MIPS: math-emu: <MAX|MAXA|MIN|MINA>.<D|S>: Fix cases of both inputs zero

Fix the value returned by <MAX|MAXA|MIN|MINA>.<D|S>, if both inputs
are zeros. The right behavior in such cases is stated in instruction
reference manual and is as follows:

   fs  ft       MAX     MIN       MAXA    MINA
  ---------------------------------------------
    0   0        0       0         0       0
    0  -0        0      -0         0      -0
   -0   0        0      -0         0      -0
   -0  -0       -0      -0        -0      -0

Prior to this patch, some of the above cases were yielding correct
results. However, for the sake of code consistency, all such cases
are rewritten in this patch.

A relevant example:

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

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: <stable@vger.kernel.org> # 4.3+
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/16881/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

diff --git a/arch/mips/math-emu/dp_fmax.c b/arch/mips/math-emu/dp_fmax.c
index 41bd6ed852b905d66c69670bdaeef5e6e1c0f569..31f091a7819bbbf9b080ad6c8c3f343eb31b50c0 100644 (file)
--- a/arch/mips/math-emu/dp_fmax.c
+++ b/arch/mips/math-emu/dp_fmax.c
@@ -92,9 +92,7 @@ union ieee754dp ieee754dp_fmax(union ieee754dp x, union ieee754dp y)
                return ys ? x : y;
 
        case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_ZERO):
-               if (xs == ys)
-                       return x;
-               return ieee754dp_zero(1);
+               return ieee754dp_zero(xs & ys);
 
        case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM):
                DPDNORMX;
@@ -204,9 +202,7 @@ union ieee754dp ieee754dp_fmaxa(union ieee754dp x, union ieee754dp y)
                return y;
 
        case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_ZERO):
-               if (xs == ys)
-                       return x;
-               return ieee754dp_zero(1);
+               return ieee754dp_zero(xs & ys);
 
        case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM):
                DPDNORMX;

diff --git a/arch/mips/math-emu/dp_fmin.c b/arch/mips/math-emu/dp_fmin.c
index 53fb8c904e32dc72903a417bb60e016489b3b317..e607d55208ad0fd2b94311b586a47590c7c6ff7d 100644 (file)
--- a/arch/mips/math-emu/dp_fmin.c
+++ b/arch/mips/math-emu/dp_fmin.c
@@ -92,9 +92,7 @@ union ieee754dp ieee754dp_fmin(union ieee754dp x, union ieee754dp y)
                return ys ? y : x;
 
        case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_ZERO):
-               if (xs == ys)
-                       return x;
-               return ieee754dp_zero(1);
+               return ieee754dp_zero(xs | ys);
 
        case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM):
                DPDNORMX;
@@ -204,9 +202,7 @@ union ieee754dp ieee754dp_fmina(union ieee754dp x, union ieee754dp y)
                return y;
 
        case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_ZERO):
-               if (xs == ys)
-                       return x;
-               return ieee754dp_zero(1);
+               return ieee754dp_zero(xs | ys);
 
        case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM):
                DPDNORMX;

diff --git a/arch/mips/math-emu/sp_fmax.c b/arch/mips/math-emu/sp_fmax.c
index d0d73c3226dc6c11a1a45895d54835c6362ded10..3ca5b204e9d01be6ce079593a98cb859ccf9515c 100644 (file)
--- a/arch/mips/math-emu/sp_fmax.c
+++ b/arch/mips/math-emu/sp_fmax.c
@@ -92,9 +92,7 @@ union ieee754sp ieee754sp_fmax(union ieee754sp x, union ieee754sp y)
                return ys ? x : y;
 
        case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_ZERO):
-               if (xs == ys)
-                       return x;
-               return ieee754sp_zero(1);
+               return ieee754sp_zero(xs & ys);
 
        case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM):
                SPDNORMX;
@@ -204,9 +202,7 @@ union ieee754sp ieee754sp_fmaxa(union ieee754sp x, union ieee754sp y)
                return y;
 
        case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_ZERO):
-               if (xs == ys)
-                       return x;
-               return ieee754sp_zero(1);
+               return ieee754sp_zero(xs & ys);
 
        case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM):
                SPDNORMX;

diff --git a/arch/mips/math-emu/sp_fmin.c b/arch/mips/math-emu/sp_fmin.c
index 011692e326af4ef31473ad05321ee6248ffd1daf..c982647df39a20f5bfacf00dd8a55389d1440bea 100644 (file)
--- a/arch/mips/math-emu/sp_fmin.c
+++ b/arch/mips/math-emu/sp_fmin.c
@@ -92,9 +92,7 @@ union ieee754sp ieee754sp_fmin(union ieee754sp x, union ieee754sp y)
                return ys ? y : x;
 
        case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_ZERO):
-               if (xs == ys)
-                       return x;
-               return ieee754sp_zero(1);
+               return ieee754sp_zero(xs | ys);
 
        case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM):
                SPDNORMX;
@@ -204,9 +202,7 @@ union ieee754sp ieee754sp_fmina(union ieee754sp x, union ieee754sp y)
                return y;
 
        case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_ZERO):
-               if (xs == ys)
-                       return x;
-               return ieee754sp_zero(1);
+               return ieee754sp_zero(xs | ys);
 
        case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM):
                SPDNORMX;