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From: Szabolcs Nagy <nsz@sourceware.org> To: glibc-cvs@sourceware.org Subject: [glibc] math: Fix exp10 undefined left shift Date: Tue, 4 Jun 2024 14:34:16 +0000 (GMT) [thread overview] Message-ID: <20240604143417.589F038B58A7@sourceware.org> (raw) https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=2a9943b4a03b6bce7c2b1b047592eee38ab74fab commit 2a9943b4a03b6bce7c2b1b047592eee38ab74fab Author: Szabolcs Nagy <szabolcs.nagy@arm.com> Date: Wed May 22 16:33:43 2024 +0100 math: Fix exp10 undefined left shift Left shift of ki is undefined when ki<0, copy the logic from exp, which uses unsigned arithmetics, to fix it. Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org> Diff: --- sysdeps/ieee754/dbl-64/e_exp10.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/sysdeps/ieee754/dbl-64/e_exp10.c b/sysdeps/ieee754/dbl-64/e_exp10.c index 225fc74c4c..7ea8270063 100644 --- a/sysdeps/ieee754/dbl-64/e_exp10.c +++ b/sysdeps/ieee754/dbl-64/e_exp10.c @@ -38,7 +38,7 @@ special_case (uint64_t sbits, double_t tmp, uint64_t ki) { double_t scale, y; - if (ki - (1ull << 16) < 0x80000000) + if ((ki & 0x80000000) == 0) { /* The exponent of scale might have overflowed by 1. */ sbits -= 1ull << 52; @@ -100,14 +100,14 @@ __exp10 (double x) /* Reduce x: z = x * N / log10(2), k = round(z). */ double_t z = __exp_data.invlog10_2N * x; double_t kd; - int64_t ki; + uint64_t ki; #if TOINT_INTRINSICS kd = roundtoint (z); ki = converttoint (z); #else kd = math_narrow_eval (z + Shift); + ki = asuint64 (kd); kd -= Shift; - ki = kd; #endif /* r = x - k * log10(2), r in [-0.5, 0.5]. */
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