[PATCH] Fix absd emulation

[PATCH] Fix absd emulation

[Raghu Gandham]

From: Robin Randhawa <robin@mips.com>

Signed-off-by: Chris Dearman <chris@mips.com>
---

 arch/mips/math-emu/dp_simple.c |   11 ++++-------
 arch/mips/math-emu/sp_simple.c |    3 ---
 2 files changed, 4 insertions(+), 10 deletions(-)

diff --git a/arch/mips/math-emu/dp_simple.c b/arch/mips/math-emu/dp_simple.c
index 1c555e6..6ff4655 100644
--- a/arch/mips/math-emu/dp_simple.c
+++ b/arch/mips/math-emu/dp_simple.c
@@ -76,15 +76,12 @@ ieee754dp ieee754dp_abs(ieee754dp x)
 	CLEARCX;
 	FLUSHXDP;
 
+	/* Clear sign ALWAYS, irrespective of NaN */
+	DPSIGN(x) = 0;
+
 	if (xc == IEEE754_CLASS_SNAN) {
 		SETCX(IEEE754_INVALID_OPERATION);
-		return ieee754dp_nanxcpt(ieee754dp_indef(), "neg");
+		return ieee754dp_nanxcpt(ieee754dp_indef(), "abs");
 	}
-
-	if (ieee754dp_isnan(x))	/* but not infinity */
-		return ieee754dp_nanxcpt(x, "abs", x);
-
-	/* quick fix up */
-	DPSIGN(x) = 0;
 	return x;
 }
diff --git a/arch/mips/math-emu/sp_simple.c b/arch/mips/math-emu/sp_simple.c
index 770f0f4..cdec1a2 100644
--- a/arch/mips/math-emu/sp_simple.c
+++ b/arch/mips/math-emu/sp_simple.c
@@ -61,9 +61,6 @@ ieee754sp ieee754sp_neg(ieee754sp x)
 		SPSIGN(y) = SPSIGN(x);
 		return ieee754sp_nanxcpt(y, "neg");
 	}
-
-	if (ieee754sp_isnan(x))	/* but not infinity */
-		return ieee754sp_nanxcpt(x, "neg", x);
 	return x;
 }
 

Re: [PATCH] Fix absd emulation

[Ralf Baechle]

On Fri, Jul 10, 2009 at 01:50:58AM -0700, Raghu Gandham wrote:

> From: Robin Randhawa <robin@mips.com>
> 
> Signed-off-by: Chris Dearman <chris@mips.com>
> ---
> 
>  arch/mips/math-emu/dp_simple.c |   11 ++++-------
>  arch/mips/math-emu/sp_simple.c |    3 ---
>  2 files changed, 4 insertions(+), 10 deletions(-)
> 
> diff --git a/arch/mips/math-emu/dp_simple.c b/arch/mips/math-emu/dp_simple.c
> index 1c555e6..6ff4655 100644
> --- a/arch/mips/math-emu/dp_simple.c
> +++ b/arch/mips/math-emu/dp_simple.c
> @@ -76,15 +76,12 @@ ieee754dp ieee754dp_abs(ieee754dp x)
>  	CLEARCX;
>  	FLUSHXDP;
>  
> +	/* Clear sign ALWAYS, irrespective of NaN */
> +	DPSIGN(x) = 0;
> +
>  	if (xc == IEEE754_CLASS_SNAN) {
>  		SETCX(IEEE754_INVALID_OPERATION);
> -		return ieee754dp_nanxcpt(ieee754dp_indef(), "neg");
> +		return ieee754dp_nanxcpt(ieee754dp_indef(), "abs");
>  	}
> -
> -	if (ieee754dp_isnan(x))	/* but not infinity */
> -		return ieee754dp_nanxcpt(x, "abs", x);
> -
> -	/* quick fix up */
> -	DPSIGN(x) = 0;
>  	return x;
>  }

It seems that abs.s needs the same changes except the string constant.  Or
why was only abs.d changed?

(And what is the official behaviour anyway.  It seems I can spend another
quality night over IEEE 754 ...)

