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 | |||||||||||||||||||||||||||||||
if !HaveMTEExt() then UNDEFINED; integer d = UInt(Xd); integer n = UInt(Xn); bits(4) tag_offset = uimm4; bits(64) offset = LSL(ZeroExtend(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(AccType_NORMAL) then rtag = AArch64.ChooseNonExcludedTag(start_tag, tag_offset, exclude); else rtag = '0000'; if ADD then (result, -) = AddWithCarry(operand1, offset, '0'); else (result, -) = AddWithCarry(operand1, NOT(offset), '1'); result = AArch64.AddressWithAllocationTag(result, AccType_NORMAL, rtag); if d == 31 then SP[] = result; else X[d] = result;
Internal version only: isa v33.11seprel, AdvSIMD v29.05, pseudocode v2021-09_rel, sve v2021-09_rc3d ; Build timestamp: 2021-10-06T11:41
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