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Subtract with Tag subtracts an immediate value scaled by the Tag granule from the address in the source register, modifies the Logical Address Tag of the address using an immediate value, and writes the result to the destination register. Tags specified in GCR_EL1.Exclude are excluded from the possible outputs when modifying the Logical Address Tag.
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 |
1 | 1 | 0 | 1 | 0 | 0 | 0 | 1 | 1 | 0 | uimm6 | (0) | (0) | uimm4 | Xn | Xd | ||||||||||||||||
op3 |
integer d = UInt(Xd);
integer n = UInt(Xn);
bits(4) tag_offset = uimm4;
bits(64) offset = LSL(ZeroExtend(uimm6, 64), LOG2_TAG_GRANULE);(uimm6, 64), LOG2_TAG_GRANULE);
boolean ADD = FALSE;
<Xd|SP> | Is the 64-bit name of the destination general-purpose register or stack pointer, encoded in the "Xd" field. |
<Xn|SP> | Is the 64-bit name of the source general-purpose register or stack pointer, encoded in the "Xn" field. |
<uimm6> | Is an unsigned immediate, a multiple of 16 in the range 0 to 1008, encoded in the "uimm6" field. |
<uimm4> | Is an unsigned immediate, in the range 0 to 15, encoded in the "uimm4" field. |
bits(64) operand1 = if n == 31 then SP[] else X[n];
bits(4) start_tag = AArch64.AllocationTagFromAddress(operand1);
bits(16) exclude = GCR_EL1.Exclude;
bits(64) result;
bits(4) rtag;
if AArch64.AllocationTagAccessIsEnabled() then
rtag = AArch64.ChooseNonExcludedTag(start_tag, uimm4, exclude);
(start_tag, tag_offset, exclude);
else
rtag = '0000';
(result, -) =if ADD then
(result, -) = AddWithCarry(operand1, NOT(offset), '1');
result =(operand1, offset, '0');
else
(result, -) = AddWithCarry(operand1, NOT(offset), '1');
result = AArch64.AddressWithAllocationTag(result, rtag);
if d == 31 then
SP[] = result;
else
X[d] = result;
Internal version only: isa v30.41, AdvSIMD v27.08, pseudocode r8p5_00bet2_rc5, sve v8.5-00bet10_rc5
; Build timestamp: 2019-03-28T072019-03-28T06:1434
Copyright © 2010-2019 Arm Limited or its affiliates. All rights reserved. This document is Non-Confidential.
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