14f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber/* ------------------------------------------------------------------ 24f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber * Copyright (C) 1998-2009 PacketVideo 34f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber * 44f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber * Licensed under the Apache License, Version 2.0 (the "License"); 54f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber * you may not use this file except in compliance with the License. 64f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber * You may obtain a copy of the License at 74f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber * 84f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber * http://www.apache.org/licenses/LICENSE-2.0 94f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber * 104f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber * Unless required by applicable law or agreed to in writing, software 114f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber * distributed under the License is distributed on an "AS IS" BASIS, 124f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either 134f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber * express or implied. 144f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber * See the License for the specific language governing permissions 154f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber * and limitations under the License. 164f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber * ------------------------------------------------------------------- 174f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber */ 184f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber/**************************************************************************************** 194f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas HuberPortions of this file are derived from the following 3GPP standard: 204f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber 214f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber 3GPP TS 26.073 224f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber ANSI-C code for the Adaptive Multi-Rate (AMR) speech codec 234f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber Available from http://www.3gpp.org 244f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber 254f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber(C) 2004, 3GPP Organizational Partners (ARIB, ATIS, CCSA, ETSI, TTA, TTC) 264f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas HuberPermission to distribute, modify and use this file under the standard license 274f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huberterms listed above has been obtained from the copyright holder. 284f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber****************************************************************************************/ 294f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber/* 304f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber Pathname: ./audio/gsm-amr/c/src/inv_sqrt.c 314f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber 324f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber------------------------------------------------------------------------------ 334f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber REVISION HISTORY 344f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber 354f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber Description: Put file into template. 364f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber 374f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber Description: Synchronized file with UMTS version 3.2.0. Updated coding 384f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber template. Removed unnecessary include files. 394f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber 404f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber Description: Replaced basic_op.h with the header files of the math functions 414f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber used in the file. 424f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber 434f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber Description: Made the following changes per comments from Phase 2/3 review: 444f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber 1. Defined one local variable per line. 454f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber 2. Used "&=", ">>=", and "+=" in the code. 464f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber 474f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber Description: Updated template. Changed function interface to pass in a 484f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber pointer to overflow flag into the function instead of using a 494f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber global flag. 504f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber 514f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber Description: Removed inclusion of inv_sqrt.tab file. Changed array name 524f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber from "table" to "inv_sqrt_tbl" 534f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber 544f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber Description: Removed math operations that were not needed as functions, 554f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber this because the numbers themselves will not saturate the 564f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber operators, so there is not need to check for saturation. 574f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber 584f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber Description: Updated copyrigth year, according to code review comments. 594f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber 604f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber Description: Replaced "int" and/or "char" with defined types. 614f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber Added proper casting (Word32) to some left shifting operations 624f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber 634f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber Who: Date: 644f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber Description: 654f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber 664f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber------------------------------------------------------------------------------ 674f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber*/ 684f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber 694f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber/*---------------------------------------------------------------------------- 704f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber; INCLUDES 714f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber----------------------------------------------------------------------------*/ 724f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber#include "inv_sqrt.h" 734f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber#include "typedef.h" 744f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber#include "basic_op.h" 754f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber 764f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber/*---------------------------------------------------------------------------- 774f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber; MACROS 784f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber; Define module specific macros here 794f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber----------------------------------------------------------------------------*/ 804f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber 814f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber 824f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber/*---------------------------------------------------------------------------- 834f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber; DEFINES 844f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber; Include all pre-processor statements here. Include conditional 854f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber; compile variables also. 864f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber----------------------------------------------------------------------------*/ 874f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber 884f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber 894f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber/*---------------------------------------------------------------------------- 904f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber; LOCAL FUNCTION DEFINITIONS 914f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber; Function Prototype declaration 924f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber----------------------------------------------------------------------------*/ 934f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber 944f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber 954f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber/*---------------------------------------------------------------------------- 964f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber; LOCAL STORE/BUFFER/POINTER DEFINITIONS 974f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber; Variable declaration - defined here and used outside this module 984f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber----------------------------------------------------------------------------*/ 994f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber 1004f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber 1014f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber/* 1024f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber------------------------------------------------------------------------------ 1034f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber FUNCTION NAME: Inv_sqrt 1044f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber------------------------------------------------------------------------------ 1054f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber INPUT AND OUTPUT DEFINITIONS 1064f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber 1074f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber Inputs: 1084f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber L_x = input value (Word32) 1094f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber pOverflow = pointer to overflow flag 1104f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber 1114f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber Outputs: 1124f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber pOverflow -> if the Inv_sqrt operation resulted in an overflow. 1134f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber 1144f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber Returns: 1154f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber L_y = inverse squareroot of L_x (Word32) 1164f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber 1174f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber Global Variables Used: 1184f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber None. 1194f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber 1204f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber Local Variables Needed: 1214f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber None. 1224f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber 1234f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber------------------------------------------------------------------------------ 1244f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber FUNCTION DESCRIPTION 1254f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber 1264f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber This function computes 1/sqrt(L_x), where L_x is positive. 1274f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber If L_x is negative or zero, the result is 1 (3fff ffff). 