Revert "Reland "Revert "[clang][CGRecordLayout] Remove dependency on isZeroSize (llvm#96422)" (#156)"" (llvm#2065)

This reverts commit c515ad9. This was
relanded in llvm#1633, but we still need it reverted to maintain the the
device function ABI.

Author: epilk

clang/lib/CodeGen/ABIInfoImpl.cpp

@@ -304,41 +304,6 @@ bool CodeGen::isEmptyRecord(ASTContext &Context, QualType T, bool AllowArrays,
   return true;
 }
 
-bool CodeGen::isEmptyFieldForLayout(const ASTContext &Context,
-                                    const FieldDecl *FD) {
-  if (FD->isZeroLengthBitField())
-    return true;
-
-  if (FD->isUnnamedBitField())
-    return false;
-
-  return isEmptyRecordForLayout(Context, FD->getType());
-}
-
-bool CodeGen::isEmptyRecordForLayout(const ASTContext &Context, QualType T) {
-  const RecordType *RT = T->getAs<RecordType>();
-  if (!RT)
-    return false;
-
-  const RecordDecl *RD = RT->getDecl();
-
-  // If this is a C++ record, check the bases first.
-  if (const CXXRecordDecl *CXXRD = dyn_cast<CXXRecordDecl>(RD)) {
-    if (CXXRD->isDynamicClass())
-      return false;
-
-    for (const auto &I : CXXRD->bases())
-      if (!isEmptyRecordForLayout(Context, I.getType()))
-        return false;
-  }
-
-  for (const auto *I : RD->fields())
-    if (!isEmptyFieldForLayout(Context, I))
-      return false;
-
-  return true;
-}
-
 const Type *CodeGen::isSingleElementStruct(QualType T, ASTContext &Context) {
   const RecordType *RT = T->getAs<RecordType>();
   if (!RT)

clang/lib/CodeGen/ABIInfoImpl.h

@@ -120,16 +120,6 @@ bool isEmptyField(ASTContext &Context, const FieldDecl *FD, bool AllowArrays,
 bool isEmptyRecord(ASTContext &Context, QualType T, bool AllowArrays,
                    bool AsIfNoUniqueAddr = false);
 
-/// isEmptyFieldForLayout - Return true iff the field is "empty", that is,
-/// either a zero-width bit-field or an \ref isEmptyRecordForLayout.
-bool isEmptyFieldForLayout(const ASTContext &Context, const FieldDecl *FD);
-
-/// isEmptyRecordForLayout - Return true iff a structure contains only empty
-/// base classes (per \ref isEmptyRecordForLayout) and fields (per
-/// \ref isEmptyFieldForLayout). Note, C++ record fields are considered empty
-/// if the [[no_unique_address]] attribute would have made them empty.
-bool isEmptyRecordForLayout(const ASTContext &Context, QualType T);
-
 /// isSingleElementStruct - Determine if a structure is a "single
 /// element struct", i.e. it has exactly one non-empty field or
 /// exactly one field which is itself a single element

clang/lib/CodeGen/CGClass.cpp

@@ -10,7 +10,6 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "ABIInfoImpl.h"
 #include "CGBlocks.h"
 #include "CGCXXABI.h"
 #include "CGDebugInfo.h"
@@ -932,7 +931,7 @@ namespace {
     }
 
     void addMemcpyableField(FieldDecl *F) {
-      if (isEmptyFieldForLayout(CGF.getContext(), F))
+      if (F->isZeroSize(CGF.getContext()))
         return;
       if (!FirstField)
         addInitialField(F);
@@ -1814,7 +1813,7 @@ namespace {
                               const CXXDestructorDecl *DD)
        : Context(Context), EHStack(EHStack), DD(DD), StartIndex(std::nullopt) {}
    void PushCleanupForField(const FieldDecl *Field) {
-     if (isEmptyFieldForLayout(Context, Field))
+     if (Field->isZeroSize(Context))
        return;
      unsigned FieldIndex = Field->getFieldIndex();
      if (FieldHasTrivialDestructorBody(Context, Field)) {