> diff --git a/arch/mips/math-emu/sp_simple.c b/arch/mips/math-emu/sp_simple.c
> index 770f0f4..cdec1a2 100644
> --- a/arch/mips/math-emu/sp_simple.c
> +++ b/arch/mips/math-emu/sp_simple.c
> @@ -61,9 +61,6 @@ ieee754sp ieee754sp_neg(ieee754sp x)
>  		SPSIGN(y) = SPSIGN(x);
>  		return ieee754sp_nanxcpt(y, "neg");
>  	}
> -
> -	if (ieee754sp_isnan(x))	/* but not infinity */
> -		return ieee754sp_nanxcpt(x, "neg", x);
>  	return x;
>  }

The subject of the patch was claiming a fix to abs.d but this is fiddling
with neg.s.  And why not the equivalent change to neg.d?

  Ralf

Re: [PATCH] Fix absd emulation

[Chris Dearman]

It seems like the original patch got mangled somewhere along the line. It
should correct the behaviour of abs.[sd] and neg.[sd]. I'll repost the
correct patch.

Chris

-- 
Chris Dearman               Desk: +1 408 530 5092  Cell: +1 650 224 8603
MIPS Technologies Inc            955 East Arques Ave, Sunnyvale CA 94085

[PATCH] Fix abs.[sd] and neg.[sd] emulation for NaN operands

[Chris Dearman]

From: Nigel Stephens <nigel@mips.com>

This patch ensures that the sign bit is always updated
for NaN operands.

Signed-off-by: Chris Dearman <chris@mips.com>
---

 arch/mips/math-emu/dp_simple.c |   13 ++++---------
 arch/mips/math-emu/sp_simple.c |   11 +++--------
 2 files changed, 7 insertions(+), 17 deletions(-)

diff --git a/arch/mips/math-emu/dp_simple.c b/arch/mips/math-emu/dp_simple.c
index 1c555e6..d9ae1db 100644
--- a/arch/mips/math-emu/dp_simple.c
+++ b/arch/mips/math-emu/dp_simple.c
@@ -62,8 +62,6 @@ ieee754dp ieee754dp_neg(ieee754dp x)
 		return ieee754dp_nanxcpt(y, "neg");
 	}
 
-	if (ieee754dp_isnan(x))	/* but not infinity */
-		return ieee754dp_nanxcpt(x, "neg", x);
 	return x;
 }
 
@@ -76,15 +74,12 @@ ieee754dp ieee754dp_abs(ieee754dp x)
 	CLEARCX;
 	FLUSHXDP;
 
+	/* Clear sign ALWAYS, irrespective of NaN */
+	DPSIGN(x) = 0;
+
 	if (xc == IEEE754_CLASS_SNAN) {
-		SETCX(IEEE754_INVALID_OPERATION);
-		return ieee754dp_nanxcpt(ieee754dp_indef(), "neg");
+		return ieee754dp_nanxcpt(ieee754dp_indef(), "abs");
 	}
 
-	if (ieee754dp_isnan(x))	/* but not infinity */
-		return ieee754dp_nanxcpt(x, "abs", x);
-
-	/* quick fix up */
-	DPSIGN(x) = 0;
 	return x;
 }
diff --git a/arch/mips/math-emu/sp_simple.c b/arch/mips/math-emu/sp_simple.c
index 770f0f4..3175477 100644
--- a/arch/mips/math-emu/sp_simple.c
+++ b/arch/mips/math-emu/sp_simple.c
@@ -62,8 +62,6 @@ ieee754sp ieee754sp_neg(ieee754sp x)
 		return ieee754sp_nanxcpt(y, "neg");
 	}
 
-	if (ieee754sp_isnan(x))	/* but not infinity */
-		return ieee754sp_nanxcpt(x, "neg", x);
 	return x;
 }
 
@@ -76,15 +74,12 @@ ieee754sp ieee754sp_abs(ieee754sp x)
 	CLEARCX;
 	FLUSHXSP;
 
