[PATCH] Fix PR87217

[Richard Biener <rguenther at suse dot de>]

This re-introduces the region boundary checking for the alias walk.  It's
really also necessary for correctness, not only for compile-time.

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

Richard.

2018-09-05  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/87217
	* tree-ssa-sccvn.c (vuse_valueize): New.
	(vn_reference_lookup_pieces): Use it.
	(vn_reference_lookup): Likewise.

	* gfortran.dg/pr87217.f: New testcase.

Index: gcc/tree-ssa-sccvn.c
===================================================================
--- gcc/tree-ssa-sccvn.c	(revision 264102)
+++ gcc/tree-ssa-sccvn.c	(working copy)
@@ -493,6 +493,25 @@ vuse_ssa_val (tree x)
   return x;
 }
 
+/* Similar to the above but used as callback for walk_non_aliases_vuses
+   and thus should stop at unvisited VUSE to not walk across region
+   boundaries.  */
+
+static tree
+vuse_valueize (tree vuse)
+{
+  do
+    {
+      bool visited;
+      vuse = SSA_VAL (vuse, &visited);
+      if (!visited)
+	return NULL_TREE;
+      gcc_assert (vuse != VN_TOP);
+    }
+  while (SSA_NAME_IN_FREE_LIST (vuse));
+  return vuse;
+}
+
 
 /* Return the vn_kind the expression computed by the stmt should be
    associated with.  */
@@ -2573,7 +2592,7 @@ vn_reference_lookup_pieces (tree vuse, a
 	  (vn_reference_t)walk_non_aliased_vuses (&r, vr1.vuse,
 						  vn_reference_lookup_2,
 						  vn_reference_lookup_3,
-						  vuse_ssa_val, &vr1);
+						  vuse_valueize, &vr1);
       gcc_checking_assert (vr1.operands == shared_lookup_references);
     }
 
@@ -2629,7 +2648,7 @@ vn_reference_lookup (tree op, tree vuse,
 	(vn_reference_t)walk_non_aliased_vuses (&r, vr1.vuse,
 						vn_reference_lookup_2,
 						vn_reference_lookup_3,
-						vuse_ssa_val, &vr1);
+						vuse_valueize, &vr1);
       gcc_checking_assert (vr1.operands == shared_lookup_references);
       if (wvnresult)
 	{
Index: gcc/testsuite/gfortran.dg/pr87217.f
===================================================================
--- gcc/testsuite/gfortran.dg/pr87217.f	(nonexistent)
+++ gcc/testsuite/gfortran.dg/pr87217.f	(working copy)
@@ -0,0 +1,32 @@
+! { dg-do compile }
+! { dg-options "-O3" }
+      implicit real*8 (a-h,o-z)
+      common clop6(3),dps(6),aml6(6,6)
+      dimension y1(3)
+      dimension dclo(3)
+      dimension dx(3),dy(3)
+      save
+      do 80 ii=1,itco
+        y1(3)=dps(1)
+        do 40 l=1,3
+          dy(l)=clop6(l)-y1(l)
+   40   continue
+        dczp=abs(dy(3))
+        if(dcx.le.c1m10.and.dcz.le.c1m10.and.dcxp.le.c1m10.and.dczp
+     +  .le.c1m10.and.dcy.le.c1m10.and.dcyp.le.c1m10) goto 90
+   80 continue
+      write(6) itco
+      ii=itco
+   90 continue
+      if(ii.ne.itco) then
+        do 65 k=1,3
+          do 55 j=1,3
+            jj=2*j
+            kk=2*k
+            dclo(k)=aml6(kk-1,jj-1)*dx(j)+dclo(k)
+            dclo(k)=aml6(kk-1,jj)*dy(j)+dclo(k)
+   55     continue
+   65   continue
+      endif
+      end
+