[PATCH] D33242: [InstCombine] add motivational comment for tests; NFC

[Sanjay Patel via Phabricator via llvm-commits]

spatel created this revision.
Herald added a subscriber: mcrosier.

The referenced tests are derived from:
https://bugs.llvm.org/show_bug.cgi?id=32791
and:
https://reviews.llvm.org/D33172

The motivation for including negative tests may not be clear, so I'm proposing an explanatory comment here.
In the post-commit thread for r303133:
http://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20170515/453793.html
...it was mentioned that we don't want to add redundant tests. This is a valid point. But in this case, we have a patch under review (https://reviews.llvm.org/D33172) that demonstrates that no existing regression tests are affected by a proposed code change, but these are. Therefore, I think these tests have value not visible in any existing regression tests regardless of whether they show a transform.


https://reviews.llvm.org/D33242

Files:
  test/Transforms/InstCombine/logical-select.ll


Index: test/Transforms/InstCombine/logical-select.ll
===================================================================
--- test/Transforms/InstCombine/logical-select.ll
+++ test/Transforms/InstCombine/logical-select.ll
@@ -62,6 +62,11 @@
   ret i32 %t3
 }
 
+; TODO: For the next 4 tests, are there potential canonicalizations and/or folds for these
+; in InstCombine? Independent of that, tests like this that may not show any transforms 
+; still have value because they can help identify conflicting canonicalization rules that 
+; lead to infinite looping. 
+
 ; PR32791 - https://bugs.llvm.org//show_bug.cgi?id=32791
 ; Fold two selects with inverted predicates and zero operands.
 define i32 @fold_inverted_icmp_preds(i32 %a, i32 %b, i32 %c, i32 %d) {


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D33242.99146.patch
Type: text/x-patch
Size: 760 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20170516/929cb76e/attachment.bin>