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PACKSSDW

Packs signed word values into signed doubleword values. It converts signed 16-bit integers from a source to 32-bit integers in a destination, with saturation. If the signed value is greater than the maximum representable signed 32-bit integer or less than the minimum, it is replaced by the maximum or minimum signed 32-bit integer, respectively.

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

DO NOT support LOCK

This instruction is only available when the processor supports SSE2. It operates exclusively on XMM registers; therefore, it is not available in standalone 64-bit mode without SSE2 support.

The instruction performs saturation. When packing from word (16-bit) to doubleword (32-bit), the values are sign-extended. Because a signed 16-bit integer always fits within a signed 32-bit integer, saturation only occurs if the operation is viewed as part of a wider packing sequence or specific SIMD lane constraints; however, for PACKSSDW specifically, the result is a sign-extension of the i16 to i32. Users MUST ensure that the destination register is correctly aligned if memory operands were supported (though this specific mnemonic utilizes xmm registers).