tree-ssa-math-opts: popcount (X) == 1 to (X ^ (X - 1)) > (X - 1) optimization for...

tree-ssa-math-opts: popcount (X) == 1 to (X ^ (X - 1)) > (X - 1) optimization for direct optab [PR90693]

On Fri, Nov 17, 2023 at 03:01:04PM +0100, Jakub Jelinek wrote:
> As a follow-up, I'm considering changing in this routine the popcount
> call to IFN_POPCOUNT with 2 arguments and during expansion test costs.

Here is the follow-up which does the rtx costs testing.

2023-11-20  Jakub Jelinek  <jakub@redhat.com>

	PR tree-optimization/90693
	* tree-ssa-math-opts.cc (match_single_bit_test): Mark POPCOUNT with
	result only used in equality comparison against 1 with direct optab
	support as .POPCOUNT call with 2 arguments.
	* internal-fn.h (expand_POPCOUNT): Declare.
	* internal-fn.def (DEF_INTERNAL_INT_EXT_FN): New macro, document it,
	undefine at the end.
	(POPCOUNT): Use it instead of DEF_INTERNAL_INT_FN.
	* internal-fn.cc (DEF_INTERNAL_INT_EXT_FN): Define to nothing before
	inclusion to define expanders.
	(expand_POPCOUNT): New function.