re PR tree-optimization/92645 (Hand written vector code is 450 times slower when compiled with GCC compared to Clang)

2019-11-26  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/92645
	* tree-vect-slp.c (vect_build_slp_tree_2): For unary ops
	do not build the operation from scalars if the operand is.

	* gcc.target/i386/pr92645.c: New testcase.

From-SVN: r278719