AE_DBI — discard bits from the head of the input bit stream (count in immediate)

Instruction Word

Slot
Inst
6
3
6
2
6
1
6
0
5
9
5
8
5
7
5
6
5
5
5
4
5
3
5
2
5
1
5
0
4
9
4
8
4
7
4
6
4
5
4
4
4
3
4
2
4
1
4
0
3
9
3
8
3
7
3
6
3
5
3
4
3
3
3
2
3
1
3
0
2
9
2
8
2
7
2
6
2
5
2
4
2
3
2
2
2
1
2
0
1
9
1
8
1
7
1
6
1
5
1
4
1
3
1
2
1
1
1
0
9876543210
Format x24 - 24 bit(s) 0
AE_DBI 011101110101 0100
s 3210
ae_fld_fhba4 3210

Assembler Syntax

AE_DBI a0..15(ars), 1..16

C Syntax

#include <xtensa/tie/xt_hifi2.h>

extern void AE_DBI(const unsigned short * a /*inout*/, immediate count);

Description

AE_DBI discards bits from the head of the input bit stream, refreshing AE_BITHEAD state from address (a + 2) if necessary. a points to the current bit stream head address in memory, and the immediate i gives the number of bits to discard, which must lie in the range [1..16]. If a load from memory takes place to refresh the AE_BITHEAD state, a is advanced by 2 so it will refer automatically to the next 16-bit chunk of the bit stream.

Implementation Pipeline

In Out
AE_BITPTR Mstage, AE_BITHEAD Mstage, ars Estage AE_BITPTR Mstage, AE_BITHEAD Mstage, ars Mstage

Protos that use AE_DBI

proto AE_DBI { inout const uint16 * a, in immediate count }{}{
AE_DBI a, count + 0;
}