FreeCalypso > hg > gsmhr-codec-ref
diff mathdp31.c @ 0:9008dbc8ca74
import original C code from GSM 06.06
author | Mychaela Falconia <falcon@freecalypso.org> |
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date | Fri, 14 Jun 2024 23:27:16 +0000 |
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--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/mathdp31.c Fri Jun 14 23:27:16 2024 +0000 @@ -0,0 +1,237 @@ +/*************************************************************************** + * + * File Name: mathdp31.c + * + * Purpose: Contains functions increased-precision arithmetic operations. + * + * Below is a listing of all the functions in this file. There + * is no interdependence among the functions. + * + * L_mpy_ls() + * L_mpy_ll() + * isLwLimit() + * isSwLimit() + * + ***************************************************************************/ +/*_________________________________________________________________________ + | | + | Include Files | + |_________________________________________________________________________| +*/ + +#include "mathhalf.h" +#include "typedefs.h" + +/**************************************************************************** + * + * FUNCTION NAME: isLwLimit + * + * PURPOSE: + * + * Check to see if the input Longword is at the + * upper or lower limit of its range. i.e. + * 0x7fff ffff or -0x8000 0000 + * + * Ostensibly this is a check for an overflow. + * This does not truly mean an overflow occurred, + * it means the value reached is the + * maximum/minimum value representable. It may + * have come about due to an overflow. + * + * INPUTS: + * + * L_In A Longword input variable + * + * + * OUTPUTS: none + * + * RETURN VALUE: 1 if input == 0x7fff ffff or -0x8000 0000 + * 0 otherwise + * + * KEYWORDS: saturation, limit + * + ***************************************************************************/ + +short isLwLimit(Longword L_In) +{ + + Longword L_ls; + short siOut; + + if (L_In != 0) + { + L_ls = L_shl(L_In, 1); + if (L_sub(L_In, L_ls) == 0) + siOut = 1; + else + siOut = 0; + } + else + { + siOut = 0; + } + return (siOut); +} + +/**************************************************************************** + * + * FUNCTION NAME: isSwLimit + * + * PURPOSE: + * + * Check to see if the input Shortword is at the + * upper or lower limit of its range. i.e. + * 0x7fff or -0x8000 + * + * Ostensibly this is a check for an overflow. + * This does not truly mean an overflow occurred, + * it means the value reached is the + * maximum/minimum value representable. It may + * have come about due to an overflow. + * + * INPUTS: + * + * swIn A Shortword input variable + * + * + * OUTPUTS: none + * + * RETURN VALUE: 1 if input == 0x7fff or -0x8000 + * 0 otherwise + * + * KEYWORDS: saturation, limit + * + ***************************************************************************/ + +short isSwLimit(Shortword swIn) +{ + + Shortword swls; + short siOut; + + if (swIn != 0) + { + swls = shl(swIn, 1); + if (sub(swIn, swls) == 0) /* logical compare outputs 1/0 */ + siOut = 1; + else + siOut = 0; + } + else + { + siOut = 0; + } + return (siOut); + +} + +/**************************************************************************** + * + * FUNCTION NAME: L_mpy_ll + * + * PURPOSE: Multiply a 32 bit number (L_var1) and a 32 bit number + * (L_var2), and return a 32 bit result. + * + * INPUTS: + * + * L_var1 A Longword input variable + * + * L_var2 A Longword input variable + * + * OUTPUTS: none + * + * IMPLEMENTATION: + * + * Performs a 31x31 bit multiply, Complexity=24 Ops. + * + * Let x1x0, or y1y0, be the two constituent halves + * of a 32 bit number. This function performs the + * following: + * + * low = ((x0 >> 1)*(y0 >> 1)) >> 16 (low * low) + * mid1 = [(x1 * (y0 >> 1)) >> 1 ] (high * low) + * mid2 = [(y1 * (x0 >> 1)) >> 1] (high * low) + * mid = (mid1 + low + mid2) >> 14 (sum so far) + * output = (y1*x1) + mid (high * high) + * + * + * RETURN VALUE: A Longword value + * + * KEYWORDS: mult,mpy,multiplication + * + ***************************************************************************/ + +Longword L_mpy_ll(Longword L_var1, Longword L_var2) +{ + Shortword swLow1, + swLow2, + swHigh1, + swHigh2; + Longword L_varOut, + L_low, + L_mid1, + L_mid2, + L_mid; + + + swLow1 = shr(extract_l(L_var1), 1); + swLow1 = SW_MAX & swLow1; + + swLow2 = shr(extract_l(L_var2), 1); + swLow2 = SW_MAX & swLow2; + swHigh1 = extract_h(L_var1); + swHigh2 = extract_h(L_var2); + + L_low = L_mult(swLow1, swLow2); + L_low = L_shr(L_low, 16); + + L_mid1 = L_mult(swHigh1, swLow2); + L_mid1 = L_shr(L_mid1, 1); + L_mid = L_add(L_mid1, L_low); + + L_mid2 = L_mult(swHigh2, swLow1); + L_mid2 = L_shr(L_mid2, 1); + L_mid = L_add(L_mid, L_mid2); + + L_mid = L_shr(L_mid, 14); + L_varOut = L_mac(L_mid, swHigh1, swHigh2); + + return (L_varOut); +} + +/**************************************************************************** + * + * FUNCTION NAME: L_mpy_ls + * + * PURPOSE: Multiply a 32 bit number (L_var2) and a 16 bit + * number (var1) returning a 32 bit result. L_var2 + * is truncated to 31 bits prior to executing the + * multiply. + * + * INPUTS: + * + * L_var2 A Longword input variable + * + * var1 A Shortword input variable + * + * OUTPUTS: none + * + * RETURN VALUE: A Longword value + * + * KEYWORDS: mult,mpy,multiplication + * + ***************************************************************************/ + +Longword L_mpy_ls(Longword L_var2, Shortword var1) +{ + Longword L_varOut; + Shortword swtemp; + + swtemp = shr(extract_l(L_var2), 1); + swtemp = (short) 32767 & (short) swtemp; + + L_varOut = L_mult(var1, swtemp); + L_varOut = L_shr(L_varOut, 15); + L_varOut = L_mac(L_varOut, var1, extract_h(L_var2)); + return (L_varOut); +}