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

[Reid Kleckner 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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rnk wrote:

Fair, but that's a pre-existing test coverage gap. This stuff relies on shared infrastructure. How much testing of immarg do we need, especially for a feature which was never productionized?

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