lib/libm: Add frexp and modf functions; use in stmhal; add tests.

Addresses issue #1081.

lib/libm/math.c

@@ -122,8 +122,6 @@ float tgammaf(float x) { return 0.0; }
 float lgammaf(float x) { return 0.0; }
 float erff(float x) { return 0.0; }
 float erfcf(float x) { return 0.0; }
-float modff(float x, float *y) { return 0.0; }
-float frexpf(float x, int *exp) { return 0.0; }
 float ldexpf(float x, int exp) { return 0.0; }
 
 /*****************************************************************************/

lib/libm/sf_frexp.c

@@ -0,0 +1,70 @@
+/*
+ * This file is part of the Micro Python project, http://micropython.org/
+ *
+ * These math functions are taken from newlib-nano-2, the newlib/libm/math
+ * directory, available from https://github.com/32bitmicro/newlib-nano-2.
+ *
+ * Appropriate copyright headers are reproduced below.
+ */
+
+/* sf_frexp.c -- float version of s_frexp.c.
+ * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
+ */
+
+/*
+ * ====================================================
+ * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
+ *
+ * Developed at SunPro, a Sun Microsystems, Inc. business.
+ * Permission to use, copy, modify, and distribute this
+ * software is freely granted, provided that this notice 
+ * is preserved.
+ * ====================================================
+ */
+
+#include "fdlibm.h"
+
+#ifdef __STDC__
+static const float
+#else
+static float
+#endif
+two25 =  3.3554432000e+07; /* 0x4c000000 */
+
+#ifdef __STDC__
+	float frexpf(float x, int *eptr)
+#else
+	float frexpf(x, eptr)
+	float x; int *eptr;
+#endif
+{
+	__int32_t hx, ix;
+	GET_FLOAT_WORD(hx,x);
+	ix = 0x7fffffff&hx;
+	*eptr = 0;
+	if(!FLT_UWORD_IS_FINITE(ix)||FLT_UWORD_IS_ZERO(ix)) return x;	/* 0,inf,nan */
+	if (FLT_UWORD_IS_SUBNORMAL(ix)) {		/* subnormal */
+	    x *= two25;
+	    GET_FLOAT_WORD(hx,x);
+	    ix = hx&0x7fffffff;
+	    *eptr = -25;
+	}
+	*eptr += (ix>>23)-126;
+	hx = (hx&0x807fffff)|0x3f000000;
+	SET_FLOAT_WORD(x,hx);
+	return x;
+}
+
+#ifdef _DOUBLE_IS_32BITS
+
+#ifdef __STDC__
+	double frexp(double x, int *eptr)
+#else
+	double frexp(x, eptr)
+	double x; int *eptr;
+#endif
+{
+	return (double) frexpf((float) x, eptr);
+}
+
+#endif /* defined(_DOUBLE_IS_32BITS) */

lib/libm/sf_modf.c

@@ -0,0 +1,82 @@
+/*
+ * This file is part of the Micro Python project, http://micropython.org/
+ *
+ * These math functions are taken from newlib-nano-2, the newlib/libm/common
+ * directory, available from https://github.com/32bitmicro/newlib-nano-2.
+ *
+ * Appropriate copyright headers are reproduced below.
+ */
+
+/* sf_modf.c -- float version of s_modf.c.
+ * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
+ */
+
+/*
+ * ====================================================
+ * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
+ *
+ * Developed at SunPro, a Sun Microsystems, Inc. business.
+ * Permission to use, copy, modify, and distribute this
+ * software is freely granted, provided that this notice 
+ * is preserved.
+ * ====================================================
+ */
+
+#include "fdlibm.h"
+
+#ifdef __STDC__
+static const float one = 1.0;
+#else
+static float one = 1.0;
+#endif
+
+#ifdef __STDC__
+	float modff(float x, float *iptr)
+#else
+	float modff(x, iptr)
+	float x,*iptr;
+#endif
+{
+	__int32_t i0,j0;
+	__uint32_t i;
+	GET_FLOAT_WORD(i0,x);
+	j0 = ((i0>>23)&0xff)-0x7f;	/* exponent of x */
+	if(j0<23) {			/* integer part in x */
+	    if(j0<0) {			/* |x|<1 */
+	        SET_FLOAT_WORD(*iptr,i0&0x80000000);	/* *iptr = +-0 */
+		return x;
+	    } else {
+		i = (0x007fffff)>>j0;
+		if((i0&i)==0) {			/* x is integral */
+		    __uint32_t ix;
+		    *iptr = x;
+		    GET_FLOAT_WORD(ix,x);
+		    SET_FLOAT_WORD(x,ix&0x80000000);	/* return +-0 */
+		    return x;
+		} else {
+		    SET_FLOAT_WORD(*iptr,i0&(~i));
+		    return x - *iptr;
+		}
+	    }
+	} else {			/* no fraction part */
+	    __uint32_t ix;
+	    *iptr = x*one;
+	    GET_FLOAT_WORD(ix,x);
+	    SET_FLOAT_WORD(x,ix&0x80000000);	/* return +-0 */
+	    return x;
+	}
+}
+
+#ifdef _DOUBLE_IS_32BITS
+
+#ifdef __STDC__
+	double modf(double x, double *iptr)
+#else
+	double modf(x, iptr)
+	double x,*iptr;
+#endif
+{
+	return (double) modff((float) x, (float *) iptr);
+}
+
+#endif /* defined(_DOUBLE_IS_32BITS) */

stmhal/Makefile

@@ -81,6 +81,8 @@ SRC_LIB = $(addprefix lib/,\
 	libm/sf_sin.c \
 	libm/sf_cos.c \
 	libm/sf_tan.c \
+	libm/sf_frexp.c \
+	libm/sf_modf.c \
 	fatfs/ff.c \
 	fatfs/option/ccsbcs.c \
 	mp-readline/readline.c \

tests/float/math_fun.py

@@ -33,7 +33,6 @@ functions = [('sqrt', sqrt, p_test_values),
              ('ceil', ceil, test_values),
              ('fabs', fabs, test_values),
              ('floor', floor, test_values),
-             #('frexp', frexp, test_values),
              ('trunc', trunc, test_values)
             ]
 
@@ -42,6 +41,16 @@ for function_name, function, test_vals in functions:
     for value in test_vals:
         print("{:.5g}".format(function(value)))
 
+tuple_functions = [('frexp', frexp, test_values),
+                   ('modf', modf, test_values),
+                  ]
+
+for function_name, function, test_vals in tuple_functions:
+    print(function_name)
+    for value in test_vals:
+        x, y = function(value)
+        print("{:.5g} {:.5g}".format(x, y))
+
 binary_functions = [('copysign', copysign, [(23., 42.), (-23., 42.), (23., -42.),
                                 (-23., -42.), (1., 0.0), (1., -0.0)])
                    ]