diff --git a/flang/lib/Optimizer/CodeGen/PreCGRewrite.cpp b/flang/lib/Optimizer/CodeGen/PreCGRewrite.cpp
--- a/flang/lib/Optimizer/CodeGen/PreCGRewrite.cpp
+++ b/flang/lib/Optimizer/CodeGen/PreCGRewrite.cpp
@@ -25,29 +25,26 @@
 // Codegen rewrite: rewriting of subgraphs of ops
 //===----------------------------------------------------------------------===//
 
-using namespace fir;
-using namespace mlir;
-
 #define DEBUG_TYPE "flang-codegen-rewrite"
 
 static void populateShape(llvm::SmallVectorImpl<mlir::Value> &vec,
-                          ShapeOp shape) {
+                          fir::ShapeOp shape) {
   vec.append(shape.getExtents().begin(), shape.getExtents().end());
 }
 
 // Operands of fir.shape_shift split into two vectors.
 static void populateShapeAndShift(llvm::SmallVectorImpl<mlir::Value> &shapeVec,
                                   llvm::SmallVectorImpl<mlir::Value> &shiftVec,
-                                  ShapeShiftOp shift) {
-  auto endIter = shift.getPairs().end();
-  for (auto i = shift.getPairs().begin(); i != endIter;) {
+                                  fir::ShapeShiftOp shift) {
+  for (auto i = shift.getPairs().begin(), endIter = shift.getPairs().end();
+       i != endIter;) {
     shiftVec.push_back(*i++);
     shapeVec.push_back(*i++);
   }
 }
 
 static void populateShift(llvm::SmallVectorImpl<mlir::Value> &vec,
-                          ShiftOp shift) {
+                          fir::ShiftOp shift) {
   vec.append(shift.getOrigins().begin(), shift.getOrigins().end());
 }
 
@@ -72,27 +69,26 @@
 /// (!fir.ref<!fir.array<?xi32>>, index, index, index, index, index) ->
 /// !fir.box<!fir.array<?xi32>>
 /// ```
-class EmboxConversion : public mlir::OpRewritePattern<EmboxOp> {
+class EmboxConversion : public mlir::OpRewritePattern<fir::EmboxOp> {
 public:
   using OpRewritePattern::OpRewritePattern;
 
   mlir::LogicalResult
-  matchAndRewrite(EmboxOp embox,
+  matchAndRewrite(fir::EmboxOp embox,
                   mlir::PatternRewriter &rewriter) const override {
-    auto shapeVal = embox.getShape();
     // If the embox does not include a shape, then do not convert it
-    if (shapeVal)
+    if (auto shapeVal = embox.getShape())
       return rewriteDynamicShape(embox, rewriter, shapeVal);
-    if (auto boxTy = embox.getType().dyn_cast<BoxType>())
-      if (auto seqTy = boxTy.getEleTy().dyn_cast<SequenceType>())
+    if (auto boxTy = embox.getType().dyn_cast<fir::BoxType>())
+      if (auto seqTy = boxTy.getEleTy().dyn_cast<fir::SequenceType>())
         if (seqTy.hasConstantShape())
           return rewriteStaticShape(embox, rewriter, seqTy);
     return mlir::failure();
   }
 
-  mlir::LogicalResult rewriteStaticShape(EmboxOp embox,
+  mlir::LogicalResult rewriteStaticShape(fir::EmboxOp embox,
                                          mlir::PatternRewriter &rewriter,
-                                         SequenceType seqTy) const {
+                                         fir::SequenceType seqTy) const {
     auto loc = embox.getLoc();
     llvm::SmallVector<mlir::Value> shapeOpers;
     auto idxTy = rewriter.getIndexType();
@@ -101,7 +97,7 @@
       auto extVal = rewriter.create<mlir::arith::ConstantOp>(loc, idxTy, iAttr);
       shapeOpers.push_back(extVal);
     }
-    auto xbox = rewriter.create<cg::XEmboxOp>(
+    auto xbox = rewriter.create<fir::cg::XEmboxOp>(
         loc, embox.getType(), embox.getMemref(), shapeOpers, llvm::None,
         llvm::None, llvm::None, llvm::None, embox.getTypeparams());
     LLVM_DEBUG(llvm::dbgs() << "rewriting " << embox << " to " << xbox << '\n');
@@ -109,17 +105,17 @@
     return mlir::success();
   }
 
