This content has not been validated; it was AI-generated following the x86-64 ISA Documentation generation process to maintain high quality. However, as no human has verified this data, errors may exist. If the accuracy of this data is critical, please consult the Intel SDM. The model used to generate this is gemma4:31b

STOSD

Stores the value from the EAX register into the memory location pointed to by the EDI or RDI register and then increments or decrements the index register by 4 bytes, depending on the direction flag (DF) state.

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

DO NOT support LOCK

The instruction is available in 32-bit mode and 64-bit mode (including compatibility mode). In 64-bit mode, the destination address is determined by the RDI register.

The behavior of the pointer increment/decrement is dependent on the Direction Flag (DF). If DF=0, the destination index is incremented; if DF=1, it is decremented. Failure to correctly set the DF via CLD or STD before execution SHALL result in unintended memory corruption. The instruction is typically used with the REP prefix to fill a block of memory.