clang/lib/CodeGen/CGExpr.cpp

@@ -4965,7 +4965,7 @@ static Address emitAddrOfZeroSizeField(CodeGenFunction &CGF, Address Base,
 /// The resulting address doesn't necessarily have the right type.
 static Address emitAddrOfFieldStorage(CodeGenFunction &CGF, Address base,
                                       const FieldDecl *field, bool IsInBounds) {
-  if (isEmptyFieldForLayout(CGF.getContext(), field))
+  if (field->isZeroSize(CGF.getContext()))
     return emitAddrOfZeroSizeField(CGF, base, field, IsInBounds);
 
   const RecordDecl *rec = field->getParent();

clang/lib/CodeGen/CGExprConstant.cpp

@@ -10,7 +10,6 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "ABIInfoImpl.h"
 #include "CGCXXABI.h"
 #include "CGObjCRuntime.h"
 #include "CGRecordLayout.h"
@@ -758,7 +757,7 @@ bool ConstStructBuilder::Build(const InitListExpr *ILE, bool AllowOverwrite) {
 
     // Zero-sized fields are not emitted, but their initializers may still
     // prevent emission of this struct as a constant.
-    if (isEmptyFieldForLayout(CGM.getContext(), Field)) {
+    if (Field->isZeroSize(CGM.getContext())) {
       if (Init && Init->HasSideEffects(CGM.getContext()))
         return false;
       continue;
@@ -894,8 +893,7 @@ bool ConstStructBuilder::Build(const APValue &Val, const RecordDecl *RD,
       continue;
 
     // Don't emit anonymous bitfields or zero-sized fields.
-    if (Field->isUnnamedBitField() ||
-        isEmptyFieldForLayout(CGM.getContext(), *Field))
+    if (Field->isUnnamedBitField() || Field->isZeroSize(CGM.getContext()))
       continue;
 
     // Emit the value of the initializer.
@@ -2637,10 +2635,8 @@ static llvm::Constant *EmitNullConstant(CodeGenModule &CGM,
         cast<CXXRecordDecl>(I.getType()->castAs<RecordType>()->getDecl());
 
       // Ignore empty bases.
-      if (isEmptyRecordForLayout(CGM.getContext(), I.getType()) ||
-          CGM.getContext()
-              .getASTRecordLayout(base)
-              .getNonVirtualSize()
+      if (base->isEmpty() ||
+          CGM.getContext().getASTRecordLayout(base).getNonVirtualSize()
               .isZero())
         continue;
 
@@ -2654,8 +2650,7 @@ static llvm::Constant *EmitNullConstant(CodeGenModule &CGM,
   for (const auto *Field : record->fields()) {
     // Fill in non-bitfields. (Bitfields always use a zero pattern, which we
     // will fill in later.)
-    if (!Field->isBitField() &&
-        !isEmptyFieldForLayout(CGM.getContext(), Field)) {
+    if (!Field->isBitField() && !Field->isZeroSize(CGM.getContext())) {
       unsigned fieldIndex = layout.getLLVMFieldNo(Field);
       elements[fieldIndex] = CGM.EmitNullConstant(Field->getType());
     }
@@ -2677,7 +2672,7 @@ static llvm::Constant *EmitNullConstant(CodeGenModule &CGM,
         cast<CXXRecordDecl>(I.getType()->castAs<RecordType>()->getDecl());
 
       // Ignore empty bases.
-      if (isEmptyRecordForLayout(CGM.getContext(), I.getType()))
+      if (base->isEmpty())
         continue;
 
       unsigned fieldIndex = layout.getVirtualBaseIndex(base);

clang/lib/CodeGen/CGOpenMPRuntime.cpp

@@ -11,7 +11,6 @@
 //===----------------------------------------------------------------------===//
 
 #include "CGOpenMPRuntime.h"
-#include "ABIInfoImpl.h"
 #include "CGCXXABI.h"
 #include "CGCleanup.h"
 #include "CGDebugInfo.h"
@@ -7762,28 +7761,23 @@ class MappableExprsHandler {
     for (const auto &I : RD->bases()) {
       if (I.isVirtual())
         continue;
-
-      QualType BaseTy = I.getType();
-      const auto *Base = BaseTy->getAsCXXRecordDecl();
+      const auto *Base = I.getType()->getAsCXXRecordDecl();
       // Ignore empty bases.
-      if (isEmptyRecordForLayout(CGF.getContext(), BaseTy) ||
-          CGF.getContext()
-              .getASTRecordLayout(Base)
-              .getNonVirtualSize()
-              .isZero())
+      if (Base->isEmpty() || CGF.getContext()
+                                 .getASTRecordLayout(Base)
+                                 .getNonVirtualSize()
+                                 .isZero())
         continue;
 
