| 1 | //===-- clzdi2.c - Implement __clzdi2 -------------------------------------===// |
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| 2 | // |
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| 3 | // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
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| 4 | // See https://llvm.org/LICENSE.txt for license information. |
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| 5 | // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
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| 6 | // |
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| 7 | //===----------------------------------------------------------------------===// |
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| 8 | // |
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| 9 | // This file implements __clzdi2 for the compiler_rt library. |
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| 10 | // |
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| 11 | //===----------------------------------------------------------------------===// |
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| 12 | |
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| 13 | #include "int_lib.h" |
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| 14 | |
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| 15 | // Returns: the number of leading 0-bits |
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| 16 | |
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| 17 | #if ((defined(__sparc__) && defined(__arch64__)) || defined(__mips64) || \ |
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| 18 | (defined(__riscv) && __SIZEOF_POINTER__ >= 8)) |
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| 19 | // On 64-bit architectures with neither a native clz instruction nor a native |
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| 20 | // ctz instruction, `__builtin_clz` resolves to `__clzdi2` rather than |
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| 21 | // __clzsi2 as libgcc does not ship with `__clzsi2`, leading to infinite |
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| 22 | // recursion. |
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| 23 | #define __builtin_clz(a) __clzsi2(a) |
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| 24 | extern int __clzsi2(si_int); |
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| 25 | #endif |
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| 26 | |
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| 27 | // Precondition: a != 0 |
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| 28 | |
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| 29 | COMPILER_RT_ABI int __clzdi2(di_int a) { |
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| 30 | dwords x; |
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| 31 | x.all = a; |
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| 32 | const si_int f = -(x.s.high == 0); |
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| 33 | return clzsi((x.s.high & ~f) | (x.s.low & f)) + |
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| 34 | (f & ((si_int)(sizeof(si_int) * CHAR_BIT))); |
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| 35 | } |
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| 36 | |
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