Patch "MIPS: math-emu: <MAX|MAXA|MIN|MINA>.<D|S>: Fix cases of both inputs zero" has been added to the 4.13-stable tree

This is a note to let you know that I've just added the patch titled

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

to the 4.13-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
mips-math-emu-max-maxa-min-mina-.-d-s-fix-cases-of-both-inputs-zero.patch
and it can be found in the queue-4.13 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Aleksandar Markovic <[email protected]>
Date: Thu, 27 Jul 2017 18:08:49 +0200
Subject: MIPS: math-emu: <MAX|MAXA|MIN|MINA>.<D|S>: Fix cases of both inputs zero

From: Aleksandar Markovic <[email protected]>

commit 15560a58bfd4ff82cdd16b2270d4ef9b06d2cc4d upstream.

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).

Patchwork: https://patchwork.linux-mips.org/patch/16881/

---
 arch/mips/math-emu/dp_fmax.c |    8 ++------
 arch/mips/math-emu/dp_fmin.c |    8 ++------
 arch/mips/math-emu/sp_fmax.c |    8 ++------
 arch/mips/math-emu/sp_fmin.c |    8 ++------
 4 files changed, 8 insertions(+), 24 deletions(-)

@@ -92,9 +92,7 @@ union ieee754dp ieee754dp_fmax(union iee
 		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 ie
 		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;

@@ -92,9 +92,7 @@ union ieee754dp ieee754dp_fmin(union iee
 		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 ie
 		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;

@@ -92,9 +92,7 @@ union ieee754sp ieee754sp_fmax(union iee
 		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 ie
 		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;

@@ -92,9 +92,7 @@ union ieee754sp ieee754sp_fmin(union iee
 		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 ie
 		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;

Patches currently in stable-queue which might be from [email protected] are

queue-4.13/mips-math-emu-maddf-msubf-.-d-s-fix-nan-propagation.patch queue-4.13/mips-math-emu-max-maxa-min-mina-.-d-s-fix-cases-of-both-inputs-zero.patch queue-4.13/mips-math-emu-max-min-.-d-s-fix-cases-of-both-inputs-negative.patch queue-4.13/mips-math-emu-max-maxa-min-mina-.-d-s-fix-quiet-nan-propagation.patch queue-4.13/mips-math-emu-maddf-msubf-.d-fix-accuracy-64-bit-case.patch queue-4.13/mips-math-emu-maddf-msubf-.s-fix-accuracy-32-bit-case.patch queue-4.13/mips-math-emu-maxa-mina-.-d-s-fix-cases-of-input-values-with-opposite-signs.patch queue-4.13/mips-math-emu-maxa-mina-.-d-s-fix-cases-of-both-infinite-inputs.patch queue-4.13/mips-math-emu-mina.-d-s-fix-some-cases-of-infinity-and-zero-inputs.patch queue-4.13/mips-math-emu-maddf-msubf-.-d-s-fix-some-cases-of-zero-inputs.patch queue-4.13/mips-math-emu-maddf-msubf-.-d-s-clean-up-maddf_flags-enumeration.patch queue-4.13/mips-math-emu-maddf-msubf-.-d-s-fix-some-cases-of-infinite-inputs.patch