wasm2js: Generalize global initializer code to use the main codegen logic (#6659)

This avoids special-casing particular global init forms. After this we should
support everything in global inits that we support anywhere else.

Author: kripken

src/wasm2js.h

@@ -192,7 +192,10 @@ class Wasm2JSBuilder {
 
   // The second pass on an expression: process it fully, generating
   // JS
-  Ref processFunctionBody(Module* m, Function* func, bool standalone);
+  Ref processExpression(Expression* curr,
+                        Module* m,
+                        Function* func = nullptr,
+                        bool standalone = false);
 
   Index getDataIndex(Name segment) {
     auto it = dataIndices.find(segment);
@@ -323,7 +326,7 @@ class Wasm2JSBuilder {
   void addTable(Ref ast, Module* wasm);
   void addStart(Ref ast, Module* wasm);
   void addExports(Ref ast, Module* wasm);
-  void addGlobal(Ref ast, Global* global);
+  void addGlobal(Ref ast, Global* global, Module* module);
   void addMemoryFuncs(Ref ast, Module* wasm);
   void addMemoryGrowFunc(Ref ast, Module* wasm);
 
@@ -503,7 +506,7 @@ Ref Wasm2JSBuilder::processWasm(Module* wasm, Name funcName) {
   // globals
   bool generateFetchHighBits = false;
   ModuleUtils::iterDefinedGlobals(*wasm, [&](Global* global) {
-    addGlobal(asmFunc[3], global);
+    addGlobal(asmFunc[3], global, wasm);
     if (flags.allowAsserts && global->name == INT64_TO_32_HIGH_BITS) {
       generateFetchHighBits = true;
     }
@@ -845,46 +848,12 @@ void Wasm2JSBuilder::addExports(Ref ast, Module* wasm) {
     ValueBuilder::makeStatement(ValueBuilder::makeReturn(exports)));
 }
 
-void Wasm2JSBuilder::addGlobal(Ref ast, Global* global) {
+void Wasm2JSBuilder::addGlobal(Ref ast, Global* global, Module* module) {
   Ref theVar = ValueBuilder::makeVar();
   ast->push_back(theVar);
-
-  auto* init = global->init;
-  Ref value;
-
-  if (auto* const_ = init->dynCast<Const>()) {
-    TODO_SINGLE_COMPOUND(const_->type);
-    switch (const_->type.getBasic()) {
-      case Type::i32: {
-        value = ValueBuilder::makeInt(const_->value.geti32());
-        break;
-      }
-      case Type::f32: {
-        value = ValueBuilder::makeCall(
-          MATH_FROUND,
-          makeJsCoercion(ValueBuilder::makeDouble(const_->value.getf32()),
-                         JS_DOUBLE));
-        break;
-      }
-      case Type::f64: {
-        value = makeJsCoercion(ValueBuilder::makeDouble(const_->value.getf64()),
-                               JS_DOUBLE);
-        break;
-      }
-      default: {
-        assert(false && "Top const type not supported");
-      }
-    }
-  } else if (auto* get = init->dynCast<GlobalGet>()) {
-    value = ValueBuilder::makeName(fromName(get->name, NameScope::Top));
-  } else if (init->is<RefNull>()) {
-    value = ValueBuilder::makeName(NULL_);
-  } else {
-    assert(false && "Top init type not supported");
-  }
-
+  Ref init = processExpression(global->init, module);
   ValueBuilder::appendToVar(
-    theVar, fromName(global->name, NameScope::Top), value);
+    theVar, fromName(global->name, NameScope::Top), init);
 }
 
 Ref Wasm2JSBuilder::processFunction(Module* m,
@@ -934,7 +903,8 @@ Ref Wasm2JSBuilder::processFunction(Module* m,
   size_t theVarIndex = ret[3]->size();
   ret[3]->push_back(theVar);
   // body
-  flattenAppend(ret, processFunctionBody(m, func, standaloneFunction));
+  flattenAppend(ret,
+                processExpression(func->body, m, func, standaloneFunction));
   // vars, including new temp vars
   for (Index i = func->getVarIndexBase(); i < func->getNumLocals(); i++) {
     ValueBuilder::appendToVar(
@@ -952,9 +922,10 @@ Ref Wasm2JSBuilder::processFunction(Module* m,
   return ret;
 }
 
