[Libre-soc-bugs] [Bug 450] Create MMU from microwatt mmu.vhdl

[bugzilla-daemon at libre-soc.org]

https://bugs.libre-soc.org/show_bug.cgi?id=450

--- Comment #50 from Cole Poirier <colepoirier at gmail.com> ---
(In reply to Luke Kenneth Casson Leighton from comment #49)
> (In reply to Cole Poirier from comment #48)

> > Sorry that's not that helpful, can you expand on this.
> 
> apologies, i assumed you'd know to expand "..." in the way that all typedefs
> (c and other languages) work.

Aha! Thanks very much for taking the time to explain this to me, I’m learning a
lot very quickly, but I am still very ignorant.

> wherever you see a subtype, LITERALLY replace the subtype with its
> declaration.

Ok, that makes sense.

> subtype way_t is integer range 0 to NUM_WAYS-1;
> 
> subtype cache_tag_t is std_logic_vector(TAG_BITS-1 downto 0);
> 
> type cache_tags_set_t is array(way_t) of cache_tag_t;
> type cache_tags_array_t is array(index_t) of cache_tags_set_t;
> 
> 
> becomes
> 
>  
> 
> subtype cache_tag_t is std_logic_vector(TAG_BITS-1 downto 0);
> 
> type cache_tags_set_t is array(range 0 to NUM_WAYS-1;) of cache_tag_t;
> type cache_tags_array_t is array(index_t) of cache_tags_set_t;
> 
> 
> 
> becomes
> 
> 
> type cache_tags_set_t is array(range 0 to NUM_WAYS-1;) of
> std_logic_vector(TAG_BITS-1 downto 0);
> 
> type cache_tags_array_t is array(index_t) of cache_tags_set_t;
> 
> 
> becomes
> 
> 
> 
> type cache_tags_array_t is array(index_t) of 
> array(range 0 to NUM_WAYS-1;) of std_logic_vector(TAG_BITS-1 downto 0);
> 
> 
> 
> and the substitution is now complete as far as you have given.
> 
> of course, it is itself also a type, therefore there will be an additional
> substitution.

That’s very helpful, thank you.


> translating that to nmigen, will invve a 2D Array of Signals.

The above us all helpful but I think this is the key insight. AFK right now but
will try this shortly and get back to you with a more useful question. Thanks
Luke :)

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