Intrinsics require investigation

[dkcumming]

Goal

• Find the definitive set of intrinics as we will see them in the MIR / SMIR
• Strip the instrinsics that we care about
• Find appropriate tests to examine intrinsics
• Observe that instrinsics are working as we expect and we are handling correctly

Sources

• ui/compiletest
• cargo build -Z build-std --target <TARGET> e.g. cargo build -Z build-std --target x86_64-unknown-linux-gnu more info can be found in Stephen's hack.md and cargo reference
  NOTE: This is a cargo flag not rustc flag.
  This will throw attempting to add the flags with smir_pretty with

error: "/home/daniel/Applications/mir-semantics/deps/smir_pretty/deps/rust/src/build/x86_64-unknown-linux-gnu/stage1/lib/rustlib/src/rust/library/Cargo.lock" does not exist, unable to build with the standard library, try:
        rustup component add rust-src --toolchain smir_serde_derive_intern_scripts

meaning that the the rust-src component is required for the toolchain. However it will not be able to do this for smir_serde_derive_intern_scripts as it is our own fork branch (If there is a way let me know).
But the compiler can be set to the same version the that is the base of the smir_serde_derive_intern_scripts fork with rustup defaulting to the day subsequent to the last rustc commit:

rustup default nightly-2024-07-27
rustup component add rust-src --toolchain nightly-2024-07-27-x86_64-unknown-linux-gnu

Then the artefacts of the std-lib can be found in <PROJECT ROOT>/target/<TARGET> e.g. hello-world/target/x86_64-unknown-linux-gnu.

Questions for the investigation:

• What are the names of all the intrinsics
  • Rv rust fork: get_instrincs.sh gets the names at source level
  • Need to find the mangled names

Noticed Behaviour

• Sometimes the compiler generates a mir body for the intrinsic?
  • Suspect: If LLVM knows the intrinsic then it doesn't generate a mir body
• Sometimes intrinsics are generic?