-Ref Wasm2JSBuilder::processFunctionBody(Module* m,
-                                        Function* func,
-                                        bool standaloneFunction) {
+Ref Wasm2JSBuilder::processExpression(Expression* curr,
+                                      Module* m,
+                                      Function* func,
+                                      bool standaloneFunction) {
   // Switches are tricky to handle - in wasm they often come with
   // massively-nested "towers" of blocks, which if naively translated
   // to JS may exceed parse recursion limits of VMs. Therefore even when
@@ -1092,9 +1063,9 @@ Ref Wasm2JSBuilder::processFunctionBody(Module* m,
       : parent(parent), func(func), module(m),
         standaloneFunction(standaloneFunction) {}
 
-    Ref process() {
-      switchProcessor.walk(func->body);
-      return visit(func->body, NO_RESULT);
+    Ref process(Expression* curr) {
+      switchProcessor.walk(curr);
+      return visit(curr, NO_RESULT);
     }
 
     // A scoped temporary variable.
@@ -2460,7 +2431,7 @@ Ref Wasm2JSBuilder::processFunctionBody(Module* m,
     }
   };
 
-  return ExpressionProcessor(this, m, func, standaloneFunction).process();
+  return ExpressionProcessor(this, m, func, standaloneFunction).process(curr);
 }
 
 void Wasm2JSBuilder::addMemoryFuncs(Ref ast, Module* wasm) {

test/wasm2js/refs.2asm.js

@@ -13,6 +13,7 @@ function asmFunc(imports) {
  var Math_trunc = Math.trunc;
  var Math_sqrt = Math.sqrt;
  var global = null;
+ var global_ref = use_global_ref;
  function null_() {
   return null;
  }
@@ -42,13 +43,21 @@ function asmFunc(imports) {
   return temp;
  }
 
+ function use_global_ref(x) {
+  var temp = null;
+  temp = global_ref;
+  global_ref = x;
+  return temp;
+ }
+ 
  return {
   "null_": null_, 
   "is_null": is_null, 
   "ref_func": ref_func, 
   "ref_eq": ref_eq, 
   "ref_as": ref_as, 
-  "use_global": use_global
+  "use_global": use_global, 
+  "use_global_ref": use_global_ref
  };
 }
 
@@ -60,3 +69,4 @@ export var ref_func = retasmFunc.ref_func;
 export var ref_eq = retasmFunc.ref_eq;
 export var ref_as = retasmFunc.ref_as;
 export var use_global = retasmFunc.use_global;
+export var use_global_ref = retasmFunc.use_global_ref;

test/wasm2js/refs.2asm.js.opt

@@ -13,6 +13,7 @@ function asmFunc(imports) {
  var Math_trunc = Math.trunc;
  var Math_sqrt = Math.sqrt;
  var global = null;
+ var global_ref = use_global_ref;
  function null_() {
   return null;
  }
@@ -40,13 +41,21 @@ function asmFunc(imports) {
   return $1;
  }
 
+ function use_global_ref($0) {
+  var $1 = null;
+  $1 = global_ref;
+  global_ref = $0;
+  return $1;
+ }
+ 
  return {
   "null_": null_, 
   "is_null": is_null, 
   "ref_func": ref_func, 
   "ref_eq": ref_eq, 
   "ref_as": ref_as, 
-  "use_global": use_global
+  "use_global": use_global, 
+  "use_global_ref": use_global_ref
  };
 }
 
@@ -58,3 +67,4 @@ export var ref_func = retasmFunc.ref_func;
 export var ref_eq = retasmFunc.ref_eq;
 export var ref_as = retasmFunc.ref_as;
 export var use_global = retasmFunc.use_global;
+export var use_global_ref = retasmFunc.use_global_ref;

test/wasm2js/refs.wast

@@ -1,6 +1,8 @@
 (module
   (global $global (mut anyref) (ref.null any))
 
+  (global $global-ref (mut funcref) (ref.func $use-global-ref))
+
   (func $null (export "null") (result anyref)
     (ref.null any)
   )
@@ -49,4 +51,15 @@
     )
     (local.get $temp)
   )
+
+  (func $use-global-ref (export "use-global-ref") (param $x funcref) (result funcref)
+    (local $temp funcref)
+    (local.set $temp
+      (global.get $global-ref)
+    )
+    (global.set $global-ref
+      (local.get $x)
+    )
+    (local.get $temp)
+  )
 )