[PATCH] Fix PR79244

[Richard Biener]

The following restores forceful propagation of assert-exprs from SSA
names which we know will restore valid IL even if the source is
abnormal.

Bootstrapped on x86_64-unknown-linux-gnu, testing in progress.

Richard.

2017-01-27  Richard Biener  <rguent...@suse.de>

        PR tree-optimization/79244
        * tree-vrp.c (remove_range_assertions): Forcefully propagate
        out SSA names even if abnormal.

        * gcc.dg/torture/pr79244.c: New testcase.

Index: gcc/tree-vrp.c
===================================================================
--- gcc/tree-vrp.c      (revision 244963)
+++ gcc/tree-vrp.c      (working copy)
@@ -6974,8 +7050,20 @@ remove_range_assertions (void)
                  }
              }
 
-           /* Propagate the RHS into every use of the LHS.  */
-           replace_uses_by (lhs, var);
+           /* Propagate the RHS into every use of the LHS.  For SSA names
+              also propagate abnormals as it merely restores the original
+              IL in this case (an replace_uses_by would assert).  */
+           if (TREE_CODE (var) == SSA_NAME)
+             {
+               imm_use_iterator iter;
+               use_operand_p use_p;
+               gimple *use_stmt;
+               FOR_EACH_IMM_USE_STMT (use_stmt, iter, lhs)
+                 FOR_EACH_IMM_USE_ON_STMT (use_p, iter)
+                   SET_USE (use_p, var);
+             }
+           else
+             replace_uses_by (lhs, var);
 
            /* And finally, remove the copy, it is not needed.  */
            gsi_remove (&si, true);
Index: gcc/testsuite/gcc.dg/torture/pr79244.c
===================================================================
--- gcc/testsuite/gcc.dg/torture/pr79244.c      (nonexistent)
+++ gcc/testsuite/gcc.dg/torture/pr79244.c      (working copy)
@@ -0,0 +1,13 @@
+/* { dg-do compile } */
+
+long buf[5];
+int bar (void);
+
+int
+foo (int x)
+{
+  int y = __builtin_setjmp (buf);
+  while (x != 3 && x && x && x != 2)
+    x = bar ();
+  return y;
+}