Avoid exponent overflow as well as checking that we don't lose information with opposing scaling. Use it in partsN(scalbn) and partsN(round_to_int_normal).
Signed-off-by: Richard Henderson <[email protected]> --- fpu/softfloat.c | 17 +++++++++++++++++ fpu/softfloat-parts.c.inc | 5 ++--- 2 files changed, 19 insertions(+), 3 deletions(-) diff --git a/fpu/softfloat.c b/fpu/softfloat.c index 6a14c5d639..a6ab3ee0f8 100644 --- a/fpu/softfloat.c +++ b/fpu/softfloat.c @@ -601,6 +601,23 @@ static float128 QEMU_FLATTEN float128_pack_raw(const FloatParts128 *p) *----------------------------------------------------------------------------*/ #include "softfloat-specialize.c.inc" +static int32_t exp_scalbn(int32_t exp, int32_t scale) +{ + /* + * Catch chains of scaling which lose information. + * In particular, if the exponent has been saturated, + * do not allow it to become unsaturated. + */ + if (unlikely(exp == INT32_MAX)) { + assert(scale >= 0); + } else if (unlikely(exp == INT32_MIN)) { + assert(scale <= 0); + } else { + exp = sadd32_saturate(exp, scale); + } + return exp; +} + /* * Helper functions for softfloat-parts.c.inc, per-size operations. */ diff --git a/fpu/softfloat-parts.c.inc b/fpu/softfloat-parts.c.inc index c5a828eb90..789a41d24e 100644 --- a/fpu/softfloat-parts.c.inc +++ b/fpu/softfloat-parts.c.inc @@ -1107,8 +1107,7 @@ static bool partsN(round_to_int_normal)(FloatPartsN *a, FloatRoundMode rmode, uint64_t frac_lsb, frac_lsbm1, rnd_even_mask, rnd_mask, inc; int shift_adj; - scale = MIN(MAX(scale, -0x10000), 0x10000); - a->exp += scale; + a->exp = exp_scalbn(a->exp, scale); if (a->exp < 0) { bool one; @@ -1632,7 +1631,7 @@ FloatPartsN partsN(scalbn)(const FloatPartsN *a, int n, float_status *s) case float_class_normal: { FloatPartsN r = *a; - r.exp += MIN(MAX(n, -0x10000), 0x10000); + r.exp = exp_scalbn(r.exp, n); return r; } default: -- 2.43.0
