diff mbox

Fix catan, catanh, __ieee754_logf in round-downward mode (bug 16799, bug 16800)

Message ID Pine.LNX.4.64.1404021425370.11925@digraph.polyomino.org.uk
State Committed
Headers

Commit Message

Joseph Myers April 2, 2014, 2:26 p.m. UTC 
  This patch fixes incorrect results from catan and catanh of certain
special inputs in round-downward mode (bug 16799), and incorrect
results of __ieee754_logf (+/-0) in round-downward mode (bug 16800)
that show up through catan/catanh when tested in all rounding modes,
but not directly in the testing for logf because the bug gets hidden
by the wrappers.

Both bugs involve a zero that should be +0 being -0 instead: one
computed as (1-x)*(1+x) in the catan/catanh case, and one as (x-x) in
the logf case.  The fixes ensure positive zero is used.  Testing of
catan and catanh in all rounding modes is duly enabled.

I expect there are various other bugs in special cases in __ieee754_*
functions that are normally hidden by the wrappers but would show up
for testing with -lieee (or in future with -fno-math-errno if we
replace -lieee and _LIB_VERSION with compile-time redirection to new
*_noerrno symbol names).

Tested x86_64 and x86 and ulps updated accordingly.

2014-04-02  Joseph Myers  <joseph@codesourcery.com>

	[BZ #16799]
	[BZ #16800]
	* math/s_catan.c (__catan): Avoid passing -0 denominator to atan2
	with 0 numerator.
	* math/s_catanf.c (__catanf): Likewise.
	* math/s_catanh.c (__catanh): Likewise.
	* math/s_catanhf.c (__catanhf): Likewise.
	* math/s_catanhl.c (__catanhl): Likewise.
	* math/s_catanl.c (__catanl): Likewise.
	* sysdeps/ieee754/flt-32/e_logf.c (__ieee754_logf): Always divide
	by positive zero when computing -Inf result.
	* math/libm-test.inc (catan_test): Use ALL_RM_TEST.
	(catanh_test): Likewise.
	* sysdeps/i386/fpu/libm-test-ulps: Update.
	* sysdeps/x86_64/fpu/libm-test-ulps: Likewise.

Comments

Andreas Jaeger April 2, 2014, 5:37 p.m. UTC | #1 
On 04/02/2014 04:26 PM, Joseph S. Myers wrote:
> This patch fixes incorrect results from catan and catanh of certain
> special inputs in round-downward mode (bug 16799), and incorrect
> results of __ieee754_logf (+/-0) in round-downward mode (bug 16800)
> that show up through catan/catanh when tested in all rounding modes,
> but not directly in the testing for logf because the bug gets hidden
> by the wrappers.
> 
> Both bugs involve a zero that should be +0 being -0 instead: one
> computed as (1-x)*(1+x) in the catan/catanh case, and one as (x-x) in
> the logf case.  The fixes ensure positive zero is used.  Testing of
> catan and catanh in all rounding modes is duly enabled.
> 
> I expect there are various other bugs in special cases in __ieee754_*
> functions that are normally hidden by the wrappers but would show up
> for testing with -lieee (or in future with -fno-math-errno if we
> replace -lieee and _LIB_VERSION with compile-time redirection to new
> *_noerrno symbol names).

Thanks,
Andreas
diff mbox

Patch

diff --git a/math/libm-test.inc b/math/libm-test.inc
index c6279e7..5e6789f 100644
--- a/math/libm-test.inc
+++ b/math/libm-test.inc
@@ -5239,9 +5239,7 @@  static const struct test_c_c_data catan_test_data[] =
 static void
 catan_test (void)
 {
-  START (catan, 0);
-  RUN_TEST_LOOP_c_c (catan, catan_test_data, );
-  END_COMPLEX;
+  ALL_RM_TEST (catan, 0, catan_test_data, RUN_TEST_LOOP_c_c, END_COMPLEX);
 }
 
 static const struct test_c_c_data catanh_test_data[] =
@@ -5746,9 +5744,7 @@  static const struct test_c_c_data catanh_test_data[] =
 static void
 catanh_test (void)
 {
-  START (catanh, 0);
-  RUN_TEST_LOOP_c_c (catanh, catanh_test_data, );
-  END_COMPLEX;
+  ALL_RM_TEST (catanh, 0, catanh_test_data, RUN_TEST_LOOP_c_c, END_COMPLEX);
 }
 
 static const struct test_f_f_data cbrt_test_data[] =
diff --git a/math/s_catan.c b/math/s_catan.c
index d6552d8..0cfa924 100644
--- a/math/s_catan.c
+++ b/math/s_catan.c
@@ -89,7 +89,11 @@  __catan (__complex__ double x)
 	    }
 
