From 098fc9715e0f0cc3aa5c6ff0512e389c24d09254 Mon Sep 17 00:00:00 2001
From: Camille GILLOT <gillot.camille@gmail.com>
Date: Mon, 18 Sep 2023 16:29:50 +0000
Subject: [PATCH 1/2] Make FnDef 1-ZST in LLVM debuginfo.

---
 .../src/debuginfo/metadata.rs                   | 12 ++++++++++--
 tests/codegen/debug-fndef-size.rs               | 17 +++++++++++++++++
 2 files changed, 27 insertions(+), 2 deletions(-)
 create mode 100644 tests/codegen/debug-fndef-size.rs

diff --git a/compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs b/compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs
index ed938761694dc..11874898a5adb 100644
--- a/compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs
+++ b/compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs
@@ -335,12 +335,20 @@ fn build_subroutine_type_di_node<'ll, 'tcx>(
 
     // This is actually a function pointer, so wrap it in pointer DI.
     let name = compute_debuginfo_type_name(cx.tcx, fn_ty, false);
+    let (size, align) = match fn_ty.kind() {
+        ty::FnDef(..) => (0, 1),
+        ty::FnPtr(..) => (
+            cx.tcx.data_layout.pointer_size.bits(),
+            cx.tcx.data_layout.pointer_align.abi.bits() as u32,
+        ),
+        _ => unreachable!(),
+    };
     let di_node = unsafe {
         llvm::LLVMRustDIBuilderCreatePointerType(
             DIB(cx),
             fn_di_node,
-            cx.tcx.data_layout.pointer_size.bits(),
-            cx.tcx.data_layout.pointer_align.abi.bits() as u32,
+            size,
+            align,
             0, // Ignore DWARF address space.
             name.as_ptr().cast(),
             name.len(),
diff --git a/tests/codegen/debug-fndef-size.rs b/tests/codegen/debug-fndef-size.rs
new file mode 100644
index 0000000000000..2bfd77bade23e
--- /dev/null
+++ b/tests/codegen/debug-fndef-size.rs
@@ -0,0 +1,17 @@
+// Verify that `i32::cmp` FnDef type is declared with size 0 and align 1 in LLVM debuginfo.
+// compile-flags: -O -g -Cno-prepopulate-passes
+
+use std::cmp::Ordering;
+
+fn foo<F: FnOnce(&i32, &i32) -> Ordering>(v1: i32, v2: i32, compare: F) -> Ordering {
+    compare(&v1, &v2)
+}
+
+pub fn main() {
+    foo(0, 1, i32::cmp);
+}
+
+// CHECK: %compare.dbg.spill = alloca {}, align 1
+// CHECK: call void @llvm.dbg.declare(metadata ptr %compare.dbg.spill, metadata ![[VAR:.*]], metadata !DIExpression()), !dbg !{{.*}}
+// CHECK: ![[TYPE:.*]] = !DIDerivedType(tag: DW_TAG_pointer_type, name: "fn(&i32, &i32) -> core::cmp::Ordering", baseType: !{{.*}}, align: 1, dwarfAddressSpace: {{.*}})
+// CHECK: ![[VAR]] = !DILocalVariable(name: "compare", scope: !{{.*}}, file: !{{.*}}, line: {{.*}}, type: ![[TYPE]], align: 1)

From 9d211b044d3198f8e2c9a3e5678fafd2a61a5308 Mon Sep 17 00:00:00 2001
From: Camille GILLOT <gillot.camille@gmail.com>
Date: Sun, 8 Oct 2023 16:43:57 +0000
Subject: [PATCH 2/2] Ignore MSVC in test.

---
 tests/codegen/debug-fndef-size.rs | 1 +
 1 file changed, 1 insertion(+)

diff --git a/tests/codegen/debug-fndef-size.rs b/tests/codegen/debug-fndef-size.rs
index 2bfd77bade23e..80eb35fa32a96 100644
--- a/tests/codegen/debug-fndef-size.rs
+++ b/tests/codegen/debug-fndef-size.rs
@@ -1,5 +1,6 @@
 // Verify that `i32::cmp` FnDef type is declared with size 0 and align 1 in LLVM debuginfo.
 // compile-flags: -O -g -Cno-prepopulate-passes
+// ignore-msvc the types are mangled differently
 
 use std::cmp::Ordering;