[llvm] [InstCombine] Only fold extract element to trunc if vector `hasOneUse` (PR #115627)

[Nikita Popov via llvm-commits]

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@@ -722,20 +722,14 @@ define i8 @bitcast_scalar_index_variable(i32 %x, i64 %y) {
   ret i8 %r
 }
 
-; extra use is ok if we don't need a shift
+; extra use is not ok, even if we don't need a shift
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nikic wrote:

This case could be okay as we're just replacing extractelement with trunc here, without also inserting a bitcast. But tentatively I'd agree that if we're going to cast to a vector anyway, it makes sense to stay in vector representation.

https://github.com/llvm/llvm-project/pull/115627