[FIRRTL] Convert CheckLayers to use InstanceInfo (#7635)

Change the `CheckLayers` pass to use the `InstanceInfo` analysis.  This
new analysis makes the error checking trivial.  However, the error
reporting is still somewhat tedious.

Signed-off-by: Schuyler Eldridge <schuyler.eldridge@sifive.com>

lib/Dialect/FIRRTL/Transforms/CheckLayers.cpp

@@ -6,10 +6,13 @@
 //
 //===----------------------------------------------------------------------===//
 
+#include "circt/Analysis/FIRRTLInstanceInfo.h"
 #include "circt/Dialect/FIRRTL/FIRRTLInstanceGraph.h"
 #include "circt/Dialect/FIRRTL/FIRRTLOps.h"
 #include "circt/Dialect/FIRRTL/Passes.h"
+#include "circt/Support/InstanceGraphInterface.h"
 #include "mlir/Pass/Pass.h"
+#include "llvm/ADT/DepthFirstIterator.h"
 #include "llvm/ADT/PostOrderIterator.h"
 
 namespace circt {
@@ -25,72 +28,56 @@ using namespace mlir;
 
 namespace {
 class CheckLayers {
-  CheckLayers(InstanceGraph &instanceGraph) : instanceGraph(instanceGraph) {}
-
-  /// Walk the LayerBlock and report any illegal instantiation found within.
-  void run(LayerBlockOp layerBlock) {
-    layerBlock.getBody()->walk([&](FInstanceLike instance) {
-      auto moduleName = instance.getReferencedModuleNameAttr();
-      auto *targetModule =
-          instanceGraph.lookup(moduleName)->getModule<Operation *>();
-      auto childLayerBlock = layerBlocks.lookup(targetModule);
-      if (childLayerBlock) {
-        auto diag = emitError(instance.getLoc())
-                    << "cannot instantiate " << moduleName
-                    << " under a layerblock, because " << moduleName
-                    << " contains a layerblock";
-        diag.attachNote(childLayerBlock.getLoc()) << "layerblock here";
-        error = true;
-      }
-    });
-  }
+  CheckLayers(InstanceGraph &instanceGraph, InstanceInfo &instanceInfo)
+      : iGraph(instanceGraph), iInfo(instanceInfo) {}
 
   /// Walk a module, reporting any illegal instantation of layers under layers,
   /// and record if this module contains any layerblocks.
   void run(FModuleOp moduleOp) {
-    // If this module directly contains a layerblock, or instantiates another
-    // module with a layerblock, then this will point to the layerblock. We use
-    // this for error reporting. We keep track of only the first layerblock
-    // found.
-    LayerBlockOp firstLayerblock = nullptr;
-    moduleOp.getBodyBlock()->walk<WalkOrder::PreOrder>([&](Operation *op) {
-      // If we are instantiating a module, check if it contains a layerblock. If
-      // it does, mark this target layerblock as our layerblock.
-      if (auto instance = dyn_cast<FInstanceLike>(op)) {
-        // If this is the first layer block in this module, record it.
-        if (!firstLayerblock) {
-          auto moduleName = instance.getReferencedModuleNameAttr();
-          auto *targetModule =
-              instanceGraph.lookup(moduleName)->getModule().getOperation();
-          firstLayerblock = layerBlocks.lookup(targetModule);
+    // No instance is under a layer block.  No further examination is necessary.
+    if (!iInfo.anyInstanceUnderLayer(moduleOp))
+      return;
+
+    // The module is under a layer block.  Verify that it has no layer blocks.
+    LayerBlockOp layerBlockOp;
+    moduleOp.getBodyBlock()->walk([&](LayerBlockOp op) {
+      layerBlockOp = op;
+      return WalkResult::interrupt();
+    });
+    if (!layerBlockOp)
+      return;
+
+    // The module contains layer blocks and is instantiated under a layer block.
+    // Walk up the instance hierarchy to find the first instance which is
+    // directly under a layer block.
+    error = true;
+    for (auto *node : llvm::inverse_depth_first(iGraph.lookup(moduleOp))) {
+      auto modOp = node->getModule();
+      if (previousErrors.contains(node) || !iInfo.anyInstanceUnderLayer(modOp))
+        continue;
+      for (auto *instNode : node->uses()) {
+        auto instanceOp = instNode->getInstance();
+        if (instanceOp->getParentOfType<LayerBlockOp>()) {
+          auto moduleName = modOp.getModuleNameAttr();
+          auto diag = emitError(instanceOp.getLoc())
+                      << "cannot instantiate " << moduleName
+                      << " under a layerblock, because " << moduleName
+                      << " contains a layerblock";
+          diag.attachNote(layerBlockOp->getLoc()) << "layerblock here";
+          previousErrors.insert(node);
+          continue;
         }
-        return WalkResult::advance();
-      }
-      if (auto layerBlock = dyn_cast<LayerBlockOp>(op)) {
-        // If this is the first layer block in this module, record it.
-        if (!firstLayerblock)
-          firstLayerblock = layerBlock;
-        // Process the layerblock.
-        run(layerBlock);
-        // Don't recurse on elements of the layerblock.  If an instance within
-        // did contain a layerblock, then an error would have been reported for
-        // it already.
-        return WalkResult::skip();
       }
-      // Do nothing for all other operations.
-      return WalkResult::advance();
-    });
-    // If this module contained a layerblock, then record it.
-    if (firstLayerblock)
-      layerBlocks.try_emplace(moduleOp, firstLayerblock);
+    }
   }
 
 public:
-  static LogicalResult run(InstanceGraph &instanceGraph) {
-    CheckLayers checkLayers(instanceGraph);
+  static LogicalResult run(InstanceGraph &instanceGraph,
+                           InstanceInfo &instanceInfo) {
+    CheckLayers checkLayers(instanceGraph, instanceInfo);
     DenseSet<InstanceGraphNode *> visited;
     for (auto *root : instanceGraph) {
-      for (auto *node : llvm::post_order_ext(root, visited)) {
+      for (auto *node : llvm::inverse_post_order_ext(root, visited)) {
         if (auto moduleOp = dyn_cast<FModuleOp>(node->getModule<Operation *>()))
           checkLayers.run(moduleOp);
       }
@@ -99,10 +86,15 @@ class CheckLayers {
   }
 
 private:
-  InstanceGraph &instanceGraph;
-  /// A mapping from a module to the first layerblock that it contains,
-  /// transitively through instances.
-  DenseMap<Operation *, LayerBlockOp> layerBlocks;
+  /// Pre-populated analyses
+  InstanceGraph &iGraph;
+  InstanceInfo &iInfo;
+
+  /// This records modules for which we have already generated errors when doing
+  /// a top-down walk.
+  DenseSet<const InstanceGraphNode *> previousErrors;
+
+  /// Indicates if this checker found an error.
   bool error = false;
 };
 } // end anonymous namespace
@@ -111,7 +103,8 @@ class CheckLayersPass
     : public circt::firrtl::impl::CheckLayersBase<CheckLayersPass> {
 public:
   void runOnOperation() override {
-    if (failed(CheckLayers::run(getAnalysis<InstanceGraph>())))
+    if (failed(CheckLayers::run(getAnalysis<InstanceGraph>(),
+                                getAnalysis<InstanceInfo>())))
       return signalPassFailure();
     markAllAnalysesPreserved();
   }