[clang] [Clang] Add fake use emission to Clang with -fextend-lifetimes (PR #110102)

[Jeremy Morse via cfe-commits]

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@@ -0,0 +1,27 @@
+// RUN: %clang %s -S -emit-llvm -fextend-lifetimes -O2 -o - -fno-discard-value-names | FileCheck %s
+//
+// Check we can correctly produce fake uses for function-level variables even
+// when we have a return in a nested conditional and there is no code at the end
+// of the function.
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jmorse wrote:

I feel this is the most egregious case of "should be tested without optimisations", as the optimisations delete the whole function body, masking the fact that the fake uses come a block or two before the return (in foo).

https://github.com/llvm/llvm-project/pull/110102