Subtract checked pointer subtracts an optionally-shifted register value from a base address register value, and writes the result to the destination register. The optionally-shifted register value is treated as the offset.
If the operation would have generated a result where the most significant 8 bits of the result register differ from the most significant 8 bits of the base register, then the result is modified such that it is likely to be non-canonical when used as an address.
| 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 | 1 | 0 | 1 | 0 | 0 | 0 | 0 | Rm | 0 | 0 | 1 | imm3 | Rn | Rd | ||||||||||||||
| sf | op | S | |||||||||||||||||||||||||||||
if !IsFeatureImplemented(FEAT_CPA) then UNDEFINED; integer d = UInt(Rd); integer n = UInt(Rn); integer m = UInt(Rm); integer shift = UInt(imm3);
| <Xd|SP> |
Is the 64-bit name of the general-purpose destination register or stack pointer, encoded in the "Rd" field. |
| <Xn|SP> |
Is the 64-bit name of the first general-purpose source register or stack pointer, encoded in the "Rn" field. |
| <Xm> |
Is the 64-bit name of the second general-purpose source register, encoded in the "Rm" field. |
| <amount> |
Is the left shift amount, in the range 0 to 7, defaulting to 0, encoded in the "imm3" field. |
bits(64) result; bits(64) base = if n == 31 then SP[] else X[n, 64]; bits(64) offset = LSL(X[m, 64], shift); result = base - offset; result = PointerAddCheck(result, base); if d == 31 then SP[] = result; else X[d, 64] = result;
Internal version only: aarchmrs v2023-12_rel, pseudocode v2023-12_rel, sve v2023-12_rel ; Build timestamp: 2023-12-15T16:46
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