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[SOL][BPF] Add BPF compiler-rt builtins (anza-xyz#8)
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//===-- udivmodti4.c - Implement __udivmodti4 -----------------------------===// | ||
// | ||
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. | ||
// See https://llvm.org/LICENSE.txt for license information. | ||
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception | ||
// | ||
//===----------------------------------------------------------------------===// | ||
// | ||
// This file implements __udivmodti4 for the compiler_rt library. | ||
// | ||
//===----------------------------------------------------------------------===// | ||
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#include "../int_lib.h" | ||
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#ifdef CRT_HAS_128BIT | ||
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// Effects: if rem != 0, *rem = a % b | ||
// Returns: a / b | ||
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// Translated from Figure 3-40 of The PowerPC Compiler Writer's Guide | ||
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COMPILER_RT_ABI tu_int __udivmodti4(tu_int a, tu_int b, tu_int *rem) { | ||
const unsigned n_udword_bits = sizeof(du_int) * CHAR_BIT; | ||
const unsigned n_utword_bits = sizeof(tu_int) * CHAR_BIT; | ||
utwords n; | ||
n.all = a; | ||
utwords d; | ||
d.all = b; | ||
utwords q; | ||
utwords r; | ||
unsigned sr; | ||
// special cases, X is unknown, K != 0 | ||
if (n.s.high == 0) { | ||
if (d.s.high == 0) { | ||
// 0 X | ||
// --- | ||
// 0 X | ||
if (rem) | ||
*rem = n.s.low % d.s.low; | ||
return n.s.low / d.s.low; | ||
} | ||
// 0 X | ||
// --- | ||
// K X | ||
if (rem) | ||
*rem = n.s.low; | ||
return 0; | ||
} | ||
// n.s.high != 0 | ||
if (d.s.low == 0) { | ||
if (d.s.high == 0) { | ||
// K X | ||
// --- | ||
// 0 0 | ||
if (rem) | ||
*rem = n.s.high % d.s.low; | ||
return n.s.high / d.s.low; | ||
} | ||
// d.s.high != 0 | ||
if (n.s.low == 0) { | ||
// K 0 | ||
// --- | ||
// K 0 | ||
if (rem) { | ||
r.s.high = n.s.high % d.s.high; | ||
r.s.low = 0; | ||
*rem = r.all; | ||
} | ||
return n.s.high / d.s.high; | ||
} | ||
// K K | ||
// --- | ||
// K 0 | ||
if ((d.s.high & (d.s.high - 1)) == 0) /* if d is a power of 2 */ { | ||
if (rem) { | ||
r.s.low = n.s.low; | ||
r.s.high = n.s.high & (d.s.high - 1); | ||
*rem = r.all; | ||
} | ||
return n.s.high >> __builtin_ctzll(d.s.high); | ||
} | ||
// K K | ||
// --- | ||
// K 0 | ||
sr = __builtin_clzll(d.s.high) - __builtin_clzll(n.s.high); | ||
// 0 <= sr <= n_udword_bits - 2 or sr large | ||
if (sr > n_udword_bits - 2) { | ||
if (rem) | ||
*rem = n.all; | ||
return 0; | ||
} | ||
++sr; | ||
// 1 <= sr <= n_udword_bits - 1 | ||
// q.all = n.all << (n_utword_bits - sr); | ||
q.s.low = 0; | ||
q.s.high = n.s.low << (n_udword_bits - sr); | ||
// r.all = n.all >> sr; | ||
r.s.high = n.s.high >> sr; | ||
