setjmp.s

Newlib 嵌入式 C库 标准实现代码

/*

Copyright (c) 2005 Red Hat Incorporated.
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    The name of Red Hat Incorporated may not be used to endorse 
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    prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" 
AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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*/

#if defined(__r8c_cpu__) || defined(__m16c_cpu__)
#define A16 1
#endif

/* We implement setjmp/longjmp much like the way gcc implements
   exceptions - we create new stack frames, then switch to them and
   return.  Thus, the two setjmp's below each push all the relevent
   registers, then copy the whole frame into the buffer (first $sp is
   moved, then smovf copies the frame itself), and the two longjmps
   restore $sp, copy the frame back into place, and issue the same
   return as the setjmp would have used.

   Since the sizes of registers differs between the 16 and 24 bit
   models, we provide separate implementations for each rather than
   trying to parameterize them.

   Jump buffer sizes: 21 bytes for 16 bit, 34 bytes for 24 bit.
*/

	.text

#ifdef A16	/* 16 bit versions */

	.global	_setjmp
_setjmp:
	enter	#0
	pushm	r1,r2,r3,a0,a1,sb,fb

; At this point, the stack looks like this:
; ... [pc:3] [oldfb:2] <fb> [r1:2] [r2:2] [r3:2] [a0:2] [a1:2] [sb:2] [fb:2] <sp> */

	mov.w	r1,a1		;  a1 is the destination of smovf
	mov.b	#0,r1h
	stc	sp,a0		;  r1h:a0 is the source of smovf
	mov.w	a0,[a1]
	add.w	#2,a1
	mov.w	#19,r3		;  plus two for sp later
	smovf.b

	; Return 0 to caller.
	mov.w	#0,r0
	popm	r1,r2,r3,a0,a1,sb,fb
	exitd

	.global	_longjmp
_longjmp:
	enter	#0
	mov.w	r1,a0		;  pointer to jump buf
	mov.w	r2,r0		;  setjmp's "new" return value

	mov.b	#0,r1h		;  r1h:	a0 is the source, now jmpbuf
	mov.w	[a0],a1		;  dest is new stack
	ldc	a1,sp
	add.w	#2,a0
	mov.w	#19,r3
	smovf.b

	;; now return to our caller with this newly restored frame
	popm	r1,r2,r3,a0,a1,sb,fb
	exitd

#else	/* 24 bit versions */

	.global	_setjmp
_setjmp:
	enter	#0
	pushm	r1,r2,r3,a0,a1,sb,fb

; At this point, the stack looks like this:
; ... [jbuf:4] [pc:4] [oldfb:4] <fb> [r1:2] [r2:2] [r3:2] [a0:4] [a1:4] [sb:4] [fb:4] <sp> */

	mov.l	8[fb],a1	;  a1 is the destination of smovf
	stc	sp,a0		;  r1h:a0 is the source of smovf
	mov.l	a0,[a1]
	add.l	#4,a1
	mov.w	#30,r3		;  plus two for sp later
	smovf.b

	; Return 0 to caller.
	mov.w	#0,r0
	popm	r1,r2,r3,a0,a1,sb,fb
	exitd

	.global	_longjmp
_longjmp:
	enter	#0
; ... [rv:2] [jbuf:4] [pc:4] [oldfb:4] <fb>
	mov.l	8[fb],a0	;  pointer to jump buf
	mov.w	12[fb],r0	;  setjmp's "new" return value

	mov.l	[a0],a1		;  dest is new stack
	ldc	a1,sp
	add.l	#4,a0
	mov.w	#30,r3
	smovf.b

	;; now return to our caller with this newly restored frame
	popm	r1,r2,r3,a0,a1,sb,fb
	exitd
#endif