autodiff: update formating, improve examples for the unstable-book

Author: ZuseZ4

src/doc/unstable-book/src/compiler-flags/autodiff.md

@@ -6,16 +6,37 @@ The tracking issue for this feature is: [#124509](https://github.com/rust-lang/r
 
 This feature allows you to differentiate functions using automatic differentiation.
 Set the `-Zautodiff=<options>` compiler flag to adjust the behaviour of the autodiff feature.
-Multiple options can be separated with a comma. Valid options are:
-
-`Enable` - Required flag to enable autodiff
-`PrintTA` - print Type Analysis Information
-`PrintTAFn` - print Type Analysis Information for a specific function
-`PrintAA` - print Activity Analysis Information
-`PrintPerf` - print Performance Warnings from Enzyme
-`PrintSteps` - prints all intermediate transformations
-`PrintModBefore` - print the whole module, before running opts
-`PrintModAfter` - print the module after Enzyme differentiated everything
-`LooseTypes` - Enzyme's loose type debug helper (can cause incorrect gradients)
-`Inline` - runs Enzyme specific Inlining
-`RuntimeActivity` - allow specifying activity at runtime
+Multiple options can be separated with a comma. 
+
+## Syntax
+```bash
+rustc -Z autodiff=Enable[,options]
+```
+
+Where `options` can be:
+
+- `Enable` - Required flag to enable autodiff
+- `PrintTA` - print Type Analysis Information
+- `PrintTAFn=<fn_name>` - print Type Analysis Information for a specific function (consider combining it with `no_mangle`)
+- `PrintAA` - print Activity Analysis Information
+- `PrintPerf` - print Performance Warnings from Enzyme
+- `PrintSteps` - prints all intermediate transformations
+- `PrintModBefore` - print the whole module, before running opts
+- `PrintModAfter` - print the module after Enzyme differentiated everything
+- `LooseTypes` - Enzyme's loose type debug helper (can cause incorrect gradients)
+- `Inline` - runs Enzyme specific Inlining
+- `RuntimeActivity` - allow specifying activity at runtime
+
+
+## Examples
+
+```bash
+# Enable autodiff via cargo, assuming `enzyme` being a toolchain that supports autodiff
+"RUSTFLAGS=-Zautodiff=Enable" cargo +enzyme build
+
+# Enable autodiff directly via rustc
+rustc -Z autodiff=Enable
+
+# Print TypeAnalysis updates for the function `foo`, as well as Activity Analysis for all differentiated code.
+rustc -Z autodiff=Enable,PrintTAFn=foo,PrintAA
+```