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Subtract (shifted register), setting flags, subtracts an optionally-shifted register value from a register value, and writes the result to the destination register. It updates the condition flags based on the result.
This instruction is used by the aliases CMP (shifted register), and NEGS.
31 | 30 | 29 | 28 | 27 | 26 | 25 | 24 | 23 | 22 | 21 | 20 | 19 | 18 | 17 | 16 | 15 | 14 | 13 | 12 | 11 | 10 | 9 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
sf | 1 | 1 | 0 | 1 | 0 | 1 | 1 | shift | 0 | Rm | imm6 | Rn | Rd | ||||||||||||||||||
op | S |
integer d = UInt(Rd); integer n = UInt(Rn); integer m = UInt(Rm); integer datasize = if sf == '1' then 64 else 32; boolean sub_op = (op == '1'); boolean setflags = (S == '1'); if shift == '11' then UNDEFINED; if sf == '0' && imm6<5> == '1' then UNDEFINED; ShiftType shift_type = DecodeShift(shift); integer shift_amount = UInt(imm6);
<Wd> | Is the 32-bit name of the general-purpose destination register, encoded in the "Rd" field. |
<Wn> | Is the 32-bit name of the first general-purpose source register, encoded in the "Rn" field. |
<Wm> | Is the 32-bit name of the second general-purpose source register, encoded in the "Rm" field. |
<Xd> | Is the 64-bit name of the general-purpose destination register, encoded in the "Rd" field. |
<Xn> | Is the 64-bit name of the first general-purpose source register, encoded in the "Rn" field. |
<Xm> | Is the 64-bit name of the second general-purpose source register, encoded in the "Rm" field. |
<amount> | For the 32-bit variant: is the shift amount, in the range 0 to 31, defaulting to 0 and encoded in the "imm6" field. |
For the 64-bit variant: is the shift amount, in the range 0 to 63, defaulting to 0 and encoded in the "imm6" field. |
Alias | Is preferred when |
---|---|
CMP (shifted register) | Rd == '11111' |
NEGS | Rn == '11111' && Rd != '11111' |
bits(datasize) result; bits(datasize) operand1 = X[n]; bits(datasize) operand2 = ShiftReg(m, shift_type, shift_amount); bits(4) nzcv; bit carry_in; if sub_op then operand2 = NOT(operand2); carry_in = '1'; else carry_in = '0'; (result, nzcv) = AddWithCarry(operand1, operand2, carry_in); if setflags then PSTATE.<N,Z,C,V> = nzcv; X[d] = result;
If PSTATE.DIT is 1:
Internal version only: isa v32.12v32.06, AdvSIMD v29.04, pseudocode v2020-09_xmlv2020-06_rel, sve v2020-09_rc3v2020-06_rel0
; Build timestamp: 2020-11-18T172020-07-03T12:2342
Copyright © 2010-2020 Arm Limited or its affiliates. All rights reserved. This document is Non-Confidential.
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