Patch "MIPS: math-emu: <MADDF|MSUBF>.<D|S>: Fix some cases of zero inputs" has been added to the 4.13-stable tree

[<gregkh@linuxfoundation.org>]

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

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

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-maddf-msubf-.-d-s-fix-some-cases-of-zero-inputs.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 <stable@vger.kernel.org> know about it.


>From 7cf64ce4d37f1b4f44365fcf77f565d523819dcd Mon Sep 17 00:00:00 2001
From: Aleksandar Markovic <aleksandar.markovic@imgtec.com>
Date: Thu, 27 Jul 2017 18:08:56 +0200
Subject: MIPS: math-emu: <MADDF|MSUBF>.<D|S>: Fix some cases of zero inputs

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

commit 7cf64ce4d37f1b4f44365fcf77f565d523819dcd upstream.

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: e24c3bec3e8e ("MIPS: math-emu: Add support for the MIPS R6 MADDF FPU instruction")
Fixes: 83d43305a1df ("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: 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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/mips/math-emu/dp_maddf.c |   18 +++++++++++++++++-
 arch/mips/math-emu/sp_maddf.c |   18 +++++++++++++++++-
 2 files changed, 34 insertions(+), 2 deletions(-)

--- a/arch/mips/math-emu/dp_maddf.c
+++ b/arch/mips/math-emu/dp_maddf.c
@@ -113,7 +113,23 @@ static union ieee754dp _dp_maddf(union i
 	case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_ZERO):
 		if (zc == IEEE754_CLASS_INF)
 			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;
 
 	case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM):
--- a/arch/mips/math-emu/sp_maddf.c
+++ b/arch/mips/math-emu/sp_maddf.c
@@ -114,7 +114,23 @@ static union ieee754sp _sp_maddf(union i
 	case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_ZERO):
 		if (zc == IEEE754_CLASS_INF)
 			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;
 
 	case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM):


Patches currently in stable-queue which might be from aleksandar.markovic@imgtec.com 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