Add option to use libdivide in maths.h functions

speeduino/maths.h

@@ -1,6 +1,8 @@
 #ifndef MATH_H
 #define MATH_H
 
+#define USE_LIBDIVIDE
+
 int fastMap1023toX(int, int);
 unsigned long percentage(byte, unsigned long);
 unsigned long halfPercentage(byte, unsigned long);
@@ -16,4 +18,6 @@ unsigned long divu100(unsigned long);
 //This is a new version that allows for out_min
 #define fastMap10Bit(x, out_min, out_max) ( ( ((unsigned long)x * (out_max-out_min)) >> 10 ) + out_min)
 
+
+
 #endif

speeduino/maths.ino

@@ -1,5 +1,14 @@
 #include "maths.h"
 #include "globals.h"
+#include "src/libdivide/libdivide.h"
+
+#ifdef USE_LIBDIVIDE
+  //Constants used for libdivide
+  struct libdivide::libdivide_u32_t libdiv_u32_10 = libdivide::libdivide_u32_gen(10);
+  struct libdivide::libdivide_u32_t libdiv_u32_100 = libdivide::libdivide_u32_gen(100);
+  struct libdivide::libdivide_s32_t libdiv_s32_100 = libdivide::libdivide_s32_gen(100);
+  struct libdivide::libdivide_u32_t libdiv_u32_200 = libdivide::libdivide_u32_gen(200);
+#endif
 
 //Replace the standard arduino map() function to use the div function instead
 int fastMap(unsigned long x, int in_min, int in_max, int out_min, int out_max)
@@ -13,65 +22,56 @@ int fastMap(unsigned long x, int in_min, int in_max, int out_min, int out_max)
   //return (x - in_min) * (out_max - out_min) / (in_max - in_min) + out_min;
 }
 
-/*
-The following are all fast versions of specific divisions
-Ref: www.hackersdelight.org/divcMore.pdf
-*/
-
 //Unsigned divide by 10
 unsigned int divu10(unsigned int n)
 {
-  unsigned long q, r;
+#ifdef USE_LIBDIVIDE
-  q = (n >> 1) + (n >> 2);
+  return libdivide::libdivide_u32_do(n, &libdiv_u32_10);
-  q = q + (q >> 4);
+#else
-  q = q + (q >> 8);
+  return (n / 10);
-  q = q + (q >> 16);
+#endif
-  q = q >> 3;
-  r = n - (q * 10);
-  return q + ((r + 6) >> 4);
 }
 
 //Signed divide by 100
 int divs100(long n)
 {
+#ifdef USE_LIBDIVIDE
+  return libdivide::libdivide_s32_do(n, &libdiv_s32_100);
+#else
   return (n / 100); // Amazingly, gcc is producing a better /divide by 100 function than this
-  /*
+#endif
-  long q, r;
-  n = n + (n>>31 & 99);
-  q = (n >> 1) + (n >> 3) + (n >> 6) - (n >> 10) +
-  (n >> 12) + (n >> 13) - (n >> 16);
-  q = q + (q >> 20);
-  q = q >> 6;
-  r = n - q*100;
-  return q + ((r + 28) >> 7);
-  */
 }
 
 //Unsigned divide by 100
 unsigned long divu100(unsigned long n)
 {
-  //return (n / 100);
+#ifdef USE_LIBDIVIDE
-  unsigned long q, r;
+  return libdivide::libdivide_u32_do(n, &libdiv_u32_100);
-  q = (n >> 1) + (n >> 3) + (n >> 6) - (n >> 10) +
+#else
-  (n >> 12) + (n >> 13) - (n >> 16);
+  return (n / 100);
-  q = q + (q >> 20);
+#endif
-  q = q >> 6;
-  r = n - (q * 100);
-  return q + ((r + 28) >> 7);
 }
 
+
 //Return x percent of y
 //This is a relatively fast approximation of a percentage value.
 unsigned long percentage(byte x, unsigned long y)
 {
-  return (y * x) / 100; //For some reason this is faster
+#ifdef USE_LIBDIVIDE
-  //return divu100(y * x);
+  return libdivide::libdivide_u32_do((y * x), &libdiv_u32_100);
+#else
+  return (y * x) / 100;
+#endif
 }
 
 //Same as above, but 0.5% accuracy
 unsigned long halfPercentage(byte x, unsigned long y)
 {
+#ifdef USE_LIBDIVIDE
+  return libdivide::libdivide_u32_do((y * x), &libdiv_u32_200); 
+#else
   return (y * x) / 200;
+#endif
 }
 
 /*