+	/* Clear sign ALWAYS, irrespective of NaN */
+	SPSIGN(x) = 0;
+
 	if (xc == IEEE754_CLASS_SNAN) {
-		SETCX(IEEE754_INVALID_OPERATION);
 		return ieee754sp_nanxcpt(ieee754sp_indef(), "abs");
 	}
 
-	if (ieee754sp_isnan(x))	/* but not infinity */
-		return ieee754sp_nanxcpt(x, "abs", x);
-
-	/* quick fix up */
-	SPSIGN(x) = 0;
 	return x;
 }

Re: [PATCH] Fix abs.[sd] and neg.[sd] emulation for NaN operands

[Atsushi Nemoto]

Excuse me for too late comment.

On Mon, 12 Oct 2009 14:57:18 -0700, Chris Dearman <chris@mips.com> wrote:
> From: Nigel Stephens <nigel@mips.com>
> 
> This patch ensures that the sign bit is always updated
> for NaN operands.
...
> @@ -76,15 +74,12 @@ ieee754dp ieee754dp_abs(ieee754dp x)
>  	CLEARCX;
>  	FLUSHXDP;
>  
> +	/* Clear sign ALWAYS, irrespective of NaN */
> +	DPSIGN(x) = 0;
> +
>  	if (xc == IEEE754_CLASS_SNAN) {
> -		SETCX(IEEE754_INVALID_OPERATION);
> -		return ieee754dp_nanxcpt(ieee754dp_indef(), "neg");
> +		return ieee754dp_nanxcpt(ieee754dp_indef(), "abs");
>  	}
>  
> -	if (ieee754dp_isnan(x))	/* but not infinity */
> -		return ieee754dp_nanxcpt(x, "abs", x);
> -
> -	/* quick fix up */
> -	DPSIGN(x) = 0;
>  	return x;
>  }

Is there any reason for removal of SETCX(IEEE754_INVALID_OPERATION)
line here?

The older version of this fix ("Fix absd emulation" by Raghu Gandham)
did not remove the line.

Without this line, a signaling NaN will not raise a signal.  It seems
not expected behaviour.

---
Atsushi Nemoto

Re: [PATCH] Fix abs.[sd] and neg.[sd] emulation for NaN operands

[Chris Dearman]

Atsushi Nemoto wrote:
> Excuse me for too late comment.
> 
> On Mon, 12 Oct 2009 14:57:18 -0700, Chris Dearman <chris@mips.com> wrote:
>> From: Nigel Stephens <nigel@mips.com>
>>
>> This patch ensures that the sign bit is always updated
>> for NaN operands.
> ...
>> @@ -76,15 +74,12 @@ ieee754dp ieee754dp_abs(ieee754dp x)
>>  	CLEARCX;
>>  	FLUSHXDP;
>>  
>> +	/* Clear sign ALWAYS, irrespective of NaN */
>> +	DPSIGN(x) = 0;
>> +
>>  	if (xc == IEEE754_CLASS_SNAN) {
>> -		SETCX(IEEE754_INVALID_OPERATION);
>> -		return ieee754dp_nanxcpt(ieee754dp_indef(), "neg");
>> +		return ieee754dp_nanxcpt(ieee754dp_indef(), "abs");
>>  	}
>>  
>> -	if (ieee754dp_isnan(x))	/* but not infinity */
>> -		return ieee754dp_nanxcpt(x, "abs", x);
>> -
>> -	/* quick fix up */
>> -	DPSIGN(x) = 0;
>>  	return x;
>>  }
> 
> Is there any reason for removal of SETCX(IEEE754_INVALID_OPERATION)
> line here?
> 
> The older version of this fix ("Fix absd emulation" by Raghu Gandham)
> did not remove the line.
> 
> Without this line, a signaling NaN will not raise a signal.  It seems
> not expected behaviour.

ieee754dp/sp_nanxcpt also sets the invalid exception bit so I think this 
is duplicated code. I think the same fix should have been applied to 
ieee754sp_neg/ieee754dp_neg for consistency.

