Compare and Swap capabilities in memory with release determines the base register to be used, derives an address from the base register, atomically loads a Capability register from the calculated address in memory, and performs a comparison between this first Capability register with a second Capability register. If the result of the comparison is equal, the second Capability register is atomically stored to the calculated address in memory. This instruction stores to memory with release semantics.
| 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 | 0 | 1 | 0 | 0 | 0 | 1 | 0 | 1 | 0 | 1 | Cs | 1 | 1 | 1 | 1 | 1 | 1 | Rn | Ct | ||||||||||||
| L | R | ||||||||||||||||||||||||||||||
AccType ldacctype = AccType_ATOMICRW; AccType stacctype = AccType_ORDEREDATOMICRW; integer t = UInt(Ct); integer s = UInt(Cs); integer n = UInt(Rn);
| <Cs> |
Is the capability name of the register to be compared and loaded, encoded in the "Cs" field. |
| <Ct> |
Is the capability name of the register to be conditionally stored, encoded in the "Ct" field. |
| <Xn|SP> |
Is the 64-bit name of the general-purpose base register or stack pointer, encoded in the "Rn" field. |
| <Cn|CSP> |
Is the capability name of the base register or stack pointer, encoded in the "Rn" field. |
CheckCapabilitiesEnabled(); VirtualAddress base; Capability comparecap; Capability newcap; Capability data; comparecap = C[s]; newcap = C[t]; base = BaseReg[n]; bits(64) addr = VAddress(base); VACheckAddress(base, addr, CAPABILITY_DBYTES, CAP_PERM_LOAD, ldacctype); bits(64) cap_required = CAP_PERM_STORE; if CapIsTagSet(newcap) then cap_required = cap_required OR CAP_PERM_STORE_CAP; if CapIsLocal(newcap) then cap_required = cap_required OR CAP_PERM_STORE_LOCAL; VACheckAddress(base, addr, CAPABILITY_DBYTES, cap_required, stacctype); // Both the original VirtualAddress and 64 bit address are passed in // order to be able to squash permissions and tags correctly. C[s] = MemAtomicCompareAndSwapC(base,addr,comparecap,newcap,ldacctype,stacctype);
Internal version only: isa v32.13, AdvSIMD v29.04, pseudocode morello-2022-01_rc2, capabilities morello-2022-01_rc2 ; Build timestamp: 2022-01-11T11:23
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