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

[Stephen Tozer via cfe-commits]

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@@ -0,0 +1,22 @@
+// RUN: %clang_cc1 %s -O2 -emit-llvm -fextend-lifetimes -o - | FileCheck %s
+// Make sure we don't generate fake.use for non-scalar variables.
+// Make sure we don't generate fake.use for volatile variables
+// and parameters even when they are scalar.
+
+struct A {
+  unsigned long t;
+  char c[1024];
+  unsigned char r[32];
+};
+
+
+int foo(volatile int param)
+{
+  struct A s;
+  volatile int vloc;
+  struct A v[128];
+  char c[33];
+  return 0;
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SLTozer wrote:

We don't need initialization to generate fake uses - adding some positive tests should give assurance within the test itself that initializing is unnecessary.

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