c9b0299034
Convert the various /* fallthrough */ comments to the pseudo-keyword fallthrough; Done via script: https://lore.kernel.org/lkml/b56602fcf79f849e733e7b521bb0e17895d390fa.1582230379.git.joe@perches.com/ Signed-off-by: Liangliang Huang <huangll@lemote.com> Reviewed-by: Huacai Chen <chenhc@lemote.com> Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
173 lines
4.0 KiB
C
173 lines
4.0 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/* IEEE754 floating point arithmetic
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* double precision: common utilities
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*/
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/*
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* MIPS floating point support
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* Copyright (C) 1994-2000 Algorithmics Ltd.
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*/
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#include "ieee754dp.h"
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union ieee754dp ieee754dp_sub(union ieee754dp x, union ieee754dp y)
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{
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int s;
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COMPXDP;
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COMPYDP;
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EXPLODEXDP;
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EXPLODEYDP;
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ieee754_clearcx();
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FLUSHXDP;
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FLUSHYDP;
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switch (CLPAIR(xc, yc)) {
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case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_SNAN):
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case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_SNAN):
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case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_SNAN):
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case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_SNAN):
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case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_SNAN):
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return ieee754dp_nanxcpt(y);
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case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_SNAN):
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case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_QNAN):
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case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_ZERO):
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case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_NORM):
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case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_DNORM):
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case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_INF):
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return ieee754dp_nanxcpt(x);
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case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_QNAN):
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case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_QNAN):
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case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_QNAN):
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case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_QNAN):
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return y;
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case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_QNAN):
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case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_ZERO):
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case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_NORM):
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case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_DNORM):
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case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_INF):
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return x;
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/*
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* Infinity handling
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*/
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case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_INF):
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if (xs != ys)
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return x;
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ieee754_setcx(IEEE754_INVALID_OPERATION);
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return ieee754dp_indef();
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case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_INF):
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case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_INF):
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case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_INF):
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return ieee754dp_inf(ys ^ 1);
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case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_ZERO):
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case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_NORM):
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case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_DNORM):
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return x;
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/*
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* Zero handling
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*/
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case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_ZERO):
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if (xs != ys)
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return x;
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else
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return ieee754dp_zero(ieee754_csr.rm == FPU_CSR_RD);
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case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_ZERO):
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case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_ZERO):
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return x;
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case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_NORM):
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case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_DNORM):
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/* quick fix up */
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DPSIGN(y) ^= 1;
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return y;
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case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM):
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DPDNORMX;
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fallthrough;
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case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_DNORM):
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/* normalize ym,ye */
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DPDNORMY;
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break;
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case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_NORM):
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/* normalize xm,xe */
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DPDNORMX;
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break;
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case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_NORM):
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break;
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}
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/* flip sign of y and handle as add */
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ys ^= 1;
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assert(xm & DP_HIDDEN_BIT);
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assert(ym & DP_HIDDEN_BIT);
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/* provide guard,round and stick bit dpace */
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xm <<= 3;
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ym <<= 3;
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if (xe > ye) {
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/*
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* Have to shift y fraction right to align
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*/
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s = xe - ye;
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ym = XDPSRS(ym, s);
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ye += s;
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} else if (ye > xe) {
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/*
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* Have to shift x fraction right to align
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*/
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s = ye - xe;
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xm = XDPSRS(xm, s);
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xe += s;
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}
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assert(xe == ye);
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assert(xe <= DP_EMAX);
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if (xs == ys) {
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/* generate 28 bit result of adding two 27 bit numbers
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*/
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xm = xm + ym;
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if (xm >> (DP_FBITS + 1 + 3)) { /* carry out */
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xm = XDPSRS1(xm); /* shift preserving sticky */
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xe++;
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}
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} else {
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if (xm >= ym) {
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xm = xm - ym;
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} else {
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xm = ym - xm;
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xs = ys;
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}
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if (xm == 0) {
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if (ieee754_csr.rm == FPU_CSR_RD)
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return ieee754dp_zero(1); /* round negative inf. => sign = -1 */
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else
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return ieee754dp_zero(0); /* other round modes => sign = 1 */
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}
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/* normalize to rounding precision
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*/
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while ((xm >> (DP_FBITS + 3)) == 0) {
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xm <<= 1;
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xe--;
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}
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}
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return ieee754dp_format(xs, xe, xm);
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}
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