Add support for null ptr-to-data-member values

llvm · Jan 20, 2024 · 4795e86 · 4795e86
1 parent c2e33c5
commit 4795e86
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Showing 5 changed files with 73 additions and 14 deletions.
diff --git a/clang/include/clang/CIR/Dialect/IR/CIRAttrs.td b/clang/include/clang/CIR/Dialect/IR/CIRAttrs.td
@@ -248,8 +248,20 @@ def DataMemberPtrAttr : CIR_Attr<"DataMemberPtr", "data_member_ptr",
       return $_get(type.getContext(), type, clsTy,
           IntegerAttr::get(IndexType::get(type.getContext()), memberIndex));
     }]>,
+    AttrBuilderWithInferredContext<(ins "Type":$type), [{
+      mlir::Type clsTy = type.cast<mlir::cir::MemberPtrType>().getClsTy();
+      return $_get(type.getContext(), type, clsTy,
+          IntegerAttr::get(IndexType::get(type.getContext()), -1));
+    }]>,
   ];
 
+  let extraClassDeclaration = [{
+    /// Determine whether the data member pointer is a null pointer value.
+    bool isNullValue() const {
+      return getMemberIndex().getValue().isNegative();
+    }
+  }];
+
   let hasCustomAssemblyFormat = 1;
   let genVerifyDecl = 1;
 }

diff --git a/clang/lib/CIR/CodeGen/CIRGenBuilder.h b/clang/lib/CIR/CodeGen/CIRGenBuilder.h
@@ -226,6 +226,11 @@ class CIRGenBuilderTy : public CIRBaseBuilderTy {
     return mlir::cir::DataMemberPtrAttr::get(ty, ty.getClsTy(), memberIndex);
   }
 
+  mlir::cir::DataMemberPtrAttr
+  getNullDataMemberPtrAttr(mlir::cir::MemberPtrType ty) {
+    return mlir::cir::DataMemberPtrAttr::get(ty);
+  }
+
   mlir::TypedAttr getZeroInitAttr(mlir::Type ty) {
     if (ty.isa<mlir::cir::IntType>())
       return mlir::cir::IntAttr::get(ty, 0);

diff --git a/clang/lib/CIR/CodeGen/CIRGenExprScalar.cpp b/clang/lib/CIR/CodeGen/CIRGenExprScalar.cpp
@@ -1422,8 +1422,19 @@ mlir::Value ScalarExprEmitter::VisitCastExpr(CastExpr *CE) {
         mlir::cir::ConstPtrAttr::get(Builder.getContext(), Ty, 0));
   }
 
-  case CK_NullToMemberPointer:
-    llvm_unreachable("NYI");
+  case CK_NullToMemberPointer: {
+    if (MustVisitNullValue(E))
+      CGF.buildIgnoredExpr(E);
+
+    assert(!UnimplementedFeature::cxxABI());
+
+    const MemberPointerType *MPT = CE->getType()->getAs<MemberPointerType>();
+    assert(!MPT->isMemberFunctionPointerType() && "NYI");
+
+    auto Ty = CGF.getCIRType(DestTy).cast<mlir::cir::MemberPtrType>();
+    return Builder.create<mlir::cir::ConstantOp>(
+        CGF.getLoc(E->getExprLoc()), Ty, Builder.getNullDataMemberPtrAttr(Ty));
+  }
   case CK_ReinterpretMemberPointer:
     llvm_unreachable("NYI");
   case CK_BaseToDerivedMemberPointer:

diff --git a/clang/lib/CIR/Dialect/IR/CIRAttrs.cpp b/clang/lib/CIR/Dialect/IR/CIRAttrs.cpp
@@ -306,15 +306,21 @@ Attribute DataMemberPtrAttr::parse(AsmParser &parser, Type type) {
     return {};
 
   Type clsTy;
-  if (parser.parseType(clsTy))
-    return {};
+  std::int64_t memberIndex;
 
-  if (parser.parseComma())
-    return {};
+  if (parser.parseOptionalKeyword("null").succeeded()) {
+    clsTy = type.cast<mlir::cir::MemberPtrType>().getClsTy();
+    memberIndex = -1;
+  } else {
+    if (parser.parseType(clsTy))
+      return {};
 
-  std::uint64_t memberIndex;
-  if (parser.parseInteger(memberIndex))
-    return {};
+    if (parser.parseComma())
+      return {};
+
+    if (parser.parseInteger(memberIndex))
+      return {};
+  }
 
   if (parser.parseGreater())
     return {};
@@ -328,9 +334,15 @@ Attribute DataMemberPtrAttr::parse(AsmParser &parser, Type type) {
 
 void DataMemberPtrAttr::print(AsmPrinter &printer) const {
   printer << '<';
-  printer.printType(getClsTy());
-  printer << ", ";
-  printer << getMemberIndex().getValue().getZExtValue();
+
+  if (isNullValue())
+    printer << "null";
+  else {
+    printer.printType(getClsTy());
+    printer << ", ";
+    printer << getMemberIndex().getValue().getZExtValue();
+  }
+
   printer << '>';
 }
 
@@ -366,12 +378,17 @@ DataMemberPtrAttr::verify(function_ref<InFlightDiagnostic()> emitError, Type ty,
     return failure();
   }
 
-  auto memberIndexValue = memberIndex.getValue().getZExtValue();
-  if (memberIndexValue >= clsStructTy.getNumElements()) {
+  auto memberIndexValue = memberIndex.getValue().getSExtValue();
+  if (memberIndexValue >= static_cast<int64_t>(clsStructTy.getNumElements())) {
     emitError() << "member index of a DataMemberPtrAttr is out of range";
     return failure();
   }
 
+  if (memberIndexValue < 0) {
+    // DataMemberPtrAttr with a negative member index represents null value.
+    return success();
+  }
+
   auto memberTy = clsStructTy.getMembers()[memberIndexValue];
   if (memberTy != memberPtrTy.getMemberTy()) {
     emitError()

diff --git a/clang/test/CIR/CodeGen/pointer-to-data-member.cpp b/clang/test/CIR/CodeGen/pointer-to-data-member.cpp
@@ -46,3 +46,17 @@ int test5(Incomplete *ic, int Incomplete::*member) {
 // CHECK: cir.func @_Z5test5P10IncompleteMS_i
 // CHECK: %{{.+}} = cir.get_indirect_member %{{.+}}[%{{.+}} : !cir.member_ptr<!s32i in !ty_22Incomplete22>] : !cir.ptr<!ty_22Incomplete22> -> !cir.ptr<!s32i>
 // CHECK: }
+
+auto test_null() -> int Point::* {
+  return nullptr;
+}
+// CHECK: cir.func @_Z9test_nullv
+// CHECK:   %{{.+}} = cir.const(#cir.data_member_ptr<null> : !cir.member_ptr<!s32i in !ty_22Point22>) : !cir.member_ptr<!s32i in !ty_22Point22>
+// CHECK: }
+
+auto test_null_incomplete() -> int Incomplete::* {
+  return nullptr;
+}
+// CHECK: cir.func @_Z20test_null_incompletev
+// CHECK:   %{{.+}} = cir.const(#cir.data_member_ptr<null> : !cir.member_ptr<!s32i in !ty_22Incomplete22>) : !cir.member_ptr<!s32i in !ty_22Incomplete22>
+// CHECK: }