[patch] Fix PR 49087 (was Re: Fix crash in vect_is_slp_reduction)

[Ira Rosen <IRAR@il.ibm.com>]

> >
> > No, we shouldn't arrive with a NULL use_stmt here.
>
> I think a proper fix will be to fail if there are no uses.
> I'll prepare a patch on Sunday.
>

Here is the patch. It bails out if LHS has no uses.

Bootstrapped and tested on powerpc64-suse-linux.
Committed.

Ira

ChangeLog:

	PR tree-optimization/49087
	* tree-vect-loop.c (vect_is_slp_reduction): Fail if
	LHS has no uses.

testsuite/ChangeLog:

	PR tree-optimization/49087
	* gcc.dg/vect/O3-pr49087.c: New test.


Index: tree-vect-loop.c
===================================================================
--- tree-vect-loop.c    (revision 174025)
+++ tree-vect-loop.c    (working copy)
@@ -1704,7 +1704,7 @@ vect_is_slp_reduction (loop_vec_info loop_info, gi
   tree lhs;
   imm_use_iterator imm_iter;
   use_operand_p use_p;
-  int nloop_uses, size = 0;
+  int nloop_uses, size = 0, nuses;
   bool found = false;

   if (loop != vect_loop)
@@ -1715,9 +1715,11 @@ vect_is_slp_reduction (loop_vec_info loop_info, gi
   while (1)
     {
       nloop_uses = 0;
+      nuses = 0;
       FOR_EACH_IMM_USE_FAST (use_p, imm_iter, lhs)
         {
           use_stmt = USE_STMT (use_p);
+          nuses++;
           if (is_gimple_debug (use_stmt))
             continue;

@@ -1739,6 +1741,10 @@ vect_is_slp_reduction (loop_vec_info loop_info, gi
             return false;
         }

+      /* We reached a statement with no uses.  */
+      if (nuses == 0)
+       return false;
+
       if (found)
         break;

Index: testsuite/gcc.dg/vect/O3-pr49087.c
===================================================================
--- testsuite/gcc.dg/vect/O3-pr49087.c  (revision 0)
+++ testsuite/gcc.dg/vect/O3-pr49087.c  (revision 0)
@@ -0,0 +1,37 @@
+/* { dg-do compile } */
+
+static char func2() { }
+
+struct S0
+{
+ int t;
+};
+
+int g;
+
+struct S0 s0;
+
+int
+foo (int arg)
+{
+  int *ptr = &g;
+  int i, j;
+  for (i = 0; i < 10; i += 1)
+    {
+      for (j = 0; j < 1; j += 1)
+       {
+         int k;
+         if (arg)
+           {
+             int l;
+             for (k = 1; arg < 10; arg = func2 ())
+               {
+                 return l;
+               }
+           }
+         *ptr = func2 () ^ s0.t;
+       }
+    }
+}
+
+/* { dg-final { cleanup-tree-dump "vect" } } */