= and_elt.bits[ix];
> > +	  }
> > +      else
> > +	for (ix = 0; ix < BITMAP_ELEMENT_WORDS; ix++)
> > +	  {
> > +	    and_elt.bits[ix] = b_elt->bits[ix] & c_elt->bits[ix];
> > +	    overall |= and_elt.bits[ix];
> > +	  }
> 
> Might be more readable by moving the if (compl_p) into the loop,
> just guarding the single statement that is different or even use a
> BITMAP_WORD temporary to load c_elt->bits[ix] into it, then conditionally
> complement and then use unconditionally in &.

As said in the followup the patch didn't acutally work.  So here's
the open-coded variant.

Bootstrapped and tested on x86_64-unknown-linux-gnu, will commit shortly.

Richard.

2019-07-30  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/91257
	* bitmap.c (bitmap_ior_and_compl_into): Open-code.

Index: gcc/bitmap.c
===================================================================
--- gcc/bitmap.c	(revision 273906)
+++ gcc/bitmap.c	(working copy)
@@ -2367,16 +2367,75 @@ bitmap_ior_and_compl (bitmap dst, const_
 bool
 bitmap_ior_and_compl_into (bitmap a, const_bitmap b, const_bitmap c)
 {
-  bitmap_head tmp;
-  bool changed;
+  bitmap_element *a_elt = a->first;
+  const bitmap_element *b_elt = b->first;
+  const bitmap_element *c_elt = c->first;
+  bitmap_element and_elt;
+  bitmap_element *a_prev = NULL;
+  bitmap_element **a_prev_pnext = &a->first;
+  bool changed = false;
+  unsigned ix;
 
   gcc_checking_assert (!a->tree_form && !b->tree_form && !c->tree_form);
 
-  bitmap_initialize (&tmp, &bitmap_default_obstack);
-  bitmap_and_compl (&tmp, b, c);
-  changed = bitmap_ior_into (a, &tmp);
-  bitmap_clear (&tmp);
+  if (a == b)
+    return false;
+  if (bitmap_empty_p (c))
+    return bitmap_ior_into (a, b);
+  else if (bitmap_empty_p (a))
+    return bitmap_and_compl (a, b, c);
 
+  and_elt.indx = -1;
+  while (b_elt)
+    {
+      /* Advance C.  */
+      while (c_elt && c_elt->indx < b_elt->indx)
+	c_elt = c_elt->next;
+
+      const bitmap_element *and_elt_ptr;
+      if (c_elt && c_elt->indx == b_elt->indx)
+	{
+	  BITMAP_WORD overall = 0;
+	  and_elt_ptr = &and_elt;
+	  and_elt.indx = b_elt->indx;
+	  for (ix = 0; ix < BITMAP_ELEMENT_WORDS; ix++)
+	    {
+	      and_elt.bits[ix] = b_elt->bits[ix] & ~c_elt->bits[ix];
+	      overall |= and_elt.bits[ix];
+	    }
+	  if (!overall)
+	    {
+	      b_elt = b_elt->next;
+	      continue;
+	    }
+	}
+      else
+	and_elt_ptr = b_elt;
+
+      b_elt = b_elt->next;
+
+      /* Now find a place to insert AND_ELT.  */
+      do
+	{
+	  ix = a_elt ? a_elt->indx : and_elt_ptr->indx;
+          if (ix == and_elt_ptr->indx)
+	    changed = bitmap_elt_ior (a, a_elt, a_prev, a_elt,
+				      and_elt_ptr, changed);
+          else if (ix > and_elt_ptr->indx)
+	    changed = bitmap_elt_copy (a, NULL, a_prev, and_elt_ptr, changed);
+
+          a_prev = *a_prev_pnext;
+          a_prev_pnext = &a_prev->next;
+          a_elt = *a_prev_pnext;
+
+          /* If A lagged behind B/C, we advanced it so loop once more.  */
+	}
+      while (ix < and_elt_ptr->indx);
+    }
+
+  gcc_checking_assert (!a->current == !a->first);
+  if (a->current)
+    a->indx = a->current->indx;
   return changed;
 }
 


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