https://bugs.gentoo.org/642300

From 36a84f43f326de14db888ba07936cc9621c23f19 Mon Sep 17 00:00:00 2001
From: Paul Zimmermann <Paul.Zimmermann@inria.fr>
Date: Sun, 10 Jan 2016 23:19:37 +0100
Subject: [PATCH] use mpfr_fmma and mpfr_fmms if provided by mpfr

---
 configure.ac | 16 ++++++++++++++++
 src/mul.c    | 15 ++++++++++++---
 2 files changed, 28 insertions(+), 3 deletions(-)

diff --git a/configure.ac b/configure.ac
index b6fa199..bdb21ff 100644
--- a/configure.ac
+++ b/configure.ac
@@ -165,6 +165,22 @@ AC_LINK_IFELSE(
         AC_MSG_ERROR([libmpfr not found or uses a different ABI (including static vs shared).])
         ])
 
+AC_MSG_CHECKING(for mpfr_fmma)
+LIBS="-lmpfr $LIBS"
+AC_LINK_IFELSE(
+        [AC_LANG_PROGRAM(
+                [[#include "mpfr.h"]],
+                [[mpfr_t x; mpfr_fmma (x, x, x, x, x, 0);]]
+        )],
+        [
+	AC_MSG_RESULT(yes)
+	AC_DEFINE(HAVE_MPFR_FMMA, 1, [mpfr_fmma is present])
+	],
+        [
+        AC_MSG_RESULT(no)
+	AC_DEFINE(HAVE_MPFR_FMMA, 0, [mpfr_fmma	is not present])
+        ])
+
 # Check for a recent GMP
 # We only guarantee that with a *functional* and recent enough GMP version,
 # MPC will compile; we do not guarantee that GMP will compile.
diff --git a/src/mul.c b/src/mul.c
index 3c9c0a7..8c4afe4 100644
--- a/src/mul.c
+++ b/src/mul.c
@@ -175,8 +175,9 @@ mul_imag (mpc_ptr z, mpc_srcptr x, mpc_srcptr y, mpc_rnd_t rnd)
 #define MPFR_EXP(x)       ((x)->_mpfr_exp)
 #define MPFR_LIMB_SIZE(x) ((MPFR_PREC (x) - 1) / GMP_NUMB_BITS + 1)
 
+#if HAVE_MPFR_FMMA == 0
 static int
-mpfr_fmma (mpfr_ptr z, mpfr_srcptr a, mpfr_srcptr b, mpfr_srcptr c,
+mpc_fmma (mpfr_ptr z, mpfr_srcptr a, mpfr_srcptr b, mpfr_srcptr c,
            mpfr_srcptr d, int sign, mpfr_rnd_t rnd)
 {
    /* Computes z = ab+cd if sign >= 0, or z = ab-cd if sign < 0.
@@ -359,6 +360,7 @@ mpfr_fmma (mpfr_ptr z, mpfr_srcptr a, mpfr_srcptr b, mpfr_srcptr c,
    return inex;
 }
+#endif
 
 
 int
 mpc_mul_naive (mpc_ptr z, mpc_srcptr x, mpc_srcptr y, mpc_rnd_t rnd)
@@ -375,10 +377,17 @@ mpc_mul_naive (mpc_ptr z, mpc_srcptr x, mpc_srcptr y, mpc_rnd_t rnd)
    else
       rop [0] = z [0];
 
-   inex = MPC_INEX (mpfr_fmma (mpc_realref (rop), mpc_realref (x), mpc_realref (y), mpc_imagref (x),
-                               mpc_imagref (y), -1, MPC_RND_RE (rnd)),
+#if HAVE_MPFR_FMMA
+   inex = MPC_INEX (mpfr_fmms (mpc_realref (rop), mpc_realref (x), mpc_realref (y), mpc_imagref (x),
+                               mpc_imagref (y), MPC_RND_RE (rnd)),
                     mpfr_fmma (mpc_imagref (rop), mpc_realref (x), mpc_imagref (y), mpc_imagref (x),
+                               mpc_realref (y), MPC_RND_IM (rnd)));
+#else
+   inex = MPC_INEX (mpc_fmma (mpc_realref (rop), mpc_realref (x), mpc_realref (y), mpc_imagref (x),
+                               mpc_imagref (y), -1, MPC_RND_RE (rnd)),
+                    mpc_fmma (mpc_imagref (rop), mpc_realref (x), mpc_imagref (y), mpc_imagref (x),
                                mpc_realref (y), +1, MPC_RND_IM (rnd)));
+#endif
 
    mpc_set (z, rop, MPC_RNDNN);
    if (overlap)
-- 
2.15.1