re PR middle-end/63155 (memory hog)

2018-09-24  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/63155
	* tree-ssa-propagate.c (add_ssa_edge): Avoid adding PHIs to
	the worklist when the edge of the respective argument isn't
	executable.

From-SVN: r264523

gcc/ChangeLog

+2018-09-24  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/63155
+	* tree-ssa-propagate.c (add_ssa_edge): Avoid adding PHIs to
+	the worklist when the edge of the respective argument isn't
+	executable.
+
 2018-09-23   Uros Bizjak  <ubizjak@gmail.com>
 
 	* config/i386/i386.h (enum reg_class): Rename MASK_REGS to

gcc/tree-ssa-propagate.c

@@ -168,10 +168,18 @@ add_ssa_edge (tree var)
   FOR_EACH_IMM_USE_FAST (use_p, iter, var)
     {
       gimple *use_stmt = USE_STMT (use_p);
+      basic_block use_bb = gimple_bb (use_stmt);
 
       /* If we did not yet simulate the block wait for this to happen
          and do not add the stmt to the SSA edge worklist.  */
-      if (! (gimple_bb (use_stmt)->flags & BB_VISITED))
+      if (! (use_bb->flags & BB_VISITED))
+	continue;
+
+      /* If this is a use on a not yet executable edge do not bother to
+	 queue it.  */
+      if (gimple_code (use_stmt) == GIMPLE_PHI
+	  && !(EDGE_PRED (use_bb, PHI_ARG_INDEX_FROM_USE (use_p))->flags
+	       & EDGE_EXECUTABLE))
 	continue;
 
       if (prop_simulate_again_p (use_stmt)