[PATCH] Fix PR80974

[Richard Biener]

The following fixes PR80974 by not being too clever when preserving
SSA info during VN.  I didn't want to invent a way to unwind changes
done in this hack.

Bootstrapped and tested on x86_64-unknown-linux-gnu, applied to trunk.

Richard.

2017-06-06  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/80974
	* tree-ssa-sccvn.c (set_ssa_val_to): Do not change but only
	keep or clear leaders SSA info.

	* gcc.dg/torture/pr80974.c: New testcase.

Index: gcc/tree-ssa-sccvn.c
===================================================================
--- gcc/tree-ssa-sccvn.c	(revision 248913)
+++ gcc/tree-ssa-sccvn.c	(working copy)
@@ -3328,6 +3328,9 @@ set_ssa_val_to (tree from, tree to)
 	       == get_addr_base_and_unit_offset (TREE_OPERAND (to, 0), &toff))
 	   && coff == toff))
     {
+      if (dump_file && (dump_flags & TDF_DETAILS))
+	fprintf (dump_file, " (changed)\n");
+
       /* If we equate two SSA names we have to make the side-band info
          of the leader conservative (and remember whatever original value
 	 was present).  */
@@ -3342,22 +3345,6 @@ set_ssa_val_to (tree from, tree to)
 			 gimple_bb (SSA_NAME_DEF_STMT (to))))
 		/* Keep the info from the dominator.  */
 		;
-	      else if (SSA_NAME_IS_DEFAULT_DEF (from)
-		       || dominated_by_p_w_unex
-			    (gimple_bb (SSA_NAME_DEF_STMT (to)),
-			     gimple_bb (SSA_NAME_DEF_STMT (from))))
-		{
-		  /* Save old info.  */
-		  if (! VN_INFO (to)->info.range_info)
-		    {
-		      VN_INFO (to)->info.range_info = SSA_NAME_RANGE_INFO (to);
-		      VN_INFO (to)->range_info_anti_range_p
-			= SSA_NAME_ANTI_RANGE_P (to);
-		    }
-		  /* Use that from the dominator.  */
-		  SSA_NAME_RANGE_INFO (to) = SSA_NAME_RANGE_INFO (from);
-		  SSA_NAME_ANTI_RANGE_P (to) = SSA_NAME_ANTI_RANGE_P (from);
-		}
 	      else
 		{
 		  /* Save old info.  */
@@ -3369,6 +3356,12 @@ set_ssa_val_to (tree from, tree to)
 		    }
 		  /* Rather than allocating memory and unioning the info
 		     just clear it.  */
+		  if (dump_file && (dump_flags & TDF_DETAILS))
+		    {
+		      fprintf (dump_file, "clearing range info of ");
+		      print_generic_expr (dump_file, to);
+		      fprintf (dump_file, "\n");
+		    }
 		  SSA_NAME_RANGE_INFO (to) = NULL;
 		}
 	    }
@@ -3381,17 +3374,6 @@ set_ssa_val_to (tree from, tree to)
 			 gimple_bb (SSA_NAME_DEF_STMT (to))))
 		/* Keep the info from the dominator.  */
 		;
-	      else if (SSA_NAME_IS_DEFAULT_DEF (from)
-		       || dominated_by_p_w_unex
-			    (gimple_bb (SSA_NAME_DEF_STMT (to)),
-			     gimple_bb (SSA_NAME_DEF_STMT (from))))
-		{
-		  /* Save old info.  */
-		  if (! VN_INFO (to)->info.ptr_info)
-		    VN_INFO (to)->info.ptr_info = SSA_NAME_PTR_INFO (to);
-		  /* Use that from the dominator.  */
-		  SSA_NAME_PTR_INFO (to) = SSA_NAME_PTR_INFO (from);
-		}
 	      else if (! SSA_NAME_PTR_INFO (from)
 		       /* Handle the case of trivially equivalent info.  */
 		       || memcmp (SSA_NAME_PTR_INFO (to),
@@ -3403,14 +3385,18 @@ set_ssa_val_to (tree from, tree to)
 		    VN_INFO (to)->info.ptr_info = SSA_NAME_PTR_INFO (to);
 		  /* Rather than allocating memory and unioning the info
 		     just clear it.  */
+		  if (dump_file && (dump_flags & TDF_DETAILS))
+		    {
+		      fprintf (dump_file, "clearing points-to info of ");
+		      print_generic_expr (dump_file, to);
+		      fprintf (dump_file, "\n");
+		    }
 		  SSA_NAME_PTR_INFO (to) = NULL;
 		}
 	    }
 	}
 
       VN_INFO (from)->valnum = to;
-      if (dump_file && (dump_flags & TDF_DETAILS))
-	fprintf (dump_file, " (changed)\n");
       return true;
     }
   if (dump_file && (dump_flags & TDF_DETAILS))
Index: gcc/testsuite/gcc.dg/torture/pr80974.c
===================================================================
--- gcc/testsuite/gcc.dg/torture/pr80974.c	(nonexistent)
+++ gcc/testsuite/gcc.dg/torture/pr80974.c	(working copy)
@@ -0,0 +1,39 @@
+/* { dg-do run } */
+
+int a, b, c, d, e, f, g[4];
+
+static int fn1 ()
+{
+  int h, i;
+  if (b)
+    goto L1;
+L2:;
+   int m = a;
+   while (1)
+     {
+       int n = 2;
+       e = !f && (n = 5);
+       if (e)
+	 for (h = 0; h < 9; h++)
+	   for (i = 0; i < 6; i++)
+	     if (a)
+	       g[h] = 4;
+       if (d)
+	 goto L2;
+       a & n || b;
+L1:
+       if (a)
+	 L3:
+	     c = m;
+       if (a)
+	 goto L3;
+       if (b < 5)
+	 return 0;
+     }
+}
+
+int main ()
+{
+  fn1 ();
+  return 0; 
+}