re PR tree-optimization/28364 (poor optimization choices when iterating over a std...

re PR tree-optimization/28364 (poor optimization choices when iterating over a std::string (probably not c++-specific))

2018-04-30  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/28364
	PR tree-optimization/85275
	* tree-ssa-loop-ch.c (ch_base::copy_headers): Stop after
	copying first exit test.

	* gcc.dg/tree-ssa/copy-headers-5.c: New testcase.
	* gcc.dg/tree-ssa/predcom-8.c: Likewise.
	* gcc.dg/tree-ssa/cunroll-13.c: Rewrite to gimple testcase.
	* gcc.dg/tree-ssa/ivopt_mult_1.c: XFAIL.
	* gcc.dg/tree-ssa/ivopt_mult_1g.c: Add gimple variant that
	still passes.
	* gcc.dg/tree-ssa/ivopt_mult_2.c: XFAIL.
	* gcc.dg/tree-ssa/ivopt_mult_2g.c: Add gimple variant that
	still passes.
	* gcc.dg/tree-ssa/ssa-dom-thread-7.c: Adjust.
	* gcc.dg/tree-ssa/20030710-1.c: Likewise.
	* gcc.dg/tree-ssa/20030711-1.c: Likewise.

From-SVN: r259754