msvcrt: Import floor implementation from musl.

dlls/msvcrt/math.c

@@ -1811,10 +1811,31 @@ double CDECL ceil( double x )
 
 /*********************************************************************
  *		floor (MSVCRT.@)
+ *
+ * Based on musl: src/math/floorf.c
  */
 double CDECL floor( double x )
 {
-  return unix_funcs->floor(x);
+    union {double f; UINT64 i;} u = {x};
+    int e = (int)(u.i >> 52 & 0x7ff) - 0x3ff;
+    UINT64 m;
+
+    if (e >= 52)
+        return x;
+    if (e >= 0) {
+        m = 0x000fffffffffffffULL >> e;
+        if ((u.i & m) == 0)
+            return x;
+        if (u.i >> 63)
+            u.i += m;
+        u.i &= ~m;
+    } else {
+        if (u.i >> 63 == 0)
+            return 0;
+        else if (u.i << 1)
+            return -1;
+    }
+    return u.f;
 }
 
 /*********************************************************************

dlls/msvcrt/unixlib.c

@@ -274,14 +274,6 @@ static float CDECL unix_expm1f(float x)
 }
 
 /*********************************************************************
- *      floor
- */
-static double CDECL unix_floor( double x )
-{
-    return floor( x );
-}
-
-/*********************************************************************
  *      fma
  */
 static double CDECL unix_fma( double x, double y, double z )
@@ -703,7 +695,6 @@ static const struct unix_funcs funcs =
     unix_exp2f,
     unix_expm1,
     unix_expm1f,
-    unix_floor,
     unix_fma,
     unix_fmaf,
     unix_fmod,

dlls/msvcrt/unixlib.h

@@ -43,7 +43,6 @@ struct unix_funcs
     float           (CDECL *exp2f)(float x);
     double          (CDECL *expm1)(double x);
     float           (CDECL *expm1f)(float x);
-    double          (CDECL *floor)(double x);
     double          (CDECL *fma)(double x, double y, double z);
     float           (CDECL *fmaf)(float x, float y, float z);
     double          (CDECL *fmod)(double x, double y);