From 348187ad3becd036b0864045da65150eb8e3715f Mon Sep 17 00:00:00 2001
From: Richard Leach <richardleach@users.noreply.github.com>
Date: Mon, 24 May 2021 00:33:36 +0100
Subject: [PATCH] Perl_newSVnv: inline relevant subset of sv_setnv

---
 sv.c | 21 ++++++++++++++++++++-
 1 file changed, 20 insertions(+), 1 deletion(-)

diff --git a/sv.c b/sv.c
index ceef9966da34..51a6df489157 100644
--- a/sv.c
+++ b/sv.c
@@ -9608,7 +9608,26 @@ Perl_newSVnv(pTHX_ const NV n)
     SV *sv;
 
     new_SV(sv);
-    sv_setnv(sv,n);
+    /* Inlining ONLY the small relevant subset of sv_setnv here
+     * for performance. */
+
+    /* We're starting from SVt_FIRST, so provided that's
+     * actual 0, we don't have to unset any SV type flags
+     * to promote to SVt_NV. */
+    STATIC_ASSERT_STMT(SVt_FIRST == 0);
+
+#if NVSIZE <= IVSIZE
+    SET_SVANY_FOR_BODYLESS_NV(sv);
+#else
+    SvANY(sv) = new_XNV();
+#endif
+
+    SvFLAGS(sv) |= SVt_NV;
+    (void)SvNOK_on(sv);
+
+    SvNV_set(sv, n);
+    SvTAINT(sv);
+
     return sv;
 }