309 lines
7.9 KiB
C
309 lines
7.9 KiB
C
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/*
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* Copyright (c) 2010 Broadcom Corporation
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*
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* Permission to use, copy, modify, and/or distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice appear in all copies.
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*
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* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
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* SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
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* OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
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* CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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*/
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#include "phy_qmath.h"
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/*
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* Description: This function make 16 bit unsigned multiplication.
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* To fit the output into 16 bits the 32 bit multiplication result is right
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* shifted by 16 bits.
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*/
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u16 qm_mulu16(u16 op1, u16 op2)
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{
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return (u16) (((u32) op1 * (u32) op2) >> 16);
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}
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/*
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* Description: This function make 16 bit multiplication and return the result
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* in 16 bits. To fit the multiplication result into 16 bits the multiplication
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* result is right shifted by 15 bits. Right shifting 15 bits instead of 16 bits
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* is done to remove the extra sign bit formed due to the multiplication.
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* When both the 16bit inputs are 0x8000 then the output is saturated to
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* 0x7fffffff.
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*/
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s16 qm_muls16(s16 op1, s16 op2)
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{
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s32 result;
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if (op1 == (s16) 0x8000 && op2 == (s16) 0x8000)
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result = 0x7fffffff;
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else
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result = ((s32) (op1) * (s32) (op2));
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return (s16) (result >> 15);
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}
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/*
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* Description: This function add two 32 bit numbers and return the 32bit
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* result. If the result overflow 32 bits, the output will be saturated to
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* 32bits.
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*/
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s32 qm_add32(s32 op1, s32 op2)
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{
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s32 result;
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result = op1 + op2;
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if (op1 < 0 && op2 < 0 && result > 0)
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result = 0x80000000;
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else if (op1 > 0 && op2 > 0 && result < 0)
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result = 0x7fffffff;
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return result;
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}
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/*
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* Description: This function add two 16 bit numbers and return the 16bit
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* result. If the result overflow 16 bits, the output will be saturated to
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* 16bits.
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*/
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s16 qm_add16(s16 op1, s16 op2)
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{
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s16 result;
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s32 temp = (s32) op1 + (s32) op2;
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if (temp > (s32) 0x7fff)
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result = (s16) 0x7fff;
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else if (temp < (s32) 0xffff8000)
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result = (s16) 0xffff8000;
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else
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result = (s16) temp;
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return result;
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}
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/*
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* Description: This function make 16 bit subtraction and return the 16bit
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* result. If the result overflow 16 bits, the output will be saturated to
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* 16bits.
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*/
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s16 qm_sub16(s16 op1, s16 op2)
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{
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s16 result;
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s32 temp = (s32) op1 - (s32) op2;
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if (temp > (s32) 0x7fff)
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result = (s16) 0x7fff;
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else if (temp < (s32) 0xffff8000)
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result = (s16) 0xffff8000;
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else
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result = (s16) temp;
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return result;
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}
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/*
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* Description: This function make a 32 bit saturated left shift when the
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* specified shift is +ve. This function will make a 32 bit right shift when
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* the specified shift is -ve. This function return the result after shifting
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* operation.
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*/
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s32 qm_shl32(s32 op, int shift)
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{
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int i;
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s32 result;
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result = op;
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if (shift > 31)
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shift = 31;
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else if (shift < -31)
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shift = -31;
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if (shift >= 0) {
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for (i = 0; i < shift; i++)
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result = qm_add32(result, result);
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} else {
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result = result >> (-shift);
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}
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return result;
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}
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/*
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* Description: This function make a 16 bit saturated left shift when the
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* specified shift is +ve. This function will make a 16 bit right shift when
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* the specified shift is -ve. This function return the result after shifting
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* operation.
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*/
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s16 qm_shl16(s16 op, int shift)
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{
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int i;
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s16 result;
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result = op;
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if (shift > 15)
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shift = 15;
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else if (shift < -15)
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shift = -15;
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if (shift > 0) {
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for (i = 0; i < shift; i++)
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result = qm_add16(result, result);
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} else {
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result = result >> (-shift);
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}
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return result;
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}
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/*
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* Description: This function make a 16 bit right shift when shift is +ve.
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* This function make a 16 bit saturated left shift when shift is -ve. This
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* function return the result of the shift operation.