-  mlir::LogicalResult rewriteDynamicShape(EmboxOp embox,
+  mlir::LogicalResult rewriteDynamicShape(fir::EmboxOp embox,
                                           mlir::PatternRewriter &rewriter,
                                           mlir::Value shapeVal) const {
     auto loc = embox.getLoc();
-    auto shapeOp = dyn_cast<ShapeOp>(shapeVal.getDefiningOp());
     llvm::SmallVector<mlir::Value> shapeOpers;
     llvm::SmallVector<mlir::Value> shiftOpers;
-    if (shapeOp) {
+    if (auto shapeOp = mlir::dyn_cast<fir::ShapeOp>(shapeVal.getDefiningOp())) {
       populateShape(shapeOpers, shapeOp);
     } else {
-      auto shiftOp = dyn_cast<ShapeShiftOp>(shapeVal.getDefiningOp());
+      auto shiftOp =
+          mlir::dyn_cast<fir::ShapeShiftOp>(shapeVal.getDefiningOp());
       assert(shiftOp && "shape is neither fir.shape nor fir.shape_shift");
       populateShapeAndShift(shapeOpers, shiftOpers, shiftOp);
     }
@@ -127,7 +123,8 @@
     llvm::SmallVector<mlir::Value> subcompOpers;
     llvm::SmallVector<mlir::Value> substrOpers;
     if (auto s = embox.getSlice())
-      if (auto sliceOp = dyn_cast_or_null<SliceOp>(s.getDefiningOp())) {
+      if (auto sliceOp =
+              mlir::dyn_cast_or_null<fir::SliceOp>(s.getDefiningOp())) {
         sliceOpers.assign(sliceOp.getTriples().begin(),
                           sliceOp.getTriples().end());
         subcompOpers.assign(sliceOp.getFields().begin(),
@@ -135,7 +132,7 @@
         substrOpers.assign(sliceOp.getSubstr().begin(),
                            sliceOp.getSubstr().end());
       }
-    auto xbox = rewriter.create<cg::XEmboxOp>(
+    auto xbox = rewriter.create<fir::cg::XEmboxOp>(
         loc, embox.getType(), embox.getMemref(), shapeOpers, shiftOpers,
         sliceOpers, subcompOpers, substrOpers, embox.getTypeparams());
     LLVM_DEBUG(llvm::dbgs() << "rewriting " << embox << " to " << xbox << '\n');
@@ -156,22 +153,24 @@
 /// %5 = fircg.ext_rebox %3(%13) origin %12 : (!fir.box<!fir.array<?xi32>>,
 /// index, index) -> !fir.box<!fir.array<?xi32>>
 /// ```
-class ReboxConversion : public mlir::OpRewritePattern<ReboxOp> {
+class ReboxConversion : public mlir::OpRewritePattern<fir::ReboxOp> {
 public:
   using OpRewritePattern::OpRewritePattern;
 
   mlir::LogicalResult
-  matchAndRewrite(ReboxOp rebox,
+  matchAndRewrite(fir::ReboxOp rebox,
                   mlir::PatternRewriter &rewriter) const override {
     auto loc = rebox.getLoc();
     llvm::SmallVector<mlir::Value> shapeOpers;
     llvm::SmallVector<mlir::Value> shiftOpers;
     if (auto shapeVal = rebox.getShape()) {
-      if (auto shapeOp = dyn_cast<ShapeOp>(shapeVal.getDefiningOp()))
+      if (auto shapeOp = mlir::dyn_cast<fir::ShapeOp>(shapeVal.getDefiningOp()))
         populateShape(shapeOpers, shapeOp);
-      else if (auto shiftOp = dyn_cast<ShapeShiftOp>(shapeVal.getDefiningOp()))
+      else if (auto shiftOp =
+                   mlir::dyn_cast<fir::ShapeShiftOp>(shapeVal.getDefiningOp()))
         populateShapeAndShift(shapeOpers, shiftOpers, shiftOp);
-      else if (auto shiftOp = dyn_cast<ShiftOp>(shapeVal.getDefiningOp()))
+      else if (auto shiftOp =
+                   mlir::dyn_cast<fir::ShiftOp>(shapeVal.getDefiningOp()))
         populateShift(shiftOpers, shiftOp);
       else
         return mlir::failure();
@@ -180,7 +179,8 @@
     llvm::SmallVector<mlir::Value> subcompOpers;
     llvm::SmallVector<mlir::Value> substrOpers;
     if (auto s = rebox.getSlice())
-      if (auto sliceOp = dyn_cast_or_null<SliceOp>(s.getDefiningOp())) {
+      if (auto sliceOp =
+              mlir::dyn_cast_or_null<fir::SliceOp>(s.getDefiningOp())) {
         sliceOpers.append(sliceOp.getTriples().begin(),
                           sliceOp.getTriples().end());
         subcompOpers.append(sliceOp.getFields().begin(),
@@ -189,7 +189,7 @@
                            sliceOp.getSubstr().end());
       }
 
