From ff7faafda68f697b38270569031f71f151d2dc0f Mon Sep 17 00:00:00 2001
From: Piotr Caban <piotr@codeweavers.com>
Date: Fri, 4 Jun 2021 18:25:30 +0200
Subject: [PATCH] msvcrt: Import log1pf implementation from musl.

Signed-off-by: Piotr Caban <piotr@codeweavers.com>
Signed-off-by: Alexandre Julliard <julliard@winehq.org>
---
 configure             |  1 -
 configure.ac          |  1 -
 dlls/msvcrt/math.c    | 66 +++++++++++++++++++++++++++++++++++++++++--
 dlls/msvcrt/unixlib.c | 13 ---------
 dlls/msvcrt/unixlib.h |  1 -
 include/config.h.in   |  3 --
 6 files changed, 63 insertions(+), 22 deletions(-)

diff --git a/configure b/configure
index e91b319c705..e73670fc110 100755
--- a/configure
+++ b/configure
@@ -19622,7 +19622,6 @@ for ac_func in \
 	fmaf \
 	lgamma \
 	lgammaf \
-	log1pf \
 	log2 \
 	log2f \
 	tgamma \
diff --git a/configure.ac b/configure.ac
index accdbaf6216..b13c2ad3182 100644
--- a/configure.ac
+++ b/configure.ac
@@ -2661,7 +2661,6 @@ AC_CHECK_FUNCS(\
 	fmaf \
 	lgamma \
 	lgammaf \
-	log1pf \
 	log2 \
 	log2f \
 	tgamma \
diff --git a/dlls/msvcrt/math.c b/dlls/msvcrt/math.c
index fbc97aedce4..5702131cec9 100644
--- a/dlls/msvcrt/math.c
+++ b/dlls/msvcrt/math.c
@@ -6972,12 +6972,72 @@ double CDECL log1p(double x)
 
 /*********************************************************************
  *      log1pf (MSVCR120.@)
+ *
+ * Copied from musl: src/math/log1pf.c
  */
 float CDECL log1pf(float x)
 {
-    if (x < -1) *_errno() = EDOM;
-    else if (x == -1) *_errno() = ERANGE;
-    return unix_funcs->log1pf( x );
+    static const float ln2_hi = 6.9313812256e-01,
+        ln2_lo = 9.0580006145e-06,
+        Lg1 = 0xaaaaaa.0p-24,
+        Lg2 = 0xccce13.0p-25,
+        Lg3 = 0x91e9ee.0p-25,
+        Lg4 = 0xf89e26.0p-26;
+
+    union {float f; UINT32 i;} u = {x};
+    float hfsq, f, c, s, z, R, w, t1, t2, dk;
+    UINT32 ix, iu;
+    int k;
+
+    ix = u.i;
+    k = 1;
+    if (ix < 0x3ed413d0 || ix >> 31) { /* 1+x < sqrt(2)+ */
+        if (ix >= 0xbf800000) { /* x <= -1.0 */
+            if (x == -1) {
+                *_errno() = ERANGE;
+                return x / 0.0f; /* log1p(-1)=+inf */
+            }
+            *_errno() = EDOM;
+            return (x - x) / 0.0f; /* log1p(x<-1)=NaN */
+        }
+        if (ix<<1 < 0x33800000<<1) { /* |x| < 2**-24 */
+            /* underflow if subnormal */
+            if ((ix & 0x7f800000) == 0)
+                fp_barrierf(x * x);
+            return x;
+        }
+        if (ix <= 0xbe95f619) { /* sqrt(2)/2- <= 1+x < sqrt(2)+ */
+            k = 0;
+            c = 0;
+            f = x;
+        }
+    } else if (ix >= 0x7f800000)
+        return x;
+    if (k) {
+        u.f = 1 + x;
+        iu = u.i;
+        iu += 0x3f800000 - 0x3f3504f3;
+        k = (int)(iu >> 23) - 0x7f;
+        /* correction term ~ log(1+x)-log(u), avoid underflow in c/u */
+        if (k < 25) {
+            c = k >= 2 ? 1 - (u.f - x) : x - (u.f - 1);
+            c /= u.f;
+        } else
+            c = 0;
+        /* reduce u into [sqrt(2)/2, sqrt(2)] */
+        iu = (iu & 0x007fffff) + 0x3f3504f3;
+        u.i = iu;
+        f = u.f - 1;
+    }
+    s = f / (2.0f + f);
+    z = s * s;
+    w = z * z;
+    t1= w * (Lg2 + w * Lg4);
+    t2= z * (Lg1 + w * Lg3);
+    R = t2 + t1;
+    hfsq = 0.5f * f * f;
+    dk = k;
+    return s * (hfsq + R) + (dk * ln2_lo + c) - hfsq + f + dk * ln2_hi;
 }
 
 /*********************************************************************
diff --git a/dlls/msvcrt/unixlib.c b/dlls/msvcrt/unixlib.c
index f98d08e4909..3b003a846c8 100644
--- a/dlls/msvcrt/unixlib.c
+++ b/dlls/msvcrt/unixlib.c
@@ -136,18 +136,6 @@ static float CDECL unix_log10f( float x )
     return log10f( x );
 }
 
-/*********************************************************************
- *      log1pf
- */
-static float CDECL unix_log1pf(float x)
-{
-#ifdef HAVE_LOG1PF
-    return log1pf(x);
-#else
-    return log(1 + x);
-#endif
-}
-
 /*********************************************************************
  *      log2
  */
@@ -225,7 +213,6 @@ static const struct unix_funcs funcs =
     unix_lgammaf,
     unix_log10,
     unix_log10f,
-    unix_log1pf,
     unix_log2,
     unix_log2f,
     unix_pow,
diff --git a/dlls/msvcrt/unixlib.h b/dlls/msvcrt/unixlib.h
index 285deb22bc2..7e976949e04 100644
--- a/dlls/msvcrt/unixlib.h
+++ b/dlls/msvcrt/unixlib.h
@@ -32,7 +32,6 @@ struct unix_funcs
     float           (CDECL *lgammaf)(float x);
     double          (CDECL *log10)(double x);
     float           (CDECL *log10f)(float x);
-    float           (CDECL *log1pf)(float x);
     double          (CDECL *log2)(double x);
     float           (CDECL *log2f)(float x);
     double          (CDECL *pow)(double x, double y);
diff --git a/include/config.h.in b/include/config.h.in
index 7e6d36112d3..1b308f3d34c 100644
--- a/include/config.h.in
+++ b/include/config.h.in
@@ -408,9 +408,6 @@
 /* Define to 1 if you have the <linux/videodev2.h> header file. */
 #undef HAVE_LINUX_VIDEODEV2_H
 
-/* Define to 1 if you have the `log1pf' function. */
-#undef HAVE_LOG1PF
-
 /* Define to 1 if you have the `log2' function. */
 #undef HAVE_LOG2