math: move x87-family fmod functions to C with inline asm

1 files changed, 10 insertions, 0 deletions

diff --git a/src/math/i386/fmod.c b/src/math/i386/fmod.c
new file mode 100644
index 00000000..ea0c58d9
--- /dev/null
+++ b/src/math/i386/fmod.c
@@ -0,0 +1,10 @@
+#include <math.h>
+
+double fmod(double x, double y)
+{
+	unsigned short fpsr;
+	// fprem does not introduce excess precision into x
+	do __asm__ ("fprem; fnstsw %%ax" : "+t"(x), "=a"(fpsr) : "u"(y));
+	while (fpsr & 0x400);
+	return x;
+}