re PR tree-optimization/62217 (DOM confuses complete unrolling which in turn causes VRP to warn)

2015-02-18  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/62217
	* tree-ssa-dom.c (cprop_operand): Avoid propagating copies
	into BIVs.

	* gcc.dg/tree-ssa/cunroll-11.c: New testcase.

From-SVN: r220785

gcc/ChangeLog

+2015-02-18  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/62217
+	* tree-ssa-dom.c (cprop_operand): Avoid propagating copies
+	into BIVs.
+
 2015-02-18  Marek Polacek  <polacek@redhat.com>
 
 	PR sanitizer/65081

gcc/testsuite/ChangeLog

+2015-02-18  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/62217
+	* gcc.dg/tree-ssa/cunroll-11.c: New testcase.
+
 2015-02-18  Marek Polacek  <polacek@redhat.com>
 
 	PR sanitizer/65081

gcc/testsuite/gcc.dg/tree-ssa/cunroll-11.c

+/* { dg-do compile } */
+/* { dg-options "-O3 -Warray-bounds -fdump-tree-cunroll-details" } */
+
+typedef struct { unsigned data; } s1;
+s1 g_x[4];
+
+extern void foo (s1 *x1, s1 *x2, int a, int b)
+{
+  int i;
+  for(i = 0; i < a; i++)
+    if(i == b)
+      g_x[i] = *x1;
+    else
+      g_x[i] = *x2;
+}
+
+/* { dg-final { scan-tree-dump "Loop 1 iterates at most 3 times" "cunroll" } } */
+/* { dg-final { cleanup-tree-dump "cunroll" } } */

gcc/tree-ssa-dom.c

@@ -2291,11 +2291,16 @@ cprop_operand (gimple stmt, use_operand_p op_p)
       if (!may_propagate_copy (op, val))
 	return;
 
-      /* Do not propagate copies into simple IV increment statements.
-         See PR23821 for how this can disturb IV analysis.  */
-      if (TREE_CODE (val) != INTEGER_CST
-	  && simple_iv_increment_p (stmt))
-	return;
+      /* Do not propagate copies into BIVs.
+         See PR23821 and PR62217 for how this can disturb IV and
+	 number of iteration analysis.  */
+      if (TREE_CODE (val) != INTEGER_CST)
+	{
+	  gimple def = SSA_NAME_DEF_STMT (op);
+	  if (gimple_code (def) == GIMPLE_PHI
+	      && gimple_bb (def)->loop_father->header == gimple_bb (def))
+	    return;
+	}
 
       /* Dump details.  */
       if (dump_file && (dump_flags & TDF_DETAILS))