diff options
Diffstat (limited to 'sysdeps/ieee754/dbl-64/s_fma.c')
| -rw-r--r-- | sysdeps/ieee754/dbl-64/s_fma.c | 12 |
1 files changed, 12 insertions, 0 deletions
diff --git a/sysdeps/ieee754/dbl-64/s_fma.c b/sysdeps/ieee754/dbl-64/s_fma.c index 108fd66192..155a773e36 100644 --- a/sysdeps/ieee754/dbl-64/s_fma.c +++ b/sysdeps/ieee754/dbl-64/s_fma.c @@ -22,6 +22,7 @@ #include <fenv.h> #include <ieee754.h> #include <math_private.h> +#include <tininess.h> /* This implementation uses rounding to odd to avoid problems with double rounding. See a paper by Boldo and Melquiond: @@ -208,6 +209,17 @@ __fma (double x, double y, double z) for proper rounding. */ if (v.ieee.exponent == 106) { + /* If the exponent would be in the normal range when + rounding to normal precision with unbounded exponent + range, the exact result is known and spurious underflows + must be avoided on systems detecting tininess after + rounding. */ + if (TININESS_AFTER_ROUNDING) + { + w.d = a1 + u.d; + if (w.ieee.exponent == 107) + return w.d * 0x1p-106; + } /* v.ieee.mantissa1 & 2 is LSB bit of the result before rounding, v.ieee.mantissa1 & 1 is the round bit and j is our sticky bit. */ |