amoxor.b

Atomic fetch-and-xor byte

This instruction is defined by:

Encoding

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Synopsis

Atomically:

  • Load the byte at address xs1

  • Write the sign-extended value into xd

  • XOR the least-significant byte of register xs2 to the loaded value

  • Write the result to the address in xs1

Access

M HS U VS VU

Always

Always

Always

Always

Always

Decode Variables

Bits<5> xs2 = $encoding[24:20];
Bits<5> xs1 = $encoding[19:15];
Bits<5> xd = $encoding[11:7];

Execution

  • Pruned, XLEN == 64

  • Original

XReg virtual_address = X[xs1];
X[xd] = sext(amo(8, virtual_address, X[xs2][7:0], AmoOperation::Xor, 1'b0, 1'b0, $encoding), 8);
XReg virtual_address = X[xs1];
X[xd] = sext(amo(8, virtual_address, X[xs2][7:0], AmoOperation::Xor, 1'b0, 1'b0, $encoding), 8);

Exceptions

This instruction may result in the following synchronous exceptions:

  • LoadAccessFault

  • StoreAmoAccessFault

  • StoreAmoPageFault