This adds these two fields to a HashMap Entry:
uint32_t hash
uint32_t distance_from_start_index
Compared to master branch, standard library tests compiled 8.4% faster
and took negligible (0.001%) more memory to complete. The amount of
memory used is still down from before 8b82c4010480 which moved indexes
to be stored separately from entries.
So, it turns out, keeping robin hood hashing plus separating indexes
did result in a performance improvement. What happened previously is
that the gains from separating indexes balanced out the losses from
removing robin hood hashing, resulting in a wash.
This also serves as an inspiration for adding a benchmark to
std.AutoHashMap and improving the implementation.
The indexes are stored separately using an array of
uint8_t, uint16_t, uint32_t, or size_t, depending on the number of
entries in the map.
Entries only contain a key and a value, no longer have
distance_from_start_index or is_used.
In theory this should be both faster and use less memory.
In practice it seems to have little to no effect. For the standard
library tests, vs master branch, the time had no discernable
difference, and it shaved off only 13 MiB of peak rss usage.
- split util_base.hpp from util.hpp
- new namespaces: `mem` and `heap`
- new `mem::Allocator` interface
- new `heap::CAllocator` impl with global `heap::c_allocator`
- new `heap::ArenaAllocator` impl
- new `mem::TypeInfo` extracts names without RTTI
- name extraction is enabled w/ ZIG_ENABLE_MEM_PROFILE=1
- new `mem::List` takes explicit `Allocator&` parameter
- new `mem::HashMap` takes explicit `Allocator&` parameter
- add Codegen.pass1_arena and use for all `ZigValue` allocs
- deinit Codegen.pass1_arena early in `zig_llvm_emit_output()`