r.s.low = (n.s.high << (n_udword_bits - sr)) | (n.s.low >> sr); | ||
} else /* d.s.low != 0 */ { | ||
if (d.s.high == 0) { | ||
// K X | ||
// --- | ||
// 0 K | ||
if ((d.s.low & (d.s.low - 1)) == 0) /* if d is a power of 2 */ { | ||
if (rem) | ||
*rem = n.s.low & (d.s.low - 1); | ||
if (d.s.low == 1) | ||
return n.all; | ||
sr = __builtin_ctzll(d.s.low); | ||
q.s.high = n.s.high >> sr; | ||
q.s.low = (n.s.high << (n_udword_bits - sr)) | (n.s.low >> sr); | ||
return q.all; | ||
} | ||
// K X | ||
// --- | ||
// 0 K | ||
sr = 1 + n_udword_bits + __builtin_clzll(d.s.low) - | ||
__builtin_clzll(n.s.high); | ||
// 2 <= sr <= n_utword_bits - 1 | ||
// q.all = n.all << (n_utword_bits - sr); | ||
// r.all = n.all >> sr; | ||
if (sr == n_udword_bits) { | ||
q.s.low = 0; | ||
q.s.high = n.s.low; | ||
r.s.high = 0; | ||
r.s.low = n.s.high; | ||
} else if (sr < n_udword_bits) /* 2 <= sr <= n_udword_bits - 1 */ { | ||
q.s.low = 0; | ||
q.s.high = n.s.low << (n_udword_bits - sr); | ||
r.s.high = n.s.high >> sr; | ||
r.s.low = (n.s.high << (n_udword_bits - sr)) | (n.s.low >> sr); | ||
} else /* n_udword_bits + 1 <= sr <= n_utword_bits - 1 */ { | ||
q.s.low = n.s.low << (n_utword_bits - sr); | ||
q.s.high = (n.s.high << (n_utword_bits - sr)) | | ||
(n.s.low >> (sr - n_udword_bits)); | ||
r.s.high = 0; | ||
r.s.low = n.s.high >> (sr - n_udword_bits); | ||
} | ||
} else { | ||
// K X | ||
// --- | ||
// K K | ||
sr = __builtin_clzll(d.s.high) - __builtin_clzll(n.s.high); | ||
// 0 <= sr <= n_udword_bits - 1 or sr large | ||
if (sr > n_udword_bits - 1) { | ||
if (rem) | ||
*rem = n.all; | ||
return 0; | ||
} | ||
++sr; | ||
// 1 <= sr <= n_udword_bits | ||
// q.all = n.all << (n_utword_bits - sr); | ||
// r.all = n.all >> sr; | ||
q.s.low = 0; | ||
if (sr == n_udword_bits) { | ||
q.s.high = n.s.low; | ||
r.s.high = 0; | ||
r.s.low = n.s.high; | ||
} else { | ||
r.s.high = n.s.high >> sr; | ||
r.s.low = (n.s.high << (n_udword_bits - sr)) | (n.s.low >> sr); | ||
q.s.high = n.s.low << (n_udword_bits - sr); | ||
} | ||
} | ||
} | ||
// Not a special case | ||
// q and r are initialized with: | ||
// q.all = n.all << (n_utword_bits - sr); | ||
// r.all = n.all >> sr; | ||
// 1 <= sr <= n_utword_bits - 1 | ||
su_int carry = 0; | ||
for (; sr > 0; --sr) { | ||
// r:q = ((r:q) << 1) | carry | ||
r.s.high = (r.s.high << 1) | (r.s.low >> (n_udword_bits - 1)); | ||
r.s.low = (r.s.low << 1) | (q.s.high >> (n_udword_bits - 1)); | ||
q.s.high = (q.s.high << 1) | (q.s.low >> (n_udword_bits - 1)); | ||
q.s.low = (q.s.low << 1) | carry; | ||
// carry = 0; | ||
// if (r.all >= d.all) | ||
// { | ||
// r.all -= d.all; | ||
// carry = 1; | ||
// } | ||
const ti_int s = (ti_int)(d.all - r.all - 1) >> (n_utword_bits - 1); | ||
carry = s & 1; | ||
r.all -= d.all & s; | ||
} | ||
q.all = (q.all << 1) | carry; | ||
if (rem) | ||
*rem = r.all; | ||
return q.all; | ||
} | ||
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#endif // CRT_HAS_128BIT |