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Subtract (immediate) subtracts an optionally-shifted immediate value from a register value, and writes the result to the destination register.
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 | 0 | 1 | 0 | 0 | 0 | 1 | 0 | sh | imm12 | Rn | Rd | |||||||||||||||||||
op | S |
integer d = UInt(Rd);
integer n = UInt(Rn);
integer datasize = if sf == '1' then 64 else 32;
boolean sub_op = (op == '1');
boolean setflags = (S == '1');
bits(datasize) imm;
case sh of
when '0' imm = ZeroExtend(imm12, datasize);
when '1' imm = ZeroExtend(imm12:(imm12 :Zeros(12), datasize);
<Wd|WSP> | Is the 32-bit name of the destination general-purpose register or stack pointer, encoded in the "Rd" field. |
<Wn|WSP> | Is the 32-bit name of the source general-purpose register or stack pointer, encoded in the "Rn" field. |
<Xd|SP> | Is the 64-bit name of the destination general-purpose register or stack pointer, encoded in the "Rd" field. |
<Xn|SP> | Is the 64-bit name of the source general-purpose register or stack pointer, encoded in the "Rn" field. |
<imm> | Is an unsigned immediate, in the range 0 to 4095, encoded in the "imm12" field. |
<shift> |
Is the optional left shift to apply to the immediate, defaulting to LSL #0 and
encoded in
sh:
|
bits(datasize) result;
bits(datasize) operand1 = if n == 31 then SP[] else X[n];
bits(datasize) operand2;
bits(datasize) operand2 = imm;
bits(4) nzcv;
bit carry_in;
operand2 = NOT(imm);
(result, -) =if sub_op then
operand2 = NOT(operand2);
carry_in = '1';
else
carry_in = '0';
(result, nzcv) = AddWithCarry(operand1, operand2, '1');
(operand1, operand2, carry_in);
if d == 31 thenif setflags then
PSTATE.<N,Z,C,V> = nzcv;
if d == 31 && !setflags then
SP[] = result;
else
X[d] = result;
If PSTATE.DIT is 1:
Internal version only: isa v30.44, AdvSIMD v27.08, pseudocode v8.5-2019-06_rc2-5-g22901f2, sve v2019-06_rc4
; Build timestamp: 2019-06-26T22:3004
Copyright © 2010-2019 Arm Limited or its affiliates. All rights reserved. This document is Non-Confidential.
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