AE_LBKI — bitstream lookahead, return bits based on immediate (keeping low bits of an AR register)

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_LBKI 11001110 0100
r 3210
s 3210
ae_fld_fhba4 3210

Assembler Syntax

AE_LBKI a0..15(arr), a0..15(ars), 1..16

C Syntax

#include <xtensa/tie/xt_hifi2.h>

extern unsigned AE_LBKI(unsigned a0, immediate ba);

Description

AE_LBKI is a look ahead in the bit stream, keeping low bits of a0. Return as few as 1 bit or as many as 16 bits from the head of the bit stream in the low bits of a, with the remaining bits of a filled with low bits from a0. The number of bits to move from the stream to a is given by the immediate value i, and must lie in the range [1..16]. No state is updated; this is a lookahead instruction.

Implementation Pipeline

In Out
AE_BITPTR Mstage, AE_BITHEAD Mstage, ars Mstage arr Mstage

Protos that use AE_LBKI

proto AE_LBKI { out uint32 a, in uint32 a0, in immediate ba }{}{
AE_LBKI a, a0, ba + 0;
}