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-rw-r--r--src/math/__expo2f.c5
1 files changed, 3 insertions, 2 deletions
diff --git a/src/math/__expo2f.c b/src/math/__expo2f.c
index 5163e418..538eb09c 100644
--- a/src/math/__expo2f.c
+++ b/src/math/__expo2f.c
@@ -5,12 +5,13 @@ static const int k = 235;
static const float kln2 = 0x1.45c778p+7f;
/* expf(x)/2 for x >= log(FLT_MAX), slightly better than 0.5f*expf(x/2)*expf(x/2) */
-float __expo2f(float x)
+float __expo2f(float x, float sign)
{
float scale;
/* note that k is odd and scale*scale overflows */
SET_FLOAT_WORD(scale, (uint32_t)(0x7f + k/2) << 23);
/* exp(x - k ln2) * 2**(k-1) */
- return expf(x - kln2) * scale * scale;
+ /* in directed rounding correct sign before rounding or overflow is important */
+ return expf(x - kln2) * (sign * scale) * scale;
}