Update docs

Author: cbeuw

README.md

@@ -23,7 +23,7 @@ always indicate a bug in them (or a bug in Rustlantis).
 - rustup
 
 ## Config
-Copy `config.toml.example` to `config.toml` and supply the paths to testing backends.
+Copy `config.toml.example` to `config.toml` and supply the paths to the *repository root* of testing backends.
 
 To prepare `rustc_codegen_cranelift`:
 ```bash
@@ -38,6 +38,40 @@ cargo install rustup-toolchain-install-master
 cd miri && ./miri toolchain && ./miri build --release && ./target/release/cargo-miri miri setup
 ```
 
+## Usage
+
+To generate and difftest one seed, run
+
+```bash
+./fuzz-one.sh <seed>
+```
+
+A program will be generated to `$TMPDIR` and tested. If difftest passes (no bug), it will exit with 0. If difftest spots a difference between testing backends, it will exit with 1 and save the reproduction file to `./repros/`.
+
+To generate a program only, run `generate`
+```
+Usage: generate [OPTIONS] <seed>
+
+Arguments:
+  <seed>  generation seed
+
+Options:
+  -d, --debug    generate a program where values are printed instead of hashed (slow)
+  -h, --help     Print help
+  -V, --version  Print version
+```
+
+To difftest an existing program, run `difftest`
+```
+Usage: difftest <file>
+
+Arguments:
+  <file>  
+
+Options:
+  -h, --help  Print help
+```
+
 ## Quirks
 - Cranelift not supported on AArch64 macOS: https://github.com/bjorn3/rustc_codegen_cranelift/issues/1248
 - `rustc_codegen_backend` can be used as a backend, but it doesn't support enough language features yet to be usable

generate/src/main.rs

@@ -26,7 +26,7 @@ fn main() {
     env_logger::init();
     let matches = command!()
         .args(&[
-            arg!(-d --debug "debug print dumpped variables"),
+            arg!(-d --debug "generate a program where values are printed instead of hashed (slow)"),
             arg!(<seed> "generation seed").value_parser(value_parser!(u64)),
         ])
         .get_matches();