From 45ca24edc0b9f2541efb0ae3c668ee7af82e22f4 Mon Sep 17 00:00:00 2001
From: Youngsuk Kim <youngsuk.kim@hpe.com>
Date: Tue, 7 Nov 2023 11:15:24 -0600
Subject: [PATCH] [clang] Remove no-op ptr-to-ptr bitcasts (NFC)

Opaque ptr cleanup effort (NFC).
---
 clang/lib/CodeGen/CGObjCGNU.cpp | 36 ++++++++++-----------------------
 clang/lib/CodeGen/CGVTables.cpp |  9 +--------
 2 files changed, 12 insertions(+), 33 deletions(-)

diff --git a/clang/lib/CodeGen/CGObjCGNU.cpp b/clang/lib/CodeGen/CGObjCGNU.cpp
index f02938cf799ac..519133055dcac 100644
--- a/clang/lib/CodeGen/CGObjCGNU.cpp
+++ b/clang/lib/CodeGen/CGObjCGNU.cpp
@@ -1784,7 +1784,7 @@ class CGObjCGNUstep2 : public CGObjCGNUstep {
         }
       }
       if (!IsCOFF)
-        classFields.add(llvm::ConstantExpr::getBitCast(SuperClass, PtrTy));
+        classFields.add(SuperClass);
       else
         classFields.addNullPointer(PtrTy);
     } else
@@ -1959,16 +1959,14 @@ class CGObjCGNUstep2 : public CGObjCGNUstep {
     // Resolve the class aliases, if they exist.
     // FIXME: Class pointer aliases shouldn't exist!
     if (ClassPtrAlias) {
-      ClassPtrAlias->replaceAllUsesWith(
-          llvm::ConstantExpr::getBitCast(classStruct, IdTy));
+      ClassPtrAlias->replaceAllUsesWith(classStruct);
       ClassPtrAlias->eraseFromParent();
       ClassPtrAlias = nullptr;
     }
     if (auto Placeholder =
         TheModule.getNamedGlobal(SymbolForClass(className)))
       if (Placeholder != classStruct) {
-        Placeholder->replaceAllUsesWith(
-            llvm::ConstantExpr::getBitCast(classStruct, Placeholder->getType()));
+        Placeholder->replaceAllUsesWith(classStruct);
         Placeholder->eraseFromParent();
         classStruct->setName(SymbolForClass(className));
       }
@@ -2415,7 +2413,7 @@ llvm::Constant *CGObjCGNUstep::GetEHType(QualType T) {
                                  false,
                                  llvm::GlobalValue::ExternalLinkage,
                                  nullptr, "__objc_id_type_info");
-    return llvm::ConstantExpr::getBitCast(IDEHType, PtrToInt8Ty);
+    return IDEHType;
   }
 
   const ObjCObjectPointerType *PT =
@@ -2429,9 +2427,8 @@ llvm::Constant *CGObjCGNUstep::GetEHType(QualType T) {
   std::string typeinfoName = "__objc_eh_typeinfo_" + className;
 
   // Return the existing typeinfo if it exists
-  llvm::Constant *typeinfo = TheModule.getGlobalVariable(typeinfoName);
-  if (typeinfo)
-    return llvm::ConstantExpr::getBitCast(typeinfo, PtrToInt8Ty);
+  if (llvm::Constant *typeinfo = TheModule.getGlobalVariable(typeinfoName))
+    return typeinfo;
 
   // Otherwise create it.
 
