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Re: [rs6000] Add documentation for __builtin_mtfsf

Hi Paul,

On Sun, Jul 21, 2019 at 04:06:32AM -0500, Paul Clarke wrote:
> @@ -16864,6 +16865,10 @@ return the value of the FPSCR register.  Note, ISA
>  @code{__builtin_mffsl()} which permits software to read the control and
>  non-sticky status bits in the FSPCR without the higher latency associated with
>  accessing the sticky status bits.  The
> +@code{__builtin_mtfsf} takes a constant 8-bit integer field mask and a
> +representation of the new value of the FPSCR and generates the @code{mtfsf}
> +instruction to copy the supplied value into the FPSCR, subject to the field
> +mask, each bit of which represents a nibble of the FPSCR.  The
>  @code{__builtin_mtfsb0} and @code{__builtin_mtfsb1} take the bit to change
>  as an argument.  The valid bit range is between 0 and 31.  The builtins map to
>  the @code{mtfsb0} and @code{mtfsb1} instructions which take the argument and

"A representation of the new value"?  I guess you want to say that it
sits in an FPR?

Before we document __builtin_mtfsf, maybe we should make it work with
the W and/or L fields first, or at least, decide how we want that?


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