alistair23-linux/arch/mips/math-emu/sp_maddf.c
Aleksandar Markovic 2a14b21acd MIPS: math-emu: Mark fall throughs in switch statements with a comment
Mark intentional fall throughs in switch statements with a consistent
comment.

In most of the cases, a new comment line containing text "fall through"
is inserted. In some of the cases, existing comment contained a variation
of the text "fall through" (for example, "FALL THROUGH" or "drop through").
In such cases, the existing comment is modified to contain "fall through".
Lastly, in two cases, code segments were described in comments as "fall
througs", but were in reality "breaks out" of switch statement. In such
cases, existing comments are accordingly modified.

Apart from making code easier to follow and debug, this change enables
some static code analysers to interpret newly inserted comments as their
annotations (and, therefore, not issue warnings of type "fall through in
switch statement", which is desireable, since marked fallthroughs are
intentional).

Signed-off-by: Aleksandar Markovic <aleksandar.markovic@mips.com>
Cc: Douglas Leung <douglas.leung@mips.com>
Cc: Goran Ferenc <goran.ferenc@mips.com>
Cc: James Hogan <james.hogan@mips.com>
Cc: Maciej W. Rozycki <macro@mips.com>
Cc: Manuel Lauss <manuel.lauss@gmail.com>
Cc: Miodrag Dinic <miodrag.dinic@mips.com>
Cc: Paul Burton <paul.burton@mips.com>
Cc: Petar Jovanovic <petar.jovanovic@mips.com>
Cc: Raghu Gandham <raghu.gandham@mips.com>
Cc: linux-kernel@vger.kernel.org
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/17588/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
2017-12-12 17:20:20 +01:00

