[llvm] [LangRef] Clarify requirement for non-pow-2 align bundle (PR #195631)

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llvmorg-github-actions[bot] wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-ir

Author: Nikita Popov (nikic)

<details>
<summary>Changes</summary>

Now that null pointers are not necessarily zero pointers, I believe that `"align"` with a non-power-of-two alignment should be requiring a zero pointer specifically, not a null pointer.

This is because a zero pointer is aligned for any alignment (which we can generalize to non-power-of-two alignments), while a -1 null pointer only has alignment 1.

---
Full diff: https://github.com/llvm/llvm-project/pull/195631.diff


1 Files Affected:

- (modified) llvm/docs/LangRef.rst (+1-1) 


``````````diff
diff --git a/llvm/docs/LangRef.rst b/llvm/docs/LangRef.rst
index a1442a2a607d3..912cca72e1ad5 100644
--- a/llvm/docs/LangRef.rst
+++ b/llvm/docs/LangRef.rst
@@ -3152,7 +3152,7 @@ the behavior is undefined, unless one of the following exceptions applies:
 
 * ``"align"`` operand bundles may specify a non-power-of-two alignment
   (including a zero alignment). If this is the case, then the pointer value
-  must be a null pointer, otherwise the behavior is undefined.
+  must be an all-zero pointer, otherwise the behavior is undefined.
 
 * ``dereferenceable(<n>)`` operand bundles only guarantee the pointer is
   dereferenceable at the point of the assumption. The pointer may not be

``````````

</details>


https://github.com/llvm/llvm-project/pull/195631