[PATCH] D65035: [DebugInfo] Don't emit incorrect descriptions of thunk params (PR42627)

[Vedant Kumar via Phabricator via llvm-commits]

vsk created this revision.
vsk added a reviewer: debug-info.

The `this` parameter of a thunk requires adjustment. Stop emitting an
incorrect dbg.declare pointing to the unadjusted pointer.

We could describe the adjusted value instead, but there may not be much
benefit in doing so as users tend not to debug thunks.

                                                                                                    

Robert O'Callahan reports that this matches gcc's behavior.

Fixes PR42627.


https://reviews.llvm.org/D65035

Files:
  clang/lib/CodeGen/CGDecl.cpp
  clang/test/CodeGenCXX/thunks.cpp


Index: clang/test/CodeGenCXX/thunks.cpp
===================================================================
--- clang/test/CodeGenCXX/thunks.cpp
+++ clang/test/CodeGenCXX/thunks.cpp
@@ -1,4 +1,5 @@
 // RUN: %clang_cc1 %s -triple=x86_64-pc-linux-gnu -munwind-tables -emit-llvm -o - | FileCheck --check-prefix=CHECK --check-prefix=CHECK-NONOPT %s
+// RUN: %clang_cc1 %s -triple=x86_64-pc-linux-gnu -debug-info-kind=standalone -dwarf-version=5 -munwind-tables -emit-llvm -o - | FileCheck --check-prefix=CHECK --check-prefix=CHECK-NONOPT --check-prefix=CHECK-DBG %s
 // RUN: %clang_cc1 %s -triple=x86_64-pc-linux-gnu -munwind-tables -emit-llvm -o - -O1 -disable-llvm-passes | FileCheck --check-prefix=CHECK --check-prefix=CHECK-OPT %s
 
 namespace Test1 {
@@ -403,3 +404,5 @@
 
 // CHECK-NONOPT: attributes [[NUW]] = { noinline nounwind optnone uwtable{{.*}} }
 // CHECK-OPT: attributes [[NUW]] = { nounwind uwtable{{.*}} }
+
+// CHECK-DBG-NOT: DILocalVariable(name: "this"
Index: clang/lib/CodeGen/CGDecl.cpp
===================================================================
--- clang/lib/CodeGen/CGDecl.cpp
+++ clang/lib/CodeGen/CGDecl.cpp
@@ -2497,10 +2497,11 @@
 
   setAddrOfLocalVar(&D, DeclPtr);
 
-  // Emit debug info for param declaration.
+  // Emit debug info for param declarations in non-thunk functions.
   if (CGDebugInfo *DI = getDebugInfo()) {
     if (CGM.getCodeGenOpts().getDebugInfo() >=
-        codegenoptions::LimitedDebugInfo) {
+            codegenoptions::LimitedDebugInfo &&
+        !CurFuncIsThunk) {
       DI->EmitDeclareOfArgVariable(&D, DeclPtr.getPointer(), ArgNo, Builder);
     }
   }


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