Re: [PATCH] BZ#13889: expl (709.75) wrongly overflows for ldbl-128ibm

[Adhemerval Zanella <azanella at linux dot vnet dot ibm dot com>]

On 03/04/2013 12:50 PM, Joseph S. Myers wrote:
> On Mon, 4 Mar 2013, Adhemerval Zanella wrote:
>
>> It also corrects spurious underflow exceptions generated with subnormal number
>> multiplication. I followed the dbl-64 implementation that does pretty much the
>> same with SET_RESTORE_ROUND macro.
> Does this underflow issue show up with the specific overflow testcase that 
> you add?  If not, it's a separate bug, and should have its own report in 
> Bugzilla and its own patch (with a testcase added if one isn't already in 
> the testsuite) separate from that for bug 13889.
>
I have split the patch to address the BZ#13889 only for this patch and
also created the BZ#15235 to address the spurious underflow exception.

--

2013-03-06  Adhemerval Zanella  <azanella@linux.vnet.ibm.com>

	[BZ #13889]
	* sysdeps/ieee754/ldbl-128ibm/e_expl.c (__ieee754_expl): Increase the high
	value to check if expl overflow.
	* sysdeps/ieee754/ldbl-128ibm/w_expl.c (__expl): Fix threshold constants
	to check for underflow and overflow.
	* math/libm-test.inc: Add exp test.


diff --git a/NEWS b/NEWS
index fcd79ec..470f513 100644
--- a/NEWS
+++ b/NEWS
@@ -9,9 +9,9 @@ Version 2.18
 
 * The following bugs are resolved with this release:
 
-  11561, 13550, 13951, 14142, 14200, 14317, 14327, 14496, 14920, 14964,
-  14981, 14982, 14985, 14994, 14996, 15003, 15006, 15020, 15023, 15036,
-  15054, 15055, 15062, 15078, 15160, 15232.
+  11561, 13550, 13889, 13951, 14142, 14200, 14317, 14327, 14496, 14920,
+  14964, 14981, 14982, 14985, 14994, 14996, 15003, 15006, 15020, 15023,
+  15036, 15054, 15055, 15062, 15078, 15160, 15232.
 
 * Add support for calling C++11 thread_local object destructors on thread
   and program exit.  This needs compiler support for offloading C++11
diff --git a/math/libm-test.inc b/math/libm-test.inc
index 6ac3cd2..dd08aff 100644
--- a/math/libm-test.inc
+++ b/math/libm-test.inc
@@ -4308,6 +4308,7 @@ exp_test (void)
   TEST_f_f (exp, 0.75L, 2.11700001661267466854536981983709561L);
   TEST_f_f (exp, 50.0L, 5184705528587072464087.45332293348538L);
   TEST_f_f (exp, 88.72269439697265625L, 3.40233126623160774937554134772290447915e38L);
+  TEST_f_f (exp, 709.75L, 1.739836873264160557698252711673830393864768e+308L);
 #if defined TEST_LDOUBLE && __LDBL_MAX_EXP__ > 1024
   /* The result can only be represented in sane long double.  */
   TEST_f_f (exp, 1000.0L, 0.197007111401704699388887935224332313e435L);
diff --git a/sysdeps/ieee754/ldbl-128ibm/e_expl.c b/sysdeps/ieee754/ldbl-128ibm/e_expl.c
index 8236390..9fd6198 100644
--- a/sysdeps/ieee754/ldbl-128ibm/e_expl.c
+++ b/sysdeps/ieee754/ldbl-128ibm/e_expl.c
@@ -70,11 +70,11 @@
 static const long double C[] = {
 /* Smallest integer x for which e^x overflows.  */
 #define himark C[0]
- 709.08956571282405153382846025171462914L,
+ 709.78271289338399678773454114191496482L,
 
 /* Largest integer x for which e^x underflows.  */
 #define lomark C[1]
--744.44007192138121808966388925909996033L,
+-744.44007192138126231410729844608163411L,
 
 /* 3x2^96 */
 #define THREEp96 C[2]
diff --git a/sysdeps/ieee754/ldbl-128ibm/w_expl.c b/sysdeps/ieee754/ldbl-128ibm/w_expl.c
index a5e72b2..5531636 100644
--- a/sysdeps/ieee754/ldbl-128ibm/w_expl.c
+++ b/sysdeps/ieee754/ldbl-128ibm/w_expl.c
@@ -1,6 +1,30 @@
-/* Looks like we can use ieee854 w_expl.c as is for IBM extended format. */
+#include <math.h>
+#include <math_private.h>
 #include <math_ldbl_opt.h>
-#undef weak_alias
-#define weak_alias(n,a)
-#include <sysdeps/ieee754/ldbl-128/w_expl.c>
+
+static const long double
+o_threshold = 709.78271289338399678773454114191496482L,
+u_threshold = -744.44007192138126231410729844608163411L;
+
+long double __expl(long double x)	/* wrapper exp */
+{
+#ifdef _IEEE_LIBM
+  return __ieee754_expl(x);
+#else
+  long double z;
+  z = __ieee754_expl(x);
+  if (_LIB_VERSION == _IEEE_)
+    return z;
+  if (__finitel(x))
+    {
+      if (x >= o_threshold)
+	return __kernel_standard_l(x,x,206); /* exp overflow */
+      else if (x <= u_threshold)
+	return __kernel_standard_l(x,x,207); /* exp underflow */
+    }
+  return z;
+#endif
+}
+hidden_def (__expl)
 long_double_symbol (libm, __expl, expl);
+
-- 
1.7.1