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FCOMPP

Compares the ST(0) floating-point stack element with a floating-point value from a source operand. The instruction compares the two values and sets the floating-point condition codes in the FPU status word.

The following table covers the supported source and destination operands.

DO NOT support LOCK

This instruction is available in 64-bit mode, but it is primarily used for x87 FPU operations. It operates on the x87 floating-point stack; therefore, the precision of the comparison depends on the current control word setting.

The instruction does not pop the operands from the stack. If the comparison involves a NaN (Not-a-Number), a #P (Inexact result) or an invalid operation exception #I may be signaled depending on the specific NaN type and the FPU control word. Users MUST ensure the FPU stack is not empty to avoid a stack underflow exception.