3 files changed, 33 insertions, 10 deletions

diff --git a/src/wasm-stack.h b/src/wasm-stack.h
index 09c8589b0..d80618225 100644
--- a/src/wasm-stack.h
+++ b/src/wasm-stack.h
@@ -84,8 +84,9 @@ public:
   BinaryInstWriter(WasmBinaryWriter& parent,
                    BufferWithRandomAccess& o,
                    Function* func,
-                   bool sourceMap)
-    : parent(parent), o(o), func(func), sourceMap(sourceMap) {}
+                   bool sourceMap,
+                   bool DWARF)
+    : parent(parent), o(o), func(func), sourceMap(sourceMap), DWARF(DWARF) {}
 
   void visit(Expression* curr) {
     if (func && !sourceMap) {
@@ -163,6 +164,7 @@ private:
   BufferWithRandomAccess& o;
   Function* func = nullptr;
   bool sourceMap;
+  bool DWARF;
 
   std::vector<Name> breakStack;
 
@@ -824,9 +826,10 @@ public:
   BinaryenIRToBinaryWriter(WasmBinaryWriter& parent,
                            BufferWithRandomAccess& o,
                            Function* func = nullptr,
-                           bool sourceMap = false)
+                           bool sourceMap = false,
+                           bool DWARF = false)
     : BinaryenIRWriter<BinaryenIRToBinaryWriter>(func), parent(parent),
-      writer(parent, o, func, sourceMap), sourceMap(sourceMap) {}
+      writer(parent, o, func, sourceMap, DWARF), sourceMap(sourceMap) {}
 
   void visit(Expression* curr) {
     BinaryenIRWriter<BinaryenIRToBinaryWriter>::visit(curr);
@@ -858,7 +861,7 @@ public:
 private:
   WasmBinaryWriter& parent;
   BinaryInstWriter writer;
-  bool sourceMap = false;
+  bool sourceMap;
 };
 
 // Binaryen IR to stack IR converter
@@ -901,7 +904,8 @@ public:
   StackIRToBinaryWriter(WasmBinaryWriter& parent,
                         BufferWithRandomAccess& o,
                         Function* func)
-    : writer(parent, o, func, false /* sourceMap */), func(func) {}
+    : writer(parent, o, func, false /* sourceMap */, false /* DWARF */),
+      func(func) {}
 
   void write();
 
diff --git a/src/wasm/wasm-binary.cpp b/src/wasm/wasm-binary.cpp
index 8a7f0d744..bb5d420a9 100644
--- a/src/wasm/wasm-binary.cpp
+++ b/src/wasm/wasm-binary.cpp
@@ -307,6 +307,7 @@ void WasmBinaryWriter::writeFunctions() {
   BYN_TRACE("== writeFunctions\n");
   auto sectionStart = startSection(BinaryConsts::Section::Code);
   o << U32LEB(importInfo->getNumDefinedFunctions());
+  bool DWARF = Debug::hasDWARFSections(*getModule());
   ModuleUtils::iterDefinedFunctions(*wasm, [&](Function* func) {
     assert(binaryLocationTrackedExpressionsForFunc.empty());
     size_t sourceMapLocationsSizeAtFunctionStart = sourceMapLocations.size();
@@ -315,12 +316,12 @@ void WasmBinaryWriter::writeFunctions() {
     size_t start = o.size();
     BYN_TRACE("writing" << func->name << std::endl);
     // Emit Stack IR if present, and if we can
-    if (func->stackIR && !sourceMap) {
+    if (func->stackIR && !sourceMap && !DWARF) {
       BYN_TRACE("write Stack IR\n");
       StackIRToBinaryWriter(*this, o, func).write();
     } else {
       BYN_TRACE("write Binaryen IR\n");
-      BinaryenIRToBinaryWriter(*this, o, func, sourceMap).write();
+      BinaryenIRToBinaryWriter(*this, o, func, sourceMap, DWARF).write();
     }
     size_t size = o.size() - start;
     assert(size <= std::numeric_limits<uint32_t>::max());
diff --git a/src/wasm/wasm-stack.cpp b/src/wasm/wasm-stack.cpp
index c6c450cfb..9e3ce2afa 100644
--- a/src/wasm/wasm-stack.cpp
+++ b/src/wasm/wasm-stack.cpp
@@ -16,6 +16,7 @@
 
 #include "wasm-stack.h"
 #include "ir/find_all.h"
+#include "wasm-debug.h"
 
 namespace wasm {
 
@@ -1780,8 +1781,25 @@ void BinaryInstWriter::mapLocalsAndEmitHeader() {
   assert(func && "BinaryInstWriter: function is not set");
   // Map params
   for (Index i = 0; i < func->getNumParams(); i++) {
-    size_t curr = mappedLocals.size();
-    mappedLocals[std::make_pair(i, 0)] = curr;
+    mappedLocals[std::make_pair(i, 0)] = i;
+  }
+  // Normally we map all locals of the same type into a range of adjacent
+  // addresses, which is more compact. However, if we need to keep DWARF valid,
+  // do not do any reordering at all - instead, do a trivial mapping that
+  // keeps everything unmoved.
+  if (DWARF) {
+    FindAll<TupleExtract> extracts(func->body);
+    if (!extracts.list.empty()) {
+      Fatal() << "DWARF + multivalue is not yet complete";
+    }
+    Index varStart = func->getVarIndexBase();
+    Index varEnd = varStart + func->getNumVars();
+    o << U32LEB(func->getNumVars());
+    for (Index i = varStart; i < varEnd; i++) {
+      mappedLocals[std::make_pair(i, 0)] = i;
+      o << U32LEB(1) << binaryType(func->getLocalType(i));
+    }
+    return;
   }
   for (auto type : func->vars) {
     for (auto t : type.expand()) {