1284f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber 1294f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber The function 1/sqrt(L_x) is approximated by a table and linear 1304f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber interpolation. The inverse square root is computed using the 1314f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber following steps: 1324f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber 1- Normalization of L_x. 1334f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber 2- If (30-exponent) is even then shift right once. 1344f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber 3- exponent = (30-exponent)/2 +1 1354f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber 4- i = bit25-b31 of L_x; 16<=i<=63 because of normalization. 1364f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber 5- a = bit10-b24 1374f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber 6- i -=16 1384f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber 7- L_y = table[i]<<16 - (table[i] - table[i+1]) * a * 2 1394f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber 8- L_y >>= exponent 1404f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber 1414f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber------------------------------------------------------------------------------ 1424f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber REQUIREMENTS 1434f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber 1444f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber None. 1454f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber 1464f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber------------------------------------------------------------------------------ 1474f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber REFERENCES 1484f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber 1494f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber inv_sqrt.c, UMTS GSM AMR speech codec, R99 - Version 3.2.0, March 2, 2001 1504f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber 1514f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber------------------------------------------------------------------------------ 1524f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber PSEUDO-CODE 1534f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber 1544f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas HuberWord32 Inv_sqrt ( // (o) : output value 1554f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber Word32 L_x // (i) : input value 1564f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber) 1574f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber{ 1584f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber Word16 exp, i, a, tmp; 1594f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber Word32 L_y; 1604f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber 1614f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber* The reference ETSI code uses a global Overflow flag. In the actual 1624f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber* implementation a pointer to the overflow flag is passed into the function. 1634f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber* This pointer is in turn passed into the basic math functions such as add(), 1644f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber* L_shl(), L_shr(), sub() called by this module. 1654f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber 1664f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber if (L_x <= (Word32) 0) 1674f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber return ((Word32) 0x3fffffffL); 1684f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber 1694f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber exp = norm_l (L_x); 1704f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber L_x = L_shl (L_x, exp); // L_x is normalize 1714f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber 1724f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber exp = sub (30, exp); 1734f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber 1744f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber if ((exp & 1) == 0) // If exponent even -> shift right 1754f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber { 1764f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber L_x = L_shr (L_x, 1); 1774f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber } 1784f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber exp = shr (exp, 1); 1794f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber exp = add (exp, 1); 1804f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber 1814f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber L_x = L_shr (L_x, 9); 1824f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber i = extract_h (L_x); // Extract b25-b31 1834f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber L_x = L_shr (L_x, 1); 1844f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber a = extract_l (L_x); // Extract b10-b24 1854f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber a = a & (Word16) 0x7fff; 1864f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber 1874f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber i = sub (i, 16); 1884f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber 1894f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber L_y = L_deposit_h (table[i]); // table[i] << 16 1904f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber tmp = sub (table[i], table[i + 1]); // table[i] - table[i+1]) 1914f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber L_y = L_msu (L_y, tmp, a); // L_y -= tmp*a*2 1924f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber 1934f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber L_y = L_shr (L_y, exp); // denormalization 1944f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber 1954f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber return (L_y); 1964f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber} 1974f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber 1984f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber------------------------------------------------------------------------------ 1994f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber RESOURCES USED [optional] 2004f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber 2014f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber When the code is written for a specific target processor the 2024f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber the resources used should be documented below. 2034f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber 2044f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber HEAP MEMORY USED: x bytes 2054f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber 2064f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber STACK MEMORY USED: x bytes 2074f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber 2084f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber CLOCK CYCLES: (cycle count equation for this function) + (variable 2094f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber used to represent cycle count for each subroutine 2104f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber called) 2114f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber where: (cycle count variable) = cycle count for [subroutine 2124f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber name] 2134f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber 2144f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber------------------------------------------------------------------------------ 2154f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber CAUTION [optional] 2164f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber [State any special notes, constraints or cautions for users of this function] 2174f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber 2184f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber------------------------------------------------------------------------------ 2194f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber*/ 2204f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber 2214f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas HuberWord32 Inv_sqrt( /* (o) : output value */ 2224f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber Word32 L_x, /* (i) : input value */ 2234f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber Flag * pOverflow /* (i) : pointer to overflow flag */ 2244f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber) 2254f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber{ 2264f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber Word16 exp; 2274f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber Word16 i; 2284f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber Word16 a; 2294f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber Word16 tmp; 2304f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber Word32 L_y; 2314f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber OSCL_UNUSED_ARG(pOverflow); 2324f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber 2334f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber if (L_x <= (Word32) 0) 2344f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber { 2354f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber return ((Word32) 0x3fffffffL); 2364f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber } 2374f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber 2384f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber exp = norm_l(L_x); 2394f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber L_x <<= exp; /* L_x is normalize */ 2404f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber 2414f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber exp = 30 - exp; 2424f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber 2434f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber if ((exp & 1) == 0) /* If exponent even -> shift right */ 2444f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber { 2454f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber L_x >>= 1; 2464f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber } 2474f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber exp >>= 1; 2484f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber exp += 1; 2494f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber 2504f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber L_x >>= 9; 2514f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber i = (Word16)(L_x >> 16); /* Extract b25-b31 */ 2524f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber a = (Word16)(L_x >> 1); /* Extract b10-b24 */ 2534f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber a &= (Word16) 0x7fff; 2544f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber 2554f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber i -= 16; 2564f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber 2574f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber L_y = (Word32)inv_sqrt_tbl[i] << 16; /* inv_sqrt_tbl[i] << 16 */ 2584f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber 2594f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber /* inv_sqrt_tbl[i] - inv_sqrt_tbl[i+1]) */ 2604f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber tmp = inv_sqrt_tbl[i] - inv_sqrt_tbl[i + 1]; 2614f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber /* always a positive number less than 200 */ 2624f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber 2634f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber L_y -= ((Word32)tmp * a) << 1; /* L_y -= tmp*a*2 */ 2644f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber /* always a positive minus a small negative number */ 2654f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber 2664f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber L_y >>= exp; /* denormalization, exp always 0< exp < 31 */ 2674f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber 2684f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber return (L_y); 2694f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber} 2704f1efc098cb5791c3e9f483f2af84aef70d2d0a0Andreas Huber 271