tablegen: add -emit-comments option

This is helpful for debugging the tablegen tool itself.

Author: nhaehnle

include/llvm-dialects/TableGen/Common.h

@@ -22,4 +22,6 @@ namespace llvm_dialects {
 
 void emitHeader(llvm::raw_ostream& out);
 
+bool shouldEmitComments();
+
 } // namespace llvm_dialects

include/llvm-dialects/TableGen/Constraints.h

@@ -78,6 +78,9 @@ class ConstraintSystem {
   bool addConstraint(llvm::raw_ostream &errs, llvm::Init *init, Variable *self);
   void merge(ConstraintSystem &&rhs);
 
+  void print(llvm::raw_ostream &out, llvm::StringRef prefix) const;
+  void dump() const;
+
 private:
   bool addConstraintImpl(llvm::raw_ostream &errs, llvm::Init *init,
                          Variable *self);
@@ -103,6 +106,8 @@ class Constraint {
 
   virtual ~Constraint() = default;
 
+  virtual void print(llvm::raw_ostream &out, llvm::StringRef prefix) const = 0;
+
   Kind getKind() const { return m_kind; }
   llvm::Init *getInit() const { return m_init; }
   Variable *getSelf() const { return m_self; }
@@ -113,6 +118,7 @@ class Constraint {
 protected:
   Constraint(Kind kind) : m_kind(kind) {}
 
+  void printVariables(llvm::raw_ostream &out) const;
   void addVariable(Variable *variable);
 
 private:
@@ -140,6 +146,8 @@ class Apply : public Constraint {
     return c->getKind() == Kind::Apply;
   }
 
+  void print(llvm::raw_ostream &out, llvm::StringRef prefix) const override;
+
   Predicate *getPredicate() const { return m_predicate; }
   llvm::ArrayRef<Variable *> arguments() const { return m_arguments; }
 
@@ -159,6 +167,8 @@ class LogicOr : public Constraint {
 
   static bool classof(const Constraint *c) { return c->getKind() == Kind::Or; }
 
+  void print(llvm::raw_ostream &out, llvm::StringRef prefix) const override;
+
   llvm::ArrayRef<ConstraintSystem> branches() const { return m_branches; }
   llvm::ArrayRef<llvm::Init *> branchInits() const { return m_branchInits; }
 

include/llvm-dialects/TableGen/Evaluator.h

@@ -131,8 +131,6 @@ class Evaluator {
   /// detected.
   bool check();
 
-  void setEmitComments(bool comments) { m_comments = comments; }
-
 private:
   void checkErrors();
   std::string evaluateImpl(Variable *variable);

lib/TableGen/Common.cpp

@@ -16,9 +16,18 @@
 
 #include "llvm-dialects/TableGen/Common.h"
 
+#include "llvm/Support/CommandLine.h"
+
 using namespace llvm_dialects;
 using namespace llvm;
 
+static cl::opt<bool>
+    g_emitComments("emit-comments",
+                   cl::desc("emit debug comments in generated source files"),
+                   cl::Hidden, cl::init(false));
+
 void llvm_dialects::emitHeader(raw_ostream& out) {
   out << "// DO NOT EDIT! This file is automatically generated by llvm-dialects-tblgen.\n\n";
 }
+
+bool llvm_dialects::shouldEmitComments() { return g_emitComments; }

lib/TableGen/Constraints.cpp

@@ -21,6 +21,7 @@
 #include "llvm-dialects/TableGen/Format.h"
 #include "llvm-dialects/TableGen/Predicates.h"
 
+#include "llvm/Support/Debug.h"
 #include "llvm/TableGen/Record.h"
 
 using namespace llvm;
@@ -60,6 +61,16 @@ Variable *Scope::createVariable(StringRef name, Predicate *predicate) {
   return variable;
 }
 
+void ConstraintSystem::print(raw_ostream &out, StringRef prefix) const {
+  for (const auto &constraintPtr : m_constraints)
+    constraintPtr->print(out, prefix);
+}
+
+void ConstraintSystem::dump() const {
+  dbgs() << "Constraint system:\n";
+  print(dbgs(), "  ");
+}
+
 bool ConstraintSystem::addConstraint(raw_ostream &errs, Init *init,
                                      Variable *self) {
   if (!addConstraintImpl(errs, init, self)) {
@@ -232,11 +243,48 @@ std::string Constraint::toString() const {
   return (Twine(m_init->getAsString()) + ":" + m_self->toString()).str();
 }
 
+void Constraint::printVariables(raw_ostream &out) const {
+  bool isFirst = true;
+  for (const Variable *var : m_variables) {
+    if (!isFirst)
+      out << ", ";
+    out << var->toString();
+    isFirst = false;
+  }
+}
+
 void Constraint::addVariable(Variable *variable) {
   if (!llvm::is_contained(m_variables, variable))
     m_variables.push_back(variable);
 }
 
+void Apply::print(raw_ostream &out, StringRef prefix) const {
+  out << prefix << "apply " << m_predicate->getInit()->getAsString() << ": ";
+  bool isFirst = true;
+  for (Variable *var : m_arguments) {
+    if (!isFirst)
+      out << ", ";
+    if (var)
+      out << var->toString();
+    else
+      out << "(null)";
+    isFirst = false;
+  }
+  out << '\n';
+
+  out << prefix << "  free variables: ";
+  printVariables(out);
+  out << '\n';
+}
+
+void LogicOr::print(raw_ostream &out, StringRef prefix) const {
+  out << prefix << "or, free variables: ";
+  printVariables(out);
+  out << '\n';
+  for (const auto &branch : m_branches)
+    branch.print(out, (Twine(prefix) + "  ").str());
+}
+
 MetaType *MetaType::type() {
   static MetaType typeMetaType(Kind::Type);
   return &typeMetaType;

lib/TableGen/Evaluator.cpp

@@ -16,6 +16,7 @@
 
 #include "llvm-dialects/TableGen/Evaluator.h"
 
+#include "llvm-dialects/TableGen/Common.h"
 #include "llvm-dialects/TableGen/Constraints.h"
 #include "llvm-dialects/TableGen/Format.h"
 #include "llvm-dialects/TableGen/Predicates.h"
@@ -204,6 +205,8 @@ Evaluator::Evaluator(SymbolTable &symbols, Assignment &assignment,
     if (!assignment.lookup(variable).empty())
       m_planner.setKnown(variable);
   }
+
+  m_comments = shouldEmitComments();
 }
 
 Evaluator::~Evaluator() { checkErrors(); }
@@ -279,7 +282,6 @@ std::string Evaluator::evaluateImpl(Variable *goal) {
     SymbolScope symbolScope{&m_symbols};
     Evaluator nested(*m_symbols, nestedAssignment, tg->getSystem(), m_out,
                      m_fmt);
-    nested.setEmitComments(m_comments);
     std::string value = nested.evaluate(tg->variables()[plan->argumentIndex]);
     if (value.empty()) {
       m_errs << "TgPredicate expression evaluation failed\n";
@@ -304,6 +306,11 @@ std::string Evaluator::evaluateImpl(Variable *goal) {
 }
 
 bool Evaluator::check() {
+  if (m_comments) {
+    m_out << "// Checking the constraint system:\n";
+    m_system.print(m_out, "//   ");
+  }
+
   SmallVector<bool> checkedConstraints;
   checkedConstraints.resize(m_system.m_constraints.size(), false);