[clang] [CIR] Upstream simple function bodies (PR #127674)

[Henrich Lauko via cfe-commits]

================
@@ -0,0 +1,53 @@
+// Simple functions
+// RUN: %clang_cc1 -std=c++20 -triple x86_64-unknown-linux-gnu -fclangir -emit-cir %s -o -  | FileCheck %s
+
+void empty() { }
+// CHECK: cir.func @empty() -> !cir.void {
----------------
xlauko wrote:

Ideally once there will be abi-lib: https://discourse.llvm.org/t/llvm-abi-a-library-for-generating-abi-compliant-llvm-ir/37196/11 to be used across codegens.

https://github.com/llvm/llvm-project/pull/127674