Differential D28779 Diff 84222 sys/amd64/amd64/support.S

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sys/amd64/amd64/support.S

Show First 20 Lines • Show All 691 Lines • ▼ Show 20 Lines	ENTRY(fillw)
movq %rsi,%rdi		movq %rsi,%rdi
movq %rdx,%rcx		movq %rdx,%rcx
rep		rep
stosw		stosw
POP_FRAME_POINTER		POP_FRAME_POINTER
ret		ret
END(fillw)		END(fillw)

		/*
		* strlen(string)
		* %rdi
		*
		* Uses the ((x - 0x01....01) & ~x & 0x80....80) trick.
		*
		* 0x01....01 is replaced with 0x0 - 0x01....01 so that it can be added
		* with leaq.
		*
		* For a description see either:
		* - "Hacker's Delight" by Henry S. Warren, Jr. for explanation.
		* - "Optimizing subroutines in assembly language: An optimization guide for x86 platforms"
		* by Agner Fog
		*
		* The latter contains a 32-bit variant of the same algorithm coded in assembly for i386.
		*/
		ENTRY(strlen)
		PUSH_FRAME_POINTER
		movabsq $0xfefefefefefefeff,%r8
		movabsq $0x8080808080808080,%r9

		movq %rdi,%r10
		movq %rdi,%rcx
		testb $7,%dil
		jz 2f

		/*
		* Handle misaligned reads: align to 8 and fill
		* the spurious bytes.
		*/
		andq $~7,%rdi
		movq (%rdi),%r11
		shlq $3,%rcx
		movq $-1,%rdx
		shlq %cl,%rdx
		notq %rdx
		orq %rdx,%r11

		leaq (%r11,%r8),%rcx
		notq %r11
		andq %r11,%rcx
		andq %r9,%rcx
		jnz 3f

		/*
		* Main loop.
		*/
		ALIGN_TEXT
		1:
		leaq 8(%rdi),%rdi
		2:
		movq (%rdi),%r11
		leaq (%r11,%r8),%rcx
		notq %r11
		andq %r11,%rcx
		andq %r9,%rcx
		jz 1b
		3:
		bsfq %rcx,%rcx
		shrq $3,%rcx
		leaq (%rcx,%rdi),%rax
		subq %r10,%rax
		POP_FRAME_POINTER
		ret
		END(strlen)

/*****************************************************************************/		/*****************************************************************************/
/* copyout and fubyte family */		/* copyout and fubyte family */
/*****************************************************************************/		/*****************************************************************************/
/*		/*
* Access user memory from inside the kernel. These routines should be		* Access user memory from inside the kernel. These routines should be
* the only places that do this.		* the only places that do this.
*		*
* These routines set curpcb->pcb_onfault for the time they execute. When a		* These routines set curpcb->pcb_onfault for the time they execute. When a
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