[KeyInstr] Disable key-instructions for coroutine scopes (#147551)

At this time (immediately prior to llvm21 branching) we haven't
instrumented coroutine generation to identify the "key" instructions of
things like co_return and similar. This will lead to worse stepping
behaviours, as there won't be any key instruction for those lines.

This patch removes the key-instructions flag from the DISubprograms for
coroutines, which will cause AsmPrinter to use the "old" / existing
linetable stepping behaviour, avoiding a regression until we can
instrument these constructs.

(I'm going to post on discourse about whether this is a good idea or not
in a moment)

1 files changed, 5 insertions, 1 deletions

diff --git a/clang/lib/CodeGen/CGDebugInfo.cpp b/clang/lib/CodeGen/CGDebugInfo.cpp
index 8bf7d24..5240853 100644
--- a/clang/lib/CodeGen/CGDebugInfo.cpp
+++ b/clang/lib/CodeGen/CGDebugInfo.cpp
@@ -4629,6 +4629,7 @@ void CGDebugInfo::emitFunctionStart(GlobalDecl GD, SourceLocation Loc,
   llvm::DIFile *Unit = getOrCreateFile(Loc);
   llvm::DIScope *FDContext = Unit;
   llvm::DINodeArray TParamsArray;
+  bool KeyInstructions = CGM.getCodeGenOpts().DebugKeyInstructions;
   if (!HasDecl) {
     // Use llvm function name.
     LinkageName = Fn->getName();
@@ -4645,6 +4646,9 @@ void CGDebugInfo::emitFunctionStart(GlobalDecl GD, SourceLocation Loc,
     }
     collectFunctionDeclProps(GD, Unit, Name, LinkageName, FDContext,
                              TParamsArray, Flags);
+    // Disable KIs if this is a coroutine.
+    KeyInstructions =
+        KeyInstructions && !isa_and_present<CoroutineBodyStmt>(FD->getBody());
   } else if (const auto *OMD = dyn_cast<ObjCMethodDecl>(D)) {
     Name = getObjCMethodName(OMD);
     Flags |= llvm::DINode::FlagPrototyped;
@@ -4706,7 +4710,7 @@ void CGDebugInfo::emitFunctionStart(GlobalDecl GD, SourceLocation Loc,
   llvm::DISubprogram *SP = DBuilder.createFunction(
       FDContext, Name, LinkageName, Unit, LineNo, DIFnType, ScopeLine,
       FlagsForDef, SPFlagsForDef, TParamsArray.get(), Decl, nullptr,
-      Annotations, "", CGM.getCodeGenOpts().DebugKeyInstructions);
+      Annotations, "", KeyInstructions);
   Fn->setSubprogram(SP);
 
   // We might get here with a VarDecl in the case we're generating