parse for loops in asm2wasm #60

Author: kripken

src/asm2wasm-main.cpp

@@ -54,6 +54,11 @@ int main(int argc, char **argv) {
   if (debug) std::cerr << "parsing...\n";
   cashew::Parser<Ref, DotZeroValueBuilder> builder;
   Ref asmjs = builder.parseToplevel(input);
+  if (debug) {
+    std::cerr << "parsed:\n";
+    asmjs->stringify(std::cerr, true);
+    std::cerr << '\n';
+  }
 
   if (debug) std::cerr << "wasming...\n";
   AllocatingModule wasm;

src/asm2wasm.h

@@ -1338,6 +1338,49 @@ Function* Asm2WasmBuilder::processFunction(Ref ast) {
       block->list.push_back(continuer);
       ret->body = block;
       return ret;
+    } else if (what == FOR) {
+      Ref finit = ast[1],
+          fcond = ast[2],
+          finc = ast[3],
+          fbody = ast[4];
+      auto ret = allocator.alloc<Loop>();
+      IString out, in;
+      if (!parentLabel.isNull()) {
+        out = getBreakLabelName(parentLabel);
+        in = getContinueLabelName(parentLabel);
+        parentLabel = IString();
+      } else {
+        out = getNextId("for-out");
+        in = getNextId("for-in");
+      }
+      ret->out = out;
+      ret->in = in;
+      breakStack.push_back(out);
+      continueStack.push_back(in);
+      Break *breakOut = allocator.alloc<Break>();
+      breakOut->name = out;
+      If *condition = allocator.alloc<If>();
+      condition->condition = process(fcond);
+      condition->ifTrue = allocator.alloc<Nop>();
+      condition->ifFalse = breakOut;
+      auto body = allocator.alloc<Block>();
+      body->list.push_back(condition);
+      body->list.push_back(process(fbody));
+      body->list.push_back(process(finc));
+      ret->body = body;
+      // loops do not automatically loop, add a branch back
+      Block* block = blockify(ret->body);
+      auto continuer = allocator.alloc<Break>();
+      continuer->name = ret->in;
+      block->list.push_back(continuer);
+      ret->body = block;
+      continueStack.pop_back();
+      breakStack.pop_back();
+      Block *outer = allocator.alloc<Block>();
+      // add an outer block for the init as well
+      outer->list.push_back(process(finit));
+      outer->list.push_back(ret);
+      return outer;
     } else if (what == LABEL) {
       assert(parentLabel.isNull());
       parentLabel = ast[1]->getIString();

src/emscripten-optimizer/parser.h

@@ -386,6 +386,7 @@ class Parser {
     else if (frag.str == CONTINUE) return parseContinue(src, seps);
     else if (frag.str == SWITCH) return parseSwitch(src, seps);
     else if (frag.str == NEW) return parseNew(src, seps);
+    else if (frag.str == FOR) return parseFor(src, seps);
     dump(frag.str.str, src);
     abort();
     return nullptr;
@@ -492,6 +493,26 @@ class Parser {
     return Builder::makeWhile(condition, body);
   }
 
+  NodeRef parseFor(char*& src, const char* seps) {
+    skipSpace(src);
+    assert(*src == '(');
+    src++;
+    NodeRef init = parseElement(src, ";");
+    skipSpace(src);
+    assert(*src == ';');
+    src++;
+    NodeRef condition = parseElement(src, ";");
+    skipSpace(src);
+    assert(*src == ';');
+    src++;
+    NodeRef inc = parseElement(src, ")");
+    skipSpace(src);
+    assert(*src == ')');
+    src++;
+    NodeRef body = parseMaybeBracketed(src, seps);
+    return Builder::makeFor(init, condition, inc, body);
+  }
+
   NodeRef parseBreak(char*& src, const char* seps) {
     skipSpace(src);
     Frag next(src);

src/emscripten-optimizer/simple_ast.h

@@ -380,7 +380,11 @@ struct Value {
     #define indentify() { for (int i = 0; i < indent; i++) os << "  "; }
     switch (type) {
       case String:
-        os << '"' << str.str << '"';
+        if (str.str) {
+          os << '"' << str.str << '"';
+        } else {
+          os << "\"(null)\"";
+        }
         break;
       case Number:
         os << std::setprecision(17) << num; // doubles can have 17 digits of precision
@@ -1561,6 +1565,14 @@ class ValueBuilder {
                             .push_back(body);
   }
 
+  static Ref makeFor(Ref init, Ref condition, Ref inc, Ref body) {
+    return &makeRawArray(5)->push_back(makeRawString(FOR))
+                            .push_back(init)
+                            .push_back(condition)
+                            .push_back(inc)
+                            .push_back(body);
+  }
+
   static Ref makeBreak(IString label) {
     return &makeRawArray(2)->push_back(makeRawString(BREAK))
                             .push_back(!!label ? makeRawString(label) : makeNull());

test/unit.asm.js

@@ -1,4 +1,4 @@
-function () {
+function asm() {
   "use asm";
 
   var t = global.NaN, u = global.Infinity;
@@ -129,6 +129,12 @@ function () {
   function cneg_nosemicolon() {
     FUNCTION_TABLE_c[1 & 7](1) // no semicolon
   }
+  function forLoop() {
+    var i = 0;
+    for (i = 1; (i | 0) < 200; i = i + 1 | 0) {
+      h(i | 0);
+    }
+  }
 
   function z() {
   }

test/unit.fromasm

@@ -409,6 +409,36 @@
       (i32.const 1)
     )
   )
+  (func $forLoop
+    (local $i i32)
+    (block
+      (set_local $i
+        (i32.const 1)
+      )
+      (loop $for-out$0 $for-in$1
+        (block
+          (if_else
+            (i32.lt_s
+              (get_local $i)
+              (i32.const 200)
+            )
+            (nop)
+            (br $for-out$0)
+          )
+          (call $h
+            (get_local $i)
+          )
+          (set_local $i
+            (i32.add
+              (get_local $i)
+              (i32.const 1)
+            )
+          )
+          (br $for-in$1)
+        )
+      )
+    )
+  )
   (func $z
     (nop)
   )