[llvm] [lit][docs] Document %if conditional substitution in lit CommandGuide (PR #225683)

[via llvm-commits]

llvmorg-github-actions[bot] wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-testing-tools

Author: Ingo Müller (ingomueller-net)

<details>
<summary>Changes</summary>

`%if ... %else` conditional substitutions (implemented in `TestRunner.py` and mentioned in `TestingGuide.md`) were missing from the `SUBSTITUTIONS` table and `available_features` description in `llvm/docs/CommandGuide/lit.md`. Add `%if` to the base substitutions table and note that `available_features` can be used in `%if` conditions.

---
Full diff: https://github.com/llvm/llvm-project/pull/225683.diff


1 Files Affected:

- (modified) llvm/docs/CommandGuide/lit.rst (+4-1) 


``````````diff
diff --git a/llvm/docs/CommandGuide/lit.rst b/llvm/docs/CommandGuide/lit.rst
index b52a09eb088a1d..a041d4d95faad5 100644
--- a/llvm/docs/CommandGuide/lit.rst
+++ b/llvm/docs/CommandGuide/lit.rst
@@ -619,7 +619,7 @@ executed, two important global variables are predefined:
  makes the test fail only if the last command in the pipe fails.
 
  **available_features** A set of features that can be used in `XFAIL`,
- `REQUIRES`, and `UNSUPPORTED` directives.
+ `REQUIRES`, and `UNSUPPORTED` directives and `%if` substitions.
 
 TEST DISCOVERY
 ~~~~~~~~~~~~~~
@@ -700,6 +700,9 @@ TestRunner.py:
  %:t                     On Windows, %/t but a ``:`` is removed if its the second character.
                          Otherwise, %t but with a single leading ``/`` removed.
  %{readfile:<filename>}  Reads the file specified.
+ %if \<cond> %{...%}     Conditional substitution
+                         (`%if <cond> %{<if-branch>%} [%else %{<else-branch>%}]`);
+                         `<cond>` uses `available_features`.
  ======================= ==============
 
 Other substitutions are provided that are variations on this base set and

``````````

</details>


https://github.com/llvm/llvm-project/pull/225683