[MooreToCore] Lower moore.net to llhd.sig (#7652)

Lower `moore.net` operations to the corresponding `llhd.sig`, similar to
how `moore.variable` is lowered. This currently only makes sense for
"wire" nets, since it's not yet clear how all the other net types map to
LLHD.

lib/Conversion/MooreToCore/MooreToCore.cpp

@@ -496,6 +496,44 @@ struct VariableOpConversion : public OpConversionPattern<VariableOp> {
   }
 };
 
+struct NetOpConversion : public OpConversionPattern<NetOp> {
+  using OpConversionPattern::OpConversionPattern;
+
+  LogicalResult
+  matchAndRewrite(NetOp op, OpAdaptor adaptor,
+                  ConversionPatternRewriter &rewriter) const override {
+    auto loc = op.getLoc();
+    if (op.getKind() != NetKind::Wire)
+      return rewriter.notifyMatchFailure(loc, "only wire nets supported");
+
+    auto resultType = typeConverter->convertType(op.getResult().getType());
+    if (!resultType)
+      return rewriter.notifyMatchFailure(loc, "invalid net type");
+
+    // TODO: Once the core dialects support four-valued integers, this code
+    // will additionally need to generate an all-X value for four-valued nets.
+    auto elementType = cast<hw::InOutType>(resultType).getElementType();
+    int64_t width = hw::getBitWidth(elementType);
+    if (width == -1)
+      return failure();
+    auto constZero = rewriter.create<hw::ConstantOp>(loc, APInt(width, 0));
+    auto init =
+        rewriter.createOrFold<hw::BitcastOp>(loc, elementType, constZero);
+
+    auto signal = rewriter.replaceOpWithNewOp<llhd::SignalOp>(
+        op, resultType, op.getNameAttr(), init);
+
+    if (auto assignedValue = adaptor.getAssignment()) {
+      auto timeAttr = llhd::TimeAttr::get(resultType.getContext(), 0U,
+                                          llvm::StringRef("ns"), 0, 1);
+      auto time = rewriter.create<llhd::ConstantTimeOp>(loc, timeAttr);
+      rewriter.create<llhd::DrvOp>(loc, signal, assignedValue, time, Value{});
+    }
+
+    return success();
+  }
+};
+
 //===----------------------------------------------------------------------===//
 // Expression Conversion
 //===----------------------------------------------------------------------===//
@@ -1342,6 +1380,7 @@ static void populateOpConversion(RewritePatternSet &patterns,
   patterns.add<
     // Patterns of declaration operations.
     VariableOpConversion,
+    NetOpConversion,
 
     // Patterns of miscellaneous operations.
     ConstantOpConv, ConcatOpConversion, ReplicateOpConversion,

test/Conversion/MooreToCore/basic.mlir

@@ -362,6 +362,7 @@ moore.module private @SubModule_0(in %a : !moore.l1, in %b : !moore.l1, out c :
   moore.output %0 : !moore.l1
 }
 
+// CHECK-LABEL: hw.module @Variable
 moore.module @Variable() {
   // CHECK: [[TMP0:%.+]] = hw.constant 0 : i32
   // CHECK: %a = llhd.sig [[TMP0]] : i32
@@ -395,6 +396,28 @@ moore.module @Variable() {
   moore.output
 }
 
+// CHECK-LABEL: hw.module @Net
+moore.module @Net() {
+  // CHECK: [[TMP:%.+]] = hw.constant 0 : i32
+  // CHECK: %a = llhd.sig [[TMP]] : i32
+  %a = moore.net wire : <i32>
+
+  // CHECK: [[PRB:%.+]] = llhd.prb %a : !hw.inout<i32>
+  %0 = moore.read %a : <i32>
+
+  // CHECK: [[TMP:%.+]] = hw.constant 0 : i32
+  // CHECK: %b = llhd.sig [[TMP]] : i32
+  // CHECK: [[TIME:%.+]] = llhd.constant_time <0ns, 0d, 1e>
+  // CHECK: llhd.drv %b, [[PRB]] after [[TIME]] : !hw.inout<i32>
+  %b = moore.net wire %0 : <i32>
+
+  // CHECK: [[TMP:%.+]] = hw.constant 10 : i32
+  %3 = moore.constant 10 : i32
+  // CHECK: [[TIME:%.+]] = llhd.constant_time <0ns, 0d, 1e>
+  // CHECK: llhd.drv %a, [[TMP]] after [[TIME]] : !hw.inout<i32>
+  moore.assign %a, %3 : i32
+}
+
 // CHECK-LABEL: hw.module @Struct
 moore.module @Struct(in %a : !moore.i32, in %b : !moore.i32, in %arg0 : !moore.struct<{exp_bits: i32, man_bits: i32}>, in %arg1 : !moore.ref<!moore.struct<{exp_bits: i32, man_bits: i32}>>, out a : !moore.i32, out b : !moore.struct<{exp_bits: i32, man_bits: i32}>, out c : !moore.struct<{exp_bits: i32, man_bits: i32}>) {
   // CHECK: hw.struct_extract %arg0["exp_bits"] : !hw.struct<exp_bits: i32, man_bits: i32>