Pass options (#788)

* add PassOptions structure, and use it for new -Os param to wasm-opt

5 files changed, 59 insertions, 11 deletions

diff --git a/src/asm2wasm.h b/src/asm2wasm.h
index 836b8044a..5df5af271 100644
--- a/src/asm2wasm.h
+++ b/src/asm2wasm.h
@@ -653,6 +653,7 @@ void Asm2WasmBuilder::processAsm(Ref ast) {
       if (body[i][0] == DEFUN) numFunctions++;
     }
     optimizingBuilder = make_unique<OptimizingIncrementalModuleBuilder>(&wasm, numFunctions, [&](PassRunner& passRunner) {
+      passRunner.options.setDefaultOptimizationOptions();
       if (debug) {
         passRunner.setDebug(true);
         passRunner.setValidateGlobally(false);
diff --git a/src/pass.h b/src/pass.h
index 35065b0a3..334f46ac8 100644
--- a/src/pass.h
+++ b/src/pass.h
@@ -55,6 +55,20 @@ private:
   std::map<std::string, PassInfo> passInfos;
 };
 
+struct PassOptions {
+  bool debug = false; // run passes in debug mode, doing extra validation and timing checks
+  bool validateGlobally = false; // when validating validate globally and not just locally
+  int optimizeLevel = 0; // 0, 1, 2 correspond to -O0, -O1, -O2, etc.
+  int shrinkLevel = 0;   // 0, 1, 2 correspond to -O0, -Os, -Oz
+  bool ignoreImplicitTraps = false; // optimize assuming things like div by 0, bad load/store, will not trap
+
+  void setDefaultOptimizationOptions() {
+    optimizeLevel = 2;
+    shrinkLevel = 1;
+    ignoreImplicitTraps = true;
+  }
+};
+
 //
 // Runs a set of passes, in order
 //
@@ -62,17 +76,17 @@ struct PassRunner {
   Module* wasm;
   MixedArena* allocator;
   std::vector<Pass*> passes;
-  bool debug = false;
-  bool validateGlobally = false;
+  PassOptions options;
 
   PassRunner(Module* wasm) : wasm(wasm), allocator(&wasm->allocator) {}
+  PassRunner(Module* wasm, PassOptions options) : wasm(wasm), allocator(&wasm->allocator), options(options) {}
 
   void setDebug(bool debug_) {
-    debug = debug_;
-    validateGlobally = debug; // validate everything by default if debugging
+    options.debug = debug_;
+    options.validateGlobally = debug_; // validate everything by default if debugging
   }
   void setValidateGlobally(bool validate) {
-    validateGlobally = validate;
+    options.validateGlobally = validate;
   }
 
   void add(std::string passName) {
@@ -173,15 +187,28 @@ protected:
 //
 template <typename WalkerType>
 class WalkerPass : public Pass, public WalkerType {
+  PassRunner *runner;
+
 public:
   void run(PassRunner* runner, Module* module) override {
+    setPassRunner(runner);
+    WalkerType::setModule(module);
     WalkerType::walkModule(module);
   }
 
   void runFunction(PassRunner* runner, Module* module, Function* func) override {
+    setPassRunner(runner);
     WalkerType::setModule(module);
     WalkerType::walkFunction(func);
   }
+
+  PassRunner* getPassRunner() {
+    return runner;
+  }
+
+  void setPassRunner(PassRunner* runner_) {
+    runner = runner_;
+  }
 };
 
 // Standard passes. All passes in /passes/ are runnable from the shell,
diff --git a/src/passes/RemoveUnusedBrs.cpp b/src/passes/RemoveUnusedBrs.cpp
index d1de0086a..328ca275b 100644
--- a/src/passes/RemoveUnusedBrs.cpp
+++ b/src/passes/RemoveUnusedBrs.cpp
@@ -423,8 +423,13 @@ struct RemoveUnusedBrs : public WalkerPass<PostWalker<RemoveUnusedBrs, Visitor<R
           }
         }
       }
+
+      bool selectify;
+
       void visitIf(If* curr) {
         // we may have simplified ifs enough to turn them into selects
+        // this is helpful for code size, but can be a tradeoff with performance as we run both code paths
+        if (!selectify) return;
         if (curr->ifFalse && isConcreteWasmType(curr->ifTrue->type) && isConcreteWasmType(curr->ifFalse->type)) {
           // if with else, consider turning it into a select if there is no control flow
           // TODO: estimate cost
@@ -448,6 +453,7 @@ struct RemoveUnusedBrs : public WalkerPass<PostWalker<RemoveUnusedBrs, Visitor<R
     };
     FinalOptimizer finalOptimizer;
     finalOptimizer.setModule(getModule());
+    finalOptimizer.selectify = getPassRunner()->options.shrinkLevel > 0;
     finalOptimizer.walkFunction(func);
   }
 };
diff --git a/src/passes/pass.cpp b/src/passes/pass.cpp
index 284bb1642..3ae0819ea 100644
--- a/src/passes/pass.cpp
+++ b/src/passes/pass.cpp
@@ -124,7 +124,7 @@ void PassRunner::addDefaultGlobalOptimizationPasses() {
 }
 
