Binary format code section offset tracking (#2515)

Optionally track the binary format code section offsets,
that is, when loading a binary, remember where each IR
node was read from. This is necessary for DWARF
debug info, as these are the offsets DWARF refers to.

(Note that eventually we may want to do something
else, like first read the DWARF and only then add
debug info annotations into the IR in a more LLVM-like
manner, but this is more straightforward and should be
enough to update debug lines and ranges).

This tracking adds noticeable overhead - every single
IR node adds an entry in a map - so avoid it unless
actually necessary. Specifically, if the user passes in
-g and there are actually DWARF sections in the
binary, and we are not about to remove those sections,
then we need it.

Print binary format code section offsets in text, when
printing with -g. This will help debug and test dwarf
support. It looks like

;; code offset: 0x7

as an annotation right before each node.

Also add support for -g in wasm-opt tests (unlike
a pass, it has just one - as a prefix).

Helps #2400

3 files changed, 22 insertions, 1 deletions

diff --git a/src/tools/wasm-emscripten-finalize.cpp b/src/tools/wasm-emscripten-finalize.cpp
index b45b61b8f..a32a265cd 100644
--- a/src/tools/wasm-emscripten-finalize.cpp
+++ b/src/tools/wasm-emscripten-finalize.cpp
@@ -49,6 +49,7 @@ int main(int argc, const char* argv[]) {
   std::string dataSegmentFile;
   bool emitBinary = true;
   bool debugInfo = false;
+  bool DWARF = false;
   bool isSideModule = false;
   bool legalizeJavaScriptFFI = true;
   bool checkStackOverflow = false;
@@ -71,6 +72,11 @@ int main(int argc, const char* argv[]) {
          "Emit names section in wasm binary (or full debuginfo in wast)",
          Options::Arguments::Zero,
          [&debugInfo](Options*, const std::string&) { debugInfo = true; })
+    .add("--dwarf",
+         "",
+         "Update DWARF debug info",
+         Options::Arguments::Zero,
+         [&DWARF](Options*, const std::string&) { DWARF = true; })
     .add("--emit-text",
          "-S",
          "Emit text instead of binary for the output file",
@@ -164,6 +170,7 @@ int main(int argc, const char* argv[]) {
 
   Module wasm;
   ModuleReader reader;
+  reader.setDWARF(DWARF);
   try {
     reader.read(infile, wasm, inputSourceMapFilename);
   } catch (ParseException& p) {
diff --git a/src/tools/wasm-metadce.cpp b/src/tools/wasm-metadce.cpp
index 7d91b3e6f..3b889b984 100644
--- a/src/tools/wasm-metadce.cpp
+++ b/src/tools/wasm-metadce.cpp
@@ -498,6 +498,7 @@ int main(int argc, const char* argv[]) {
       std::cerr << "reading...\n";
     }
     ModuleReader reader;
+    reader.setDWARF(debugInfo);
     try {
       reader.read(options.extra["infile"], wasm);
     } catch (ParseException& p) {
diff --git a/src/tools/wasm-opt.cpp b/src/tools/wasm-opt.cpp
index 7b04f5449..2fd78a3da 100644
--- a/src/tools/wasm-opt.cpp
+++ b/src/tools/wasm-opt.cpp
@@ -43,7 +43,7 @@
 using namespace wasm;
 
 // runs a command and returns its output TODO: portability, return code checking
-std::string runCommand(std::string command) {
+static std::string runCommand(std::string command) {
 #ifdef __linux__
   std::string output;
   const int MAX_BUFFER = 1024;
@@ -59,6 +59,15 @@ std::string runCommand(std::string command) {
 #endif
 }
 
+static bool willRemoveDebugInfo(const std::vector<std::string>& passes) {
+  for (auto& pass : passes) {
+    if (pass == "strip" || pass == "strip-debug" || pass == "strip-dwarf") {
+      return true;
+    }
+  }
+  return false;
+}
+
 //
 // main
 //
@@ -210,6 +219,10 @@ int main(int argc, const char* argv[]) {
 
   if (!translateToFuzz) {
     ModuleReader reader;
+    // Enable DWARF parsing if we were asked for debug info, and were not
+    // asked to remove it.
+    reader.setDWARF(options.passOptions.debugInfo &&
+                    !willRemoveDebugInfo(options.passes));
     try {
       reader.read(options.extra["infile"], wasm, inputSourceMapFilename);
     } catch (ParseException& p) {