Enhanced Orthogonal Persistence: Use Passive Data Segments (32-Bit)

[luc-blaeser]

Enhanced Orthogonal Persistence: Use Passive Data Segments (32-Bit)

Only passive Wasm data segments are used by the compiler and runtime system. In contrast to ordinary active data segments, passive segments can be explicitly loaded to a dynamic address.

This simplifies two aspects:

• The generated Motoko code can contain arbitrarily large data segments which can loaded to dynamic heap when needed.
• The IC can simply retain the main memory on an upgrade without needing to patch the active data segments of the new program version to the persistent memory.

However, more specific handling is required for the Rust-implemented runtime system:
The Rust-generated active data segments of the runtime system is changed to passive and loaded to the expected static address at the program start (canister initialization and upgrade).
The location and size of the RTS data segments is therefore limited to a defined reserve, see above.
This is acceptable because the RTS only uses small size for data segments (e.g. 54KB) that is independent of the compiled Motoko program.

[github-actions]

Comparing from be54eca to 0b857fc:
The produced WebAssembly code seems to be completely unchanged.