make FOR_EACH_IMM_USE_STMT safe for early exits

Use a dtor to automatically remove ITER from IMM_USE list in
FOR_EACH_IMM_USE_STMT.


for  gcc/ChangeLog

	* ssa-iterators.h (end_imm_use_stmt_traverse): Forward
	declare.
	(auto_end_imm_use_stmt_traverse): New struct.
	(FOR_EACH_IMM_USE_STMT): Use it.
	(BREAK_FROM_IMM_USE_STMT, RETURN_FROM_IMM_USE_STMT): Remove,
	along with uses...
	* gimple-ssa-strength-reduction.c: ... here, ...
	* graphite-scop-detection.c: ... here, ...
	* ipa-modref.c, ipa-pure-const.c, ipa-sra.c: ... here, ...
	* tree-predcom.c, tree-ssa-ccp.c: ... here, ...
	* tree-ssa-dce.c, tree-ssa-dse.c: ... here, ...
	* tree-ssa-loop-ivopts.c, tree-ssa-math-opts.c: ... here, ...
	* tree-ssa-phiprop.c, tree-ssa.c: ... here, ...
	* tree-vect-slp.c: ... and here, ...
	* doc/tree-ssa.texi: ... and the example here.

1 files changed, 1 insertions, 3 deletions

diff --git a/gcc/graphite-scop-detection.c b/gcc/graphite-scop-detection.c
index 4f7bbe5..3e729b1 100644
--- a/gcc/graphite-scop-detection.c
+++ b/gcc/graphite-scop-detection.c
@@ -1262,9 +1262,7 @@ build_cross_bb_scalars_def (scop_p scop, tree def, basic_block def_bb,
 	&& (def_bb != gimple_bb (use_stmt) && !is_gimple_debug (use_stmt)))
       {
 	add_write (writes, def);
-	/* This is required by the FOR_EACH_IMM_USE_STMT when we want to break
-	   before all the uses have been visited.  */
-	BREAK_FROM_IMM_USE_STMT (imm_iter);
+	break;
       }
 }