From: law <law@138bc75d-0d04-0410-961f-82ee72b054a4>
Date: Tue, 22 Dec 2015 21:49:12 +0000 (+0000)
Subject: [PATCH] Avoid unnecessary block copying in path splitting
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=fc7a3a00ad5089bd13f7e4646f7a319e7eee407c;p=thirdparty%2Fgcc.git

[PATCH] Avoid unnecessary block copying in path splitting

	* gimple-ssa-split-paths.c (split_paths): Avoid unnecessary block
	copying.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@231915 138bc75d-0d04-0410-961f-82ee72b054a4
---

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 73ab7d408189..5e1e8192949c 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,8 @@
+2015-12-22  Jeff Law  <law@redhat.com>
+
+	* gimple-ssa-split-paths.c (split_paths): Avoid unnecessary block
+	copying.
+
 2015-12-22  Jakub Jelinek  <jakub@redhat.com>
 
 	PR c++/67376
diff --git a/gcc/gimple-ssa-split-paths.c b/gcc/gimple-ssa-split-paths.c
index 540fdf3c33aa..294a1afb3fcc 100644
--- a/gcc/gimple-ssa-split-paths.c
+++ b/gcc/gimple-ssa-split-paths.c
@@ -192,9 +192,10 @@ split_paths ()
 
       /* BB is the merge point for an IF-THEN-ELSE we want to transform.
 
-	 Essentially we want to create two duplicates of BB and append
-	 a duplicate to the THEN and ELSE clauses.  This will split the
-	 path leading to the latch.  BB will be unreachable and removed.  */
+	 Essentially we want to create a duplicate of bb and redirect the
+	 first predecessor of BB to the duplicate (leaving the second
+	 predecessor as is.  This will split the path leading to the latch
+	 re-using BB to avoid useless copying.  */
       if (bb && is_feasible_trace (bb))
 	{
 	  if (dump_file && (dump_flags & TDF_DETAILS))
@@ -202,9 +203,7 @@ split_paths ()
 		     "Duplicating join block %d into predecessor paths\n",
 		     bb->index);
 	  basic_block pred0 = EDGE_PRED (bb, 0)->src;
-	  basic_block pred1 = EDGE_PRED (bb, 1)->src;
 	  transform_duplicate (pred0, bb);
-	  transform_duplicate (pred1, bb);
 	  changed = true;
 	}
     }