[CIR] Upstream new SetBitfieldOp for handling C and C++ struct bitfields

Andres-Salamanca · Andres-Salamanca · commit 38b98a54b718 · 2025-07-08T17:33:52.000-05:00
diff --git a/clang/include/clang/CIR/Dialect/IR/CIROps.td b/clang/include/clang/CIR/Dialect/IR/CIROps.td
@@ -1669,6 +1669,90 @@ def GetGlobalOp : CIR_Op<"get_global",
   }];
 }
 
+//===----------------------------------------------------------------------===//
+// SetBitfieldOp
+//===----------------------------------------------------------------------===//
+
+def SetBitfieldOp : CIR_Op<"set_bitfield"> {
+  let summary = "Set the value of a bitfield member";
+  let description = [{
+    The `cir.set_bitfield` operation provides a store-like access to
+    a bit field of a record.
+
+    It expects an address of a storage where to store, a type of the storage,
+    a value being stored, a name of a bit field, a pointer to the storage in the
+    base record, a size of the storage, a size the bit field, an offset
+    of the bit field and a sign. Returns a value being stored.
+
+    A unit attribute `volatile` can be used to indicate a volatile load of the
+    bitfield.
+
+    Example.
+    Suppose we have a struct with multiple bitfields stored in
+    different storages. The `cir.set_bitfield` operation sets the value
+    of the bitfield.
+    ```C++
+    typedef struct {
+      int a : 4;
+      int b : 27;
+      int c : 17;
+      int d : 2;
+      int e : 15;
+    } S;
+
+    void store_bitfield(S& s) {
+      s.e = 3;
+    }
+    ```
+
+    ```mlir
+    // 'e' is in the storage with the index 1
+    !record_type = !cir.record<struct "S" packed padded {!u64i, !u16i,
+                               !cir.array<!u8i x 2>} #cir.record.decl.ast>
+    #bfi_e = #cir.bitfield_info<name = "e", storage_type = !u16i, size = 15,
+                                offset = 0, is_signed = true>
+
+    %1 = cir.const #cir.int<3> : !s32i
+    %2 = cir.load %0 : !cir.ptr<!cir.ptr<!record_type>>, !cir.ptr<!record_type>
+    %3 = cir.get_member %2[1] {name = "e"} : !cir.ptr<!record_type>
+                                                             -> !cir.ptr<!u16i>
+    %4 = cir.set_bitfield(#bfi_e, %3 : !cir.ptr<!u16i>, %1 : !s32i) -> !s32i
+    ```
+   }];
+
+  let arguments = (ins
+    Arg<CIR_PointerType, "the address to store the value", [MemWrite]>:$addr,
+    CIR_AnyType:$src,
+    BitfieldInfoAttr:$bitfield_info,
+    UnitAttr:$is_volatile
+  );
+
+  let results = (outs CIR_IntType:$result);
+
+  let assemblyFormat = [{ `(`$bitfield_info`,` $addr`:`qualified(type($addr))`,`
+    $src`:`type($src) `)`  attr-dict `->` type($result) }];
+
+  let builders = [
+    OpBuilder<(ins "mlir::Type":$type,
+                   "mlir::Value":$addr,
+                   "mlir::Type":$storage_type,
+                   "mlir::Value":$src,
+                   "llvm::StringRef":$name,
+                   "unsigned":$size,
+                   "unsigned":$offset,
+                   "bool":$is_signed,
+                   "bool":$is_volatile
+                   ),
+   [{
+      BitfieldInfoAttr info =
+        BitfieldInfoAttr::get($_builder.getContext(),
+                              name, storage_type,
+                              size, offset, is_signed);
+      build($_builder, $_state, type, addr, src, info, is_volatile);
+    }]>
+  ];
+}
+
 //===----------------------------------------------------------------------===//
 // GetBitfieldOp
 //===----------------------------------------------------------------------===//
diff --git a/clang/lib/CIR/CodeGen/CIRGenBuilder.h b/clang/lib/CIR/CodeGen/CIRGenBuilder.h
@@ -394,6 +394,15 @@ class CIRGenBuilderTy : public cir::CIRBaseBuilderTy {
     return createGlobal(module, loc, uniqueName, type, linkage);
   }
 
