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FRSTOR

Restores the state of the x87 floating-point unit (FPU) by loading the FPU register stack and the control word from a specified memory location.

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

DO NOT support LOCK

This instruction is available in 64-bit mode, but it operates exclusively on the x87 FPU state. In x86-64, the FPU is maintained for compatibility, but the architectural state is handled as a legacy entity.

It is MANDATORY to ensure that the memory region m108 is correctly aligned and contains a valid FPU state save-area created by FSAVE. Failure to provide a valid save-area will result in an inconsistent FPU state. Use of this instruction in environments where the FPU state is managed by XSAVE/XRSTOR may lead to state corruption if the x87 component is not correctly tracked.