From 09bac500fc57a399ef7df847f29c21b956280306 Mon Sep 17 00:00:00 2001
From: Jan Hubicka <hubicka@gcc.gnu.org>
Date: Thu, 28 Jul 2005 07:41:29 +0000
Subject: cfg.c (update_bb_profile_for_threading): Use RDIV.

	* cfg.c (update_bb_profile_for_threading): Use RDIV.
	(scale_bbs_frequencies_int): Likewise, assert for possible overflow.
	(scale_bbs_frequencies_gcov_type): Be more curefull about overflows and
	roundoff errors.
	* tree-cfg.c (tree_duplicate_sese_region): Use counts for updating
	profile when available.
	* update-loopch.c: New testcase.

From-SVN: r102466
---
 gcc/cfg.c | 53 +++++++++++++++++++++++++++++++++++++++++------------
 1 file changed, 41 insertions(+), 12 deletions(-)

(limited to 'gcc/cfg.c')

diff --git a/gcc/cfg.c b/gcc/cfg.c
index e6af6cf..9644132 100644
--- a/gcc/cfg.c
+++ b/gcc/cfg.c
@@ -893,11 +893,11 @@ update_bb_profile_for_threading (basic_block bb, int edge_frequency,
     }
   else if (prob != REG_BR_PROB_BASE)
     {
-      int scale = 65536 * REG_BR_PROB_BASE / prob;
+      int scale = RDIV (65536 * REG_BR_PROB_BASE, prob);
 
       FOR_EACH_EDGE (c, ei, bb->succs)
 	{
-	  c->probability = (c->probability * scale) / 65536;
+	  c->probability = RDIV (c->probability * scale, 65536);
 	  if (c->probability > REG_BR_PROB_BASE)
 	    c->probability = REG_BR_PROB_BASE;
 	}
@@ -925,16 +925,23 @@ scale_bbs_frequencies_int (basic_block *bbs, int nbbs, int num, int den)
     num = 0;
   if (num > den)
     return;
+  /* Assume that the users are producing the fraction from frequencies
+     that never grow far enought to risk arithmetic overflow.  */
+  gcc_assert (num < 65536);
   for (i = 0; i < nbbs; i++)
     {
       edge_iterator ei;
-      bbs[i]->frequency = (bbs[i]->frequency * num) / den;
+      bbs[i]->frequency = RDIV (bbs[i]->frequency * num, den);
       bbs[i]->count = RDIV (bbs[i]->count * num, den);
       FOR_EACH_EDGE (e, ei, bbs[i]->succs)
-	e->count = (e->count * num) /den;
+	e->count = RDIV (e->count * num, den);
     }
 }
 
+/* numbers smaller than this value are safe to multiply without getting
+   64bit overflow.  */
+#define MAX_SAFE_MULTIPLIER (1 << (sizeof (HOST_WIDEST_INT) * 4 - 1))
+
 /* Multiply all frequencies of basic blocks in array BBS of length NBBS
    by NUM/DEN, in gcov_type arithmetic.  More accurate than previous
    function but considerably slower.  */
@@ -944,15 +951,37 @@ scale_bbs_frequencies_gcov_type (basic_block *bbs, int nbbs, gcov_type num,
 {
   int i;
   edge e;
+  gcov_type fraction = RDIV (num * 65536, den);
 
-  for (i = 0; i < nbbs; i++)
-    {
-      edge_iterator ei;
-      bbs[i]->frequency = (bbs[i]->frequency * num) / den;
-      bbs[i]->count = RDIV (bbs[i]->count * num, den);
-      FOR_EACH_EDGE (e, ei, bbs[i]->succs)
-	e->count = (e->count * num) /den;
-    }
+  gcc_assert (fraction >= 0);
+
+  if (num < MAX_SAFE_MULTIPLIER)
+    for (i = 0; i < nbbs; i++)
+      {
+	edge_iterator ei;
+	bbs[i]->frequency = RDIV (bbs[i]->frequency * num, den);
+	if (bbs[i]->count <= MAX_SAFE_MULTIPLIER)
+	  bbs[i]->count = RDIV (bbs[i]->count * num, den);
+	else
+	  bbs[i]->count = RDIV (bbs[i]->count * fraction, 65536);
+	FOR_EACH_EDGE (e, ei, bbs[i]->succs)
+	  if (bbs[i]->count <= MAX_SAFE_MULTIPLIER)
+	    e->count = RDIV (e->count * num, den);
+	  else
+	    e->count = RDIV (e->count * fraction, 65536);
+      }
+   else
+    for (i = 0; i < nbbs; i++)
+      {
+	edge_iterator ei;
+	if (sizeof (gcov_type) > sizeof (int))
+	  bbs[i]->frequency = RDIV (bbs[i]->frequency * num, den);
+	else
+	  bbs[i]->frequency = RDIV (bbs[i]->frequency * fraction, 65536);
+	bbs[i]->count = RDIV (bbs[i]->count * fraction, 65536);
+	FOR_EACH_EDGE (e, ei, bbs[i]->succs)
+	  e->count = RDIV (e->count * fraction, 65536);
+      }
 }
 
 /* Data structures used to maintain mapping between basic blocks and
-- 
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