+  mlir::Value createSetBitfield(mlir::Location loc, mlir::Type resultType,
+                                mlir::Value dstAddr, mlir::Type storageType,
+                                mlir::Value src, const CIRGenBitFieldInfo &info,
+                                bool isLvalueVolatile, bool useVolatile) {
+    return create<cir::SetBitfieldOp>(loc, resultType, dstAddr, storageType,
+                                      src, info.name, info.size, info.offset,
+                                      info.isSigned, isLvalueVolatile);
+  }
+
   mlir::Value createGetBitfield(mlir::Location loc, mlir::Type resultType,
                                 mlir::Value addr, mlir::Type storageType,
                                 const CIRGenBitFieldInfo &info,
diff --git a/clang/lib/CIR/CodeGen/CIRGenExpr.cpp b/clang/lib/CIR/CodeGen/CIRGenExpr.cpp
@@ -224,6 +224,10 @@ void CIRGenFunction::emitStoreThroughLValue(RValue src, LValue dst,
       return;
     }
 
+    assert(dst.isBitField() && "NIY LValue type");
+    emitStoreThroughBitfieldLValue(src, dst);
+    return;
+
     cgm.errorNYI(dst.getPointer().getLoc(),
                  "emitStoreThroughLValue: non-simple lvalue");
     return;
@@ -321,9 +325,20 @@ void CIRGenFunction::emitStoreOfScalar(mlir::Value value, Address addr,
 
 mlir::Value CIRGenFunction::emitStoreThroughBitfieldLValue(RValue src,
                                                            LValue dst) {
-  assert(!cir::MissingFeatures::bitfields());
-  cgm.errorNYI("bitfields");
-  return {};
+
+  assert(!cir::MissingFeatures::armComputeVolatileBitfields());
+
+  const CIRGenBitFieldInfo &info = dst.getBitFieldInfo();
+  mlir::Type resLTy = convertTypeForMem(dst.getType());
+  Address ptr = dst.getBitFieldAddress();
+
+  const bool useVolatile = false;
+
+  mlir::Value dstAddr = dst.getAddress().getPointer();
+
+  return builder.createSetBitfield(dstAddr.getLoc(), resLTy, dstAddr,
+                                   ptr.getElementType(), src.getValue(), info,
+                                   dst.isVolatileQualified(), useVolatile);
 }
 
 RValue CIRGenFunction::emitLoadOfBitfieldLValue(LValue lv, SourceLocation loc) {
@@ -1063,10 +1078,10 @@ LValue CIRGenFunction::emitBinaryOperatorLValue(const BinaryOperator *e) {
 
     SourceLocRAIIObject loc{*this, getLoc(e->getSourceRange())};
     if (lv.isBitField()) {
-      cgm.errorNYI(e->getSourceRange(), "bitfields");
-      return {};
+      emitStoreThroughBitfieldLValue(rv, lv);
+    } else {
+      emitStoreThroughLValue(rv, lv);
     }
-    emitStoreThroughLValue(rv, lv);
 
     if (getLangOpts().OpenMP) {
       cgm.errorNYI(e->getSourceRange(), "openmp");
diff --git a/clang/lib/CIR/CodeGen/CIRGenValue.h b/clang/lib/CIR/CodeGen/CIRGenValue.h
@@ -186,6 +186,8 @@ class LValue {
   bool isBitField() const { return lvType == BitField; }
   bool isVolatile() const { return quals.hasVolatile(); }
 
+  bool isVolatileQualified() const { return quals.hasVolatile(); }
+
   unsigned getVRQualifiers() const {
     return quals.getCVRQualifiers() & ~clang::Qualifiers::Const;
   }
diff --git a/clang/lib/CIR/Lowering/DirectToLLVM/LowerToLLVM.cpp b/clang/lib/CIR/Lowering/DirectToLLVM/LowerToLLVM.cpp
@@ -2049,6 +2049,7 @@ void ConvertCIRToLLVMPass::runOnOperation() {
                CIRToLLVMGetGlobalOpLowering,
                CIRToLLVMGetMemberOpLowering,
                CIRToLLVMSelectOpLowering,
+               CIRToLLVMSetBitfieldOpLowering,
                CIRToLLVMShiftOpLowering,
                CIRToLLVMStackRestoreOpLowering,
                CIRToLLVMStackSaveOpLowering,
@@ -2384,6 +2385,82 @@ mlir::LogicalResult CIRToLLVMComplexImagOpLowering::matchAndRewrite(
   return mlir::success();
 }
 
