[PATCH 4.13 020/109] MIPS: math-emu: <MAXA|MINA>.<D|S>: Fix cases of input values with opposite signs

Greg Kroah-Hartman
2017-09-24T21:02:01Z

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

commit 1a41b3b441508ae63b1a9ec699ec94065739eb60 upstream.

Fix the value returned by <MAXA|MINA>.<D|S>, if the inputs are normal
fp numbers of the same absolute value, but opposite signs.

A relevant example:

MAXA.S fd,fs,ft:
If fs contains -3.0, and ft contains +3.0, fd is going to contain
+3.0 (without this patch, it used to contain -3.0).

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/16883/
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 | 8 ++++++--
arch/mips/math-emu/dp_fmin.c | 6 +++++-
arch/mips/math-emu/sp_fmax.c | 8 ++++++--
arch/mips/math-emu/sp_fmin.c | 6 +++++-
4 files changed, 22 insertions(+), 6 deletions(-)

--- a/arch/mips/math-emu/dp_fmax.c
+++ b/arch/mips/math-emu/dp_fmax.c
@@ -243,7 +243,11 @@ union ieee754dp ieee754dp_fmaxa(union ie
return y;

/* Compare mantissa */
- if (xm <= ym)
+ if (xm < ym)
return y;
- return x;
+ else if (xm > ym)
+ return x;
+ else if (xs == 0)
+ return x;
+ return y;
}
--- a/arch/mips/math-emu/dp_fmin.c
+++ b/arch/mips/math-emu/dp_fmin.c
@@ -243,7 +243,11 @@ union ieee754dp ieee754dp_fmina(union ie
return x;

/* Compare mantissa */
- if (xm <= ym)
+ if (xm < ym)
+ return x;
+ else if (xm > ym)
+ return y;
+ else if (xs == 1)
return x;
return y;
}
--- a/arch/mips/math-emu/sp_fmax.c
+++ b/arch/mips/math-emu/sp_fmax.c
@@ -243,7 +243,11 @@ union ieee754sp ieee754sp_fmaxa(union ie
return y;

/* Compare mantissa */
- if (xm <= ym)
+ if (xm < ym)
return y;
- return x;
+ else if (xm > ym)
+ return x;
+ else if (xs == 0)
+ return x;
+ return y;
}
--- a/arch/mips/math-emu/sp_fmin.c
+++ b/arch/mips/math-emu/sp_fmin.c
@@ -243,7 +243,11 @@ union ieee754sp ieee754sp_fmina(union ie
return x;

/* Compare mantissa */
- if (xm <= ym)
+ if (xm < ym)
+ return x;
+ else if (xm > ym)
+ return y;
+ else if (xs == 1)
return x;
return y;
}