[llvm] [IR] Use immarg for preallocated intrinsics (NFC) (PR #155835)

[Nikita Popov via llvm-commits]

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@@ -65,7 +65,7 @@ define void @preallocated_one_call() {
     ret void
 }
 
-; CHECK: must be a constant
+; CHECK: immarg operand has non-immediate parameter
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nikic wrote:

Heh, this did end up catching an issue in this case. Because part of the validation for preallocated.arg is done when visiting the preallocated.setup, we can't actually assume that the argument is constant in the verifier at that point, so it ended up asserting. I've restored that check, which also means that this doesn't actually produce the immarg message now.

https://github.com/llvm/llvm-project/pull/155835