This patch addresses two issues with NBAs in non-inlined functions/tasks:
- If the NBA writes to a local automatic var, the var could cease to exist before the NBA executes. This is normally addressed by fork dynscopes (#4356), but NBA-to-fork transformation happens way after `V3Fork` (in `V3Timing`). To solve this, we put NBAs that write to locals under forks in `V3Fork` already. This way, such locals will be put in dynscopes, and will still exist after the task containing the NBA exits.
- The above change means that any writes in forks other than `fork..join` should be handled by `V3Fork`. Thus, in `V3SchedTiming`, we only have to worry about read references, so we can simply copy all remaining locals. Because we copy, lifetimes are not an issue. This fixes a bug that allowed assignment intravals to be overwritten if they go out of scope in the containing function.
This patch enforces the use of the most specific accessors for operands
which have an '@astgen alias' declaration, by making the superclass
accessors of the same operands private. This ensures client code is
cleaner as you can't use multiple different methods to reference the
same operands (which we used to in some places). Also prep for some
refactoring.
V3Subst is currently the pass responsible for peak memory usage. This
patch saves ~16% of peak memory on OpenTitan.
2 changes:
- It is actually safe to delete the substituted expressions immediately,
but this is the lesser contribution
- More importantly, we only ever substitute STMTTEMP variables, which
are always defined within the same CFunc, so we can limit the scope of
the optimization to CFunc. This allows us to reclaim the SubstVarEntry
structures at the end of every CFunc, rather than at the end of the
whole pass, which gives us most of the memory savings.
Generated output is identical
Used to set the wrong public flag on forceEn/forceVal, which means they
were not included in ICO as necessary, but V3Gate tended to inline them,
so this was hard to hit.
Fixes#4577
This saves about 5% memory. V3AstUserAllocator is appropriate for most use
cases, performance is marginally up as we are mostly D-cache bound on
large designs.
The typical find/if-not-exists-insert pattern can be achieved with 1
lookup instead of 2 using emplace with a sentinel value. Also maps value
initialize their values when inserted with the [] operator, this is
defined and so there is no need to explicitly insert zeroes for integer
values.
