Revert "Add option to generate additional debug info for expression dereferencing pointer to pointers. llvm#94100" (llvm#95174)

The option is causing the binary output to be different when compiled
under `-O0`, because it introduce dbg.declare on pseudovariables. Going
to change this implementation to use dbg.value instead.

Author: huangjd

clang/lib/CodeGen/CGDebugInfo.cpp

@@ -5746,78 +5746,6 @@ void CGDebugInfo::EmitExternalVariable(llvm::GlobalVariable *Var,
   Var->addDebugInfo(GVE);
 }
 
-void CGDebugInfo::EmitPseudoVariable(CGBuilderTy &Builder,
-                                     llvm::Instruction *Value, QualType Ty) {
-  // Only when -g2 or above is specified, debug info for variables will be
-  // generated.
-  if (CGM.getCodeGenOpts().getDebugInfo() <=
-      llvm::codegenoptions::DebugLineTablesOnly)
-    return;
-
-  llvm::DebugLoc SaveDebugLoc = Builder.getCurrentDebugLocation();
-  if (!SaveDebugLoc.get())
-    return;
-
-  llvm::DIFile *Unit = SaveDebugLoc->getFile();
-  llvm::DIType *Type = getOrCreateType(Ty, Unit);
-
-  // Check if Value is already a declared variable and has debug info, in this
-  // case we have nothing to do. Clang emits declared variable as alloca, and
-  // it is loaded upon use, so we identify such pattern here.
-  if (llvm::LoadInst *Load = dyn_cast<llvm::LoadInst>(Value)) {
-    llvm::Value *Var = Load->getPointerOperand();
-    // There can be implicit type cast applied on a variable if it is an opaque
-    // ptr, in this case its debug info may not match the actual type of object
-    // being used as in the next instruction, so we will need to emit a pseudo
-    // variable for type-casted value.
-    auto DeclareTypeMatches = [&](auto *DbgDeclare) {
-      return DbgDeclare->getVariable()->getType() == Type;
-    };
-    if (any_of(llvm::findDbgDeclares(Var), DeclareTypeMatches) ||
-        any_of(llvm::findDVRDeclares(Var), DeclareTypeMatches))
-      return;
-  }
-
-  // Find the correct location to insert a sequence of instructions to
-  // materialize Value on the stack.
-  auto SaveInsertionPoint = Builder.saveIP();
-  if (llvm::InvokeInst *Invoke = dyn_cast<llvm::InvokeInst>(Value))
-    Builder.SetInsertPoint(Invoke->getNormalDest()->begin());
-  else if (llvm::Instruction *Next = Value->getIterator()->getNextNode())
-    Builder.SetInsertPoint(Next);
-  else
-    Builder.SetInsertPoint(Value->getParent());
-  llvm::DebugLoc DL = Value->getDebugLoc();
-  if (DL.get())
-    Builder.SetCurrentDebugLocation(DL);
-  else if (!Builder.getCurrentDebugLocation().get())
-    Builder.SetCurrentDebugLocation(SaveDebugLoc);
-
-  llvm::AllocaInst *PseudoVar = Builder.CreateAlloca(Value->getType());
-  Address PseudoVarAddr(PseudoVar, Value->getType(),
-                        CharUnits::fromQuantity(PseudoVar->getAlign()));
-  llvm::LoadInst *Load = Builder.CreateLoad(PseudoVarAddr);
-  Value->replaceAllUsesWith(Load);
-  Builder.SetInsertPoint(Load);
-  Builder.CreateStore(Value, PseudoVarAddr);
-
-  // Emit debug info for materialized Value.
-  unsigned Line = Builder.getCurrentDebugLocation().getLine();
-  unsigned Column = Builder.getCurrentDebugLocation().getCol();
-  llvm::DILocalVariable *D = DBuilder.createAutoVariable(
-      LexicalBlockStack.back(), "", nullptr, 0, Type, false,
-      llvm::DINode::FlagArtificial);
-  llvm::DILocation *DIL =
-      llvm::DILocation::get(CGM.getLLVMContext(), Line, Column,
-                            LexicalBlockStack.back(), CurInlinedAt);
-  SmallVector<uint64_t> Expr;
-  DBuilder.insertDeclare(PseudoVar, D, DBuilder.createExpression(Expr), DIL,
-                         Load);
-
-  Builder.restoreIP(SaveInsertionPoint);
-  Builder.SetCurrentDebugLocation(SaveDebugLoc);
-}
-
 void CGDebugInfo::EmitGlobalAlias(const llvm::GlobalValue *GV,
                                   const GlobalDecl GD) {
 

clang/lib/CodeGen/CGDebugInfo.h

@@ -530,12 +530,6 @@ class CGDebugInfo {
   /// Emit information about an external variable.
   void EmitExternalVariable(llvm::GlobalVariable *GV, const VarDecl *Decl);
 
-  /// Emit a pseudo variable and debug info for an intermediate value if it does
-  /// not correspond to a variable in the source code, so that a profiler can
-  /// track more accurate usage of certain instructions of interest.
-  void EmitPseudoVariable(CGBuilderTy &Builder, llvm::Instruction *Value,
-                          QualType Ty);
-
   /// Emit information about global variable alias.
   void EmitGlobalAlias(const llvm::GlobalValue *GV, const GlobalDecl Decl);
 

clang/lib/CodeGen/CGExprScalar.cpp

@@ -1937,26 +1937,7 @@ Value *ScalarExprEmitter::VisitMemberExpr(MemberExpr *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;
+  return EmitLoadOfLValue(E);
 }
 
 Value *ScalarExprEmitter::VisitArraySubscriptExpr(ArraySubscriptExpr *E) {