Add a new crate for the FLIR data structures

Cargo.toml

@@ -7,6 +7,7 @@ members = [
   "crates/compiler",
   "crates/driver",
   "crates/error",
+  "crates/flir",
   "crates/rust-test-input",
 ]
 
@@ -42,6 +43,7 @@ itertools = "0.13.0"
 ltc-cli = { path = "crates/cli" }
 ltc-driver = { path = "crates/driver" }
 ltc-errors = { path = "crates/error" }
+ltc-flir = { path = "crates/flir" }
 thiserror = "1.0.63"
 tracing = "0.1.40"
 

crates/flir/Cargo.toml

@@ -0,0 +1,16 @@
+[package]
+name = "ltc-flir"
+version.workspace = true
+homepage.workspace = true
+repository.workspace = true
+license-file.workspace = true
+
+authors.workspace = true
+description = "The FlatLowered Intermediate Representation, or FLIR, is a FlatLowered-based IR customized to the needs of the LTC project."
+keywords.workspace = true
+categories.workspace = true
+
+edition.workspace = true
+rust-version.workspace = true
+
+[dependencies]

crates/flir/README.md

@@ -0,0 +1,17 @@
+# `FlatLowered` Intermediate Representation
+
+The `FlatLowered` Intermediate Representation (`FLIR`) is an intermediate representation for the
+LLVM to Cairo project that is based on Cairo's `FlatLowered` but tailored for our use-case.
+
+In particular, it removes any dependency on the [Salsa](https://github.com/salsa-rs/salsa) database
+structures, as well as:
+
+- Allowing round-tripping to and from `FlatLowered`.
+- Forming the basis of the `.flo` (FlatLowered Object) object format for exchange between tools in
+  the LTC pipeline.
+- Adding support for features (such as linkage and relocations) that are not supported by the
+  `FlatLowered`.
+
+While we could spend the time to add these features to upstream `FlatLowered`, having our own IR
+means that we can iterate and experiment far more rapidly as needed. Some portions of this work
+_may_ be upstreamed in the future, but we make no guarantees.

crates/flir/src/lib.rs

@@ -0,0 +1,3 @@
+//! The `FlatLowered` Intermediate Representation (`FLIR`) is the IR designed
+//! for use as an interchange format between tools in the LLVM to Cairo project,
+//! and the basis for the `.flo` object format.