Motivation: to make progress in the new compiler stack, we have
to preserve join points during lambda lifting. Right now, they are
lifted as regular lambdas. So, to keep them, we need some basic
support for them in the old VM. The implementation here is quick and
dirty. This is not an issue since this code will be deleted soon.
This commit also add two new instructions to the old VM: `updt` and
`updt_cidx`.
They allow us to test the new new memory reuse technique.
TODO: We need to reset fields after we project. Otherwise, we prevent
destructive updates on nested objects.
- Lean strings (like std::string) may contain null characters. The
codebase was ignoring this issue.
- We now have a wrapper `string_ref` for wrapping Lean string objects in
C++. This wrapper also implements correctly the coercions std::string <-> string_ref.
Remark: I also found a few places where the code relies on the
following property which is not true
Forall s : std::string, std::string(s.c_str()) == s
- `name` object wrapper was assuming that all numerals were small
`nat` values. This is true in most cases, but the system would
crash when processing if it is a big number.
- The commit tries to make sure runtime/util/kernel are correct.
Modules that will be deleted contain many `TODO` comments
indicating they may crash and/or produce incorrect results
when strings contain null characters and numerals are big.
cc @kha
@kha: I thought about using `string` instead of `string_ref`.
We consistently use `std::string`. So, it should be fine, but I
was concerned about code readability.
After we bootstrap Lean4, we will be able to delete `lean::list`
template, and rename `lean::list_ref` to `lean::list`.
I am going to add `pair_ref` for wrapping Lean pair objects.
If we use `lean::string` instead of `lean::string_ref`, then
we should also use `lean::pair` instead of `lean::pair_ref`.
But, there is a problem in this case since we have
https://github.com/leanprover/lean4/blob/master/src/util/pair.h#L13
:(
@kha The runtime folder includes what is needed to link a
standalone Lean program. It is still contains some unnecessary files.
We will be able to remove them after we release Lean4.
memory_pool object introduces memory contention and unnecessary
complexity. Moreover, it actually reduces performance when we compile
Lean using JEMALLOC.
Here are the numbers for corelib
jemalloc with memory_pool: 13.83 secs
jemalloc without memory_pool: 13.60 secs
We use small_object_allocator to allocate vm_obj's.
However small_object_allocator is not thread safe. So, we need to copy
vm_obj's between threads. Moreover, in our experiments, we observed that
JEMALLOC is actually faster than the small_object_allocator.
Here are numbers for the reduced corelib.
small_object_allocator: 15.62 secs
gcc 4.9 allocator: 16.19 secs
jemalloc: 13.83 secs
@kha I have added a few performance counters.
I collect their values at each snapshot.
Right now, I am printing only the values in the last snapshot, but if we want
we can even display their progress over time.
Right now, I track the following information
- number of allocated closures
- number of allocated constructors/objects
- number of allocated big numbers
The equation compiler uses different strategies for processing
recursive equations. Some of them may produce unclear runtime cost
model. For example, the following fibonacci functions was running in
linear time instead of exponential time because the equation compiler
used the brec_on recursor.
def fib : nat → nat
| 0 := 1
| 1 := 1
| (n+2) := fib (n+1) + fib n
@dselsam and @jroesch have reported examples were the equation compiler
produces a negative performance impact. The new test (`eval` function)
captures the problem reported by @jroesch. In this example, the runtime
should not depend on the "amount of fuel".
This commit addresses this issue.
closes#1175
The types `string_imp` and `string.iterator_imp` were supposed to be
marked private, but we cannot do it because we need to provide
`string_imp.mk`, `string_imp.cases_on`, `string.iterator_imp.mk` and
`string.iterator_imp.cases_on` in the VM since we use a different
internal representation. Note that marking them as private does not
work since users can still access `string_imp.cases_on` using
meta-programming.
So, we need better support for private declarations.
Missing feature, char literals do not support non ASCII values.
That is, in the current implementation, we cannot write 'α'.
This will be implemented in the future.
The VM native implementation does not behave correctly for huge
strings (i.e., strings with more than 4G characters).
The problem is that the current implementation relies on
```
size_t force_to_size_t(vm_obj const & o, size_t def)
```
We may also have overflow problems in the string.iterator implementation
code. This is not a big deal right now, since I doubt we will try
to process string with more than 2^32 characters.
@Kha the `core_lib` and tests seem to be working correctly, but
we need more tests.
Older gcc compilers generate a warning when the attribute is used.
I found out that GCC 7 will not produce a warning if comments
such as /* fall-thru */ or /* FALLTHRU */ are used instead of the
attribute [[fallthrough]]
