add simple example

8 files changed, 86 insertions, 11 deletions

diff --git a/README.md b/README.md
index 4483a1a22..d8a059720 100644
--- a/README.md
+++ b/README.md
@@ -6,7 +6,9 @@ Binaryen is a C++ library for processing WebAssembly. It can:
  * **Compile** asm.js to WebAssembly, which together with [Emscripten](http://emscripten.org), gives you a complete compiler toolchain from C and C++ to WebAssembly.
  * **Polyfill** WebAssembly, by running it in the interpreter compiled to JavaScript, if the browser does not yet have native support.
 
-To provide those capabilities, Binaryen has a simple and flexible API for representing and processing WebAssembly modules. The interpreter, validator, pretty-printer, etc. are built on that foundation. (TODO: an example of writing a new processing pass.)
+To provide those capabilities, Binaryen has a simple and flexible API for representing and processing WebAssembly modules. The interpreter, validator, pretty-printer, etc. are built on that foundation. The core of this is in [wasm.h](https://github.com/WebAssembly/binaryen/blob/master/src/wasm.h), which contains both classes that define a WebAssembly module, and tools to process those.
+
+(TODO: an example of writing a new processing pass.)
 
 ## Tools
 
diff --git a/build.sh b/build.sh
index 9794de42f..db3033cdc 100755
--- a/build.sh
+++ b/build.sh
@@ -1,8 +1,8 @@
 echo "building binaryen shell"
-g++ -O2 -std=c++11 src/binaryen-shell.cpp -g -o bin/binaryen-shell -Isrc/emscripten-optimizer
+g++ -O2 -std=c++11 src/binaryen-shell.cpp -g -o bin/binaryen-shell
 echo "building asm2wasm"
-g++ -O2 -std=c++11 src/asm2wasm-main.cpp src/emscripten-optimizer/parser.cpp src/emscripten-optimizer/simple_ast.cpp src/emscripten-optimizer/optimizer-shared.cpp -g -o bin/asm2wasm -Isrc/emscripten-optimizer
+g++ -O2 -std=c++11 src/asm2wasm-main.cpp src/emscripten-optimizer/parser.cpp src/emscripten-optimizer/simple_ast.cpp src/emscripten-optimizer/optimizer-shared.cpp -g -o bin/asm2wasm
 echo "building interpreter/js"
-em++ -std=c++11 src/wasm-js.cpp src/emscripten-optimizer/parser.cpp src/emscripten-optimizer/simple_ast.cpp src/emscripten-optimizer/optimizer-shared.cpp -o bin/wasm.js -s MODULARIZE=1 -s 'EXPORT_NAME="WasmJS"' --memory-init-file 0 -s DEMANGLE_SUPPORT=1 -O3 -profiling -s TOTAL_MEMORY=67108864 -s SAFE_HEAP=1 -s ASSERTIONS=1  -Isrc/emscripten-optimizer #-DWASM_JS_DEBUG #-DWASM_INTERPRETER_DEBUG
+em++ -std=c++11 src/wasm-js.cpp src/emscripten-optimizer/parser.cpp src/emscripten-optimizer/simple_ast.cpp src/emscripten-optimizer/optimizer-shared.cpp -o bin/wasm.js -s MODULARIZE=1 -s 'EXPORT_NAME="WasmJS"' --memory-init-file 0 -s DEMANGLE_SUPPORT=1 -O3 -profiling -s TOTAL_MEMORY=67108864 -s SAFE_HEAP=1 -s ASSERTIONS=1 #-DWASM_JS_DEBUG #-DWASM_INTERPRETER_DEBUG
 cat src/js/post.js >> bin/wasm.js
 
diff --git a/check.py b/check.py
index 6717fccb2..c4bce02aa 100755
--- a/check.py
+++ b/check.py
@@ -77,6 +77,14 @@ for t in tests:
     if actual != expected:
       fail(actual, expected)
 
+print '\n[ checking example testcases... ]\n'
+
+subprocess.check_call(['g++', '-std=c++11', os.path.join('test', 'example', 'find_div0s.cpp'), '-Isrc', '-g'])
+actual = subprocess.Popen(['./a.out'], stdout=subprocess.PIPE).communicate()[0]
+expected = open(os.path.join('test', 'example', 'find_div0s.txt')).read()
+if actual != expected:
+  fail(actual, expected)
+
 print '\n[ checking binaryen-shell spec testcases... ]\n'
 
 if len(requested) == 0:
diff --git a/src/asm2wasm.h b/src/asm2wasm.h
index 61c67c5d8..ce5b669d1 100644
--- a/src/asm2wasm.h
+++ b/src/asm2wasm.h
@@ -5,7 +5,7 @@
 //
 