Chris

-- 
Chris Dearman               Desk: +1 408 530 5092  Cell: +1 408 398 5531
MIPS Technologies Inc            955 East Arques Ave, Sunnyvale CA 94085

Re: [PATCH] Fix abs.[sd] and neg.[sd] emulation for NaN operands

[Atsushi Nemoto]

On Mon, 10 May 2010 11:37:10 -0700, Chris Dearman <chris@mips.com> wrote:
> >>  	if (xc == IEEE754_CLASS_SNAN) {
> >> -		SETCX(IEEE754_INVALID_OPERATION);
> >> -		return ieee754dp_nanxcpt(ieee754dp_indef(), "neg");
> >> +		return ieee754dp_nanxcpt(ieee754dp_indef(), "abs");
> >>  	}
...
> ieee754dp/sp_nanxcpt also sets the invalid exception bit so I think this 
> is duplicated code. I think the same fix should have been applied to 
> ieee754sp_neg/ieee754dp_neg for consistency.

ieee754d/sp_nanxcpt will set the invalid exception bit if its first
argument was a signaling NaN.  And ieee754dp/sp_indef() is a quiet
NaN.

---
Atsushi Nemoto

Re: [PATCH] Fix abs.[sd] and neg.[sd] emulation for NaN operands

[Chris Dearman]

Atsushi Nemoto wrote:
> 
> ieee754d/sp_nanxcpt will set the invalid exception bit if its first
> argument was a signaling NaN.  And ieee754dp/sp_indef() is a quiet
> NaN.

You're right! I'll send a separate patch with an appropriate subject to 
correct this.

Thanks
Chris

-- 
Chris Dearman               Desk: +1 408 530 5092  Cell: +1 408 398 5531
MIPS Technologies Inc            955 East Arques Ave, Sunnyvale CA 94085

[PATCH] Restore signalling NaN behaviour for abs.[sd]

[Chris Dearman]

Atsushi Nemoto <anemo@mba.ocn.ne.jp> spotted that this had been
incorrectly removed in a previous patch

Signed-off-by: Chris Dearman <chris@mips.com>
---

 arch/mips/math-emu/dp_simple.c |    1 +
 arch/mips/math-emu/sp_simple.c |    1 +
 2 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/arch/mips/math-emu/dp_simple.c b/arch/mips/math-emu/dp_simple.c
index d9ae1db..b909742 100644
--- a/arch/mips/math-emu/dp_simple.c
+++ b/arch/mips/math-emu/dp_simple.c
@@ -78,6 +78,7 @@ ieee754dp ieee754dp_abs(ieee754dp x)
 	DPSIGN(x) = 0;
 
 	if (xc == IEEE754_CLASS_SNAN) {
+		SETCX(IEEE754_INVALID_OPERATION);
 		return ieee754dp_nanxcpt(ieee754dp_indef(), "abs");
 	}
 
diff --git a/arch/mips/math-emu/sp_simple.c b/arch/mips/math-emu/sp_simple.c
index 3175477..2fd53c9 100644
--- a/arch/mips/math-emu/sp_simple.c
+++ b/arch/mips/math-emu/sp_simple.c
@@ -78,6 +78,7 @@ ieee754sp ieee754sp_abs(ieee754sp x)
 	SPSIGN(x) = 0;
 
 	if (xc == IEEE754_CLASS_SNAN) {
+		SETCX(IEEE754_INVALID_OPERATION);
 		return ieee754sp_nanxcpt(ieee754sp_indef(), "abs");
 	}
 

Re: [PATCH] Restore signalling NaN behaviour for abs.[sd]

[Atsushi Nemoto]

On Tue, 11 May 2010 18:30:34 -0700, Chris Dearman <chris@mips.com> wrote:
> Atsushi Nemoto <anemo@mba.ocn.ne.jp> spotted that this had been
> incorrectly removed in a previous patch
> 
> Signed-off-by: Chris Dearman <chris@mips.com>

Thanks!

Tested-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>

Re: [PATCH] Restore signalling NaN behaviour for abs.[sd]

[Ralf Baechle]

On Tue, May 11, 2010 at 06:30:34PM -0700, Chris Dearman wrote:

Thanks, applied.

  Ralf