1. ffmpeg
  2. Commit a2fd60437d0c7cf21a9365024efaa764bddaf3ab
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floating point "emulation" code unused currently, but might come in handy for some fpu-less cpus

Originally committed as revision 5955 to svn://svn.ffmpeg.org/ffmpeg/trunk

Michael Niedermayer authored on 2006/08/08 16:58:10
Showing 2 changed files
libavutil/softfloat.c
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+#include <inttypes.h>
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+#include <stdio.h>
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+#include <assert.h>
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+#include "softfloat.h"
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+#include "common.h"
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+#include "log.h"
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+
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+#undef printf
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+
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+int main(){
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+    SoftFloat one= av_int2sf(1, 0);
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+    SoftFloat sf1, sf2;
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+    double d1, d2;
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+    int i, j;
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+av_log_level = AV_LOG_DEBUG;
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+
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+    d1= 1;
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+    for(i= 0; i<10; i++){
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+        d1= 1/(d1+1);
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+    }
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+    printf("test1 double=%d\n", (int)(d1 * (1<<24)));
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+
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+    sf1= one;
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+    for(i= 0; i<10; i++){
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+        sf1= av_div_sf(one, av_normalize_sf(av_add_sf(one, sf1)));
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+    }
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+    printf("test1 sf    =%d\n", av_sf2int(sf1, 24));
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+
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+
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+    for(i= 0; i<100; i++){
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+        START_TIMER
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+        d1= i;
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+        d2= i/100.0;
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+        for(j= 0; j<1000; j++){
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+            d1= (d1+1)*d2;
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+        }
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+        STOP_TIMER("float add mul")
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+    }
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+    printf("test2 double=%d\n", (int)(d1 * (1<<24)));
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+
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+    for(i= 0; i<100; i++){
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+        START_TIMER
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+        sf1= av_int2sf(i, 0);
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+        sf2= av_div_sf(av_int2sf(i, 2), av_int2sf(200, 3));
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+        for(j= 0; j<1000; j++){
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+            sf1= av_mul_sf(av_add_sf(sf1, one),sf2);
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+        }
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+        STOP_TIMER("softfloat add mul")
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+    }
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+    printf("test2 sf    =%d (%d %d)\n", av_sf2int(sf1, 24), sf1.exp, sf1.mant);
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+    return 0;
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+}
libavutil/softfloat.h
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+//copyright Michael Niedermayer 2006 license:LGPL
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+
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+#define MIN_EXP -126
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+#define MAX_EXP  126
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+#define ONE_BITS 29
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+
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+typedef struct SoftFloat{
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+    int32_t  exp;
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+    int32_t mant;
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+}SoftFloat;
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+
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+static SoftFloat av_normalize_sf(SoftFloat a){
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+    if(a.mant){
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+#if 1
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+        while((a.mant + 0x20000000U)<0x40000000U){
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+            a.mant += a.mant;
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+            a.exp  -= 1;
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+        }
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+#else
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+        int s=ONE_BITS + 1 - av_log2(a.mant ^ (a.mant<<1));
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+        a.exp   -= s;
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+        a.mant <<= s;
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+#endif
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+        if(a.exp < MIN_EXP){
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+            a.exp = MIN_EXP;
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+            a.mant= 0;
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+        }
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+    }else{
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+        a.exp= MIN_EXP;
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+    }
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+    return a;
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+}
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+
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+static inline SoftFloat av_normalize1_sf(SoftFloat a){
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+#if 1
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+    if(a.mant + 0x40000000 < 0){
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+        a.exp++;
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+        a.mant>>=1;
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+    }
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+    return a;
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+#elif 1
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+    int t= a.mant + 0x40000000 < 0;
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+    return (SoftFloat){a.exp+t, a.mant>>t};
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+#else
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+    int t= (a.mant + 0x40000000U)>>31;
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+    return (SoftFloat){a.exp+t, a.mant>>t};
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+#endif
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+}
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+
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+/**
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+ *
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+ * @return will not be more denormalized then a+b, so if either input is
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+ *         normalized then the output wont be worse then the other input
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+ *         if both are normalized then the output will be normalized
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+ */
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+static inline SoftFloat av_mul_sf(SoftFloat a, SoftFloat b){
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+    a.exp += b.exp;
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+    a.mant = (a.mant * (int64_t)b.mant) >> ONE_BITS;
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+    return av_normalize1_sf(a);
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+}
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+
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+/**
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+ *
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+ * b has to be normalized and not zero
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+ * @return will not be more denormalized then a
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+ */
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+static SoftFloat av_div_sf(SoftFloat a, SoftFloat b){
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+    a.exp -= b.exp+1;
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+    a.mant = ((int64_t)a.mant<<(ONE_BITS+1)) / b.mant;
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+    return av_normalize1_sf(a);
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+}
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+
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+static inline int av_cmp_sf(SoftFloat a, SoftFloat b){
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+    int t= a.exp - b.exp;
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+    if(t<0) return (a.mant >> (-t)) -  b.mant      ;
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+    else    return  a.mant          - (b.mant >> t);
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+}
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+
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+static inline SoftFloat av_add_sf(SoftFloat a, SoftFloat b){
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+    int t= a.exp - b.exp;
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+    if(t<0) return av_normalize1_sf((SoftFloat){b.exp, b.mant + (a.mant >> (-t))});
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+    else    return av_normalize1_sf((SoftFloat){a.exp, a.mant + (b.mant >>   t )});
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+}
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+
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+static inline SoftFloat av_sub_sf(SoftFloat a, SoftFloat b){
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+    return av_add_sf(a, (SoftFloat){b.exp, -b.mant});
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+}
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+
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+//FIXME sqrt, log, exp, pow, sin, cos
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+
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+static inline SoftFloat av_int2sf(int v, int frac_bits){
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+    return av_normalize_sf((SoftFloat){ONE_BITS-frac_bits, v});
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+}
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+
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+/**
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+ *
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+ * rounding is to -inf
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+ */
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+static inline int av_sf2int(SoftFloat v, int frac_bits){
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+    v.exp += frac_bits - ONE_BITS;
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+    if(v.exp >= 0) return v.mant <<  v.exp ;
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+    else           return v.mant >>(-v.exp);
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+}