+mlir::LogicalResult CIRToLLVMSetBitfieldOpLowering::matchAndRewrite(
+    cir::SetBitfieldOp op, OpAdaptor adaptor,
+    mlir::ConversionPatternRewriter &rewriter) const {
+  mlir::OpBuilder::InsertionGuard guard(rewriter);
+  rewriter.setInsertionPoint(op);
+
+  cir::BitfieldInfoAttr info = op.getBitfieldInfo();
+  uint64_t size = info.getSize();
+  uint64_t offset = info.getOffset();
+  mlir::Type storageType = info.getStorageType();
+  mlir::MLIRContext *context = storageType.getContext();
+
+  unsigned storageSize = 0;
+
+  mlir::IntegerType intType =
+      TypeSwitch<mlir::Type, mlir::IntegerType>(storageType)
+          .Case<cir::ArrayType>([&](cir::ArrayType atTy) {
+            storageSize = atTy.getSize() * 8;
+            return mlir::IntegerType::get(context, storageSize);
+          })
+          .Case<cir::IntType>([&](cir::IntType intTy) {
+            storageSize = intTy.getWidth();
+            return mlir::IntegerType::get(context, storageSize);
+          })
+          .Default([](mlir::Type) -> mlir::IntegerType {
+            llvm_unreachable(
+                "Either ArrayType or IntType expected for bitfields storage");
+          });
+
+  mlir::Value srcVal = createIntCast(rewriter, adaptor.getSrc(), intType);
+  unsigned srcWidth = storageSize;
+  mlir::Value resultVal = srcVal;
+
+  if (storageSize != size) {
+    assert(storageSize > size && "Invalid bitfield size.");
+
+    mlir::Value val = rewriter.create<mlir::LLVM::LoadOp>(
+        op.getLoc(), intType, adaptor.getAddr(), /* alignment */ 0,
+        op.getIsVolatile());
+
+    srcVal =
+        createAnd(rewriter, srcVal, llvm::APInt::getLowBitsSet(srcWidth, size));
+    resultVal = srcVal;
+    srcVal = createShL(rewriter, srcVal, offset);
+
+    // Mask out the original value.
+    val = createAnd(rewriter, val,
+                    ~llvm::APInt::getBitsSet(srcWidth, offset, offset + size));
+
+    // Or together the unchanged values and the source value.
+    srcVal = rewriter.create<mlir::LLVM::OrOp>(op.getLoc(), val, srcVal);
+  }
+
+  rewriter.create<mlir::LLVM::StoreOp>(op.getLoc(), srcVal, adaptor.getAddr(),
+                                       /* alignment */ 0, op.getIsVolatile());
+
+  mlir::Type resultTy = getTypeConverter()->convertType(op.getType());
+
+  if (info.getIsSigned()) {
+    assert(size <= storageSize);
+    unsigned highBits = storageSize - size;
+
+    if (highBits) {
+      resultVal = createShL(rewriter, resultVal, highBits);
+      resultVal = createAShR(rewriter, resultVal, highBits);
+    }
+  }
+
+  resultVal = createIntCast(rewriter, resultVal,
+                            mlir::cast<mlir::IntegerType>(resultTy),
+                            info.getIsSigned());
+
+  rewriter.replaceOp(op, resultVal);
+  return mlir::success();
+}
+
 mlir::LogicalResult CIRToLLVMGetBitfieldOpLowering::matchAndRewrite(
     cir::GetBitfieldOp op, OpAdaptor adaptor,
     mlir::ConversionPatternRewriter &rewriter) const {
diff --git a/clang/lib/CIR/Lowering/DirectToLLVM/LowerToLLVM.h b/clang/lib/CIR/Lowering/DirectToLLVM/LowerToLLVM.h
@@ -513,6 +513,16 @@ class CIRToLLVMComplexImagOpLowering
                   mlir::ConversionPatternRewriter &) const override;
 };
 