@@ -2495,9 +2492,7 @@ ConstantAddress CGObjCGNU::GenerateConstantString(const StringLiteral *SL) {
   Fields.add(isa);
   Fields.add(MakeConstantString(Str));
   Fields.addInt(IntTy, Str.size());
-  llvm::Constant *ObjCStr =
-    Fields.finishAndCreateGlobal(".objc_str", Align);
-  ObjCStr = llvm::ConstantExpr::getBitCast(ObjCStr, PtrToInt8Ty);
+  llvm::Constant *ObjCStr = Fields.finishAndCreateGlobal(".objc_str", Align);
   ObjCStrings[Str] = ObjCStr;
   ConstantStrings.push_back(ObjCStr);
   return ConstantAddress(ObjCStr, Int8Ty, Align);
@@ -3060,8 +3055,7 @@ llvm::Constant *CGObjCGNU::GenerateClassStructure(
     Elements.finishAndCreateGlobal(ClassSym, CGM.getPointerAlign(), false,
                                    llvm::GlobalValue::ExternalLinkage);
   if (ClassRef) {
-    ClassRef->replaceAllUsesWith(llvm::ConstantExpr::getBitCast(Class,
-                  ClassRef->getType()));
+    ClassRef->replaceAllUsesWith(Class);
     ClassRef->removeFromParent();
     Class->setName(ClassSym);
   }
@@ -3227,9 +3221,7 @@ void CGObjCGNU::GenerateProtocol(const ObjCProtocolDecl *PD) {
   Elements.add(PropertyList);
   Elements.add(OptionalPropertyList);
   ExistingProtocols[ProtocolName] =
-    llvm::ConstantExpr::getBitCast(
-      Elements.finishAndCreateGlobal(".objc_protocol", CGM.getPointerAlign()),
-      IdTy);
+      Elements.finishAndCreateGlobal(".objc_protocol", CGM.getPointerAlign());
 }
 void CGObjCGNU::GenerateProtocolHolderCategory() {
   // Collect information about instance methods
@@ -3263,9 +3255,8 @@ void CGObjCGNU::GenerateProtocolHolderCategory() {
                    ProtocolList.finishAndCreateGlobal(".objc_protocol_list",
                                                       CGM.getPointerAlign()),
                    PtrTy);
-  Categories.push_back(llvm::ConstantExpr::getBitCast(
-        Elements.finishAndCreateGlobal("", CGM.getPointerAlign()),
-        PtrTy));
+  Categories.push_back(
+      Elements.finishAndCreateGlobal("", CGM.getPointerAlign()));
 }
 
 /// Libobjc2 uses a bitfield representation where small(ish) bitfields are
@@ -3736,7 +3727,6 @@ llvm::Function *CGObjCGNU::ModuleInitFunction() {
 
     statics = allStaticsArray.finishAndCreateGlobal(".objc_statics_ptr",
                                                     CGM.getPointerAlign());
-    statics = llvm::ConstantExpr::getBitCast(statics, PtrTy);
   }
 
   // Array of classes, categories, and constant objects.
@@ -3799,9 +3789,6 @@ llvm::Function *CGObjCGNU::ModuleInitFunction() {
     // FIXME: We're generating redundant loads and stores here!
     llvm::Constant *selPtr = llvm::ConstantExpr::getGetElementPtr(
         selectorList->getValueType(), selectorList, idxs);
-    // If selectors are defined as an opaque type, cast the pointer to this
-    // type.
-    selPtr = llvm::ConstantExpr::getBitCast(selPtr, SelectorTy);
     selectorAliases[i]->replaceAllUsesWith(selPtr);
     selectorAliases[i]->eraseFromParent();
   }
@@ -3922,7 +3909,6 @@ llvm::Function *CGObjCGNU::ModuleInitFunction() {
        llvm::Constant *TheClass =
           TheModule.getGlobalVariable("_OBJC_CLASS_" + iter->first, true);
        if (TheClass) {
-         TheClass = llvm::ConstantExpr::getBitCast(TheClass, PtrTy);
          Builder.CreateCall(RegisterAlias,
                             {TheClass, MakeConstantString(iter->second)});
        }
diff --git a/clang/lib/CodeGen/CGVTables.cpp b/clang/lib/CodeGen/CGVTables.cpp
index 959940775ee80..27a2cab4f7531 100644
--- a/clang/lib/CodeGen/CGVTables.cpp
+++ b/clang/lib/CodeGen/CGVTables.cpp
@@ -465,10 +465,6 @@ void CodeGenFunction::generateThunk(llvm::Function *Fn,
 
   llvm::Constant *Callee = CGM.GetAddrOfFunction(GD, Ty, /*ForVTable=*/true);
 
-  // Fix up the function type for an unprototyped musttail call.
-  if (IsUnprototyped)
-    Callee = llvm::ConstantExpr::getBitCast(Callee, Fn->getType());
-
   // Make the call and return the result.
   EmitCallAndReturnForThunk(llvm::FunctionCallee(Fn->getFunctionType(), Callee),
                             &Thunk, IsUnprototyped);
@@ -537,11 +533,8 @@ llvm::Constant *CodeGenVTables::maybeEmitThunk(GlobalDecl GD,
                                      Name.str(), &CGM.getModule());
     CGM.SetLLVMFunctionAttributes(MD, FnInfo, ThunkFn, /*IsThunk=*/false);
 
-    // If needed, replace the old thunk with a bitcast.
     if (!OldThunkFn->use_empty()) {
-      llvm::Constant *NewPtrForOldDecl =
-          llvm::ConstantExpr::getBitCast(ThunkFn, OldThunkFn->getType());
-      OldThunkFn->replaceAllUsesWith(NewPtrForOldDecl);
+      OldThunkFn->replaceAllUsesWith(ThunkFn);
     }
 
     // Remove the old thunk.