54 lines
1.3 KiB
C
54 lines
1.3 KiB
C
/*
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* This file is part of the coreboot project.
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*
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* Copyright 2015 Google Inc.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; version 2 of the License.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*/
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#include <types.h>
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/*
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* Provide platform-independent backend implementation for __builtin_clz() in
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* <lib.h> in case GCC does not have an assembly version for this arch.
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*/
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#if !CONFIG(ARCH_X86) /* work around lack of --gc-sections on x86 */ \
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&& !CONFIG(ARCH_RISCV_RV32) /* defined in rv32 libgcc.a */
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int __clzsi2(u32 a);
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int __clzsi2(u32 a)
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{
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static const u8 four_bit_table[] = {
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[0x0] = 4, [0x1] = 3, [0x2] = 2, [0x3] = 2,
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[0x4] = 1, [0x5] = 1, [0x6] = 1, [0x7] = 1,
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[0x8] = 0, [0x9] = 0, [0xa] = 0, [0xb] = 0,
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[0xc] = 0, [0xd] = 0, [0xe] = 0, [0xf] = 0,
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};
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int r = 0;
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if (!(a & (0xffffU << 16))) {
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r += 16;
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a <<= 16;
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}
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if (!(a & (0xffU << 24))) {
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r += 8;
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a <<= 8;
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}
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if (!(a & (0xfU << 28))) {
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r += 4;
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a <<= 4;
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}
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return r + four_bit_table[a >> 28];
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}
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#endif
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