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Re: k_sinl bug fix for ldbl-128 and ldbl-128ibm


On Fri, 16 Mar 2012, Joseph S. Myers wrote:

> On Thu, 15 Mar 2012, David Miller wrote:
> 
> > This gives new ULPs on sparc, this is test-ldouble.out:
> 
> Hopefully it also reduces some ULPs (which is less visible) so being on 
> average better (as was the case when making this fix for ldbl-96).
> 
> I had the idea last night that this issue only affected k_sinl, but on 
> looking at it again I think k_cosl is affected as well (and k_sincosl, 
> which I didn't pay much attention to because I'm keeping the existing 
> ldbl-96 s_sincosl for now which doesn't use k_sincosl).  So I'll post 
> revised versions of both patches that fix those other functions as well.

Like so.  The corresponding cosl fix for ldbl-96 reduces the number of 
ulps changes for test-ldouble on x86 from 20 to 16 (fixing sinl having 
reduced the number from 30 to 20).  (These are figures in the presence of 
the testsuite changes from the ldbl-96 patch - so include both ULPs for 
tests that patch newly enables as well as ULPs for tests that were already 
being run for long double.)

2012-03-16  Joseph Myers  <joseph@codesourcery.com>

	* sysdeps/ieee754/ldbl-128/k_cosl.c (__kernel_cosl): Negate y if
	negating x to take absolute value.
	* sysdeps/ieee754/ldbl-128/k_sincosl.c (__kernel_sincosl):
	Likewise.
	* sysdeps/ieee754/ldbl-128ibm/k_cosl.c (__kernel_cosl): Likewise.
	* sysdeps/ieee754/ldbl-128ibm/k_sincosl.c (__kernel_sincosl):
	Likewise.
	* sysdeps/ieee754/ldbl-128/k_sinl.c (__kernel_sinl): Negate y when
	computing low part if x was negated.
	* sysdeps/ieee754/ldbl-128ibm/k_sinl.c (__kernel_sinl): Likewise.

diff --git a/sysdeps/ieee754/ldbl-128/k_cosl.c b/sysdeps/ieee754/ldbl-128/k_cosl.c
index 4cb9dd1..aa447ec 100644
--- a/sysdeps/ieee754/ldbl-128/k_cosl.c
+++ b/sysdeps/ieee754/ldbl-128/k_cosl.c
@@ -105,7 +105,11 @@ __kernel_cosl(long double x, long double y)
 	 cosl(h+l) = cosl(h)cosl(l) - sinl(h)sinl(l).  */
       index = 0x3ffe - (tix >> 16);
       hix = (tix + (0x200 << index)) & (0xfffffc00 << index);
-      x = fabsl (x);
+      if (signbit (x))
+	{
+	  x = -x;
+	  y = -y;
+	}
       switch (index)
 	{
 	case 0: index = ((45 << 10) + hix - 0x3ffe0000) >> 8; break;
diff --git a/sysdeps/ieee754/ldbl-128/k_sincosl.c b/sysdeps/ieee754/ldbl-128/k_sincosl.c
index 98c5d62..00a21c4 100644
--- a/sysdeps/ieee754/ldbl-128/k_sincosl.c
+++ b/sysdeps/ieee754/ldbl-128/k_sincosl.c
@@ -132,7 +132,11 @@ __kernel_sincosl(long double x, long double y, long double *sinx, long double *c
 	 cosl(h+l) = cosl(h)cosl(l) - sinl(h)sinl(l).  */
       index = 0x3ffe - (tix >> 16);
       hix = (tix + (0x200 << index)) & (0xfffffc00 << index);
-      x = fabsl (x);
+      if (signbit (x))
+	{
+	  x = -x;
+	  y = -y;
+	}
       switch (index)
 	{
 	case 0: index = ((45 << 10) + hix - 0x3ffe0000) >> 8; break;
diff --git a/sysdeps/ieee754/ldbl-128/k_sinl.c b/sysdeps/ieee754/ldbl-128/k_sinl.c
index 6eaf878..1f0ca8c 100644
--- a/sysdeps/ieee754/ldbl-128/k_sinl.c
+++ b/sysdeps/ieee754/ldbl-128/k_sinl.c
@@ -116,7 +116,7 @@ __kernel_sinl(long double x, long double y, int iy)
 
       SET_LDOUBLE_WORDS64(h, ((u_int64_t)hix) << 32, 0);
       if (iy)
-	l = y - (h - x);
+	l = (ix < 0 ? -y : y) - (h - x);
       else
 	l = x - h;
       z = l * l;
diff --git a/sysdeps/ieee754/ldbl-128ibm/k_cosl.c b/sysdeps/ieee754/ldbl-128ibm/k_cosl.c
index 5241431..fc01374 100644
--- a/sysdeps/ieee754/ldbl-128ibm/k_cosl.c
+++ b/sysdeps/ieee754/ldbl-128ibm/k_cosl.c
@@ -123,7 +123,11 @@ __kernel_cosl(long double x, long double y)
     
       index = 0x3fe - (tix >> 20);
       hix = (tix + (0x200 << index)) & (0xfffffc00 << index);
-      x = fabsl (x);
+      if (signbit (x))
+	{
+	  x = -x;
+	  y = -y;
+	}
       switch (index)
 	{
 	case 0: index = ((45 << 14) + hix - 0x3fe00000) >> 12; break;
diff --git a/sysdeps/ieee754/ldbl-128ibm/k_sincosl.c b/sysdeps/ieee754/ldbl-128ibm/k_sincosl.c
index f3dd954..98fe07d 100644
--- a/sysdeps/ieee754/ldbl-128ibm/k_sincosl.c
+++ b/sysdeps/ieee754/ldbl-128ibm/k_sincosl.c
@@ -151,7 +151,11 @@ __kernel_sincosl(long double x, long double y, long double *sinx, long double *c
 
       index = 0x3fe - (tix >> 20);
       hix = (tix + (0x2000 << index)) & (0xffffc000 << index);
-      x = fabsl (x);
+      if (signbit (x))
+	{
+	  x = -x;
+	  y = -y;
+	}
       switch (index)
 	{
 	case 0: index = ((45 << 14) + hix - 0x3fe00000) >> 12; break;
diff --git a/sysdeps/ieee754/ldbl-128ibm/k_sinl.c b/sysdeps/ieee754/ldbl-128ibm/k_sinl.c
index 484b65f..94aba0b 100644
--- a/sysdeps/ieee754/ldbl-128ibm/k_sinl.c
+++ b/sysdeps/ieee754/ldbl-128ibm/k_sinl.c
@@ -134,7 +134,7 @@ __kernel_sinl(long double x, long double y, int iy)
 */
       SET_LDOUBLE_WORDS64(h, ((u_int64_t)hix) << 32, 0);
       if (iy)
-	l = y - (h - x);
+	l = (ix < 0 ? -y : y) - (h - x);
       else
 	l = x - h;
       z = l * l;

-- 
Joseph S. Myers
joseph@codesourcery.com


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