[Libre-soc-bugs] [Bug 782] add galois field bitmanip instructions

[bugzilla-daemon at libre-soc.org]

https://bugs.libre-soc.org/show_bug.cgi?id=782

--- Comment #27 from Luke Kenneth Casson Leighton <lkcl at lkcl.net> ---
https://libre-soc.org/openpower/isa/svfparith/

Floating Multiply-Add FFT [Single]
A-Form

ffmadds FRT,FRA,FRC,FRB (Rc=0)
ffmadds. FRT,FRA,FRC,FRB (Rc=1)

Pseudo-code:

FRT <- FPMULADD32(FRA, FRC, FRB, 1, 1)
FRS <- FPMULADD32(FRA, FRC, FRB, -1, 1)


note **FRS**

there are *five* operands only *four* listed in
the mnemonic.

FRS is implicitly calculated

* scalar: FRS=FRT+1
* vector: FRS=FRT+svstep+VL
* v/REMAP: FRS=FRT+REMAP(svstep)

the gfmuladdsub needs to be the same form.

anything else requires such extensive interference with SV REMAP
it would be prohibitively disruptive for absolutely no
good reason whatsoever.

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