[Clang][DebugInfo] Clang generates an extra spurious unnamed 'dbg.declare' (#69681)

Do not emit call to llvm.dbg.declare when the variable declaration
is a DecompositionDecl as its instance class is always unnamed.

The emitted debug declare looks like:

call void @llvm.dbg.declare(metadata ..., metadata !xx, metadata ...)
!xx = !DILocalVariable(scope: !..., file: !..., line: ..., type: !...)

1 files changed, 5 insertions, 1 deletions

diff --git a/clang/lib/CodeGen/CGDebugInfo.cpp b/clang/lib/CodeGen/CGDebugInfo.cpp
index 181e500..0aaf678 100644
--- a/clang/lib/CodeGen/CGDebugInfo.cpp
+++ b/clang/lib/CodeGen/CGDebugInfo.cpp
@@ -4881,11 +4881,15 @@ CGDebugInfo::EmitDeclareOfAutoVariable(const VarDecl *VD, llvm::Value *Storage,
                                        const bool UsePointerValue) {
   assert(CGM.getCodeGenOpts().hasReducedDebugInfo());
 
-  if (auto *DD = dyn_cast<DecompositionDecl>(VD))
+  if (auto *DD = dyn_cast<DecompositionDecl>(VD)) {
     for (auto *B : DD->bindings()) {
       EmitDeclare(B, Storage, std::nullopt, Builder,
                   VD->getType()->isReferenceType());
     }
+    // Don't emit an llvm.dbg.declare for the composite storage as it doesn't
+    // correspond to a user variable.
+    return nullptr;
+  }
 
   return EmitDeclare(VD, Storage, std::nullopt, Builder, UsePointerValue);
 }