45 lines
733 B
C
45 lines
733 B
C
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/* Copyright 2014 The Chromium OS Authors. All rights reserved.
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* Use of this source code is governed by a BSD-style license that can be
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* found in the LICENSE file.
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*
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* Software emulation for CLZ instruction
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*/
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#include "common.h"
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/**
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* Count leading zeros
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*
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* @param x non null integer.
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* @return the number of leading 0-bits in x,
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* starting at the most significant bit position.
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*/
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int __keep __clzsi2(int x)
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{
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int r = 0;
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if (!x)
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return 32;
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if (!(x & 0xffff0000u)) {
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x <<= 16;
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r += 16;
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}
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if (!(x & 0xff000000u)) {
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x <<= 8;
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r += 8;
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}
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if (!(x & 0xf0000000u)) {
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x <<= 4;
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r += 4;
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}
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if (!(x & 0xc0000000u)) {
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x <<= 2;
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r += 2;
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}
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if (!(x & 0x80000000u)) {
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x <<= 1;
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r += 1;
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}
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return r;
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}
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