+class CIRToLLVMSetBitfieldOpLowering
+    : public mlir::OpConversionPattern<cir::SetBitfieldOp> {
+public:
+  using mlir::OpConversionPattern<cir::SetBitfieldOp>::OpConversionPattern;
+
+  mlir::LogicalResult
+  matchAndRewrite(cir::SetBitfieldOp op, OpAdaptor,
+                  mlir::ConversionPatternRewriter &) const override;
+};
+
 class CIRToLLVMGetBitfieldOpLowering
     : public mlir::OpConversionPattern<cir::GetBitfieldOp> {
 public:
diff --git a/clang/test/CIR/CodeGen/bitfields.c b/clang/test/CIR/CodeGen/bitfields.c
@@ -134,3 +134,29 @@ unsigned int load_field_unsigned(A* s) {
 //OGCG:   [[TMP4:%.*]] = lshr i16 [[TMP3]], 3
 //OGCG:   [[TMP5:%.*]] = and i16 [[TMP4]], 15
 //OGCG:   [[TMP6:%.*]] = zext i16 [[TMP5]] to i32
+
+void store_field() {
+  S s;
+  s.e = 3;
+}
+// CIR: cir.func {{.*@store_field}}
+// CIR:   [[TMP0:%.*]] = cir.alloca !rec_S, !cir.ptr<!rec_S>
+// CIR:   [[TMP1:%.*]] = cir.const #cir.int<3> : !s32i
+// CIR:   [[TMP2:%.*]] = cir.get_member [[TMP0]][1] {name = "e"} : !cir.ptr<!rec_S> -> !cir.ptr<!u16i>
+// CIR:   cir.set_bitfield(#bfi_e, [[TMP2]] : !cir.ptr<!u16i>, [[TMP1]] : !s32i)
+
+// LLVM: define dso_local void @store_field()
+// LLVM:   [[TMP0:%.*]] = alloca %struct.S, i64 1, align 4
+// LLVM:   [[TMP1:%.*]] = getelementptr %struct.S, ptr [[TMP0]], i32 0, i32 1
+// LLVM:   [[TMP2:%.*]] = load i16, ptr [[TMP1]], align 2
+// LLVM:   [[TMP3:%.*]] = and i16 [[TMP2]], -32768
+// LLVM:   [[TMP4:%.*]] = or i16 [[TMP3]], 3
+// LLVM:   store i16 [[TMP4]], ptr [[TMP1]], align 2
+
+// OGCG: define dso_local void @store_field()
+// OGCG:   [[TMP0:%.*]] = alloca %struct.S, align 4
+// OGCG:   [[TMP1:%.*]] = getelementptr inbounds nuw %struct.S, ptr [[TMP0]], i32 0, i32 1
+// OGCG:   [[TMP2:%.*]] = load i16, ptr [[TMP1]], align 4
+// OGCG:   [[TMP3:%.*]] = and i16 [[TMP2]], -32768
+// OGCG:   [[TMP4:%.*]] = or i16 [[TMP3]], 3
+// OGCG:   store i16 [[TMP4]], ptr [[TMP1]], align 4
diff --git a/clang/test/CIR/CodeGen/bitfields.cpp b/clang/test/CIR/CodeGen/bitfields.cpp
@@ -58,3 +58,28 @@ int load_field(S* s) {
 // OGCG:  [[TMP3:%.*]] = shl i64 [[TMP2]], 15
 // OGCG:  [[TMP4:%.*]] = ashr i64 [[TMP3]], 47
 // OGCG:  [[TMP5:%.*]] = trunc i64 [[TMP4]] to i32
+
+void store_field() {
+  S s;
+  s.a = 3;
+}
+// CIR: cir.func dso_local @_Z11store_field
+// CIR:   [[TMP0:%.*]] = cir.alloca !rec_S, !cir.ptr<!rec_S>
+// CIR:   [[TMP1:%.*]] = cir.const #cir.int<3> : !s32i
+// CIR:   [[TMP2:%.*]] = cir.get_member [[TMP0]][0] {name = "a"} : !cir.ptr<!rec_S> -> !cir.ptr<!u64i>
+// CIR:   cir.set_bitfield(#bfi_a, [[TMP2]] : !cir.ptr<!u64i>, [[TMP1]] : !s32i)
+
+// LLVM: define dso_local void @_Z11store_fieldv
+// LLVM:   [[TMP0:%.*]] = alloca %struct.S, i64 1, align 4
+// LLVM:   [[TMP1:%.*]] = getelementptr %struct.S, ptr [[TMP0]], i32 0, i32 0
+// LLVM:   [[TMP2:%.*]] = load i64, ptr [[TMP1]], align 8
+// LLVM:   [[TMP3:%.*]] = and i64 [[TMP2]], -16
+// LLVM:   [[TMP4:%.*]] = or i64 [[TMP3]], 3
+// LLVM:   store i64 [[TMP4]], ptr [[TMP1]], align 8
+
+// OGCG: define dso_local void @_Z11store_fieldv()
+// OGCG:   [[TMP0:%.*]] = alloca %struct.S, align 4
+// OGCG:   [[TMP1:%.*]] = load i64, ptr [[TMP0]], align 4
+// OGCG:   [[TMP2:%.*]] = and i64 [[TMP1]], -16
+// OGCG:   [[TMP3:%.*]] = or i64 [[TMP2]], 3
+// OGCG:   store i64 [[TMP3]], ptr [[TMP0]], align 4
diff --git a/clang/test/CIR/CodeGen/bitfields_be.c b/clang/test/CIR/CodeGen/bitfields_be.c

Original file line number	Diff line number	Diff line change
`@@ -186,6 +186,8 @@ class LValue {`
`186`	`186`	`bool isBitField() const { return lvType == BitField; }`
`187`	`187`	`bool isVolatile() const { return quals.hasVolatile(); }`
`188`	`188`
	`189`	`+ bool isVolatileQualified() const { return quals.hasVolatile(); }`
	`190`	`+`
`189`	`191`	`unsigned getVRQualifiers() const {`
`190`	`192`	`return quals.getCVRQualifiers() & ~clang::Qualifiers::Const;`
`191`	`193`	`}`