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MIPS: math-emu: <MADDF|MSUBF>.<D|S>: Fix some cases of zero inputs

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Fix the cases of <MADDF|MSUBF>.<D|S> when any of two multiplicands is
+0 or -0, and the third input is also +0 or -0. Depending on the signs
of inputs, certain special cases must be handled.

A relevant example:

MADDF.S fd,fs,ft:
  If fs contains +0.0, ft contains -0.0, and fd contains 0.0, fd is
  going to contain +0.0 (without this patch, it used to contain -0.0).

Fixes: e24c3bec3e ("MIPS: math-emu: Add support for the MIPS R6 MADDF FPU instruction")
Fixes: 83d43305a1 ("MIPS: math-emu: Add support for the MIPS R6 MSUBF FPU instruction")

Signed-off-by: Miodrag Dinic <miodrag.dinic@imgtec.com>
Signed-off-by: Goran Ferenc <goran.ferenc@imgtec.com>
Signed-off-by: Aleksandar Markovic <aleksandar.markovic@imgtec.com>
Reviewed-by: James Hogan <james.hogan@imgtec.com>
Cc: Bo Hu <bohu@google.com>
Cc: Douglas Leung <douglas.leung@imgtec.com>
Cc: Jin Qian <jinqian@google.com>
Cc: Paul Burton <paul.burton@imgtec.com>
Cc: Petar Jovanovic <petar.jovanovic@imgtec.com>
Cc: Raghu Gandham <raghu.gandham@imgtec.com>
Cc: <stable@vger.kernel.org> # 4.7+
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/16888/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
This commit is contained in:
Aleksandar Markovic 2017-07-27 18:08:56 +02:00 committed by Ralf Baechle
parent 0c64fe6348
commit 7cf64ce4d3
2 changed files with 34 additions and 2 deletions
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18
arch/mips/math-emu/dp_maddf.c
View File

@ -113,7 +113,23 @@ static union ieee754dp _dp_maddf(union ieee754dp z, union ieee754dp x,
case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_ZERO): case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_ZERO):
if (zc == IEEE754_CLASS_INF) if (zc == IEEE754_CLASS_INF)
return ieee754dp_inf(zs); return ieee754dp_inf(zs);
/* Multiplication is 0 so just return z */ 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 ieee754dp_zero(ieee754_csr.rm == FPU_CSR_RD);
}
/* x*y is here 0, and z is not 0, so just return z */
return z; return z;
case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM): case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM):

18
arch/mips/math-emu/sp_maddf.c
View File

@ -114,7 +114,23 @@ static union ieee754sp _sp_maddf(union ieee754sp z, union ieee754sp x,
case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_ZERO): case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_ZERO):
if (zc == IEEE754_CLASS_INF) if (zc == IEEE754_CLASS_INF)
return ieee754sp_inf(zs); return ieee754sp_inf(zs);
/* Multiplication is 0 so just return z */ 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; return z;
case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM): case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM):