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, 4 insertions, 4 deletions

diff --git a/gcc/ipa-pure-const.c b/gcc/ipa-pure-const.c
index 66f2177..957217a 100644
--- a/gcc/ipa-pure-const.c
+++ b/gcc/ipa-pure-const.c
@@ -842,20 +842,20 @@ check_retval_uses (tree retval, gimple *stmt)
       {
 	tree op2 = gimple_cond_rhs (cond);
 	if (!integer_zerop (op2))
-	  RETURN_FROM_IMM_USE_STMT (use_iter, false);
+	  return false;
       }
     else if (gassign *ga = dyn_cast<gassign *> (use_stmt))
       {
 	enum tree_code code = gimple_assign_rhs_code (ga);
 	if (TREE_CODE_CLASS (code) != tcc_comparison)
-	  RETURN_FROM_IMM_USE_STMT (use_iter, false);
+	  return false;
 	if (!integer_zerop (gimple_assign_rhs2 (ga)))
-	  RETURN_FROM_IMM_USE_STMT (use_iter, false);
+	  return false;
       }
     else if (is_gimple_debug (use_stmt))
       ;
     else if (use_stmt != stmt)
-      RETURN_FROM_IMM_USE_STMT (use_iter, false);
+      return false;
 
   return true;
 }