.section	.icode,"ax",@progbits
    	.global		_bitswap
	.align 		4
	.type		_bitswap,@function

/* Registers used:
 *
 * r0	Temporary (required by some instructions)
 * r1	Low byte
 * r2	High byte
 * r3	Result after flip
 * r4	Data
 * r5	Length
 * r6	Current (position in Data)
 * r7	Flip table
 */

_bitswap:
	mov.l	.fliptable,r7
	mov	r4,r6
	add	r5,r6				/* goto end of buffer */
	add	r5,r6				/* (direction IS important) */
	bra	.init
.loop:
	mov.w	@r6,r1				/* data to flip */
	swap.b	r1,r2
	extu.b	r2,r0				/* high byte */
	mov.b	@(r0,r7),r2
	extu.b	r2,r0				/* remove any sign extend */
	swap.b	r0,r3				/* put high byte in result */
	extu.b	r1,r0				/* low byte */
	mov.b	@(r0,r7),r1
	extu.b	r1,r0				/* remove any sign extend */
	or	r0,r3				/* put low byte in result */
	mov.w	r3,@r6				/* store result */
	add	#-2,r6
.init:
	cmp/gt	r4,r6				/* while (current > data) */
	bt	.loop
	rts

	.align	4

.fliptable:
	.long	_fliptable

_fliptable:
	.byte	0x00, 0x80, 0x40, 0xc0, 0x20, 0xa0, 0x60, 0xe0
	.byte	0x10, 0x90, 0x50, 0xd0, 0x30, 0xb0, 0x70, 0xf0
	.byte	0x08, 0x88, 0x48, 0xc8, 0x28, 0xa8, 0x68, 0xe8
	.byte	0x18, 0x98, 0x58, 0xd8, 0x38, 0xb8, 0x78, 0xf8
	.byte	0x04, 0x84, 0x44, 0xc4, 0x24, 0xa4, 0x64, 0xe4
	.byte	0x14, 0x94, 0x54, 0xd4, 0x34, 0xb4, 0x74, 0xf4
	.byte	0x0c, 0x8c, 0x4c, 0xcc, 0x2c, 0xac, 0x6c, 0xec
	.byte	0x1c, 0x9c, 0x5c, 0xdc, 0x3c, 0xbc, 0x7c, 0xfc
	.byte	0x02, 0x82, 0x42, 0xc2, 0x22, 0xa2, 0x62, 0xe2
	.byte	0x12, 0x92, 0x52, 0xd2, 0x32, 0xb2, 0x72, 0xf2
	.byte	0x0a, 0x8a, 0x4a, 0xca, 0x2a, 0xaa, 0x6a, 0xea
	.byte	0x1a, 0x9a, 0x5a, 0xda, 0x3a, 0xba, 0x7a, 0xfa
	.byte	0x06, 0x86, 0x46, 0xc6, 0x26, 0xa6, 0x66, 0xe6
	.byte	0x16, 0x96, 0x56, 0xd6, 0x36, 0xb6, 0x76, 0xf6
	.byte	0x0e, 0x8e, 0x4e, 0xce, 0x2e, 0xae, 0x6e, 0xee
	.byte	0x1e, 0x9e, 0x5e, 0xde, 0x3e, 0xbe, 0x7e, 0xfe
	.byte	0x01, 0x81, 0x41, 0xc1, 0x21, 0xa1, 0x61, 0xe1
	.byte	0x11, 0x91, 0x51, 0xd1, 0x31, 0xb1, 0x71, 0xf1
	.byte	0x09, 0x89, 0x49, 0xc9, 0x29, 0xa9, 0x69, 0xe9
	.byte	0x19, 0x99, 0x59, 0xd9, 0x39, 0xb9, 0x79, 0xf9
	.byte	0x05, 0x85, 0x45, 0xc5, 0x25, 0xa5, 0x65, 0xe5
	.byte	0x15, 0x95, 0x55, 0xd5, 0x35, 0xb5, 0x75, 0xf5
	.byte	0x0d, 0x8d, 0x4d, 0xcd, 0x2d, 0xad, 0x6d, 0xed
	.byte	0x1d, 0x9d, 0x5d, 0xdd, 0x3d, 0xbd, 0x7d, 0xfd
	.byte	0x03, 0x83, 0x43, 0xc3, 0x23, 0xa3, 0x63, 0xe3
	.byte	0x13, 0x93, 0x53, 0xd3, 0x33, 0xb3, 0x73, 0xf3
	.byte	0x0b, 0x8b, 0x4b, 0xcb, 0x2b, 0xab, 0x6b, 0xeb
	.byte	0x1b, 0x9b, 0x5b, 0xdb, 0x3b, 0xbb, 0x7b, 0xfb
	.byte	0x07, 0x87, 0x47, 0xc7, 0x27, 0xa7, 0x67, 0xe7
	.byte	0x17, 0x97, 0x57, 0xd7, 0x37, 0xb7, 0x77, 0xf7
	.byte	0x0f, 0x8f, 0x4f, 0xcf, 0x2f, 0xaf, 0x6f, 0xef
	.byte	0x1f, 0x9f, 0x5f, 0xdf, 0x3f, 0xbf, 0x7f, 0xff

.end:
	.size	_bitswap,.end-_bitswap