apps/fracmul.h

   1 #ifndef _FRACMUL_H
   2 #define _FRACMUL_H
   3
   4 #include <stdint.h>
   5 #include "gcc_extensions.h"
   6
   7 /** FRACTIONAL MULTIPLICATION
   8  *  Multiply two fixed point numbers with 31 fractional bits:
   9  *      FRACMUL(x, y)
  10  *
  11  *  Multiply two fixed point numbers with 31 fractional bits,
  12  *          then shift left by z bits:
  13  *      FRACMUL_SHL(x, y, z)
  14  *          NOTE: z must be in the range 1-8 on Coldfire targets.
  15  */
  16
  17
  18 /* A bunch of fixed point assembler helper macros */
  19 #if defined(CPU_COLDFIRE)
  20 /* These macros use the Coldfire EMAC extension and need the MACSR flags set
  21  * to fractional mode with no rounding.
  22  */
  23
  24 /* Multiply two S.31 fractional integers and return the sign bit and the
  25  * 31 most significant bits of the result.
  26  */
  27 static inline int32_t FRACMUL(int32_t x, int32_t y)
  28 {
  29     int32_t t;
  30     asm ("mac.l    %[a], %[b], %%acc0\n\t"
  31          "movclr.l %%acc0, %[t]\n\t"
  32          : [t] "=r" (t) : [a] "r" (x), [b] "r" (y));
  33     return t;
  34 }
  35
  36 /* Multiply two S.31 fractional integers, and return the 32 most significant
  37  * bits after a shift left by the constant z. NOTE: Only works for shifts of
  38  * 1 to 8 on Coldfire!
  39  */
  40 static FORCE_INLINE int32_t FRACMUL_SHL(int32_t x, int32_t y, int z)
  41 {
  42     int32_t t, t2;
  43     asm ("mac.l    %[a], %[b], %%acc0\n\t"
  44          "move.l   %[d], %[t]\n\t"
  45          "move.l   %%accext01, %[t2]\n\t"
  46          "and.l    %[mask], %[t2]\n\t"
  47          "lsr.l    %[t], %[t2]\n\t"
  48          "movclr.l %%acc0, %[t]\n\t"
  49          "asl.l    %[c], %[t]\n\t"
  50          "or.l     %[t2], %[t]\n\t"
  51          : [t] "=&d" (t), [t2] "=&d" (t2)
  52          : [a] "r" (x), [b] "r" (y), [mask] "d" (0xff),
  53            [c] "id" ((z)), [d] "id" (8 - (z)));
  54     return t;
  55 }
  56
  57 #elif defined(CPU_ARM)
  58
  59 /* Multiply two S.31 fractional integers and return the sign bit and the
  60  * 31 most significant bits of the result.
  61  */
  62 static inline int32_t FRACMUL(int32_t x, int32_t y)
  63 {
  64     int32_t t, t2;
  65     asm ("smull    %[t], %[t2], %[a], %[b]\n\t"
  66          "mov      %[t2], %[t2], asl #1\n\t"
  67          "orr      %[t], %[t2], %[t], lsr #31\n\t"
  68          : [t] "=&r" (t), [t2] "=&r" (t2)
  69          : [a] "r" (x), [b] "r" (y));
  70     return t;
  71 }
  72
  73 /* Multiply two S.31 fractional integers, and return the 32 most significant
  74  * bits after a shift left by the constant z.
  75  */
  76 static FORCE_INLINE int32_t FRACMUL_SHL(int32_t x, int32_t y, int z)
  77 {
  78     int32_t t, t2;
  79     asm ("smull    %[t], %[t2], %[a], %[b]\n\t"
  80          "mov      %[t2], %[t2], asl %[c]\n\t"
  81          "orr      %[t], %[t2], %[t], lsr %[d]\n\t"
  82          : [t] "=&r" (t), [t2] "=&r" (t2)
  83          : [a] "r" (x), [b] "r" (y),
  84            [c] "Mr" ((z) + 1), [d] "Mr" (31 - (z)));
  85     return t;
  86 }
  87
  88 #else
  89
  90 static inline int32_t FRACMUL(int32_t x, int32_t y)
  91 {
  92     return (int32_t) (((int64_t)x * y) >> 31);
  93 }
  94
  95 static inline int32_t FRACMUL_SHL(int32_t x, int32_t y, int z)
  96 {
  97     return (int32_t) (((int64_t)x * y) >> (31 - z));
  98 }
  99
 100 #endif
 101
 102 #endif