On i386, gcc truncates long double constants to double precision

at compile time regardless of the dynamic precision, and there's
no way to disable this misfeature at compile time. Hence, it's
impossible to generate the appropriate tables of constants for the
long double inverse trig functions in a straightforward way on i386;
this change hacks around the problem by encoding the underlying bits
in the table.

Note that these functions won't pass the regression test on i386,
even with the FPU set to extended precision, because the regression
test is similarly damaged by gcc. However, the tests all pass when
compiled with a modified version of gcc.

Reported by:  	bde

1 files changed, 12 insertions, 2 deletions

diff --git a/lib/msun/src/e_atan2l.c b/lib/msun/src/e_atan2l.c
index 8368bbf..0071a7c 100644
--- a/lib/msun/src/e_atan2l.c
+++ b/lib/msun/src/e_atan2l.c
@@ -30,8 +30,18 @@ __FBSDID("$FreeBSD$");
 static volatile long double
 tiny  = 1.0e-300;
 static const long double
-zero  = 0.0,
-pi = 3.14159265358979323846264338327950280e+00L;
+zero  = 0.0;
+
+#ifdef __i386__
+/* XXX Work around the fact that gcc truncates long double constants on i386 */
+static volatile double
+pi1 =  3.14159265358979311600e+00,	/*  0x1.921fb54442d18p+1  */
+pi2 =  1.22514845490862001043e-16;	/*  0x1.1a80000000000p-53 */
+#define	pi	((long double)pi1 + pi2)
+#else
+static const long double
+pi =  3.14159265358979323846264338327950280e+00L;
+#endif
 
 long double
 atan2l(long double y, long double x)