(New) Add option to generate additional debug info for expression dereferencing pointer to pointers (#95298)

This is a different implementation to #94100, which has been reverted.

When -fdebug-info-for-profiling is specified, for any Load expression if
the pointer operand is not a declared variable, clang will emit debug
info describing the type of the pointer operand (which can be an
intermediate expr)

1 files changed, 20 insertions, 1 deletions

diff --git a/clang/lib/CodeGen/CGExprScalar.cpp b/clang/lib/CodeGen/CGExprScalar.cpp
index 1b144c178ce9..58f0a3113b4f 100644
--- a/clang/lib/CodeGen/CGExprScalar.cpp
+++ b/clang/lib/CodeGen/CGExprScalar.cpp
@@ -1937,7 +1937,26 @@ Value *ScalarExprEmitter::VisitMemberExpr(MemberExpr *E) {
     }
   }
 
-  return EmitLoadOfLValue(E);
+  llvm::Value *Result = EmitLoadOfLValue(E);
+
+  // If -fdebug-info-for-profiling is specified, emit a pseudo variable and its
+  // debug info for the pointer, even if there is no variable associated with
+  // the pointer's expression.
+  if (CGF.CGM.getCodeGenOpts().DebugInfoForProfiling && CGF.getDebugInfo()) {
+    if (llvm::LoadInst *Load = dyn_cast<llvm::LoadInst>(Result)) {
+      if (llvm::GetElementPtrInst *GEP =
+              dyn_cast<llvm::GetElementPtrInst>(Load->getPointerOperand())) {
+        if (llvm::Instruction *Pointer =
+                dyn_cast<llvm::Instruction>(GEP->getPointerOperand())) {
+          QualType Ty = E->getBase()->getType();
+          if (!E->isArrow())
+            Ty = CGF.getContext().getPointerType(Ty);
+          CGF.getDebugInfo()->EmitPseudoVariable(Builder, Pointer, Ty);
+        }
+      }
+    }
+  }
+  return Result;
 }
 
 Value *ScalarExprEmitter::VisitArraySubscriptExpr(ArraySubscriptExpr *E) {