4 files changed, 119 insertions, 2 deletions
diff --git a/src/support/CMakeLists.txt b/src/support/CMakeLists.txt
index c8d7632e4..73025d063 100644
--- a/src/support/CMakeLists.txt
+++ b/src/support/CMakeLists.txt
@@ -3,6 +3,7 @@ SET(support_SOURCES
   bits.cpp
   colors.cpp
   command-line.cpp
+  debug.cpp
   file.cpp
   path.cpp
   safe_integer.cpp
diff --git a/src/support/command-line.cpp b/src/support/command-line.cpp
index be5098677..0986a49ff 100644
--- a/src/support/command-line.cpp
+++ b/src/support/command-line.cpp
@@ -16,6 +16,7 @@
 
 #include "support/command-line.h"
 #include "config.h"
+#include "support/debug.h"
 
 using namespace wasm;
 
@@ -91,8 +92,11 @@ Options::Options(const std::string& command, const std::string& description)
   add("--debug",
       "-d",
       "Print debug information to stderr",
-      Arguments::Zero,
-      [&](Options* o, const std::string& arguments) { debug = true; });
+      Arguments::Optional,
+      [&](Options* o, const std::string& arguments) {
+        debug = true;
+        setDebugEnabled(arguments.c_str());
+      });
 }
 
 Options::~Options() {}
diff --git a/src/support/debug.cpp b/src/support/debug.cpp
new file mode 100644
index 000000000..15b708d5e
--- /dev/null
+++ b/src/support/debug.cpp
@@ -0,0 +1,51 @@
+/*
+ * Copyright 2019 WebAssembly Community Group participants
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "support/debug.h"
+
+#include <cstring>
+#include <set>
+#include <string>
+
+static bool debugEnabled = false;
+static std::set<std::string> debugTypesEnabled;
+
+bool wasm::isDebugEnabled(const char* type) {
+  if (!debugEnabled) {
+    return false;
+  }
+  if (debugTypesEnabled.empty()) {
+    return true;
+  }
+  return debugTypesEnabled.count(type) > 0;
+}
+
+void wasm::setDebugEnabled(const char* types) {
+  debugEnabled = true;
+  // split types on comma and add each string to debugTypesEnabled
+  size_t start = 0;
+  size_t end = strlen(types);
+  while (start < end) {
+    const char* type_end = strchr(types + start, ',');
+    if (type_end == nullptr) {
+      type_end = types + end;
+    }
+    size_t type_size = type_end - types + start;
+    std::string type(types + start, type_size);
+    debugTypesEnabled.insert(type);
+    start += type_size + 1;
+  }
+}
diff --git a/src/support/debug.h b/src/support/debug.h
new file mode 100644
index 000000000..960082d1a
--- /dev/null
+++ b/src/support/debug.h
@@ -0,0 +1,61 @@
+/*
+ * Copyright 2019 WebAssembly Community Group participants
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+// Implements BYN_DEBUG macro similar to llvm's include/llvm/Support/Debug.h,
+// which can include any code, and in addition and printf-file BYN_TRACE.
+//
+// To use these macros you must define DEBUG_TYPE to a C string within your
+// source code which then acts as the name of a channel which can be
+// individually enabled via --debug=<chan>.  Specifying --debug without any
+// argument enables all channels.
+
+#ifndef wasm_support_debug_h
+#define wasm_support_debug_h
+
+#ifndef NDEBUG
+
+namespace wasm {
+bool isDebugEnabled(const char* type);
+void setDebugEnabled(const char* types);
+} // namespace wasm
+
+#define BYN_DEBUG_WITH_TYPE(TYPE, X)                                           \
+  do {                                                                         \
+    if (::wasm::isDebugEnabled(TYPE)) {                                        \
+      X;                                                                       \
+    }                                                                          \
+  } while (false)
+
+#define BYN_TRACE_WITH_TYPE(TYPE, MSG)                                         \
+  BYN_DEBUG_WITH_TYPE(TYPE, std::cerr << MSG);
+
+#else
+
+#define BYN_DEBUG_WITH_TYPE(...)                                               \
+  do {                                                                         \
+  } while (false)
+#define BYN_TRACE_WITH_TYPE(...)                                               \
+  do {                                                                         \
+  } while (false)
+#define isDebugEnabled() (false)
+#define setDebugEnabled()
+
+#endif
+
+#define BYN_DEBUG(X) BYN_DEBUG_WITH_TYPE(DEBUG_TYPE, X)
+#define BYN_TRACE(MSG) BYN_TRACE_WITH_TYPE(DEBUG_TYPE, MSG)
+
+#endif // wasm_support_debug_h