[PATCH 4.13 021/109] MIPS: math-emu: <MAXA|MINA>.<D|S>: Fix cases of both infinite inputs

Greg Kroah-Hartman
2017-09-24T20:40:48Z

From: Aleksandar Markovic <aleksandar.markovic@imgtec.com>

commit 3444c4eb534c20e44f0d6670b34263efaf8b531f upstream.

Fix the value returned by <MAXA|MINA>.<D|S> fd,fs,ft, if both inputs
are infinite. The previous implementation returned always the value
contained in ft in such cases. The correct behavior is specified
in Mips instruction set manual and is as follows:

fs ft MAXA MINA
---------------------------------
inf inf inf inf
inf -inf inf -inf
-inf inf inf -inf
-inf -inf -inf -inf

A relevant example:

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

Fixes: a79f5f9ba508 ("MIPS: math-emu: Add support for the MIPS R6 MAX{, A} FPU instruction")
Fixes: 4e9561b20e2f ("MIPS: math-emu: Add support for the MIPS R6 MIN{, A} 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: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/16884/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/mips/math-emu/dp_fmax.c | 4 +++-
arch/mips/math-emu/dp_fmin.c | 4 +++-
arch/mips/math-emu/sp_fmax.c | 4 +++-
arch/mips/math-emu/sp_fmin.c | 4 +++-
4 files changed, 12 insertions(+), 4 deletions(-)

--- a/arch/mips/math-emu/dp_fmax.c
+++ b/arch/mips/math-emu/dp_fmax.c
@@ -202,6 +202,9 @@ union ieee754dp ieee754dp_fmaxa(union ie
/*
* Infinity and zero handling
*/
+ case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_INF):
+ return ieee754dp_inf(xs & ys);
+
case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_ZERO):
case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_NORM):
case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_DNORM):
@@ -209,7 +212,6 @@ union ieee754dp ieee754dp_fmaxa(union ie
case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_ZERO):
return x;

- case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_INF):
case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_INF):
case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_INF):
case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_INF):
--- a/arch/mips/math-emu/dp_fmin.c
+++ b/arch/mips/math-emu/dp_fmin.c
@@ -202,6 +202,9 @@ union ieee754dp ieee754dp_fmina(union ie
/*
* Infinity and zero handling
*/
+ case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_INF):
+ return ieee754dp_inf(xs | ys);
+
case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_ZERO):
case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_NORM):
case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_DNORM):
@@ -209,7 +212,6 @@ union ieee754dp ieee754dp_fmina(union ie
case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_ZERO):
return x;

- case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_INF):
case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_INF):
case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_INF):
case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_INF):
--- a/arch/mips/math-emu/sp_fmax.c
+++ b/arch/mips/math-emu/sp_fmax.c
@@ -202,6 +202,9 @@ union ieee754sp ieee754sp_fmaxa(union ie
/*
* Infinity and zero handling
*/
+ case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_INF):
+ return ieee754sp_inf(xs & ys);
+
case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_ZERO):
case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_NORM):
case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_DNORM):
@@ -209,7 +212,6 @@ union ieee754sp ieee754sp_fmaxa(union ie
case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_ZERO):
return x;

- case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_INF):
case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_INF):
case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_INF):
case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_INF):
--- a/arch/mips/math-emu/sp_fmin.c
+++ b/arch/mips/math-emu/sp_fmin.c
@@ -202,6 +202,9 @@ union ieee754sp ieee754sp_fmina(union ie
/*
* Infinity and zero handling
*/
+ case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_INF):
+ return ieee754sp_inf(xs | ys);
+
case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_ZERO):
case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_NORM):
case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_DNORM):
@@ -209,7 +212,6 @@ union ieee754sp ieee754sp_fmina(union ie
case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_ZERO):
return x;

- case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_INF):
case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_INF):
case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_INF):
case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_INF):