       unsigned FieldIndex = RL.getNonVirtualBaseLLVMFieldNo(Base);
       RecordLayout[FieldIndex] = Base;
     }
     // Fill in virtual bases.
     for (const auto &I : RD->vbases()) {
-      QualType BaseTy = I.getType();
+      const auto *Base = I.getType()->getAsCXXRecordDecl();
       // Ignore empty bases.
-      if (isEmptyRecordForLayout(CGF.getContext(), BaseTy))
+      if (Base->isEmpty())
         continue;
-
-      const auto *Base = BaseTy->getAsCXXRecordDecl();
       unsigned FieldIndex = RL.getVirtualBaseIndex(Base);
       if (RecordLayout[FieldIndex])
         continue;
@@ -7794,8 +7788,7 @@ class MappableExprsHandler {
     for (const auto *Field : RD->fields()) {
       // Fill in non-bitfields. (Bitfields always use a zero pattern, which we
       // will fill in later.)
-      if (!Field->isBitField() &&
-          !isEmptyFieldForLayout(CGF.getContext(), Field)) {
+      if (!Field->isBitField() && !Field->isZeroSize(CGF.getContext())) {
         unsigned FieldIndex = RL.getLLVMFieldNo(Field);
         RecordLayout[FieldIndex] = Field;
       }

clang/lib/CodeGen/CGRecordLayoutBuilder.cpp

@@ -10,9 +10,8 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "ABIInfoImpl.h"
-#include "CGCXXABI.h"
 #include "CGRecordLayout.h"
+#include "CGCXXABI.h"
 #include "CodeGenTypes.h"
 #include "clang/AST/ASTContext.h"
 #include "clang/AST/Attr.h"
@@ -385,7 +384,7 @@ void CGRecordLowering::accumulateFields(bool isNonVirtualBaseType) {
       Field = accumulateBitFields(isNonVirtualBaseType, Field, FieldEnd);
       assert((Field == FieldEnd || !Field->isBitField()) &&
              "Failed to accumulate all the bitfields");
-    } else if (isEmptyFieldForLayout(Context, *Field)) {
+    } else if (Field->isZeroSize(Context)) {
       // Empty fields have no storage.
       ++Field;
     } else {
@@ -634,7 +633,7 @@ CGRecordLowering::accumulateBitFields(bool isNonVirtualBaseType,
           // non-reusable tail padding.
           CharUnits LimitOffset;
           for (auto Probe = Field; Probe != FieldEnd; ++Probe)
-            if (!isEmptyFieldForLayout(Context, *Probe)) {
+            if (!Probe->isZeroSize(Context)) {
               // A member with storage sets the limit.
               assert((getFieldBitOffset(*Probe) % CharBits) == 0 &&
                      "Next storage is not byte-aligned");
@@ -732,7 +731,7 @@ void CGRecordLowering::accumulateBases() {
     // Bases can be zero-sized even if not technically empty if they
     // contain only a trailing array member.
     const CXXRecordDecl *BaseDecl = Base.getType()->getAsCXXRecordDecl();
-    if (!isEmptyRecordForLayout(Context, Base.getType()) &&
+    if (!BaseDecl->isEmpty() &&
         !Context.getASTRecordLayout(BaseDecl).getNonVirtualSize().isZero())
       Members.push_back(MemberInfo(Layout.getBaseClassOffset(BaseDecl),
           MemberInfo::Base, getStorageType(BaseDecl), BaseDecl));
@@ -880,7 +879,7 @@ CGRecordLowering::calculateTailClippingOffset(bool isNonVirtualBaseType) const {
   if (!isNonVirtualBaseType && isOverlappingVBaseABI())
     for (const auto &Base : RD->vbases()) {
       const CXXRecordDecl *BaseDecl = Base.getType()->getAsCXXRecordDecl();
-      if (isEmptyRecordForLayout(Context, Base.getType()))
+      if (BaseDecl->isEmpty())
         continue;
       // If the vbase is a primary virtual base of some base, then it doesn't
       // get its own storage location but instead lives inside of that base.
@@ -896,7 +895,7 @@ CGRecordLowering::calculateTailClippingOffset(bool isNonVirtualBaseType) const {
 void CGRecordLowering::accumulateVBases() {
   for (const auto &Base : RD->vbases()) {
     const CXXRecordDecl *BaseDecl = Base.getType()->getAsCXXRecordDecl();
-    if (isEmptyRecordForLayout(Context, Base.getType()))
+    if (BaseDecl->isEmpty())
       continue;
     CharUnits Offset = Layout.getVBaseClassOffset(BaseDecl);
     // If the vbase is a primary virtual base of some base, then it doesn't
@@ -1162,7 +1161,7 @@ CodeGenTypes::ComputeRecordLayout(const RecordDecl *D, llvm::StructType *Ty) {
     const FieldDecl *FD = *it;
 
