Auto merge of #109808 - jyn514:debuginfo-options, r=michaelwoerister

Extend -Cdebuginfo with new options and named aliases

This is a rebase of https://github.com/rust-lang/rust/pull/83947, along with my best guess at what the new options mean. I tried to follow the LLVM source code to get a better idea but ran into quite a lot of trouble (https://rust-lang.zulipchat.com/#narrow/stream/187780-t-compiler.2Fwg-llvm/topic/go-to-definition.20in.20src.2Fllvm-project.3F). The description for the original PR follows below.

Note that the changes in this PR have already been through FCP: https://github.com/rust-lang/rust/pull/83947#issuecomment-878384979

Closes https://github.com/rust-lang/rust/pull/109311. Helps with https://github.com/rust-lang/rust/pull/104968.
r? `@michaelwoerister` cc `@cuviper`

---

The -Cdebuginfo=1 option was never line tables only and can't be due to backwards compatibility issues. This was clarified and an option for emitting line tables only was added. Additionally an option for emitting line info directives only was added, which is needed for some targets, i.e. nvptx. The debug info options should now behave similarly to clang's debug info options.

Fix https://github.com/rust-lang/rust/issues/60020
Fix https://github.com/rust-lang/rust/issues/64405

3 files changed, 16 insertions, 21 deletions

diff --git a/compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs b/compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs
index e2a592d851a..4bf6762d1f6 100644
--- a/compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs
+++ b/compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs
@@ -830,24 +830,7 @@ pub fn build_compile_unit_di_node<'ll, 'tcx>(
     }
     .unwrap_or_default();
     let split_name = split_name.to_str().unwrap();
-
-    // FIXME(#60020):
-    //
-    //    This should actually be
-    //
-    //        let kind = DebugEmissionKind::from_generic(tcx.sess.opts.debuginfo);
-    //
-    //    That is, we should set LLVM's emission kind to `LineTablesOnly` if
-    //    we are compiling with "limited" debuginfo. However, some of the
-    //    existing tools relied on slightly more debuginfo being generated than
-    //    would be the case with `LineTablesOnly`, and we did not want to break
-    //    these tools in a "drive-by fix", without a good idea or plan about
-    //    what limited debuginfo should exactly look like. So for now we keep
-    //    the emission kind as `FullDebug`.
-    //
-    //    See https://github.com/rust-lang/rust/issues/60020 for details.
-    let kind = DebugEmissionKind::FullDebug;
-    assert!(tcx.sess.opts.debuginfo != DebugInfo::None);
+    let kind = DebugEmissionKind::from_generic(tcx.sess.opts.debuginfo);
 
     unsafe {
         let compile_unit_file = llvm::LLVMRustDIBuilderCreateFile(
diff --git a/compiler/rustc_codegen_llvm/src/debuginfo/mod.rs b/compiler/rustc_codegen_llvm/src/debuginfo/mod.rs
index 5392534cfcb..41a75c9d775 100644
--- a/compiler/rustc_codegen_llvm/src/debuginfo/mod.rs
+++ b/compiler/rustc_codegen_llvm/src/debuginfo/mod.rs
@@ -402,7 +402,7 @@ impl<'ll, 'tcx> DebugInfoMethods<'tcx> for CodegenCx<'ll, 'tcx> {
             cx: &CodegenCx<'ll, 'tcx>,
             fn_abi: &FnAbi<'tcx, Ty<'tcx>>,
         ) -> &'ll DIArray {
-            if cx.sess().opts.debuginfo == DebugInfo::Limited {
+            if cx.sess().opts.debuginfo != DebugInfo::Full {
                 return create_DIArray(DIB(cx), &[]);
             }
 
diff --git a/compiler/rustc_codegen_llvm/src/llvm/ffi.rs b/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
index 0d63e634ad8..556c6602ff4 100644
--- a/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
+++ b/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
@@ -946,15 +946,27 @@ pub mod debuginfo {
         NoDebug,
         FullDebug,
         LineTablesOnly,
+        DebugDirectivesOnly,
     }
 
     impl DebugEmissionKind {
         pub fn from_generic(kind: rustc_session::config::DebugInfo) -> Self {
+            // We should be setting LLVM's emission kind to `LineTablesOnly` if
+            // we are compiling with "limited" debuginfo. However, some of the
+            // existing tools relied on slightly more debuginfo being generated than
+            // would be the case with `LineTablesOnly`, and we did not want to break
+            // these tools in a "drive-by fix", without a good idea or plan about
+            // what limited debuginfo should exactly look like. So for now we are
+            // instead adding a new debuginfo option "line-tables-only" so as to
+            // not break anything and to allow users to have 'limited' debug info.
+            //
+            // See https://github.com/rust-lang/rust/issues/60020 for details.
             use rustc_session::config::DebugInfo;
             match kind {
                 DebugInfo::None => DebugEmissionKind::NoDebug,
-                DebugInfo::Limited => DebugEmissionKind::LineTablesOnly,
-                DebugInfo::Full => DebugEmissionKind::FullDebug,
+                DebugInfo::LineDirectivesOnly => DebugEmissionKind::DebugDirectivesOnly,
+                DebugInfo::LineTablesOnly => DebugEmissionKind::LineTablesOnly,
+                DebugInfo::Limited | DebugInfo::Full => DebugEmissionKind::FullDebug,
             }
         }
     }