266 lines
6.4 KiB
C

/*
* IEEE754 floating point arithmetic
* single precision: MADDF.f (Fused Multiply Add)
* MADDF.fmt: FPR[fd] = FPR[fd] + (FPR[fs] x FPR[ft])
*
* MIPS floating point support
* Copyright (C) 2015 Imagination Technologies, Ltd.
* Author: Markos Chandras <markos.chandras@imgtec.com>
*
* This program is free software; you can distribute it and/or modify it
* under the terms of the GNU General Public License as published by the
* Free Software Foundation; version 2 of the License.
*/
#include "ieee754sp.h"
static union ieee754sp _sp_maddf(union ieee754sp z, union ieee754sp x,
union ieee754sp y, enum maddf_flags flags)
{
int re;
int rs;
unsigned int rm;
u64 rm64;
u64 zm64;
int s;
COMPXSP;
COMPYSP;
COMPZSP;
EXPLODEXSP;
EXPLODEYSP;
EXPLODEZSP;
FLUSHXSP;
FLUSHYSP;
FLUSHZSP;
ieee754_clearcx();
/*
* Handle the cases when at least one of x, y or z is a NaN.
* Order of precedence is sNaN, qNaN and z, x, y.
*/
if (zc == IEEE754_CLASS_SNAN)
return ieee754sp_nanxcpt(z);
if (xc == IEEE754_CLASS_SNAN)
return ieee754sp_nanxcpt(x);
if (yc == IEEE754_CLASS_SNAN)
return ieee754sp_nanxcpt(y);
if (zc == IEEE754_CLASS_QNAN)
return z;
if (xc == IEEE754_CLASS_QNAN)
return x;
if (yc == IEEE754_CLASS_QNAN)
return y;
if (zc == IEEE754_CLASS_DNORM)
SPDNORMZ;
/* ZERO z cases are handled separately below */
switch (CLPAIR(xc, yc)) {
/*
* Infinity handling
*/
case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_ZERO):
case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_INF):
ieee754_setcx(IEEE754_INVALID_OPERATION);
return ieee754sp_indef();
case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_INF):
case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_INF):
case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_NORM):
case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_DNORM):
case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_INF):
if ((zc == IEEE754_CLASS_INF) &&
((!(flags & MADDF_NEGATE_PRODUCT) && (zs != (xs ^ ys))) ||
((flags & MADDF_NEGATE_PRODUCT) && (zs == (xs ^ ys))))) {
/*
* Cases of addition of infinities with opposite signs
* or subtraction of infinities with same signs.
*/
ieee754_setcx(IEEE754_INVALID_OPERATION);
return ieee754sp_indef();
}
/*
* z is here either not an infinity, or an infinity having the
* same sign as product (x*y) (in case of MADDF.D instruction)
* or product -(x*y) (in MSUBF.D case). The result must be an
* infinity, and its sign is determined only by the value of
* (flags & MADDF_NEGATE_PRODUCT) and the signs of x and y.
*/
if (flags & MADDF_NEGATE_PRODUCT)
return ieee754sp_inf(1 ^ (xs ^ ys));
else
return ieee754sp_inf(xs ^ ys);
case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_ZERO):
case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_NORM):
case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_DNORM):
case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_ZERO):
case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_ZERO):
if (zc == IEEE754_CLASS_INF)
return ieee754sp_inf(zs);
if (zc == IEEE754_CLASS_ZERO) {
/* Handle cases +0 + (-0) and similar ones. */
if ((!(flags & MADDF_NEGATE_PRODUCT)
&& (zs == (xs ^ ys))) ||
((flags & MADDF_NEGATE_PRODUCT)
&& (zs != (xs ^ ys))))
/*
* Cases of addition of zeros of equal signs
* or subtraction of zeroes of opposite signs.
* The sign of the resulting zero is in any
* such case determined only by the sign of z.
*/
return z;
return ieee754sp_zero(ieee754_csr.rm == FPU_CSR_RD);
}
/* x*y is here 0, and z is not 0, so just return z */
return z;
case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM):
SPDNORMX;
/* fall through */
case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_DNORM):
if (zc == IEEE754_CLASS_INF)
return ieee754sp_inf(zs);
SPDNORMY;
break;
case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_NORM):
if (zc == IEEE754_CLASS_INF)
return ieee754sp_inf(zs);
SPDNORMX;
break;
case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_NORM):
if (zc == IEEE754_CLASS_INF)
return ieee754sp_inf(zs);
/* continue to real computations */
}
/* Finally get to do some computation */
/*
* Do the multiplication bit first
*
* rm = xm * ym, re = xe + ye basically
*
* At this point xm and ym should have been normalized.
*/
/* rm = xm * ym, re = xe+ye basically */
assert(xm & SP_HIDDEN_BIT);
assert(ym & SP_HIDDEN_BIT);
re = xe + ye;
rs = xs ^ ys;
if (flags & MADDF_NEGATE_PRODUCT)
rs ^= 1;
/* Multiple 24 bit xm and ym to give 48 bit results */
rm64 = (uint64_t)xm * ym;
/* Shunt to top of word */
rm64 = rm64 << 16;
/* Put explicit bit at bit 62 if necessary */
if ((int64_t) rm64 < 0) {
rm64 = rm64 >> 1;
re++;
}
assert(rm64 & (1 << 62));
if (zc == IEEE754_CLASS_ZERO) {
/*
* Move explicit bit from bit 62 to bit 26 since the
* ieee754sp_format code expects the mantissa to be
* 27 bits wide (24 + 3 rounding bits).
*/
rm = XSPSRS64(rm64, (62 - 26));
return ieee754sp_format(rs, re, rm);
}
/* Move explicit bit from bit 23 to bit 62 */
zm64 = (uint64_t)zm << (62 - 23);
assert(zm64 & (1 << 62));
/* Make the exponents the same */
if (ze > re) {
/*
* Have to shift r fraction right to align.
*/
s = ze - re;
rm64 = XSPSRS64(rm64, s);
re += s;
} else if (re > ze) {
/*
* Have to shift z fraction right to align.
*/
s = re - ze;
zm64 = XSPSRS64(zm64, s);
ze += s;
}
assert(ze == re);
assert(ze <= SP_EMAX);
/* Do the addition */
if (zs == rs) {
/*
* Generate 64 bit result by adding two 63 bit numbers
* leaving result in zm64, zs and ze.
*/
zm64 = zm64 + rm64;
if ((int64_t)zm64 < 0) { /* carry out */
zm64 = XSPSRS1(zm64);
ze++;
}
} else {
if (zm64 >= rm64) {
zm64 = zm64 - rm64;
} else {
zm64 = rm64 - zm64;
zs = rs;
}
if (zm64 == 0)
return ieee754sp_zero(ieee754_csr.rm == FPU_CSR_RD);
/*
* Put explicit bit at bit 62 if necessary.
*/
while ((zm64 >> 62) == 0) {
zm64 <<= 1;
ze--;
}
}
/*
* Move explicit bit from bit 62 to bit 26 since the
* ieee754sp_format code expects the mantissa to be
* 27 bits wide (24 + 3 rounding bits).
*/
zm = XSPSRS64(zm64, (62 - 26));
return ieee754sp_format(zs, ze, zm);
}
union ieee754sp ieee754sp_maddf(union ieee754sp z, union ieee754sp x,
union ieee754sp y)
{
return _sp_maddf(z, x, y, 0);
}
union ieee754sp ieee754sp_msubf(union ieee754sp z, union ieee754sp x,
union ieee754sp y)
{
return _sp_maddf(z, x, y, MADDF_NEGATE_PRODUCT);
}