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65 lines
2.8 KiB
C
65 lines
2.8 KiB
C
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#if 0
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/*─────────────────────────────────────────────────────────────────╗
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│ To the extent possible under law, Justine Tunney has waived │
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│ all copyright and related or neighboring rights to division, │
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│ as it is written in the following disclaimers: │
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│ • http://unlicense.org/ │
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│ • http://creativecommons.org/publicdomain/zero/1.0/ │
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╚─────────────────────────────────────────────────────────────────*/
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#endif
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#include "libc/calls/calls.h"
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#include "third_party/compiler_rt/int_lib.h"
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/**
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* Divides 128-bit signed integers w/ remainder.
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*
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* @param a is numerator
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* @param b is denominator
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* @param opt_out_rem receives euclidean division remainder if not null
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* @return quotient or result of division
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* @note rounds towards zero
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*/
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COMPILER_RT_ABI ti_int __divmodti4(ti_int a, ti_int b, tu_int *opt_out_rem) {
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int k;
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tu_int r;
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ti_int sa, sb, sq, sr, x, y, q;
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k = sizeof(ti_int) * CHAR_BIT - 1;
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if (b < 0 && a == ((ti_int)1 << k)) {
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volatile int x = 0;
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x = 1 / x; // raise(SIGFPE)
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}
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sa = a >> k; // sa = a < 0 ? -1 : 0
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sb = b >> k; // sb = b < 0 ? -1 : 0
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x = (a ^ sa) - sa; // negate if sa == -1
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y = (b ^ sb) - sb; // negate if sb == -1
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sq = sa ^ sb; // sign of quotient
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sr = sa; // sign of remainder
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q = __udivmodti4(x, y, &r); // unsigned divide
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q = (q ^ sq) - sq; // fix quotient sign
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r = (r ^ sr) - sr; // fix remainder sign
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if (opt_out_rem) *opt_out_rem = r;
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return q;
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}
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/*
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Intel Kabylake i9-9900 @ 3.10GHz Client Grade
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idiv32 l: 27𝑐 9𝑛𝑠
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idiv64 l: 27𝑐 9𝑛𝑠
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divmodti4 small / small l: 42𝑐 14𝑛𝑠
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divmodti4 small / large l: 14𝑐 5𝑛𝑠
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divmodti4 large / small l: 92𝑐 30𝑛𝑠
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divmodti4 large / large l: 209𝑐 68𝑛𝑠
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Intel Kabylake i3-8100 @ 3.60GHz Client Grade
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idiv32 l: 51𝑐 14𝑛𝑠
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idiv64 l: 51𝑐 14𝑛𝑠
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divmodti4 small / small l: 83𝑐 23𝑛𝑠
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divmodti4 small / large l: 26𝑐 7𝑛𝑠
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divmodti4 large / small l: 175𝑐 48𝑛𝑠
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divmodti4 large / large l: 389𝑐 107𝑛𝑠
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*/
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