Move several DWARF constants into their own submodule

The main advantage of doing this is that we can apply a single
`#![allow(non_upper_case_globals)]` to the whole module, though it's also
helpful when manually checking values against LLVM or the DWARF spec.

Author: Zalathar

compiler/rustc_codegen_llvm/src/debuginfo/dwarf_const.rs

@@ -0,0 +1,18 @@
+//! Definitions of various DWARF-related constants.
+//! These should agree with `llvm/include/llvm/BinaryFormat/Dwarf.def`.
+
+#![allow(non_upper_case_globals)] // Allow names to match their LLVM equivalents
+
+use libc::c_uint;
+
+/// DWARF constant representing the Rust language. Introduced in DWARF 5.
+/// Defined by http://www.dwarfstd.org/ShowIssue.php?issue=140129.1.
+pub(crate) const DW_LANG_RUST: c_uint = 0x1c;
+
+// DWARF attribute type encodings
+
+pub(crate) const DW_ATE_boolean: c_uint = 0x02;
+pub(crate) const DW_ATE_float: c_uint = 0x04;
+pub(crate) const DW_ATE_signed: c_uint = 0x05;
+pub(crate) const DW_ATE_unsigned: c_uint = 0x07;
+pub(crate) const DW_ATE_UTF: c_uint = 0x10;

compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs

@@ -59,20 +59,6 @@ impl fmt::Debug for llvm::Metadata {
     }
 }
 
-// From DWARF 5.
-// See http://www.dwarfstd.org/ShowIssue.php?issue=140129.1.
-const DW_LANG_RUST: c_uint = 0x1c;
-#[allow(non_upper_case_globals)]
-const DW_ATE_boolean: c_uint = 0x02;
-#[allow(non_upper_case_globals)]
-const DW_ATE_float: c_uint = 0x04;
-#[allow(non_upper_case_globals)]
-const DW_ATE_signed: c_uint = 0x05;
-#[allow(non_upper_case_globals)]
-const DW_ATE_unsigned: c_uint = 0x07;
-#[allow(non_upper_case_globals)]
-const DW_ATE_UTF: c_uint = 0x10;
-
 pub(super) const UNKNOWN_LINE_NUMBER: c_uint = 0;
 pub(super) const UNKNOWN_COLUMN_NUMBER: c_uint = 0;
 
@@ -89,6 +75,8 @@ mod type_map;
 
 pub(crate) use type_map::TypeMap;
 
+use crate::debuginfo::dwarf_const;
+
 /// Returns from the enclosing function if the type debuginfo node with the given
 /// unique ID can be found in the type map.
 macro_rules! return_if_di_node_created_in_meantime {
@@ -519,7 +507,7 @@ fn recursion_marker_type_di_node<'ll, 'tcx>(cx: &CodegenCx<'ll, 'tcx>) -> &'ll D
                 name.as_c_char_ptr(),
                 name.len(),
                 cx.tcx.data_layout.pointer_size.bits(),
-                DW_ATE_unsigned,
+                dwarf_const::DW_ATE_unsigned,
             )
         }
     })
@@ -778,6 +766,8 @@ fn build_basic_type_di_node<'ll, 'tcx>(
     // .natvis visualizers (and perhaps other existing native debuggers?)
     let cpp_like_debuginfo = cpp_like_debuginfo(cx.tcx);
 
+    use dwarf_const::{DW_ATE_UTF, DW_ATE_boolean, DW_ATE_float, DW_ATE_signed, DW_ATE_unsigned};
+
     let (name, encoding) = match t.kind() {
         ty::Never => ("!", DW_ATE_unsigned),
         ty::Tuple(elements) if elements.is_empty() => {
@@ -958,7 +948,7 @@ pub(crate) fn build_compile_unit_di_node<'ll, 'tcx>(
 
         let unit_metadata = llvm::LLVMRustDIBuilderCreateCompileUnit(
             debug_context.builder,
-            DW_LANG_RUST,
+            dwarf_const::DW_LANG_RUST,
             compile_unit_file,
             producer.as_c_char_ptr(),
             producer.len(),

compiler/rustc_codegen_llvm/src/debuginfo/mod.rs

@@ -39,6 +39,7 @@ use crate::llvm::debuginfo::{
 use crate::value::Value;
 
 mod create_scope_map;
+mod dwarf_const;
 mod gdb;
 pub(crate) mod metadata;
 mod namespace;