[Seq] Add a new pass to sink clock_gate ops to the users

include/circt/Dialect/HW/HWStructure.td

@@ -231,6 +231,11 @@ def HWModuleOp : HWModuleOpBase<"module",
 
     /// Verifies the body of the function.
     LogicalResult verifyBody();
+
+    /// Append ports to the module, use the `outputVals` to update the output op
+    /// and set the `inputVals` with the new block args added.
+    void appendPorts(ArrayRef<PortInfo> ports, ArrayRef<Value> outputVals,
+                     SmallVectorImpl<Value> &inputVals);
   }];
 
   let hasCustomAssemblyFormat = 1;

include/circt/Dialect/Seq/SeqPasses.h

@@ -22,6 +22,7 @@ namespace seq {
 
 #define GEN_PASS_DECL_EXTERNALIZECLOCKGATE
 #define GEN_PASS_DECL_HWMEMSIMIMPL
+#define GEN_PASS_DECL_SINKCLOCKGATES
 #include "circt/Dialect/Seq/SeqPasses.h.inc"
 
 std::unique_ptr<mlir::Pass> createLowerSeqHLMemPass();
@@ -31,6 +32,7 @@ std::unique_ptr<mlir::Pass> createLowerSeqFIFOPass();
 std::unique_ptr<mlir::Pass>
 createHWMemSimImplPass(const HWMemSimImplOptions &options = {});
 std::unique_ptr<mlir::Pass> createLowerSeqShiftRegPass();
+std::unique_ptr<mlir::Pass> createSinkClockGatesPass();
 
 /// Generate the code for registering passes.
 #define GEN_PASS_REGISTRATION

include/circt/Dialect/Seq/SeqPasses.td

@@ -107,4 +107,15 @@ def LowerSeqShiftReg : Pass<"lower-seq-shiftreg", "hw::HWModuleOp"> {
   let dependentDialects = ["circt::hw::HWDialect"];
 }
 
+def SinkClockGates : Pass<"sink-clock-gates", "mlir::ModuleOp"> {
+  let summary = "Sink the gated clock enables into the op that is driven by the clock.";
+  let constructor = "circt::seq::createSinkClockGatesPass()";
+  let dependentDialects = ["circt::hw::HWDialect", "circt::comb::CombDialect"];
+  let statistics = [
+    Statistic<"numClockGatesConverted", "num-clock-gates-converted",
+      "Number of clock gates that this transformation was applied to">
+  ];
+}
+
+
 #endif // CIRCT_DIALECT_SEQ_SEQPASSES

lib/Dialect/HW/HWOps.cpp

@@ -22,11 +22,13 @@
 #include "circt/Support/Namespace.h"
 #include "circt/Support/Naming.h"
 #include "mlir/IR/Builders.h"
+#include "mlir/IR/Location.h"
 #include "mlir/IR/PatternMatch.h"
 #include "mlir/Interfaces/FunctionImplementation.h"
 #include "llvm/ADT/BitVector.h"
 #include "llvm/ADT/SmallPtrSet.h"
 #include "llvm/ADT/StringSet.h"
+#include <tuple>
 
 using namespace circt;
 using namespace hw;
@@ -501,6 +503,65 @@ OpFoldResult ParamValueOp::fold(FoldAdaptor adaptor) {
   return getValueAttr();
 }
 
+void HWModuleOp::appendPorts(ArrayRef<PortInfo> ports,
+                             ArrayRef<Value> outputVals,
+                             SmallVectorImpl<Value> &inputVals) {
+
+  HWModuleOp module = *this;
+  auto *context = module->getContext();
+  auto oldType = module.getHWModuleType();
+  auto *body = module.getBodyBlock();
+
+  ArrayRef<ModulePort> oldPorts = oldType.getPorts();
+
+  unsigned newPortsCount = oldPorts.size() + ports.size();
+
+  SmallVector<ModulePort> newPorts;
+  newPorts.reserve(newPortsCount);
+  newPorts.append(oldPorts.begin(), oldPorts.end());
+
+  SmallVector<Attribute> newResultLocs;
+  if (!outputVals.empty()) {
+    // Update the output op.
+    auto oldResultLocs = module.getResultLocs();
+    if (oldResultLocs.has_value())
+      newResultLocs.append(oldResultLocs->getValue().begin(),
+                           oldResultLocs->getValue().end());
+    auto outputOp = cast<OutputOp>(body->getTerminator());
+    auto oldOperands = outputOp->getOperands();
+
+    SmallVector<Value> newOutputOperands;
+    llvm::append_range(newOutputOperands, oldOperands);
+    llvm::append_range(newOutputOperands, outputVals);
+    outputOp->setOperands(newOutputOperands);
+  }
+  auto oldPortAttrs = module.getAllPortAttrs();
+  SmallVector<Attribute> newPortAttrs(oldPortAttrs);
+  inputVals.reserve(ports.size() - outputVals.size());
+
+  for (auto &portInfo : ports) {
+    assert(!portInfo.isInOut() && "can only handle input or output ports");
+    if (portInfo.isInput())
+      inputVals.push_back(body->addArgument(portInfo.type, portInfo.loc));
+    else if (portInfo.isOutput())
+      newResultLocs.emplace_back(portInfo.loc);
+    newPorts.push_back(portInfo);
+    if (portInfo.attrs) {
+      if (newPortAttrs.empty() || newPortAttrs.size() < newPortsCount)
+        newPortAttrs.append(newPortsCount, {});
+      newPortAttrs[newPorts.size() - 1] = portInfo.attrs;
+    }
+  }
+
+  if (!outputVals.empty())
+    module.setResultLocsAttr(ArrayAttr::get(context, newResultLocs));
+
+  auto newType = ModuleType::get(context, newPorts);
+
+  module.setModuleType(newType);
+  module.setAllPortAttrs(newPortAttrs);
+}
+
 //===----------------------------------------------------------------------===//
 // HWModuleOp
 //===----------------------------------------------------------------------===/

lib/Dialect/Seq/Transforms/CMakeLists.txt

@@ -4,6 +4,7 @@ add_circt_dialect_library(CIRCTSeqTransforms
   LowerSeqHLMem.cpp
   LowerSeqFIFO.cpp
   LowerSeqShiftReg.cpp
+  SinkClockGates.cpp
 
   DEPENDS
   CIRCTSeqTransformsIncGen