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*/
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s16 qm_shr16(s16 op, int shift)
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{
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return qm_shl16(op, -shift);
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}
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/*
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* Description: This function return the number of redundant sign bits in a
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* 32 bit number. Example: qm_norm32(0x00000080) = 23
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*/
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s16 qm_norm32(s32 op)
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{
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u16 u16extraSignBits;
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if (op == 0) {
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return 31;
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} else {
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u16extraSignBits = 0;
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while ((op >> 31) == (op >> 30)) {
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u16extraSignBits++;
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op = op << 1;
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}
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}
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return u16extraSignBits;
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}
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/* This table is log2(1+(i/32)) where i=[0:1:31], in q.15 format */
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static const s16 log_table[] = {
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0,
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1455,
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2866,
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4236,
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5568,
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6863,
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8124,
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9352,
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10549,
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11716,
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12855,
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13968,
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15055,
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16117,
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17156,
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18173,
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19168,
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20143,
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21098,
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22034,
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22952,
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23852,
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24736,
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25604,
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26455,
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27292,
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28114,
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28922,
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29717,
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30498,
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31267,
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32024
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};
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#define LOG_TABLE_SIZE 32 /* log_table size */
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#define LOG2_LOG_TABLE_SIZE 5 /* log2(log_table size) */
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#define Q_LOG_TABLE 15 /* qformat of log_table */
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#define LOG10_2 19728 /* log10(2) in q.16 */
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/*
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* Description:
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* This routine takes the input number N and its q format qN and compute
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* the log10(N). This routine first normalizes the input no N. Then N is in
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* mag*(2^x) format. mag is any number in the range 2^30-(2^31 - 1).
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* Then log2(mag * 2^x) = log2(mag) + x is computed. From that
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* log10(mag * 2^x) = log2(mag * 2^x) * log10(2) is computed.
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* This routine looks the log2 value in the table considering
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* LOG2_LOG_TABLE_SIZE+1 MSBs. As the MSB is always 1, only next
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* LOG2_OF_LOG_TABLE_SIZE MSBs are used for table lookup. Next 16 MSBs are used
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* for interpolation.
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* Inputs:
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* N - number to which log10 has to be found.
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* qN - q format of N
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* log10N - address where log10(N) will be written.
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* qLog10N - address where log10N qformat will be written.
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* Note/Problem:
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* For accurate results input should be in normalized or near normalized form.
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*/
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void qm_log10(s32 N, s16 qN, s16 *log10N, s16 *qLog10N)
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{
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s16 s16norm, s16tableIndex, s16errorApproximation;
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u16 u16offset;
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s32 s32log;
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/* normalize the N. */
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s16norm = qm_norm32(N);
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N = N << s16norm;
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/* The qformat of N after normalization.
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* -30 is added to treat the no as between 1.0 to 2.0
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* i.e. after adding the -30 to the qformat the decimal point will be
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* just rigtht of the MSB. (i.e. after sign bit and 1st MSB). i.e.
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* at the right side of 30th bit.
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*/
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qN = qN + s16norm - 30;
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/* take the table index as the LOG2_OF_LOG_TABLE_SIZE bits right of the
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* MSB */
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s16tableIndex = (s16) (N >> (32 - (2 + LOG2_LOG_TABLE_SIZE)));
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/* remove the MSB. the MSB is always 1 after normalization. */
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s16tableIndex =
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s16tableIndex & (s16) ((1 << LOG2_LOG_TABLE_SIZE) - 1);
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/* remove the (1+LOG2_OF_LOG_TABLE_SIZE) MSBs in the N. */
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N = N & ((1 << (32 - (2 + LOG2_LOG_TABLE_SIZE))) - 1);
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/* take the offset as the 16 MSBS after table index.
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*/
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u16offset = (u16) (N >> (32 - (2 + LOG2_LOG_TABLE_SIZE + 16)));
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/* look the log value in the table. */
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s32log = log_table[s16tableIndex]; /* q.15 format */
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/* interpolate using the offset. q.15 format. */
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s16errorApproximation = (s16) qm_mulu16(u16offset,
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(u16) (log_table[s16tableIndex + 1] -
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log_table[s16tableIndex]));
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/* q.15 format */
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s32log = qm_add16((s16) s32log, s16errorApproximation);
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/* adjust for the qformat of the N as
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* log2(mag * 2^x) = log2(mag) + x
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*/
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s32log = qm_add32(s32log, ((s32) -qN) << 15); /* q.15 format */
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/* normalize the result. */
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s16norm = qm_norm32(s32log);
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/* bring all the important bits into lower 16 bits */
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/* q.15+s16norm-16 format */
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s32log = qm_shl32(s32log, s16norm - 16);
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/* compute the log10(N) by multiplying log2(N) with log10(2).
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* as log10(mag * 2^x) = log2(mag * 2^x) * log10(2)
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* log10N in q.15+s16norm-16+1 (LOG10_2 is in q.16)
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*/
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*log10N = qm_muls16((s16) s32log, (s16) LOG10_2);
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/* write the q format of the result. */
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*qLog10N = 15 + s16norm - 16 + 1;
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return;
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}
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