[OpenPOWER-HDL-Cores] bug in microwatt stfsu and stfdu

Paul Mackerras paulus at ozlabs.org
Thu May 20 00:51:46 UTC 2021


On Thu, May 20, 2021 at 01:21:50AM +0100, Luke Kenneth Casson Leighton wrote:
> On Thursday, May 20, 2021, Paul Mackerras <paulus at ozlabs.org> wrote:
> 
> >
> > Writing down for future reference what we discussed on the call:
> 
> 
> good idea
> 
> 
> >
> > The spec says, for the update-form floating-point loads and stores
> > ({l,st}f[sd]u{,x}) that if RA=0 the instruction form is invalid.
> 
> 
> arrgh and of course that's not in the pseudocode, and i'm taking that as
> "literal gospel" [deliberately, so as to find exactly these issues]

Arguably the spec could/should have something like this in the RTL:

	if RA = 0 then
		invalid_form()
	else
		... (existing RTL)
	endif

Paul.


More information about the OpenPOWER-HDL-Cores mailing list