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## Determine CPUID support
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## Determine CPUID support
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#
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#
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# Return 0 in EAX if CPUID is not support, 1 if supported.
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# Return 0 in EAX if CPUID is not support, 1 if supported.
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#
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#
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has_cpuid:
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has_cpuid:
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	pushq %rbx
 - 
 
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- 
 
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	pushfq			# store flags
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	pushfq			# store flags
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	popq %rax		# read flags
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	popq %rax		# read flags
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	movq %rax,%rbx		# copy flags
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	movq %rax,%rdx		# copy flags
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	btcl $21,%ebx		# swap the ID bit
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	btcl $21,%edx		# swap the ID bit
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	pushq %rbx
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	pushq %rdx
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	popfq			# propagate the change into flags
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	popfq			# propagate the change into flags
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	pushfq
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	pushfq
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	popq %rbx		# read flags
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	popq %rdx		# read flags
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	andl $(1<<21),%eax	# interested only in ID bit
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	andl $(1<<21),%eax	# interested only in ID bit
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	andl $(1<<21),%ebx
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	andl $(1<<21),%edx
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	xorl %ebx,%eax		# 0 if not supported, 1 if supported
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	xorl %edx,%eax		# 0 if not supported, 1 if supported
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- 
 
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	popq %rbx
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	ret
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	ret
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cpuid:
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cpuid:
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	movq %rbx, %r10  # we have to preserve rbx across function calls
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	movq %rbx, %r10  # we have to preserve rbx across function calls
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