Texas Instruments TMS320C67X/C67X+ DSP - Manual (Page 318)

SUBC Subtract Conditionally and Shift−Used for Division
3-258 Instruction Set SPRU733
Subtract Conditionally and Shift—Used for Division SUBC
Syntax SUBC (.unit) src1, src2, dst
.unit = .L1 or .L2
Compatibility C62x, C64x, C67x, and C67x+ CPU
Opcode
31 29 28 27 23 22 18 17 13 12 11 5 4 3 2 1 0
creg z dst src2 src1 x 1 0 0 1 0 1 1 1 1 0 s p
3 1 5 5 5 1 1 1
Opcode map field used... For operand type... Unit
src1
src2
dst uint
xuint
uint .L1, .L2
Description Subtract src2 from src1. If result is greater than or equal to 0, left shift result
by 1, add 1 to it, and place it in dst. If result is less than 0, left shift src1 by 1,
and place it in dst. This step is commonly used in division.
Execution if (cond) {
if (src1 − src2 w 0)
( (src1−src2) << 1) + 1 → dst
else src1 << 1 → dst
}
else nop
Pipeline
Stage
E1
Read src1, src2
Written dst
Unit in use .L
Instruction Type Single-cycle
Delay Slots 0
See Also ADD, SSUB, SUB, SUBDP, SUBSP, SUBU, SUB2
Pipeline