[FtdCfToHandshake] Fix FTD regen self-loop creation with proper channelification

experimental/lib/Support/FtdImplementation.cpp

@@ -676,6 +676,18 @@ getLoopExitCondition(CFGLoop *loop, std::vector<std::string> *cofactorList,
   return fLoopExit;
 }
 
+// Helper: create a conversion to the desired type. Uses
+// UnrealizedConversionCastOp as a generic no-op conversion placeholder.
+static Value ensureType(PatternRewriter &rewriter, Location loc, Value v,
+                        Type desiredTy) {
+  if (v.getType() == desiredTy)
+    return v;
+  // Use UnrealizedConversionCastOp to produce a Value of `desiredTy`.
+  auto cast = rewriter.create<mlir::UnrealizedConversionCastOp>(
+      loc, ArrayRef<Type>{desiredTy}, v);
+  return cast.getResult(0);
+}
+
 void ftd::addRegenOperandConsumer(PatternRewriter &rewriter,
                                   handshake::FuncOp &funcOp,
                                   Operation *consumerOp, Value operand) {
@@ -726,9 +738,9 @@ void ftd::addRegenOperandConsumer(PatternRewriter &rewriter,
   auto cstType = rewriter.getIntegerType(1);
   auto cstAttr = IntegerAttr::get(cstType, 0);
 
-  auto createRegenMux = [&](CFGLoop *loop) -> handshake::MuxOp {
+  auto createRegenMux = [&](CFGLoop *loop) -> Value {
     rewriter.setInsertionPointToStart(loop->getHeader());
-    regeneratedValue.setType(channelifyType(regeneratedValue.getType()));
+    Location loc = consumerOp->getLoc();
 
     // Determine the loop exit condition:
     // - If the condition spans multiple cofactors, build a BDD and
@@ -738,50 +750,48 @@ void ftd::addRegenOperandConsumer(PatternRewriter &rewriter,
     std::vector<std::string> cofactorList;
     BoolExpression *exitCondition =
         getLoopExitCondition(loop, &cofactorList, loopInfo, bi);
-    if (size(cofactorList) > 1) {
+    if (cofactorList.size() > 1) {
       BDD *bdd = buildBDD(exitCondition, cofactorList);
       conditionValue =
           bddToCircuit(rewriter, bdd, loop->getHeader(), bi, false);
     } else
       conditionValue = loop->getExitingBlock()->getTerminator()->getOperand(0);
 
-    // Create the false constant to feed `init`
-    auto constOp = rewriter.create<handshake::ConstantOp>(consumerOp->getLoc(),
-                                                          cstAttr, startValue);
+    // Determine data channel type for regeneratedValue
+    Type dataChanTy = channelifyType(regeneratedValue.getType());
+
+    auto constOp =
+        rewriter.create<handshake::ConstantOp>(loc, cstAttr, startValue);
     constOp->setAttr(FTD_INIT_MERGE, rewriter.getUnitAttr());
+    Value initConst = constOp.getResult();
 
-    // Create the `init` operation
-    SmallVector<Value> mergeOperands = {constOp.getResult(), conditionValue};
-    auto initMergeOp = rewriter.create<handshake::MergeOp>(consumerOp->getLoc(),
-                                                           mergeOperands);
+    // Ensure condition is in the correct form for merge operands:
+    Type condChanTy = channelifyType(conditionValue.getType());
+    Value condChan = ensureType(rewriter, loc, conditionValue, condChanTy);
+
+    SmallVector<Value, 2> mergeOperands = {initConst, condChan};
+    auto initMergeOp = rewriter.create<handshake::MergeOp>(loc, mergeOperands);
     initMergeOp->setAttr(FTD_INIT_MERGE, rewriter.getUnitAttr());
 
-    // The multiplexer is to be fed by the init block, and takes as inputs the
-    // regenerated value and the result itself (to be set after) it was created.
-    auto selectSignal = initMergeOp.getResult();
-    selectSignal.setType(channelifyType(selectSignal.getType()));
+    Value selectResult = initMergeOp.getResult();
+    Value chanRegVal = ensureType(rewriter, loc, regeneratedValue, dataChanTy);
 
-    SmallVector<Value> muxOperands = {regeneratedValue, regeneratedValue};
-    auto muxOp = rewriter.create<handshake::MuxOp>(regeneratedValue.getLoc(),
-                                                   regeneratedValue.getType(),
-                                                   selectSignal, muxOperands);
+    auto muxOp = rewriter.create<handshake::MuxOp>(
+        loc, dataChanTy, selectResult,
+        SmallVector<Value, 2>{chanRegVal, chanRegVal});
 
     muxOp->setOperand(2, muxOp->getResult(0));
     muxOp->setAttr(FTD_REGEN, rewriter.getUnitAttr());
 
-    return muxOp;
+    return muxOp.getResult();
   };
 
   // For each of the loop, from the outermost to the innermost
-  for (unsigned i = 0; i < numberOfLoops; i++) {
-
-    // If we are in the innermost loop (thus the iterator is at its end)
-    // and the consumer is a loop merge, stop
+  for (unsigned i = 0; i < numberOfLoops; ++i) {
     if (i == numberOfLoops - 1 && consumerOp->hasAttr(NEW_PHI))
       break;
-
-    auto muxOp = createRegenMux(loops[i]);
-    regeneratedValue = muxOp.getResult();
+    Value newReg = createRegenMux(loops[i]);
+    regeneratedValue = newReg;
   }
 
   // Final replace the usage of the operand in the consumer with the output of