 	  if (absy < DBL_EPSILON / 2.0)
-	    den = (1.0 - absx) * (1.0 + absx);
+	    {
+	      den = (1.0 - absx) * (1.0 + absx);
+	      if (den == -0.0)
+		den = 0.0;
+	    }
 	  else if (absx >= 1.0)
 	    den = (1.0 - absx) * (1.0 + absx) - absy * absy;
 	  else if (absx >= 0.75 || absy >= 0.5)
diff --git a/math/s_catanf.c b/math/s_catanf.c
index 41e419d..b478684 100644
--- a/math/s_catanf.c
+++ b/math/s_catanf.c
@@ -90,7 +90,11 @@  __catanf (__complex__ float x)
 	    }
 
 	  if (absy < FLT_EPSILON / 2.0f)
-	    den = (1.0f - absx) * (1.0f + absx);
+	    {
+	      den = (1.0f - absx) * (1.0f + absx);
+	      if (den == -0.0f)
+		den = 0.0f;
+	    }
 	  else if (absx >= 1.0f)
 	    den = (1.0f - absx) * (1.0f + absx) - absy * absy;
 	  else if (absx >= 0.75f || absy >= 0.5f)
diff --git a/math/s_catanh.c b/math/s_catanh.c
index 2ba1298..7ef9142 100644
--- a/math/s_catanh.c
+++ b/math/s_catanh.c
@@ -110,7 +110,11 @@  __catanh (__complex__ double x)
 	    }
 
 	  if (absy < DBL_EPSILON / 2.0)
-	    den = (1.0 - absx) * (1.0 + absx);
+	    {
+	      den = (1.0 - absx) * (1.0 + absx);
+	      if (den == -0.0)
+		den = 0.0;
+	    }
 	  else if (absx >= 1.0)
 	    den = (1.0 - absx) * (1.0 + absx) - absy * absy;
 	  else if (absx >= 0.75 || absy >= 0.5)
diff --git a/math/s_catanhf.c b/math/s_catanhf.c
index 0ee69a5..0e55aff 100644
--- a/math/s_catanhf.c
+++ b/math/s_catanhf.c
@@ -112,7 +112,11 @@  __catanhf (__complex__ float x)
 	    }
 
 	  if (absy < FLT_EPSILON / 2.0f)
-	    den = (1.0f - absx) * (1.0f + absx);
+	    {
+	      den = (1.0f - absx) * (1.0f + absx);
+	      if (den == -0.0f)
+		den = 0.0f;
+	    }
 	  else if (absx >= 1.0f)
 	    den = (1.0f - absx) * (1.0f + absx) - absy * absy;
 	  else if (absx >= 0.75f || absy >= 0.5f)
diff --git a/math/s_catanhl.c b/math/s_catanhl.c
index 537bb3e..6410afe 100644
--- a/math/s_catanhl.c
+++ b/math/s_catanhl.c
@@ -118,7 +118,11 @@  __catanhl (__complex__ long double x)
 	    }
 
 	  if (absy < LDBL_EPSILON / 2.0L)
-	    den = (1.0L - absx) * (1.0L + absx);
+	    {
+	      den = (1.0L - absx) * (1.0L + absx);
+	      if (den == -0.0L)
+		den = 0.0L;
+	    }
 	  else if (absx >= 1.0L)
 	    den = (1.0L - absx) * (1.0L + absx) - absy * absy;
 	  else if (absx >= 0.75L || absy >= 0.5L)
diff --git a/math/s_catanl.c b/math/s_catanl.c
index cea9282..dd01d16 100644
--- a/math/s_catanl.c
+++ b/math/s_catanl.c
@@ -97,7 +97,11 @@  __catanl (__complex__ long double x)
 	    }
 
 	  if (absy < LDBL_EPSILON / 2.0L)
-	    den = (1.0L - absx) * (1.0L + absx);
+	    {
+	      den = (1.0L - absx) * (1.0L + absx);
+	      if (den == -0.0L)
+		den = 0.0L;
+	    }
 	  else if (absx >= 1.0L)
 	    den = (1.0L - absx) * (1.0L + absx) - absy * absy;
 	  else if (absx >= 0.75L || absy >= 0.5L)
diff --git a/sysdeps/i386/fpu/libm-test-ulps b/sysdeps/i386/fpu/libm-test-ulps
index 0252d5b..aea6c51 100644
--- a/sysdeps/i386/fpu/libm-test-ulps
+++ b/sysdeps/i386/fpu/libm-test-ulps
@@ -383,6 +383,54 @@  ifloat: 1
 ildouble: 1
 ldouble: 1
 
+Function: Real part of "catan_downward":
+double: 1
+float: 1
+idouble: 1
+ifloat: 1
+ildouble: 1
+ldouble: 1
+
+Function: Imaginary part of "catan_downward":
+double: 2
+float: 1
+idouble: 2
+ifloat: 1
+ildouble: 4
+ldouble: 4
+
+Function: Real part of "catan_towardzero":
+double: 1
+float: 1
+idouble: 1
+ifloat: 1
+ildouble: 1
+ldouble: 1
+
+Function: Imaginary part of "catan_towardzero":
+double: 2
+float: 1
+idouble: 2
+ifloat: 1
+ildouble: 4
+ldouble: 4
+
+Function: Real part of "catan_upward":
+double: 1
+float: 1
+idouble: 1
+ifloat: 1
+ildouble: 1
+ldouble: 1
+
+Function: Imaginary part of "catan_upward":
+double: 2
+float: 2
+idouble: 2
+ifloat: 2
+ildouble: 3
+ldouble: 3
+
 Function: Real part of "catanh":
 double: 1
 float: 1
@@ -391,6 +439,54 @@  ifloat: 1
 ildouble: 1
 ldouble: 1
 
