From d47ffe2d90e9aa970d9401e1846559c941a09a84 Mon Sep 17 00:00:00 2001
From: Schuyler Eldridge <schuyler.eldridge@sifive.com>
Date: Fri, 26 Jan 2024 20:04:17 -0500
Subject: [PATCH] fixup! [FIRRTL] Prerequisites for Layer-Associated Probes

---
 .../circt/Dialect/FIRRTL/FIRRTLExpressions.td |  1 +
 lib/Dialect/FIRRTL/FIRRTLOps.cpp              | 40 +++++++++++++++++++
 test/Dialect/FIRRTL/errors.mlir               | 29 ++++++++++++++
 3 files changed, 70 insertions(+)

diff --git a/include/circt/Dialect/FIRRTL/FIRRTLExpressions.td b/include/circt/Dialect/FIRRTL/FIRRTLExpressions.td
index ebf873de4523..7918c5cfca72 100644
--- a/include/circt/Dialect/FIRRTL/FIRRTLExpressions.td
+++ b/include/circt/Dialect/FIRRTL/FIRRTLExpressions.td
@@ -1239,6 +1239,7 @@ def RefResolveOp: FIRRTLExprOp<"ref.resolve",
   let results = (outs FIRRTLBaseType:$result);
 
   let hasCanonicalizer = true;
+  let hasVerifier = 1;
 
   let assemblyFormat = "$ref attr-dict `:` qualified(type($ref))";
 }
diff --git a/lib/Dialect/FIRRTL/FIRRTLOps.cpp b/lib/Dialect/FIRRTL/FIRRTLOps.cpp
index b48809c9b179..73e4014bff19 100644
--- a/lib/Dialect/FIRRTL/FIRRTLOps.cpp
+++ b/lib/Dialect/FIRRTL/FIRRTLOps.cpp
@@ -5810,6 +5810,46 @@ LogicalResult RefCastOp::verify() {
   return success();
 }
 
+LogicalResult RefResolveOp::verify() {
+
+  SymbolRefAttr layer;
+  auto layerBlockOp = (*this)->getParentOfType<LayerBlockOp>();
+  if (layerBlockOp)
+    layer = layerBlockOp.getLayerName();
+
+  // The dest layer must be the same as the source layer or a parent of it.
+  SymbolRefAttr layerPointer = layer;
+  auto destLayer = getRef().getType().getLayer();
+  for (;;) {
+    if (layerPointer == destLayer)
+      break;
+
+    if (!layerPointer) {
+      if (!layer)
+        return emitOpError() << "cannot read from a layer-colored probe from "
+                                "outside a layerblock";
+      auto diag = emitOpError()
+                  << "reads from a probe colored with layer '" << destLayer
+                  << "' from a layerblock associated with layer '" << layer
+                  << "'. The resolve op must be in a layerblock associated "
+                     "with or a child of layer '"
+                  << destLayer << "'.";
+      return diag.attachNote(layerBlockOp.getLoc())
+             << "the layerblock was declared here";
+    }
+
+    if (layerPointer.getNestedReferences().empty()) {
+      layerPointer = {};
+      continue;
+    }
+    layerPointer =
+        SymbolRefAttr::get(layerPointer.getRootReference(),
+                           layerPointer.getNestedReferences().drop_back());
+  }
+
+  return success();
+}
+
 LogicalResult RWProbeOp::verifyInnerRefs(hw::InnerRefNamespace &ns) {
   auto targetRef = getTarget();
   if (targetRef.getModule() !=
diff --git a/test/Dialect/FIRRTL/errors.mlir b/test/Dialect/FIRRTL/errors.mlir
index f9e7b9ec7e22..b694a408e4d1 100644
--- a/test/Dialect/FIRRTL/errors.mlir
+++ b/test/Dialect/FIRRTL/errors.mlir
@@ -1947,6 +1947,35 @@ firrtl.circuit "IllegalRefCastDestLayerBlock" {
 
 // -----
 
+firrtl.circuit "IllegalRefResolve_NotInLayerBlock" {
+  firrtl.layer @A bind {
+  }
+  firrtl.module @IllegalRefResolve_NotInLayerBlock() {
+    %0 = firrtl.wire : !firrtl.probe<uint<1>, @A>
+    // expected-error @below {{'firrtl.ref.resolve' op cannot read from a layer-colored probe from outside a layerblock}}
+    %1 = firrtl.ref.resolve %0 : !firrtl.probe<uint<1>, @A>
+  }
+}
+
+// -----
+
+firrtl.circuit "IllegalRefResolve_IllegalLayer" {
+  firrtl.layer @A bind {
+  }
+  firrtl.layer @B bind {
+  }
+  firrtl.module @IllegalRefResolve_IllegalLayer() {
+    %0 = firrtl.wire : !firrtl.probe<uint<1>, @A>
+    // expected-note @below {{the layerblock was declared here}}
+    firrtl.layerblock @B {
+      // expected-error @below {{'firrtl.ref.resolve' op reads from a probe colored with layer '@A' from a layerblock associated with layer '@B'. The resolve op must be in a layerblock associated with or a child of layer '@A'.}}
+      %1 = firrtl.ref.resolve %0 : !firrtl.probe<uint<1>, @A>
+    }
+  }
+}
+
+// -----
+
 firrtl.circuit "InvalidProbeAssociationPort_SymbolDoesNotExist" {
   // expected-error @below {{probe port 'a' is associated with layer '@B', but this layer was not defined}}
   firrtl.module @InvalidProbeAssociationPort_SymbolDoesNotExist(out %a: !firrtl.probe<uint<1>, @B>) {