Piotr Caban : msvcrt: Import exp2f implementation from musl.

[Alexandre Julliard]

Module: wine
Branch: master
Commit: 07e31f4eaf47c6f079d52d1069b2d384c837b021
URL:    https://source.winehq.org/git/wine.git/?a=commit;h=07e31f4eaf47c6f079d52d1069b2d384c837b021

Author: Piotr Caban <piotr at codeweavers.com>
Date:   Thu Jun 10 19:04:27 2021 +0200

msvcrt: Import exp2f implementation from musl.

Signed-off-by: Piotr Caban <piotr at codeweavers.com>
Signed-off-by: Alexandre Julliard <julliard at winehq.org>

---

 configure             |  3 +--
 configure.ac          |  3 +--
 dlls/msvcrt/math.c    | 58 ++++++++++++++++++++++++++++++++++++++++++++++++---
 dlls/msvcrt/unixlib.c | 13 ------------
 dlls/msvcrt/unixlib.h |  1 -
 include/config.h.in   |  3 ---
 6 files changed, 57 insertions(+), 24 deletions(-)

diff --git a/configure b/configure
index 3e798c50788..74c72003827 100755
--- a/configure
+++ b/configure
@@ -19620,8 +19620,7 @@ $as_echo "#define HAVE_ISNAN 1" >>confdefs.h
 fi
 
 for ac_func in \
-	exp2 \
-	exp2f
+	exp2
 
 do :
   as_ac_var=`$as_echo "ac_cv_func_$ac_func" | $as_tr_sh`
diff --git a/configure.ac b/configure.ac
index db1fc0462b1..dc43d73858f 100644
--- a/configure.ac
+++ b/configure.ac
@@ -2659,8 +2659,7 @@ then
 fi
 
 AC_CHECK_FUNCS(\
-	exp2 \
-	exp2f
+	exp2
 )
 LIBS="$ac_save_LIBS"
 
diff --git a/dlls/msvcrt/math.c b/dlls/msvcrt/math.c
index 4d7cc6ab727..ae943e845e8 100644
--- a/dlls/msvcrt/math.c
+++ b/dlls/msvcrt/math.c
@@ -7025,12 +7025,64 @@ double CDECL exp2(double x)
 