 void PassRunner::run() {
-  if (debug) {
+  if (options.debug) {
     // for debug logging purposes, run each pass in full before running the other
     auto totalTime = std::chrono::duration<double>(0);
     size_t padding = 0;
@@ -159,7 +159,7 @@ void PassRunner::run() {
       totalTime += diff;
       // validate, ignoring the time
       std::cerr << "[PassRunner]   (validating)\n";
-      if (!WasmValidator().validate(*wasm, false, validateGlobally)) {
+      if (!WasmValidator().validate(*wasm, false, options.validateGlobally)) {
         if (passDebug) {
           std::cerr << "Last pass (" << pass->name << ") broke validation. Here is the module before: \n" << moduleBefore.str() << "\n";
         } else {
@@ -171,7 +171,7 @@ void PassRunner::run() {
     std::cerr << "[PassRunner] passes took " << totalTime.count() << " seconds." << std::endl;
     // validate
     std::cerr << "[PassRunner] (final validation)\n";
-    if (!WasmValidator().validate(*wasm, false, validateGlobally)) {
+    if (!WasmValidator().validate(*wasm, false, options.validateGlobally)) {
       std::cerr << "final module does not validate\n";
       abort();
     }
@@ -222,7 +222,7 @@ void PassRunner::run() {
 }
 
 void PassRunner::runFunction(Function* func) {
-  if (debug) {
+  if (options.debug) {
     std::cerr << "[PassRunner] running passes on function " << func->name << std::endl;
   }
   for (auto* pass : passes) {
diff --git a/src/tools/wasm-opt.cpp b/src/tools/wasm-opt.cpp
index d6e7d3bd6..aad87726b 100644
--- a/src/tools/wasm-opt.cpp
+++ b/src/tools/wasm-opt.cpp
@@ -37,6 +37,7 @@ using namespace wasm;
 int main(int argc, const char* argv[]) {
   Name entry;
   std::vector<std::string> passes;
+  PassOptions passOptions;
 
   Options options("wasm-opt", "Optimize .wast files");
   options
@@ -48,9 +49,22 @@ int main(int argc, const char* argv[]) {
            })
       .add("", "-O", "execute default optimization passes",
            Options::Arguments::Zero,
-           [&passes](Options*, const std::string&) {
+           [&passes, &passOptions](Options*, const std::string&) {
+             passOptions.setDefaultOptimizationOptions();
              passes.push_back("O");
            })
+      .add("", "-Os", "execute default optimization passes, focusing on code size",
+           Options::Arguments::Zero,
+           [&passes, &passOptions](Options*, const std::string&) {
+             passOptions.setDefaultOptimizationOptions();
+             passOptions.shrinkLevel = 1;
+             passes.push_back("O");
+           })
+      .add("--shrink-level", "-s", "How much to focus on shrinking code size",
+           Options::Arguments::One,
+           [&passOptions](Options* o, const std::string& argument) {
+             passOptions.shrinkLevel = atoi(argument.c_str());
+           })
       .add_positional("INFILE", Options::Arguments::One,
                       [](Options* o, const std::string& argument) {
                         o->extra["infile"] = argument;
@@ -84,7 +98,7 @@ int main(int argc, const char* argv[]) {
 
   if (passes.size() > 0) {
     if (options.debug) std::cerr << "running passes...\n";
-    PassRunner passRunner(&wasm);
+    PassRunner passRunner(&wasm, passOptions);
     if (options.debug) passRunner.setDebug(true);
     for (auto& passName : passes) {
       if (passName == "O") {