[Libre-soc-dev] we need two XLENs
Luke Kenneth Casson Leighton
lkcl at lkcl.net
Fri Sep 9 06:53:56 BST 2022
On Fri, Sep 9, 2022 at 2:49 AM Jacob Lifshay <programmerjake at gmail.com> wrote:
> imho it's a waay better idea to have the two variables, a post-analysis isn't sufficient because of things like combined fp arithmetic and fp format conversion, (e.g. fsqrt with srcelwid=64 and destelwid=f16) where rounding correctly requires fsqrt to know what the actual destination format is, if it just rounds to f64 and then rounds again to f16, it'll give the wrong result in some cases.
risk is: DLEN/SLEN start to bleed into pseudocode making a mess
and freaking out OPF ISA WG.
FP ops drop down to functions where what happens behind the
scenes can be over-ridden. FPMUL32 in helpers.py.
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