Fix more of cases where block is incorrectly marked as cold

Message ID 20180124081700.GA64093@kam.mff.cuni.cz
State New
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Series
  • Fix more of cases where block is incorrectly marked as cold
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Commit Message

Jan Hubicka Jan. 24, 2018, 8:17 a.m.
Hi,
this patch fixes another issue where basic block is incorrectly marked as
unlikely which is caught by Martin's hack to bb-reorder to insert trap
to all blocks in cold partition.

The problem solved here is that I have missed logic to set probabilities
to adjusted when doing basic arithmetic on them. While looking into this
I have also noticed that there is remaining FIXME in cfgcleanup and because
combine_with_freq was also wrong, I merged the RTL and tree tailmerging
logic.

Finally I have noticed that we do not put into cold section functions which
have local guessed profile but globally they are known to be executed 0
times.  This is the case of all functions not executed in train run wiht
profile feedback that definitly are supposed to land in cold section.
This is fixed in probably_never_executed predicate.

Bootstrapped/regtested x86_64-linux, comitted.

Honza

	* cfgcleanup.c (try_crossjump_to_edge): Use combine_with_count
	to merge probabilities.
	* predict.c (probably_never_executed): Also mark as cold functions
	with global 0 profile and guessed local profile.
	* profile-count.c (profile_probability::combine_with_count): New
	member function.
	* profile-count.h (profile_probability::operator*,
	profile_probability::operator*=, profile_probability::operator/,
	profile_probability::operator/=): Reduce precision to adjusted
	and set value to guessed on contradictory divisions.
	(profile_probability::combine_with_freq): Remove.
	(profile_probability::combine_wiht_count): Declare.
	(profile_count::force_nonzero):: Set to adjusted.
	(profile_count::probability_in):: Set quality to adjusted.
	* tree-ssa-tail-merge.c (replace_block_by): Use
	combine_with_count.

Patch

Index: cfgcleanup.c
===================================================================
--- cfgcleanup.c	(revision 256987)
+++ cfgcleanup.c	(working copy)
@@ -2130,11 +2130,9 @@  try_crossjump_to_edge (int mode, edge e1
       if (FORWARDER_BLOCK_P (s2->dest))
 	s2->dest->count -= s->count ();
 
-      /* FIXME: Is this correct? Should be rewritten to count API.  */
-      if (redirect_edges_to->count.nonzero_p () && src1->count.nonzero_p ())
-	s->probability = s->probability.combine_with_freq
-			   (redirect_edges_to->count.to_frequency (cfun),
-			    s2->probability, src1->count.to_frequency (cfun));
+      s->probability = s->probability.combine_with_count
+			  (redirect_edges_to->count,
+			   s2->probability, src1->count);
     }
 
   /* Adjust count for the block.  An earlier jump
Index: predict.c
===================================================================
--- predict.c	(revision 256987)
+++ predict.c	(working copy)
@@ -210,7 +210,7 @@  probably_never_executed (struct function
                          profile_count count)
 {
   gcc_checking_assert (fun);
-  if (count == profile_count::zero ())
+  if (count.ipa () == profile_count::zero ())
     return true;
   /* Do not trust adjusted counts.  This will make us to drop int cold section
      code with low execution count as a result of inlining. These low counts
Index: profile-count.c
===================================================================
--- profile-count.c	(revision 256987)
+++ profile-count.c	(working copy)
@@ -345,3 +345,29 @@  profile_count::from_gcov_type (gcov_type
     return ret;
   }
 
+
+/* COUNT1 times event happens with *THIS probability, COUNT2 times OTHER
+   happens with COUNT2 probablity. Return probablity that either *THIS or
+   OTHER happens.  */
+
+profile_probability
+profile_probability::combine_with_count (profile_count count1,
+					 profile_probability other,
+					 profile_count count2) const
+{
+  /* If probabilities are same, we are done.
+     If counts are nonzero we can distribute accordingly. In remaining
+     cases just avreage the values and hope for the best.  */
+  if (*this == other || count1 == count2
+      || (count2 == profile_count::zero ()
+	  && !(count1 == profile_count::zero ())))
+    return *this;
+  if (count1 == profile_count::zero () && !(count2 == profile_count::zero ()))
+    return other;
+  else if (count1.nonzero_p () || count2.nonzero_p ())
+    return *this * count1.probability_in (count1 + count2)
+	   + other * count2.probability_in (count1 + count2);
+  else
+    return *this * profile_probability::even ()
+	   + other * profile_probability::even ();
+}
Index: profile-count.h
===================================================================
--- profile-count.h	(revision 256987)
+++ profile-count.h	(working copy)
@@ -22,6 +22,7 @@  along with GCC; see the file COPYING3.
 #define GCC_PROFILE_COUNT_H
 
 struct function;
+class profile_count;
 