 #include "wasm.h"
-#include "optimizer.h"
+#include "emscripten-optimizer/optimizer.h"
 #include "mixed_arena.h"
 
 namespace wasm {
diff --git a/src/pretty_printing.h b/src/pretty_printing.h
index cc2d88272..88028fdec 100644
--- a/src/pretty_printing.h
+++ b/src/pretty_printing.h
@@ -5,7 +5,7 @@
 
 #include <ostream>
 
-#include "colors.h"
+#include "emscripten-optimizer/colors.h"
 
 std::ostream &doIndent(std::ostream &o, unsigned indent) {
   for (unsigned i = 0; i < indent; i++) {
diff --git a/src/wasm.h b/src/wasm.h
index 769c0ecad..dfd540155 100644
--- a/src/wasm.h
+++ b/src/wasm.h
@@ -24,7 +24,7 @@
 #include <map>
 #include <vector>
 
-#include "simple_ast.h"
+#include "emscripten-optimizer/simple_ast.h"
 #include "pretty_printing.h"
 
 namespace wasm {
@@ -263,12 +263,10 @@ public:
   };
   Id _id;
 
-  Expression() : _id(InvalidId) {}
-  Expression(Id id) : _id(id) {}
-
   WasmType type; // the type of the expression: its *output*, not necessarily its input(s)
 
-  std::ostream& print(std::ostream &o, unsigned indent); // avoid virtual here, for performance
+  Expression() : _id(InvalidId), type(none) {}
+  Expression(Id id) : _id(id), type(none) {}
 
   template<class T>
   bool is() {
@@ -280,6 +278,12 @@ public:
     return _id == T()._id ? (T*)this : nullptr;
   }
 
+  std::ostream& print(std::ostream &o, unsigned indent); // avoid virtual here, for performance
+
+  friend std::ostream& operator<<(std::ostream &o, Expression* expression) {
+    return expression->print(o, 0);
+  }
+
   static std::ostream& printFullLine(std::ostream &o, unsigned indent, Expression *expression) {
     doIndent(o, indent);
     expression->print(o, indent);
@@ -704,6 +708,11 @@ public:
     printFullLine(o, indent, right);
     return decIndent(o, indent);
   }
+
+  // the type is always the type of the operands
+  void finalize() {
+    type = left->type;
+  }
 };
 
 class Compare : public Expression {
@@ -849,6 +858,8 @@ public:
   Name type; // if null, it is implicit in params and result
   Expression *body;
 
+  Function() : result(none) {}
+
   std::ostream& print(std::ostream &o, unsigned indent) {
     printOpening(o, "func ", true) << name;
     if (params.size() > 0) {
diff --git a/test/example/find_div0s.cpp b/test/example/find_div0s.cpp
new file mode 100644
index 000000000..77a5d2c61
--- /dev/null
+++ b/test/example/find_div0s.cpp
@@ -0,0 +1,44 @@
+
+#include <ostream>
+#include <wasm.h>
+
+using namespace wasm;
+
+int main() {
+  // A module with a function with a division by zero in the body
+  Module module;
+  Function func;
+  func.name = "func";
+  Binary div;
+  div.op = BinaryOp::DivS;
+  Const left;
+  left.value = 5;
+  Const right;
+  right.value = 0;
+  div.left = &left;
+  div.right = &right;
+  div.finalize();
+  func.body = &div;
+  module.addFunction(&func);
+
+  // Print it out
+  std::cout << module;
+
+  // Search it for divisions by zero: Walk the module, looking for
+  // that operation.
+  struct DivZeroSeeker : public WasmWalker {
+    void visitBinary(Binary* curr) {
+      // In every Binary, look for integer divisions
+      if (curr->op == BinaryOp::DivS || curr->op == BinaryOp::DivU) {
+        // Check if the right operand is a constant, and if it is 0
+        auto right = curr->right->dyn_cast<Const>();
+        if (right && right->value.getInteger() == 0) {
+          std::cout << "We found that " << curr->left << " is divided by zero\n";
+        }
+      }
+    }
+  };
+  DivZeroSeeker seeker;
+  seeker.startWalk(&module);
+}
+
diff --git a/test/example/find_div0s.txt b/test/example/find_div0s.txt
new file mode 100644
index 000000000..44397fbde
--- /dev/null
+++ b/test/example/find_div0s.txt
@@ -0,0 +1,10 @@
+(module
+  (memory 0 4294967295)
+  (func $func
+    (none.div_s
+      (i32.const 5)
+      (i32.const 0)
+    )
+  )
+)
+We found that (i32.const 5) is divided by zero