[PATCH] D122569: [lit] Support %if ... %else syntax for RUN lines

[Andrew Savonichev via Phabricator via llvm-commits]

asavonic added inline comments.


================
Comment at: llvm/utils/lit/lit/TestRunner.py:1301
+        # RUN: foo %if feature {if_branch} %else {else_branch}
+        # Stack: [['foo', [token_if, 'feature', 'if_branch', 'else_branch']]]
+        #
----------------
MaskRay wrote:
> It's conventional to use tuples instead of lists to represent immutable objects (stack elements here).
Expression lists are mutable. When we pop the stack, all items are evaluated and the resulting value is appended to the last expression on the previous stack level. For example:

    foo-%if feature { bar }
                          ^~~ cursor
    stack: [ ['foo-', [token_if, 'feature']],
             [' bar '] ] 

When we reach the closing brace, 'bar' is poped out and appended to the 'if' expression:

    stack: [ ['foo-', [token_if, 'feature', ' bar ']] ] 



CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D122569/new/

https://reviews.llvm.org/D122569