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CQO
Sets the canonical form of the quadword operand.
The table after the description covers what the source and destinations can be.
| source | destination(s) |
|---|---|
| #I | reg |
| #I | m8 |
DO NOT support LOCK
This instruction is only available in 64-bit mode. It is NOT supported in compatibility mode.
The instruction modifies the destination operand to ensure it is in canonical form. If the destination is a register, the upper 64 bits of the internal register representation are cleared, and the canonical form is applied to the r64 field. If the destination is a memory location, the value is updated in the m8 region.
Failure to maintain canonical form when performing memory accesses or using certain registers may result in a General Protection fault (#GP). Use CQO to normalize the quadword operand before it is used as a linear address.