fab/gimple-fold: Move __builtin_constant_p folding to gimple-fold [PR121762]

fab/gimple-fold: Move __builtin_constant_p folding to gimple-fold [PR121762]

This is the first patch in removing fold_all_builtins pass.
We want to fold __builtin_constant_p into 0 if we know the argument can't be
a constant. So currently that is done in fab pass (though ranger handles it now too).
Instead of having fab do it we can check PROP_last_full_fold if set and set it
to 0 instead.

Note for -Og, fab was the only place which did this conversion, so we need to
set PROP_last_full_fold for it; later on fab will be removed and isel will do
it instead but that is for another day.

Also instead of going through fold_call_stmt to call fold_builtin_constant_p,
fold_builtin_constant_p is called directly from gimple_fold_builtin_constant_p.
This should speed up the compiling slight :).

Note fab was originally added to do this transformation during the development
of the ssa branch.

Bootstrapped and tested on x86_64-linux-gnu.

	PR tree-optimization/121762
gcc/ChangeLog:

	* builtins.cc (fold_builtin_constant_p): Make non-static.
	* builtins.h (fold_builtin_constant_p): New declaration.
	* gimple-fold.cc (gimple_fold_builtin_constant_p): New function.
	(gimple_fold_builtin): Call gimple_fold_builtin_constant_p
	for BUILT_IN_CONSTANT_P.
	* tree-ssa-ccp.cc (pass_fold_builtins::execute): Set PROP_last_full_fold
	on curr_properties. Remove handling of BUILT_IN_CONSTANT_P.

Signed-off-by: Andrew Pinski <andrew.pinski@oss.qualcomm.com>