[clang] [Clang][HTO] Add clang attribute for propagating llvm-level information (PR #83059)

[Johannes Doerfert via cfe-commits]

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@@ -0,0 +1,14 @@
+// RUN: %clang_cc1 -debug-info-kind=limited -emit-llvm -o - | FileCheck %s
+
+void t1() __attribute__((llvm_fn_attr("custom_attr", "custom_value"), llvm_fn_attr("second_attr", "second_value")));
+
+void t1()
+{
+}
+
+void t2();
+
+void t3() {
+	t2() ____attribute__((llvm_fn_attr("custom_attr", "custom_value"), llvm_fn_attr("second_attr", "second_value")));
+}
+
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jdoerfert wrote:

1. Check lines
2. existing attributes need to be tested
3. negative tests are missing, e.g., too many/few arguments, values like "foo,bar" or "300qqqq", etc.

https://github.com/llvm/llvm-project/pull/83059