stillwater-sc / universal / 23407092263

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master: 84%

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github

Committed by web-flow

Commit Message

fix(lns): subtract exponents in non-saturating division path (#609)

* fix(cfloat): add rounding and overflow handling to wide-significand convert path

* fix(cfloat): clear hidden bit before rounding in wide-significand path

The wide-significand convert path was missing the hidden-bit mask that
the narrow path applies (fracbits &= ALL_ONES_FR). Without it,
fracbits.test(fbits) always evaluated true for normalized numbers,
causing fracbits.clear() to zero out the entire significand on every
conversion — producing pure powers of 2 instead of correct results.

Add fracbits.setbit(fbits, false) after the right-shift, mirroring the
narrow path's mask, so the rounding-overflow check only fires when
incrementing genuinely carries into the hidden-bit position.

* fix(lns): subtract exponents in non-saturating division path

The non-saturating (Behavior::Wrapping) branch of operator/= was
adding exponents (lexp += rexp) instead of subtracting them
(lexp -= rexp). Since LNS represents values as 2^exponent,
division requires log(a/b) = log(a) - log(b), i.e. exponent
subtraction. The saturating path already used ursub correctly;
only the wrapping else-branch had the wrong operator, producing
a*b instead of a/b for every division.

Coverage Stats

11 of 14 new or added lines in 1 file covered. (78.57%)

14 existing lines in 3 files now uncovered.

44348 of 52560 relevant lines covered (84.38%)

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