 /*********************************************************************
  *      exp2f (MSVCR120.@)
+ *
+ * Copied from musl: src/math/exp2f.c
  */
 float CDECL exp2f(float x)
 {
-    float ret = unix_funcs->exp2f( x );
-    if (isfinite(x) && !isfinite(ret)) *_errno() = ERANGE;
-    return ret;
+    static const UINT64 T[] = {
+        0x3ff0000000000000ULL, 0x3fefd9b0d3158574ULL, 0x3fefb5586cf9890fULL, 0x3fef9301d0125b51ULL,
+        0x3fef72b83c7d517bULL, 0x3fef54873168b9aaULL, 0x3fef387a6e756238ULL, 0x3fef1e9df51fdee1ULL,
+        0x3fef06fe0a31b715ULL, 0x3feef1a7373aa9cbULL, 0x3feedea64c123422ULL, 0x3feece086061892dULL,
+        0x3feebfdad5362a27ULL, 0x3feeb42b569d4f82ULL, 0x3feeab07dd485429ULL, 0x3feea47eb03a5585ULL,
+        0x3feea09e667f3bcdULL, 0x3fee9f75e8ec5f74ULL, 0x3feea11473eb0187ULL, 0x3feea589994cce13ULL,
+        0x3feeace5422aa0dbULL, 0x3feeb737b0cdc5e5ULL, 0x3feec49182a3f090ULL, 0x3feed503b23e255dULL,
+        0x3feee89f995ad3adULL, 0x3feeff76f2fb5e47ULL, 0x3fef199bdd85529cULL, 0x3fef3720dcef9069ULL,
+        0x3fef5818dcfba487ULL, 0x3fef7c97337b9b5fULL, 0x3fefa4afa2a490daULL, 0x3fefd0765b6e4540ULL
+    };
+    static const double C[] = {
+        0x1.c6af84b912394p-5, 0x1.ebfce50fac4f3p-3, 0x1.62e42ff0c52d6p-1
+    };
+    static const double shift = 0x1.8p+52 / (1 << 5);
+
+    double kd, xd, z, r, r2, y, s;
+    UINT32 abstop;
+    UINT64 ki, t;
+
+    xd = x;
+    abstop = (*(UINT32*)&x >> 20) & 0x7ff;
+    if (abstop >= 0x430) {
+        /* |x| >= 128 or x is nan.  */
+        if (*(UINT32*)&x == 0xff800000)
+            return 0.0f;
+        if (abstop >= 0x7f8)
+            return x + x;
+        if (x > 0.0f) {
+            *_errno() = ERANGE;
+            return fp_barrierf(x * FLT_MAX);
+        }
+        if (x <= -150.0f) {
+            fp_barrierf(x - 0x1p120);
+            return 0;
+        }
+    }
+
+    /* x = k/N + r with r in [-1/(2N), 1/(2N)] and int k, N = 1 << 5. */
+    kd = xd + shift;
+    ki = *(UINT64*)&kd;
+    kd -= shift; /* k/(1<<5) for int k.  */
+    r = xd - kd;
+
+    /* exp2(x) = 2^(k/N) * 2^r ~= s * (C0*r^3 + C1*r^2 + C2*r + 1) */
+    t = T[ki % (1 << 5)];
+    t += ki << (52 - 5);
+    s = *(double*)&t;
+    z = C[0] * r + C[1];
+    r2 = r * r;
+    y = C[2] * r + 1;
+    y = z * r2 + y;
+    y = y * s;
+    return y;
 }
 
 /*********************************************************************
diff --git a/dlls/msvcrt/unixlib.c b/dlls/msvcrt/unixlib.c
index 91c6bc4c2f0..0adf402068f 100644
--- a/dlls/msvcrt/unixlib.c
+++ b/dlls/msvcrt/unixlib.c
@@ -70,18 +70,6 @@ static double CDECL unix_exp2( double x )
 #endif
 }
 
-/*********************************************************************
- *      exp2f
- */
-static float CDECL unix_exp2f( float x )
-{
-#ifdef HAVE_EXP2F
-    return exp2f(x);
-#else
-    return unix_exp2(x);
-#endif
-}
-
 /*********************************************************************
  *      pow
  */
@@ -103,7 +91,6 @@ static const struct unix_funcs funcs =
     unix_exp,
     unix_expf,
     unix_exp2,
-    unix_exp2f,
     unix_pow,
     unix_powf,
 };
diff --git a/dlls/msvcrt/unixlib.h b/dlls/msvcrt/unixlib.h
index b7afa6cdf8b..c10f25e73f9 100644
--- a/dlls/msvcrt/unixlib.h
+++ b/dlls/msvcrt/unixlib.h
@@ -26,7 +26,6 @@ struct unix_funcs
     double          (CDECL *exp)(double x);
     float           (CDECL *expf)(float x);
     double          (CDECL *exp2)(double x);
-    float           (CDECL *exp2f)(float x);
     double          (CDECL *pow)(double x, double y);
     float           (CDECL *powf)(float x, float y);
 };
diff --git a/include/config.h.in b/include/config.h.in
index 09bcdd70983..68122959035 100644
--- a/include/config.h.in
+++ b/include/config.h.in
@@ -95,9 +95,6 @@
 /* Define to 1 if you have the `exp2' function. */
 #undef HAVE_EXP2
 
-/* Define to 1 if you have the `exp2f' function. */
-#undef HAVE_EXP2F
-
 /* Define to 1 if you have the `F3DAudioInitialize8' function. */
 #undef HAVE_F3DAUDIOINITIALIZE8