96 lines
1.9 KiB
C
96 lines
1.9 KiB
C
#include "silleee.h"
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silleee silleee_sub(silleee x, silleee y) {
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y ^= 0x80000000;
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return silleee_add(x, y);
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}
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silleee shift_and_round(int val, int bits) {
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static unsigned masks[24]= {
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0, 1, 3, 7, 0xf, 0x1f, 0x3f, 0x7f, 0xff, 0x1ff, 0x7ff, 0xfff, 0x1fff,
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0x3fff, 0x7fff, 0xffff, 0x1ffff, 0x3ffff, 0x7ffff, 0xfffff, 0x1fffff,
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0x3fffff, 0x7fffff
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};
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static unsigned masks_ho[24] = {
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0, 1, 2, 4, 8, 0x10, 0x20, 0x40, 0x80, 0x100, 0x200, 0x400, 0x8000, 0x1000,
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0x2000, 0x4000, 0x8000, 0x10000, 0x20000, 0x40000, 0x80000, 0x100000,
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0x200000, 0x400000
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};
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int so = val & masks[bits];
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val >>= bits;
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if (so > masks_ho[bits]) val++;
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else if(so == masks_ho[bits]) val += val&1;
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return val;
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}
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silleee silleee_add(silleee x, silleee y) {
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silleee dest = 0;
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int dexp;
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long unsigned dmant;
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int dsign;
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int xexp = exponent(x);
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long unsigned xmant = mantissa(x);
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int xsign = sign(x);
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int yexp = exponent(y);
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long unsigned ymant = mantissa(y);
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int ysign = sign(y);
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if (xexp == 127) {
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if (!xmant) {
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if (yexp == 127) {
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if(!ymant) return xsign == ysign ? y : 0x7fc0000;
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else return y;
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}
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} else {
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return x;
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}
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} else if (yexp == 127) {
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return y;
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}
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dexp = yexp;
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if (yexp > xexp) xmant = shift_and_round(xmant, yexp-xexp);
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else if (yexp < xexp) {
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ymant = shift_and_round(ymant, xexp-yexp);
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dexp = xexp;
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}
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if (ysign ^ xsign) {
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if (xmant > ymant) {
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dmant = xmant - ymant;
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dsign = xmant;
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} else {
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dmant = ymant - xmant;
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dsign = ysign;
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}
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} else {
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dsign = xsign;
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dmant = xmant + ymant;
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}
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if (dmant >= 0x1000000) {
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dmant = shift_and_round(dmant, 1);
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++dexp;
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} else {
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if (dmant) {
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while (dmant < sign_bit && dexp > -127) {
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dmant = dmant << 1;
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--dexp;
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}
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} else {
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dsign = 0;
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dexp = 0;
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}
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}
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return pack_silleee(dsign, dexp, dmant);
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}
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