[clang] [CIR] Use destination type when emitting constant function ptrs (PR #189741)

[Andy Kaylor via cfe-commits]

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@@ -0,0 +1,71 @@
+// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -w -fclangir -emit-cir %s -o %t.cir
+// RUN: FileCheck --input-file=%t.cir %s
+
+// Because LLVM IR uses opaque pointers, nothing in this test would be worth
+// checking there, so LLVM and OGCG checks are omitted.
+
+// Exercise replacing a no-prototype declaration with a prototyped definition
+// when a global struct initializer already took the address of that function.
+// The initializer must use the struct field's function-pointer type (not the
+// FuncOp's no-prototype type) so CIR stays valid after the replacement.
+
+// CHECK: !{{[^ ]+}} = !cir.record<struct "S1" {!cir.ptr<!cir.func<()>>, !s32i, !s32i}>
+// CHECK: !{{[^ ]+}} = !cir.record<struct "S2" {!cir.ptr<!cir.func<(...)>>, !s32i, !s32i}>
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andykaylor wrote:

I feel like for any code written in the last 20 years, if someone writes `f()` they meant for it to be `f(void)`. Of course, not all C code was written in the last 20 years... 

https://github.com/llvm/llvm-project/pull/189741