2 files changed, 51 insertions, 28 deletions

diff --git a/src/passes/Metrics.cpp b/src/passes/Metrics.cpp
index 5b5e1c8ab..8cbf96db5 100644
--- a/src/passes/Metrics.cpp
+++ b/src/passes/Metrics.cpp
@@ -22,19 +22,21 @@
 #include <wasm-binary.h>
 #include <ir/module-utils.h>
 
+using namespace std;
+
 namespace wasm {
 
-using namespace std;
+typedef map<const char *, int> Counts;
+
+static Counts lastCounts;
 
 // Prints metrics between optimization passes.
 struct Metrics : public WalkerPass<PostWalker<Metrics, UnifiedExpressionVisitor<Metrics>>> {
   bool byFunction;
 
-  Metrics(bool byFunction) : byFunction(byFunction) {}
-
-  static Metrics *lastMetricsPass;
+  Counts counts;
 
-  map<const char *, int> counts;
+  Metrics(bool byFunction) : byFunction(byFunction) {}
 
   void visitExpression(Expression* curr) {
     auto name = getExpressionName(curr);
@@ -130,7 +132,7 @@ struct Metrics : public WalkerPass<PostWalker<Metrics, UnifiedExpressionVisitor<
         printCounts(std::string("start: ") + module->start.str);
       }
       // can't compare detailed info between passes yet
-      lastMetricsPass = nullptr;
+      lastCounts.clear();
     } else {
       // add function info
       size_t vars = 0;
@@ -142,7 +144,7 @@ struct Metrics : public WalkerPass<PostWalker<Metrics, UnifiedExpressionVisitor<
       // print
       printCounts("total");
       // compare to next time
-      lastMetricsPass = this;
+      lastCounts = counts;
     }
   }
 
@@ -170,20 +172,18 @@ struct Metrics : public WalkerPass<PostWalker<Metrics, UnifiedExpressionVisitor<
       if (value == 0) continue;
       o << " " << left << setw(15) << key << ": " << setw(8)
         << value;
-      if (lastMetricsPass) {
-        if (lastMetricsPass->counts.count(key)) {
-          int before = lastMetricsPass->counts[key];
-          int after = value;
-          if (after - before) {
-            if (after > before) {
-              Colors::red(o);
-            } else {
-              Colors::green(o);
-            }
-            o << right << setw(8);
-            o << showpos << after - before << noshowpos;
-            Colors::normal(o);
+      if (lastCounts.count(key)) {
+        int before = lastCounts[key];
+        int after = value;
+        if (after - before) {
+          if (after > before) {
+            Colors::red(o);
+          } else {
+            Colors::green(o);
           }
+          o << right << setw(8);
+          o << showpos << after - before << noshowpos;
+          Colors::normal(o);
         }
       }
       o << "\n";
@@ -199,6 +199,4 @@ Pass *createFunctionMetricsPass() {
   return new Metrics(true);
 }
 
-Metrics *Metrics::lastMetricsPass;
-
 } // namespace wasm
diff --git a/src/tools/wasm-opt.cpp b/src/tools/wasm-opt.cpp
index a82dc4a2f..7d7d44b2b 100644
--- a/src/tools/wasm-opt.cpp
+++ b/src/tools/wasm-opt.cpp
@@ -64,6 +64,7 @@ int main(int argc, const char* argv[]) {
   Name entry;
   bool emitBinary = true;
   bool debugInfo = false;
+  bool converge = false;
   bool fuzzExec = false;
   bool fuzzBinary = false;
   std::string extraFuzzCommand;
@@ -86,6 +87,9 @@ int main(int argc, const char* argv[]) {
       .add("--debuginfo", "-g", "Emit names section and debug info",
            Options::Arguments::Zero,
            [&](Options *o, const std::string& arguments) { debugInfo = true; })
+      .add("--converge", "-c", "Run passes to convergence, continuing while binary size decreases",
+           Options::Arguments::Zero,
+           [&](Options *o, const std::string& arguments) { converge = true; })
       .add("--fuzz-exec", "-fe", "Execute functions before and after optimization, helping fuzzing find bugs",
            Options::Arguments::Zero,
            [&](Options *o, const std::string& arguments) { fuzzExec = true; })
@@ -211,13 +215,34 @@ int main(int argc, const char* argv[]) {
 
   if (options.runningPasses()) {
     if (options.debug) std::cerr << "running passes...\n";
-    options.runPasses(*curr);
-    if (options.passOptions.validate) {
-      bool valid = WasmValidator().validate(*curr, features);
-      if (!valid) {
-        WasmPrinter::printModule(&*curr);
+    auto runPasses = [&]() {
+      options.runPasses(*curr);
+      if (options.passOptions.validate) {
+        bool valid = WasmValidator().validate(*curr, features);
+        if (!valid) {
+          WasmPrinter::printModule(&*curr);
+        }
+        assert(valid);
+      }
+    };
+    runPasses();
+    if (converge) {
+      // Keep on running passes to convergence, defined as binary
+      // size no longer decreasing.
+      auto getSize = [&]() {
+        BufferWithRandomAccess buffer;
+        WasmBinaryWriter writer(curr, buffer);
+        writer.write();
+        return buffer.size();
+      };
+      auto lastSize = getSize();
+      while (1) {
+        if (options.debug) std::cerr << "running iteration for convergence (" << lastSize << ")...\n";
+        runPasses();
+        auto currSize = getSize();
+        if (currSize >= lastSize) break;
+        lastSize = currSize;
       }
-      assert(valid);
     }
   }