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view libgsmhr1/mathdp31.c @ 509:b7ddcb178ef6 default tip
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author | Mychaela Falconia <falcon@freecalypso.org> |
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date | Sat, 17 Aug 2024 23:11:51 +0000 |
parents | 024615de06fe |
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/*************************************************************************** * * 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 "typedefs.h" #include "namespace.h" #include "mathhalf.h" #include "mathdp31.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); }