selects on differing subsets of a query

First post, be gentle as I have terminology problems and so the
subject might be wrongly worded.

Say I have a table with fields
...
gender
diet_pref
...

What I am trying to construct is a *single* query showing the total
number of males in the table
and also the total number of male vegetarians in the table, i.e. the
2nd value is computed on a subset of the records needed for the first
value.

As 2 queries this would be:
select count(*) from mytab where gender='m'
select count(*) from mytab where gender='m' and diet_pref='veg'

The table is big and I'd like to do the select where gender='m' only
once. (In the actual situation the select is on a date range)

If there is a TFM, please point me at it with an indication of exactly
what it is I am trying to achieve. If I'm trying to do something
stupid, gentle advice would be appreciated.