[FirParser] Add instance choice selection as circt attribute (#7951)

Add a select option to firtool for instance choice specialization.
The specified select argument is added as an attribute on the `CircuitOp`. The
 attribute is an array of strings, each string specifies the selected
 specialization for an option. The error checking will be done by the
 `SpecializeOptions` pass.

Author: prithayan

include/circt/Dialect/FIRRTL/FIRParser.h

@@ -55,6 +55,7 @@ struct FIRParserOptions {
   std::vector<std::string> enableLayers;
   std::vector<std::string> disableLayers;
   std::optional<LayerSpecialization> defaultLayerSpecialization;
+  std::vector<std::string> selectInstanceChoice;
 };
 
 mlir::OwningOpRef<mlir::ModuleOp> importFIRFile(llvm::SourceMgr &sourceMgr,

include/circt/Dialect/FIRRTL/FIRRTLStructure.td

@@ -36,7 +36,8 @@ def CircuitOp : FIRRTLOp<"circuit",
     DefaultValuedAttr<AnnotationArrayAttr, "{}">:$annotations,
     OptionalAttr<SymbolRefArrayAttr>:$enable_layers,
     OptionalAttr<SymbolRefArrayAttr>:$disable_layers,
-    OptionalAttr<LayerSpecializationAttr>:$default_layer_specialization
+    OptionalAttr<LayerSpecializationAttr>:$default_layer_specialization,
+    OptionalAttr<ArrayAttr>:$select_inst_choice
   );
   let results = (outs);
   let regions = (region SizedRegion<1>:$body);

lib/Dialect/FIRRTL/Import/FIRParser.cpp

@@ -5804,7 +5804,7 @@ ParseResult FIRCircuitParser::parseCircuit(
 
   // Helper to transform a layer name specification of the form `A::B::C` into
   // a SymbolRefAttr.
-  auto parseLayerName = [&](StringRef name) {
+  auto parseLayerName = [&](StringRef name) -> Attribute {
     // Parse the layer name into a SymbolRefAttr.
     auto [head, rest] = name.split(".");
     SmallVector<FlatSymbolRefAttr> nestedRefs;
@@ -5816,19 +5816,31 @@ ParseResult FIRCircuitParser::parseCircuit(
     return SymbolRefAttr::get(getContext(), head, nestedRefs);
   };
 
-  auto parseLayers = [&](const auto &layers) {
-    SmallVector<Attribute> layersAttr;
-    for (const auto &layer : layers)
-      layersAttr.push_back(parseLayerName(layer));
-    if (layersAttr.empty())
+  auto getArrayAttr = [&](ArrayRef<std::string> strArray, auto getAttr) {
+    SmallVector<Attribute> attrArray;
+    auto *context = getContext();
+    for (const auto &str : strArray)
+      attrArray.push_back(getAttr(str));
+    if (attrArray.empty())
       return ArrayAttr();
-    return ArrayAttr::get(getContext(), layersAttr);
+    return ArrayAttr::get(context, attrArray);
   };
 
-  if (auto enableLayers = parseLayers(getConstants().options.enableLayers))
+  if (auto enableLayers =
+          getArrayAttr(getConstants().options.enableLayers, parseLayerName))
     circuit.setEnableLayersAttr(enableLayers);
-  if (auto disableLayers = parseLayers(getConstants().options.disableLayers))
+  if (auto disableLayers =
+          getArrayAttr(getConstants().options.disableLayers, parseLayerName))
     circuit.setDisableLayersAttr(disableLayers);
+
+  auto getStrAttr = [&](StringRef str) -> Attribute {
+    return StringAttr::get(getContext(), str);
+  };
+
+  if (auto selectInstChoice =
+          getArrayAttr(getConstants().options.selectInstanceChoice, getStrAttr))
+    circuit.setSelectInstChoiceAttr(selectInstChoice);
+
   circuit.setDefaultLayerSpecialization(
       getConstants().options.defaultLayerSpecialization);
 

test/firtool/instchoice.fir

@@ -1,6 +1,7 @@
-; RUN: firtool %s --parse-only | FileCheck %s
+; RUN: firtool %s --parse-only --select-instance-choice=Platform=ASIC | FileCheck %s
 
 FIRRTL version 4.1.0
+; CHECK: firrtl.circuit "Foo" attributes {select_inst_choice = ["Platform=ASIC"]} {
 circuit Foo:
   ; CHECK: firrtl.option @Platform
   option Platform:
@@ -21,7 +22,7 @@ circuit Foo:
   public module Foo:
     input clock: Clock
 
-    ; CHECK: %inst_clock = firrtl.instance_choice inst interesting_name @DefaultTarget
+    ; CHECK:      %inst_clock = firrtl.instance_choice inst interesting_name @DefaultTarget
     ; CHECK-SAME: alternatives @Platform {
     ; CHECK-SAME:   @FPGA -> @FPGATarget,
     ; CHECK-SAME:   @ASIC -> @ASICTarget

tools/firtool/firtool.cpp

@@ -275,6 +275,13 @@ static llvm::cl::opt<LayerSpecializationOpt> defaultLayerSpecialization{
                    "Layers are enabled")),
     cl::init(LayerSpecializationOpt::None), cl::cat(mainCategory)};
 
+/// Specify the select option for specializing instance choice. Currently
+/// firtool does not support partially specified instance choice.
+static cl::list<std::string> selectInstanceChoice(
+    "select-instance-choice",
+    cl::desc("Options to specialize instance choice, in option=case format"),
+    cl::MiscFlags::CommaSeparated, cl::cat(mainCategory));
+
 /// Check output stream before writing bytecode to it.
 /// Warn and return true if output is known to be displayed.
 static bool checkBytecodeOutputToConsole(raw_ostream &os) {
@@ -370,6 +377,7 @@ static LogicalResult processBuffer(
     options.scalarizeExtModules = scalarizeExtModules;
     options.enableLayers = enableLayers;
     options.disableLayers = disableLayers;
+    options.selectInstanceChoice = selectInstanceChoice;
 
     switch (defaultLayerSpecialization) {
     case LayerSpecializationOpt::None: