2010-05-17 18:44:26 +02:00
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/* bsr64() - 64 bit bit scan reverse Author: Erik van der Kouwe */
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/* 15 May 2010 */
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#include <minix/compiler.h>
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2010-08-17 18:44:07 +02:00
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#include <machine/asm.h>
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2010-05-17 18:44:26 +02:00
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2010-08-17 18:44:07 +02:00
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ENTRY(bsr64)
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2010-05-17 18:44:26 +02:00
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/* int bsr64(u64_t i); */
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bsr 8(%esp), %eax /* check high-order DWORD */
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jnz 0f /* non-zero: return index+32 */
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bsr 4(%esp), %eax /* check low-order DWORD */
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jnz 1f /* non-zero: return index */
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movl $-1, %eax /* both were zero, return -1 */
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jmp 1f
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0: addl $32, %eax /* add 32 to high-order index */
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1: ret
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