Allow some NOP conversions in (X+CST1)+CST2 in match.pd

2017-05-25  Marc Glisse  <marc.glisse@inria.fr>

gcc/
	* match.pd ((A +- CST1) +- CST2): Allow some conversions.
	* tree.c (drop_tree_overflow): Handle COMPLEX_CST and VECTOR_CST.

gcc/testsuite/
	* gcc.dg/tree-ssa/addadd.c: New file.

From-SVN: r248448