rs6000.c (rs6000_gimple_builtin): Add gimple folding support for merge[hl].

rs6000.c (rs6000_gimple_builtin): Add gimple folding support for merge[hl].

[gcc]

2018-01-17  Will Schmidt  <will_schmidt@vnet.ibm.com>

	* config/rs6000/rs6000.c (rs6000_gimple_builtin): Add gimple folding
	support for merge[hl].
	(fold_mergehl_helper): New helper function.
	(tree-vector-builder.h): New #include for tree_vector_builder usage.
	* config/rs6000/altivec.md (altivec_vmrghw_direct): Add xxmrghw insn.
	(altivec_vmrglw_direct): Add xxmrglw insn.

[testsuite]

2018-01-17  Will Schmidt  <will_schmidt@vnet.ibm.com>

	* gcc.target/powerpc/fold-vec-mergehl-char.c: New.
	* gcc.target/powerpc/fold-vec-mergehl-double.c: New.
	* gcc.target/powerpc/fold-vec-mergehl-float.c: New.
	* gcc.target/powerpc/fold-vec-mergehl-int.c: New.
	* gcc.target/powerpc/fold-vec-mergehl-longlong.c: New.
	* gcc.target/powerpc/fold-vec-mergehl-pixel.c: New.
	* gcc.target/powerpc/fold-vec-mergehl-short.c: New.
	* gcc.target/powerpc/builtins-1-be.c: Disable gimple-folding.
	* gcc.target/powerpc/builtins-1-le.c: Disable gimple-folding.
	* gcc.target/powerpc/builtins-1-be-folded.c: New.
	* gcc.target/powerpc/builtins-1-le-folded.c: New.
	* gcc.target/powerpc/builtins-1.fold.h: New.

From-SVN: r256814