add missing __expo2[f].c files; fixes #3101

system/lib/libc/musl/src/math/__expo2.c

@@ -0,0 +1,16 @@
+#include "libm.h"
+
+/* k is such that k*ln2 has minimal relative error and x - kln2 > log(DBL_MIN) */
+static const int k = 2043;
+static const double kln2 = 0x1.62066151add8bp+10;
+
+/* exp(x)/2 for x >= log(DBL_MAX), slightly better than 0.5*exp(x/2)*exp(x/2) */
+double __expo2(double x)
+{
+	double scale;
+
+	/* note that k is odd and scale*scale overflows */
+	INSERT_WORDS(scale, (uint32_t)(0x3ff + k/2) << 20, 0);
+	/* exp(x - k ln2) * 2**(k-1) */
+	return exp(x - kln2) * scale * scale;
+}

system/lib/libc/musl/src/math/__expo2f.c

@@ -0,0 +1,16 @@
+#include "libm.h"
+
+/* k is such that k*ln2 has minimal relative error and x - kln2 > log(FLT_MIN) */
+static const int k = 235;
+static const float kln2 = 0x1.45c778p+7f;
+
+/* expf(x)/2 for x >= log(FLT_MAX), slightly better than 0.5f*expf(x/2)*expf(x/2) */
+float __expo2f(float x)
+{
+	float scale;
+
+	/* note that k is odd and scale*scale overflows */
+	SET_FLOAT_WORD(scale, (uint32_t)(0x7f + k/2) << 23);
+	/* exp(x - k ln2) * 2**(k-1) */
+	return expf(x - kln2) * scale * scale;
+}

tools/system_libs.py

@@ -107,6 +107,8 @@ def calculate(temp_files, in_temp, stdout_, stderr_, forced=[]):
        'shgetc.c',
       ]],
       ['math', [
+       '__expo2.c',
+       '__expo2f.c',
        '__fpclassify.c',
        '__fpclassifyf.c',
        '__fpclassifyl.c',