add do_ncmp fn and make pp_ncmp, pp_eq etc use it

Extract most of the body of pp_ncmp() (numeric compare) into a separate
function, do_ncmp(), then make the following ops use it:
    pp_ncmp
    pp_lt
    pp_le
    pp_eq
    pp_ne
    pp_ge
    pp_gt

This removes a lot of similar or duplicated code, most of which is
dedicated to handling the various combinations of IV verses UV verses NV
verses NaN.

The various ops first check for, and directly process, the simple and common
case of both args being SvIOK_notUV(), and pass the processing on to
do_ncmp() otherwise. Benchmarking seems to indicate (but with a lot of
noise) that the SvIOK_notUV case is slightly faster than before, and the
do_ncmp() branch slightly slower.

1 files changed, 7 insertions, 0 deletions

diff --git a/proto.h b/proto.h
index 8fc49deea1..984fc80b7c 100644
--- a/proto.h
+++ b/proto.h
@@ -776,6 +776,13 @@ PERL_CALLCONV void	Perl_do_magic_dump(pTHX_ I32 level, PerlIO *file, const MAGIC
 #define PERL_ARGS_ASSERT_DO_MAGIC_DUMP	\
 	assert(file); assert(mg)
 
+PERL_CALLCONV I32	Perl_do_ncmp(pTHX_ SV *const left, SV *const right)
+			__attribute__warn_unused_result__
+			__attribute__nonnull__(pTHX_1)
+			__attribute__nonnull__(pTHX_2);
+#define PERL_ARGS_ASSERT_DO_NCMP	\
+	assert(left); assert(right)
+
 PERL_CALLCONV void	Perl_do_op_dump(pTHX_ I32 level, PerlIO *file, const OP *o)
 			__attribute__nonnull__(pTHX_2);
 #define PERL_ARGS_ASSERT_DO_OP_DUMP	\