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REPNE

Repeats the SCAS or CMPS instruction until CX/ECX/RCX is 0 or the Zero Flag (ZF) is set.

The following table covers what the source and destinations can be.

Support LOCK

The instruction is available in 64-bit mode, compatibility mode, and 32-bit protected mode. The behavior depends on the destination index register (EDI/RDI) and source index register (ESI/RSI) and the Direction Flag (DF). If DF=0, indices are incremented; if DF=1, indices are decremented.

To avoid infinite loops, RCX MUST be initialized to a non-zero value unless the intent is to skip the operation. If RCX is set to 0, the instruction is treated as a no-operation and RCX remains 0. In 64-bit mode, if a 32-bit ECX is used, the upper 32 bits of RCX MUST be handled carefully to avoid unexpected iteration counts. Ensure that the memory regions pointed to by RSI and RDI are valid and do not overlap in a way that violates the logic of the search/compare operation to avoid memory access violations.