transform: Add a debug flag to dump WGSL

Before and after each transform of a transform::Manager.

This change makes the transforms use the Castable system so we can get the transform name.

Change-Id: I2cf9335960f1aca56f1d32c5ba0d104db4cc46c1
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/54581
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: Ryan Harrison <rharrison@chromium.org>
Reviewed-by: James Price <jrprice@google.com>
Reviewed-by: Antonio Maiorano <amaiorano@google.com>
Commit-Queue: Ben Clayton <bclayton@google.com>

samples/main.cc

@@ -773,6 +773,16 @@ int main(int argc, const char** argv) {
 
   tint::SetInternalCompilerErrorReporter(&TintInternalCompilerErrorReporter);
 
+#if TINT_BUILD_WGSL_WRITER
+  tint::Program::printer = [](const tint::Program* program) {
+    auto result = tint::writer::wgsl::Generate(program, {});
+    if (!result.error.empty()) {
+      return "error: " + result.error;
+    }
+    return result.wgsl;
+  };
+#endif  //  TINT_BUILD_WGSL_WRITER
+
   if (!ParseArgs(args, &options)) {
     std::cerr << "Failed to parse arguments." << std::endl;
     return 1;

src/program.cc

@@ -21,6 +21,15 @@
 #include "src/sem/expression.h"
 
 namespace tint {
+namespace {
+
+std::string DefaultPrinter(const Program*) {
+  return "<no program printer assigned>";
+}
+
+}  // namespace
+
+Program::Printer Program::printer = DefaultPrinter;
 
 Program::Program() = default;
 

src/program.h

@@ -186,6 +186,12 @@ class Program {
   /// @returns a string representation of the node
   std::string str(const ast::Node* node) const;
 
+  /// A function that can be used to print a program
+  using Printer = std::string (*)(const Program*);
+
+  /// The Program printer used for testing and debugging.
+  static Printer printer;
+
  private:
   Program(const Program&) = delete;
 

src/test_main.cc

@@ -13,9 +13,9 @@
 // limitations under the License.
 
 #include "gmock/gmock.h"
+#include "src/program.h"
 #include "src/reader/spirv/parser_impl_test_helper.h"
-#include "src/writer/hlsl/test_helper.h"
-#include "src/writer/msl/test_helper.h"
+#include "src/writer/wgsl/generator.h"
 
 namespace {
 
@@ -48,6 +48,16 @@ struct Flags {
 int main(int argc, char** argv) {
   testing::InitGoogleMock(&argc, argv);
 
+#if TINT_BUILD_WGSL_WRITER
+  tint::Program::printer = [](const tint::Program* program) {
+    auto result = tint::writer::wgsl::Generate(program, {});
+    if (!result.error.empty()) {
+      return "error: " + result.error;
+    }
+    return result.wgsl;
+  };
+#endif  //  TINT_BUILD_WGSL_WRITER
+
   Flags flags;
   if (!flags.parse(argc, argv)) {
     return -1;

src/transform/manager.cc

@@ -14,6 +14,16 @@
 
 #include "src/transform/manager.h"
 
+/// If set to 1 then the transform::Manager will dump the WGSL of the program
+/// before and after each transform. Helpful for debugging bad output.
+#define PRINT_PROGRAM_FOR_EACH_TRANSFORM 0
+
+#if PRINT_PROGRAM_FOR_EACH_TRANSFORM
+#define IF_PRINT_PROGRAM(x) x
+#else  // PRINT_PROGRAM_FOR_EACH_TRANSFORM
+#define IF_PRINT_PROGRAM(x)
+#endif  // PRINT_PROGRAM_FOR_EACH_TRANSFORM
+
 TINT_INSTANTIATE_TYPEINFO(tint::transform::Manager);
 
 namespace tint {
@@ -23,16 +33,39 @@ Manager::Manager() = default;
 Manager::~Manager() = default;
 
 Output Manager::Run(const Program* program, const DataMap& data) {
+#if PRINT_PROGRAM_FOR_EACH_TRANSFORM
+  auto print_program = [&](const char* msg, const Transform* transform) {
+    auto wgsl = Program::printer(program);
+    std::cout << "---------------------------------------------------------"
+              << std::endl;
+    std::cout << "-- " << msg << " " << transform->TypeInfo().name << ":"
+              << std::endl;
+    std::cout << "---------------------------------------------------------"
+              << std::endl;
+    std::cout << wgsl << std::endl;
+    std::cout << "---------------------------------------------------------"
+              << std::endl
+              << std::endl;
+  };
+#endif
+
   Output out;
   if (!transforms_.empty()) {
-    for (auto& transform : transforms_) {
+    for (const auto& transform : transforms_) {
+      IF_PRINT_PROGRAM(print_program("Input to", transform.get()));
+
       auto res = transform->Run(program, data);
       out.program = std::move(res.program);
       out.data.Add(std::move(res.data));
-      if (!out.program.IsValid()) {
+      program = &out.program;
+      if (!program->IsValid()) {
+        IF_PRINT_PROGRAM(print_program("Invalid output of", transform.get()));
         return out;
       }
-      program = &out.program;
+
+      if (transform == transforms_.back()) {
+        IF_PRINT_PROGRAM(print_program("Output of", transform.get()));
+      }
     }
   } else {
     out.program = program->Clone();