[llvm] [ExtendLifetimes] Implement llvm.fake.use to extend variable lifetimes (PR #86149)

[Matt Arsenault via llvm-commits]

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@@ -0,0 +1,95 @@
+# RUN: llc < %s -x mir -run-pass=codegenprepare | FileCheck %s --implicit-check-not="llvm.fake.use"
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arsenm wrote:

This test doesn't make sense, and I'm surprised this doesn't error on you. You're trying to run an IR pass on MIR, and the IR is supposed to just be a constant here and the MIR should not exist yet. You should move this to test/CodeGenPrepare and run it with opt 

https://github.com/llvm/llvm-project/pull/86149