-    auto xRebox = rewriter.create<cg::XReboxOp>(
+    auto xRebox = rewriter.create<fir::cg::XReboxOp>(
         loc, rebox.getType(), rebox.getBox(), shapeOpers, shiftOpers,
         sliceOpers, subcompOpers, substrOpers);
     LLVM_DEBUG(llvm::dbgs()
@@ -212,22 +212,24 @@
 /// (!fir.ref<!fir.array<?xi32>>, index, index, index, index, index, index) ->
 /// !fir.ref<i32>
 /// ```
-class ArrayCoorConversion : public mlir::OpRewritePattern<ArrayCoorOp> {
+class ArrayCoorConversion : public mlir::OpRewritePattern<fir::ArrayCoorOp> {
 public:
   using OpRewritePattern::OpRewritePattern;
 
   mlir::LogicalResult
-  matchAndRewrite(ArrayCoorOp arrCoor,
+  matchAndRewrite(fir::ArrayCoorOp arrCoor,
                   mlir::PatternRewriter &rewriter) const override {
     auto loc = arrCoor.getLoc();
     llvm::SmallVector<mlir::Value> shapeOpers;
     llvm::SmallVector<mlir::Value> shiftOpers;
     if (auto shapeVal = arrCoor.getShape()) {
-      if (auto shapeOp = dyn_cast<ShapeOp>(shapeVal.getDefiningOp()))
+      if (auto shapeOp = mlir::dyn_cast<fir::ShapeOp>(shapeVal.getDefiningOp()))
         populateShape(shapeOpers, shapeOp);
-      else if (auto shiftOp = dyn_cast<ShapeShiftOp>(shapeVal.getDefiningOp()))
+      else if (auto shiftOp =
+                   mlir::dyn_cast<fir::ShapeShiftOp>(shapeVal.getDefiningOp()))
         populateShapeAndShift(shapeOpers, shiftOpers, shiftOp);
-      else if (auto shiftOp = dyn_cast<ShiftOp>(shapeVal.getDefiningOp()))
+      else if (auto shiftOp =
+                   mlir::dyn_cast<fir::ShiftOp>(shapeVal.getDefiningOp()))
         populateShift(shiftOpers, shiftOp);
       else
         return mlir::failure();
@@ -235,7 +237,8 @@
     llvm::SmallVector<mlir::Value> sliceOpers;
     llvm::SmallVector<mlir::Value> subcompOpers;
     if (auto s = arrCoor.getSlice())
-      if (auto sliceOp = dyn_cast_or_null<SliceOp>(s.getDefiningOp())) {
+      if (auto sliceOp =
+              mlir::dyn_cast_or_null<fir::SliceOp>(s.getDefiningOp())) {
         sliceOpers.append(sliceOp.getTriples().begin(),
                           sliceOp.getTriples().end());
         subcompOpers.append(sliceOp.getFields().begin(),
@@ -244,7 +247,7 @@
                "Don't allow substring operations on array_coor. This "
                "restriction may be lifted in the future.");
       }
-    auto xArrCoor = rewriter.create<cg::XArrayCoorOp>(
+    auto xArrCoor = rewriter.create<fir::cg::XArrayCoorOp>(
         loc, arrCoor.getType(), arrCoor.getMemref(), shapeOpers, shiftOpers,
         sliceOpers, subcompOpers, arrCoor.getIndices(),
         arrCoor.getTypeparams());
@@ -255,20 +258,22 @@
   }
 };
 
-class CodeGenRewrite : public CodeGenRewriteBase<CodeGenRewrite> {
+class CodeGenRewrite : public fir::CodeGenRewriteBase<CodeGenRewrite> {
 public:
   void runOnOperation() override final {
     auto op = getOperation();
     auto &context = getContext();
     mlir::OpBuilder rewriter(&context);
     mlir::ConversionTarget target(context);
-    target.addLegalDialect<mlir::arith::ArithmeticDialect, FIROpsDialect,
-                           FIRCodeGenDialect, mlir::func::FuncDialect>();
-    target.addIllegalOp<ArrayCoorOp>();
-    target.addIllegalOp<ReboxOp>();
-    target.addDynamicallyLegalOp<EmboxOp>([](EmboxOp embox) {
-      return !(embox.getShape() ||
-               embox.getType().cast<BoxType>().getEleTy().isa<SequenceType>());
+    target.addLegalDialect<mlir::arith::ArithmeticDialect, fir::FIROpsDialect,
+                           fir::FIRCodeGenDialect, mlir::func::FuncDialect>();
+    target.addIllegalOp<fir::ArrayCoorOp>();
+    target.addIllegalOp<fir::ReboxOp>();
+    target.addDynamicallyLegalOp<fir::EmboxOp>([](fir::EmboxOp embox) {
+      return !(embox.getShape() || embox.getType()
+                                       .cast<fir::BoxType>()
+                                       .getEleTy()
+                                       .isa<fir::SequenceType>());
     });
     mlir::RewritePatternSet patterns(&context);
     patterns.insert<EmboxConversion, ArrayCoorConversion, ReboxConversion>(