+Function: Real part of "catanh_downward":
+double: 2
+float: 1
+idouble: 2
+ifloat: 1
+ildouble: 4
+ldouble: 4
+
+Function: Imaginary part of "catanh_downward":
+double: 1
+float: 1
+idouble: 1
+ifloat: 1
+ildouble: 1
+ldouble: 1
+
+Function: Real part of "catanh_towardzero":
+double: 2
+float: 1
+idouble: 2
+ifloat: 1
+ildouble: 4
+ldouble: 4
+
+Function: Imaginary part of "catanh_towardzero":
+double: 1
+float: 1
+idouble: 1
+ifloat: 1
+ildouble: 1
+ldouble: 1
+
+Function: Real part of "catanh_upward":
+double: 2
+float: 2
+idouble: 2
+ifloat: 2
+ildouble: 4
+ldouble: 4
+
+Function: Imaginary part of "catanh_upward":
+double: 1
+float: 1
+idouble: 1
+ifloat: 1
+ildouble: 1
+ldouble: 1
+
 Function: "cbrt":
 double: 1
 idouble: 1
diff --git a/sysdeps/ieee754/flt-32/e_logf.c b/sysdeps/ieee754/flt-32/e_logf.c
index 7da6489..cf75e11 100644
--- a/sysdeps/ieee754/flt-32/e_logf.c
+++ b/sysdeps/ieee754/flt-32/e_logf.c
@@ -41,7 +41,7 @@  __ieee754_logf(float x)
 	k=0;
 	if (ix < 0x00800000) {			/* x < 2**-126  */
 	    if (__builtin_expect((ix&0x7fffffff)==0, 0))
-		return -two25/(x-x);		/* log(+-0)=-inf */
+		return -two25/zero;		/* log(+-0)=-inf */
 	    if (__builtin_expect(ix<0, 0))
 		return (x-x)/(x-x);	/* log(-#) = NaN */
 	    k -= 25; x *= two25; /* subnormal number, scale up x */
diff --git a/sysdeps/x86_64/fpu/libm-test-ulps b/sysdeps/x86_64/fpu/libm-test-ulps
index 1b6ebe2..4ba83a4 100644
--- a/sysdeps/x86_64/fpu/libm-test-ulps
+++ b/sysdeps/x86_64/fpu/libm-test-ulps
@@ -410,6 +410,54 @@  ifloat: 1
 ildouble: 1
 ldouble: 1
 
+Function: Real part of "catan_downward":
+double: 1
+float: 1
+idouble: 1
+ifloat: 1
+ildouble: 1
+ldouble: 1
+
+Function: Imaginary part of "catan_downward":
+double: 2
+float: 2
+idouble: 2
+ifloat: 2
+ildouble: 4
+ldouble: 4
+
+Function: Real part of "catan_towardzero":
+double: 1
+float: 1
+idouble: 1
+ifloat: 1
+ildouble: 1
+ldouble: 1
+
+Function: Imaginary part of "catan_towardzero":
+double: 2
+float: 1
+idouble: 2
+ifloat: 1
+ildouble: 4
+ldouble: 4
+
+Function: Real part of "catan_upward":
+double: 1
+float: 1
+idouble: 1
+ifloat: 1
+ildouble: 1
+ldouble: 1
+
+Function: Imaginary part of "catan_upward":
+double: 3
+float: 3
+idouble: 3
+ifloat: 3
+ildouble: 3
+ldouble: 3
+
 Function: Real part of "catanh":
 double: 1
 float: 1
@@ -422,6 +470,54 @@  Function: Imaginary part of "catanh":
 float: 1
 ifloat: 1
 
+Function: Real part of "catanh_downward":
+double: 2
+float: 2
+idouble: 2
+ifloat: 2
+ildouble: 4
+ldouble: 4
+
+Function: Imaginary part of "catanh_downward":
+double: 1
+float: 2
+idouble: 1
+ifloat: 2
+ildouble: 1
+ldouble: 1
+
+Function: Real part of "catanh_towardzero":
+double: 2
+float: 1
+idouble: 2
+ifloat: 1
+ildouble: 4
+ldouble: 4
+
+Function: Imaginary part of "catanh_towardzero":
+double: 1
+float: 2
+idouble: 1
+ifloat: 2
+ildouble: 1
+ldouble: 1
+
+Function: Real part of "catanh_upward":
+double: 4
+float: 3
+idouble: 4
+ifloat: 3
+ildouble: 4
+ldouble: 4
+
+Function: Imaginary part of "catanh_upward":
+double: 1
+float: 1
+idouble: 1
+ifloat: 1
+ildouble: 1
+ldouble: 1
+
 Function: "cbrt":
 double: 1
 float: 1