FCMOV is a floating point conditional move opcode of the Intel x86 architecture, first introduced in Pentium Pro processors. It copies the contents of one of the floating point stack register, depending on the contents of EFLAGS integer flag register, to the ST(0) (top of stack) register. There are 8 variants of the instruction selected by the condition codes that need be set for the instruction to perform the move.
Similar to the CMOV instruction, FCMOV allows to perform some conditional operations without the usual branching overhead. However, it has a higher latency than conditional branch instructions. Therefore, it is most useful for simple yet unpredictable comparison or conditional operations, where it can provide substantial performance gains.
The instruction is usually used with the FCOMI instruction or the FCOM-FSTSW-SAHF idiom to set the relevant condition codes based on the result of a floating point comparison.
Variants
This table shows the variants of the FCMOV instructions. In the Opcode column, i denotes the number of the floating point stack register used as the second operand (the first is always the ST° register – the top of the stack). Add it to the given number to obtain the corresponding opcode.
Opcode Mnemonic Meaning Condition
DA C0+i FCMOVB Move if below Carry flag set
DA C8+i FCMOVE Move if equal Zero flag set
DA D0+i FCMOVBE Move if below or equal Carry flag or Zero flag set
DA D8+i FCMOVU Move if unordered Parity flag set
DB C0+i FCMOVNB Move if not below Carry flag cleared
DB C8+i FCMOVNE Move if not equal Zero flag cleared
DB D0+i FCMOVNBE Move if not below or equal Carry flag and Zero flag cleared
DB D8+i FCMOVNU Move if not unordered Parity flag cleared
Sorry to post this up but at first I thought I could look cool with all this leet speak.
But I am even more confused and in the dark after trying to work out all this…:)
Comments
Old...
Wow, some of that gear looks old :-P. Even mine is newer!
They got it spot on with the OS and the CPU from intel…
But an NVIDIA GeForce 8800…? Pft.
Other settings – FCMOV – 100%. If it’s 100%, what the point of telling us? IDK what FCMOV is…
FCMOV
FCMOV
FCMOV is a floating point conditional move opcode of the Intel x86 architecture, first introduced in Pentium Pro processors. It copies the contents of one of the floating point stack register, depending on the contents of EFLAGS integer flag register, to the ST(0) (top of stack) register. There are 8 variants of the instruction selected by the condition codes that need be set for the instruction to perform the move.
Similar to the CMOV instruction, FCMOV allows to perform some conditional operations without the usual branching overhead. However, it has a higher latency than conditional branch instructions. Therefore, it is most useful for simple yet unpredictable comparison or conditional operations, where it can provide substantial performance gains.
The instruction is usually used with the FCOMI instruction or the FCOM-FSTSW-SAHF idiom to set the relevant condition codes based on the result of a floating point comparison.
Variants
This table shows the variants of the FCMOV instructions. In the Opcode column, i denotes the number of the floating point stack register used as the second operand (the first is always the ST° register – the top of the stack). Add it to the given number to obtain the corresponding opcode.
Opcode Mnemonic Meaning Condition
DA C0+i FCMOVB Move if below Carry flag set
DA C8+i FCMOVE Move if equal Zero flag set
DA D0+i FCMOVBE Move if below or equal Carry flag or Zero flag set
DA D8+i FCMOVU Move if unordered Parity flag set
DB C0+i FCMOVNB Move if not below Carry flag cleared
DB C8+i FCMOVNE Move if not equal Zero flag cleared
DB D0+i FCMOVNBE Move if not below or equal Carry flag and Zero flag cleared
DB D8+i FCMOVNU Move if not unordered Parity flag cleared
Sorry to post this up but at first I thought I could look cool with all this leet speak.
But I am even more confused and in the dark after trying to work out all this…:)
Assembler
Ah yes, assembler :-P. I tried learning that back when I started out with microcontrollers… I got so far as a blinking LED…
I was quickly swayed by the ease of BASIC. After learning C, BASIC feels very restrictive…
lost me at
you lost me technically before the first “,”
I gave up before the end of the 1st para….
but good on ya for knowing that stuff pinge…..
/me now wonders where the concrete is poured and the steel is erected!?
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