Auto merge of #82285 - nhwn:nonzero-debug, r=nagisa

Use u32 over Option<u32> in DebugLoc

~~Changes `Option<u32>` fields in `DebugLoc` to `Option<NonZeroU32>`. Since the respective fields (`line` and `col`) are guaranteed to be 1-based, this layout optimization is a freebie.~~

EDIT: Changes `Option<u32>` fields in `DebugLoc` to `u32`. As `@bugadani` pointed out, an `Option<NonZeroU32>` is probably an unnecessary layer of abstraction since the `None` variant is always used as `UNKNOWN_LINE_NUMBER` (which is just `0`).  Also, `SourceInfo` in `metadata.rs` already uses a `u32` instead of an `Option<u32>` to encode the same information, so I think this change is warranted.

Since `@jyn514` raised some concerns over measuring performance in a similar PR (#82255), does this need a perf run?

compiler/rustc_codegen_llvm/src/debuginfo/create_scope_map.rs

@@ -1,4 +1,4 @@
-use super::metadata::{file_metadata, UNKNOWN_COLUMN_NUMBER, UNKNOWN_LINE_NUMBER};
+use super::metadata::file_metadata;
 use super::utils::DIB;
 use rustc_codegen_ssa::mir::debuginfo::{DebugScope, FunctionDebugContext};
 use rustc_codegen_ssa::traits::*;
@@ -102,8 +102,8 @@ fn make_mir_scope(
                 DIB(cx),
                 parent_scope.dbg_scope.unwrap(),
                 file_metadata,
-                loc.line.unwrap_or(UNKNOWN_LINE_NUMBER),
-                loc.col.unwrap_or(UNKNOWN_COLUMN_NUMBER),
+                loc.line,
+                loc.col,
             )
         },
     };

compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs

@@ -1842,10 +1842,7 @@ impl<'tcx> VariantInfo<'_, 'tcx> {
                     .span;
                 if !span.is_dummy() {
                     let loc = cx.lookup_debug_loc(span.lo());
-                    return Some(SourceInfo {
-                        file: file_metadata(cx, &loc.file),
-                        line: loc.line.unwrap_or(UNKNOWN_LINE_NUMBER),
-                    });
+                    return Some(SourceInfo { file: file_metadata(cx, &loc.file), line: loc.line });
                 }
             }
             _ => {}
@@ -2484,7 +2481,7 @@ pub fn create_global_var_metadata(cx: &CodegenCx<'ll, '_>, def_id: DefId, global
         let loc = cx.lookup_debug_loc(span.lo());
         (file_metadata(cx, &loc.file), loc.line)
     } else {
-        (unknown_file_metadata(cx), None)
+        (unknown_file_metadata(cx), UNKNOWN_LINE_NUMBER)
     };
 
     let is_local_to_unit = is_node_local_to_unit(cx, def_id);
@@ -2507,7 +2504,7 @@ pub fn create_global_var_metadata(cx: &CodegenCx<'ll, '_>, def_id: DefId, global
             linkage_name.as_ptr().cast(),
             linkage_name.len(),
             file_metadata,
-            line_number.unwrap_or(UNKNOWN_LINE_NUMBER),
+            line_number,
             type_metadata,
             is_local_to_unit,
             global,

compiler/rustc_codegen_llvm/src/debuginfo/mod.rs

@@ -224,9 +224,9 @@ pub struct DebugLoc {
     /// Information about the original source file.
     pub file: Lrc<SourceFile>,
     /// The (1-based) line number.
-    pub line: Option<u32>,
+    pub line: u32,
     /// The (1-based) column number.
-    pub col: Option<u32>,
+    pub col: u32,
 }
 
 impl CodegenCx<'ll, '_> {
@@ -243,16 +243,16 @@ impl CodegenCx<'ll, '_> {
                 let line = (line + 1) as u32;
                 let col = (pos - line_pos).to_u32() + 1;
 
-                (file, Some(line), Some(col))
+                (file, line, col)
             }
-            Err(file) => (file, None, None),
+            Err(file) => (file, UNKNOWN_LINE_NUMBER, UNKNOWN_COLUMN_NUMBER),
         };
 
         // For MSVC, omit the column number.
         // Otherwise, emit it. This mimics clang behaviour.
         // See discussion in https://github.com/rust-lang/rust/issues/42921
         if self.sess().target.is_like_msvc {
-            DebugLoc { file, line, col: None }
+            DebugLoc { file, line, col: UNKNOWN_COLUMN_NUMBER }
         } else {
             DebugLoc { file, line, col }
         }
@@ -358,9 +358,9 @@ impl DebugInfoMethods<'tcx> for CodegenCx<'ll, 'tcx> {
                 linkage_name.as_ptr().cast(),
                 linkage_name.len(),
                 file_metadata,
-                loc.line.unwrap_or(UNKNOWN_LINE_NUMBER),
+                loc.line,
                 function_type_metadata,
-                scope_line.unwrap_or(UNKNOWN_LINE_NUMBER),
+                scope_line,
                 flags,
                 spflags,
                 maybe_definition_llfn,
@@ -550,14 +550,7 @@ impl DebugInfoMethods<'tcx> for CodegenCx<'ll, 'tcx> {
     ) -> &'ll DILocation {
         let DebugLoc { line, col, .. } = self.lookup_debug_loc(span.lo());
 
-        unsafe {
-            llvm::LLVMRustDIBuilderCreateDebugLocation(
-                line.unwrap_or(UNKNOWN_LINE_NUMBER),
-                col.unwrap_or(UNKNOWN_COLUMN_NUMBER),
-                scope,
-                inlined_at,
-            )
-        }
+        unsafe { llvm::LLVMRustDIBuilderCreateDebugLocation(line, col, scope, inlined_at) }
     }
 
     fn create_vtable_metadata(&self, ty: Ty<'tcx>, vtable: Self::Value) {
@@ -606,7 +599,7 @@ impl DebugInfoMethods<'tcx> for CodegenCx<'ll, 'tcx> {
                 name.as_ptr().cast(),
                 name.len(),
                 file_metadata,
-                loc.line.unwrap_or(UNKNOWN_LINE_NUMBER),
+                loc.line,
                 type_metadata,
                 true,
                 DIFlags::FlagZero,