diff options
Diffstat (limited to 'newlib')
| -rw-r--r-- | newlib/libm/common/pow.c | 6 |
1 files changed, 4 insertions, 2 deletions
diff --git a/newlib/libm/common/pow.c b/newlib/libm/common/pow.c index 11964e343..a5504e5e9 100644 --- a/newlib/libm/common/pow.c +++ b/newlib/libm/common/pow.c @@ -79,11 +79,13 @@ log_inline (uint64_t ix, double_t *tail) logc = T[i].logc; logctail = T[i].logctail; - /* r = z/c - 1, arranged to be exact. */ + /* Note: 1/c is j/N or j/N/2 where j is an integer in [N,2N) and + |z/c - 1| < 1/N, so r = z/c - 1 is exactly representible. */ #if HAVE_FAST_FMA r = fma (z, invc, -1.0); #else - double_t zhi = asdouble (iz & (-1ULL << 32)); + /* Split z such that rhi, rlo and rhi*rhi are exact and |rlo| <= |r|. */ + double_t zhi = asdouble ((iz + (1ULL << 31)) & (-1ULL << 32)); double_t zlo = z - zhi; double_t rhi = zhi * invc - 1.0; double_t rlo = zlo * invc; |