 /* Quality of the profile count.  Because gengtype does not support enums
    inside of classes, this is in global namespace.  */
@@ -350,7 +351,7 @@  public:
 	return profile_probability::uninitialized ();
       profile_probability ret;
       ret.m_val = RDIV ((uint64_t)m_val * other.m_val, max_probability);
-      ret.m_quality = MIN (m_quality, other.m_quality);
+      ret.m_quality = MIN (MIN (m_quality, other.m_quality), profile_adjusted);
       return ret;
     }
   profile_probability &operator*= (const profile_probability &other)
@@ -363,7 +364,7 @@  public:
       else
 	{
 	  m_val = RDIV ((uint64_t)m_val * other.m_val, max_probability);
-	  m_quality = MIN (m_quality, other.m_quality);
+	  m_quality = MIN (MIN (m_quality, other.m_quality), profile_adjusted);
 	}
       return *this;
     }
@@ -374,8 +375,14 @@  public:
       if (!initialized_p () || !other.initialized_p ())
 	return profile_probability::uninitialized ();
       profile_probability ret;
+      /* If we get probability above 1, mark it as unreliable and return 1. */
       if (m_val >= other.m_val)
-	ret.m_val = max_probability;
+	{
+	  ret.m_val = max_probability;
+          ret.m_quality = MIN (MIN (m_quality, other.m_quality),
+			       profile_guessed);
+	  return ret;
+	}
       else if (!m_val)
 	ret.m_val = 0;
       else
@@ -385,7 +392,7 @@  public:
 				 other.m_val),
 			   max_probability);
 	}
-      ret.m_quality = MIN (m_quality, other.m_quality);
+      ret.m_quality = MIN (MIN (m_quality, other.m_quality), profile_adjusted);
       return ret;
     }
   profile_probability &operator/= (const profile_probability &other)
@@ -396,8 +403,15 @@  public:
 	return *this = profile_probability::uninitialized ();
       else
 	{
+          /* If we get probability above 1, mark it as unreliable
+	     and return 1. */
 	  if (m_val > other.m_val)
-	    m_val = max_probability;
+	    {
+	      m_val = max_probability;
+              m_quality = MIN (MIN (m_quality, other.m_quality),
+			       profile_guessed);
+	      return *this;
+	    }
 	  else if (!m_val)
 	    ;
 	  else
@@ -407,7 +421,7 @@  public:
 				 other.m_val),
 			   max_probability);
 	    }
-	  m_quality = MIN (m_quality, other.m_quality);
+	  m_quality = MIN (MIN (m_quality, other.m_quality), profile_adjusted);
 	}
       return *this;
     }
@@ -465,27 +479,6 @@  public:
       return ret;
     }
 
-  profile_probability combine_with_freq (int freq1, profile_probability other,
-					 int freq2) const
-    {
-      profile_probability ret;
-
-      if (*this == profile_probability::uninitialized ()
-	  || other == profile_probability::uninitialized ())
-	return profile_probability::uninitialized ();
-
-      gcc_checking_assert (freq1 >= 0 && freq2 >= 0);
-      if (!freq1 && !freq2)
-	{
-	  ret.m_val = (m_val + other.m_val) / 2;
-	}
-      else
-	ret.m_val = RDIV (m_val * (uint64_t) freq1
-			  + other.m_val * (uint64_t) freq2, freq1 + freq2);
-      ret.m_quality = MIN (m_quality, other.m_quality);
-      return ret;
-    }
-
   /* Return *THIS * NUM / DEN.  */
   profile_probability apply_scale (int64_t num, int64_t den) const
     {
@@ -569,6 +562,12 @@  public:
   bool differs_from_p (profile_probability other) const;
   /* Return if difference is greater than 50%.  */
   bool differs_lot_from_p (profile_probability other) const;
+  /* COUNT1 times event happens with *THIS probability, COUNT2 times OTHER
+     happens with COUNT2 probablity. Return probablity that either *THIS or
+     OTHER happens.  */
+  profile_probability combine_with_count (profile_count count1,
+					  profile_probability other,
+					  profile_count count2) const;
 
   /* LTO streaming support.  */
   static profile_probability stream_in (struct lto_input_block *);
@@ -906,7 +905,10 @@  public:
 	return *this;
       profile_count ret = *this;
       if (ret.m_val == 0)
-	ret.m_val = 1;
+	{
+	  ret.m_val = 1;
+          ret.m_quality = MIN (m_quality, profile_adjusted);
+	}
       return ret;
     }
 
@@ -1062,20 +1064,28 @@  public:
      OVERALL.  */
   profile_probability probability_in (const profile_count overall) const
     {
-      if (*this == profile_count::zero ())
+      if (*this == profile_count::zero ()
+	  && !(overall == profile_count::zero ()))
 	return profile_probability::never ();
       if (!initialized_p () || !overall.initialized_p ()
 	  || !overall.m_val)
 	return profile_probability::uninitialized ();
+      if (*this == overall && m_quality == profile_precise)
+	return profile_probability::always ();
       profile_probability ret;
       gcc_checking_assert (compatible_p (overall));
 
       if (overall.m_val < m_val)
-	ret.m_val = profile_probability::max_probability;
+	{
+	  ret.m_val = profile_probability::max_probability;
+	  ret.m_quality = profile_guessed;
+	  return ret;
+	}
       else
 	ret.m_val = RDIV (m_val * profile_probability::max_probability,
 			  overall.m_val);
-      ret.m_quality = MAX (MIN (m_quality, overall.m_quality), profile_guessed);
+      ret.m_quality = MIN (MAX (MIN (m_quality, overall.m_quality),
+				profile_guessed), profile_adjusted);
       return ret;
     }
 
Index: tree-ssa-tail-merge.c
===================================================================
--- tree-ssa-tail-merge.c	(revision 256987)
+++ tree-ssa-tail-merge.c	(working copy)
@@ -1570,17 +1570,8 @@  replace_block_by (basic_block bb1, basic
 	/* If probabilities are same, we are done.
 	   If counts are nonzero we can distribute accordingly. In remaining
 	   cases just avreage the values and hope for the best.  */
-	if (e1->probability == e2->probability)
-	  ;
-	else if (bb1->count.nonzero_p () || bb2->count.nonzero_p ())
-	  e2->probability
-	     = e2->probability
-		 * bb2->count.probability_in (bb1->count + bb2->count)
-	       + e1->probability
-		 * bb1->count.probability_in (bb1->count + bb2->count);
-	else
-	  e2->probability = e2->probability * profile_probability::even ()
-			    + e1->probability * profile_probability::even ();
+	e2->probability = e1->probability.combine_with_count
+	                     (bb1->count, e2->probability, bb2->count);
       }
   bb2->count += bb1->count;