     // Ignore zero-sized fields.
-    if (isEmptyFieldForLayout(getContext(), FD))
+    if (FD->isZeroSize(getContext()))
       continue;
 
     // For non-bit-fields, just check that the LLVM struct offset matches the

clang/lib/CodeGen/CodeGenTBAA.cpp

@@ -15,7 +15,6 @@
 //===----------------------------------------------------------------------===//
 
 #include "CodeGenTBAA.h"
-#include "ABIInfoImpl.h"
 #include "CGCXXABI.h"
 #include "CGRecordLayout.h"
 #include "CodeGenTypes.h"
@@ -441,7 +440,7 @@ CodeGenTBAA::CollectFields(uint64_t BaseOffset,
     unsigned idx = 0;
     for (RecordDecl::field_iterator i = RD->field_begin(), e = RD->field_end();
          i != e; ++i, ++idx) {
-      if (isEmptyFieldForLayout(Context, *i))
+      if ((*i)->isZeroSize(Context))
         continue;
 
       uint64_t Offset =

clang/test/CodeGen/2009-06-14-anonymous-union-init.c

@@ -1,19 +1,8 @@
-// RUN: %clang_cc1 %s -emit-llvm -triple x86_64-linux-gnu -o - | FileCheck %s --check-prefixes=CHECK,EMPTY
-// RUN: %clang_cc1 %s -emit-llvm -triple x86_64-windows-msvc -o - | FileCheck %s --check-prefixes=CHECK,EMPTY-MSVC
+// RUN: %clang_cc1 -emit-llvm < %s | grep "zeroinitializer, i16 16877"
 // PR4390
 struct sysfs_dirent {
- union { struct sysfs_elem_dir { int x; } s_dir; };
+ union { struct sysfs_elem_dir {} s_dir; };
  unsigned short s_mode;
 };
 struct sysfs_dirent sysfs_root = { {}, 16877 };
 
-// CHECK: @sysfs_root = {{.*}}global { %union.anon, i16, [2 x i8] } { %union.anon zeroinitializer, i16 16877, [2 x i8] zeroinitializer }
-
-struct Foo {
- union { struct empty {} x; };
- unsigned short s_mode;
-};
-struct Foo foo = { {}, 16877 };
-
-// EMPTY:      @foo = {{.*}}global %struct.Foo { i16 16877 }
-// EMPTY-MSVC: @foo = {{.*}}global %struct.Foo { [4 x i8] zeroinitializer, i16 16877 }

clang/test/CodeGen/X86/x86_64-vaarg.c

@@ -56,8 +56,7 @@ typedef struct {
 // CHECK:       vaarg.end:
 // CHECK-NEXT:    [[VAARG_ADDR:%.*]] = phi ptr [ [[TMP1]], [[VAARG_IN_REG]] ], [ [[OVERFLOW_ARG_AREA]], [[VAARG_IN_MEM]] ]
 // CHECK-NEXT:    call void @llvm.memcpy.p0.p0.i64(ptr align 8 [[RETVAL]], ptr align 8 [[VAARG_ADDR]], i64 8, i1 false)
-// CHECK-NEXT:    [[COERCE_DIVE:%.*]] = getelementptr inbounds nuw [[STRUCT_S1]], ptr [[RETVAL]], i32 0, i32 0
-// CHECK-NEXT:    [[TMP3:%.*]] = load double, ptr [[COERCE_DIVE]], align 8
+// CHECK-NEXT:    [[TMP3:%.*]] = load double, ptr [[RETVAL]], align 8
 // CHECK-NEXT:    ret double [[TMP3]]
 //
 s1 f(int z, ...) {