[llvm] [LangRef] Add aligned attribute description into masked.compress/expandload sections. (PR #83808)

[Matt Arsenault via llvm-commits]

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@@ -24276,6 +24276,9 @@ Arguments:
 
 The first operand is the base pointer for the load. It has the same underlying type as the element of the returned vector. The second operand, mask, is a vector of boolean values with the same number of elements as the return type. The third is a pass-through value that is used to fill the masked-off lanes of the result. The return type and the type of the '``passthru``' operand have the same vector type.
 
+The :ref:`align <attr_align>` parameter attribute can be provided for the first
+operand.
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arsenm wrote:

Mention default of 1?

https://github.com/llvm/llvm-project/pull/83808