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PHADDD

Adds two packed double-precision floating-point values from the source and destination operands and stores the result in the destination operand.

The following table specifies the supported source and destination operands.

DO NOT support LOCK

This instruction SHALL ONLY be executed in 64-bit mode or compatibility mode. It is not supported in 32-bit mode.

The result SHALL be subject to the rounding control and exception masking defined in the MXCSR register. If the operation results in a value that cannot be represented in the target format, the processor SHALL trigger #O or #U according to the IEEE 754 standard.

Ensure that the xmm registers are aligned to 16-byte boundaries when using memory operands (m128) to avoid performance penalties or alignment check exceptions depending on the processor configuration. Improper alignment MAY result in a general protection fault (#GP) if alignment checking is enabled.