Bug 1636796 - Add ScriptStencil::intoScript. r=mgaudet

This performs JSScript allocation by consuming the Stencil. For now we leave
handling of delazification compiles alone.

Differential Revision: https://phabricator.services.mozilla.com/D74572

js/src/frontend/BytecodeEmitter.cpp

@@ -2433,27 +2433,12 @@ bool BytecodeEmitter::emitScript(ParseNode* body) {
     return false;
   }
 
+  // Create a Stencil and convert it into a JSScript.
+  SourceExtent extent = sc->getScriptExtent();
   BCEScriptStencil stencil(*this, std::move(immutableScriptData));
+  outputScript = stencil.intoScript(cx, compilationInfo, extent);
 
-  RootedObject functionOrGlobal(cx);
-  if (sc->isFunctionBox()) {
-    functionOrGlobal = sc->asFunctionBox()->function();
-  } else {
-    functionOrGlobal = cx->global();
-  }
-
-  RootedScript script(
-      cx, JSScript::Create(cx, functionOrGlobal, compilationInfo.sourceObject,
-                           sc->getScriptExtent(), stencil.immutableFlags));
-  if (!script) {
-    return false;
-  }
-  if (!JSScript::fullyInitFromStencil(cx, compilationInfo, script, stencil)) {
-    return false;
-  }
-  // Script is allocated now.
-  outputScript = script;
-  return true;
+  return !!outputScript;
 }
 
 js::UniquePtr<ImmutableScriptData> BytecodeEmitter::createImmutableScriptData(

js/src/frontend/Frontend2.cpp

@@ -414,20 +414,6 @@ JSScript* Smoosh::compileGlobalScript(CompilationInfo& compilationInfo,
 
   *unimplemented = false;
 
-  RootedScriptSourceObject sso(cx,
-                               frontend::CreateScriptSourceObject(cx, options));
-  if (!sso) {
-    return nullptr;
-  }
-
-  RootedObject proto(cx);
-  if (!GetFunctionPrototype(cx, GeneratorKind::NotGenerator,
-                            FunctionAsyncKind::SyncFunction, &proto)) {
-    return nullptr;
-  }
-
-  SourceExtent extent = SourceExtent::makeGlobalExtent(length);
-
   Vector<ScopeNote, 0, SystemAllocPolicy> scopeNotes;
   if (!scopeNotes.resize(smoosh.scope_notes.len)) {
     return nullptr;
@@ -461,19 +447,16 @@ JSScript* Smoosh::compileGlobalScript(CompilationInfo& compilationInfo,
     return nullptr;
   }
 
+  SourceExtent extent = SourceExtent::makeGlobalExtent(length);
   SmooshScriptStencil stencil(smoosh, compilationInfo);
   if (!stencil.init(cx, std::move(immutableScriptData))) {
     return nullptr;
   }
 
-  RootedScript script(cx, JSScript::Create(cx, cx->global(), sso, extent,
-                                           stencil.immutableFlags));
+  RootedScript script(cx, stencil.intoScript(cx, compilationInfo, extent));
   if (!script) {
     return nullptr;
   }
-  if (!JSScript::fullyInitFromStencil(cx, compilationInfo, script, stencil)) {
-    return nullptr;
-  }
 
 #if defined(DEBUG) || defined(JS_JITSPEW)
   Sprinter sprinter(cx);

js/src/frontend/FunctionEmitter.cpp

@@ -702,34 +702,39 @@ bool FunctionScriptEmitter::emitEndBody() {
 
 bool FunctionScriptEmitter::initScript() {
   MOZ_ASSERT(state_ == State::EndBody);
+  MOZ_ASSERT(!bce_->outputScript);
+
+  JSContext* cx = bce_->cx;
 
   js::UniquePtr<ImmutableScriptData> immutableScriptData =
-      bce_->createImmutableScriptData(bce_->cx);
+      bce_->createImmutableScriptData(cx);
   if (!immutableScriptData) {
     return false;
   }
 
-  BCEScriptStencil stencil(*bce_, std::move(immutableScriptData));
-
-  RootedFunction function(bce_->cx, funbox_->function());
-  RootedScript script(bce_->cx);
   if (bce_->emitterMode == BytecodeEmitter::LazyFunction) {
-    script = JSScript::CastFromLazy(funbox_->function()->baseScript());
+    BCEScriptStencil stencil(*bce_, std::move(immutableScriptData));
+    RootedScript script(
+        cx, JSScript::CastFromLazy(funbox_->function()->baseScript()));
+
+    if (!JSScript::fullyInitFromStencil(cx, bce_->compilationInfo, script,
+                                        stencil)) {
+      return false;
+    }
+
+    bce_->outputScript = script;
   } else {
-    script =
-        JSScript::Create(bce_->cx, function, bce_->compilationInfo.sourceObject,
-                         funbox_->getScriptExtent(), stencil.immutableFlags);
+    SourceExtent extent = funbox_->getScriptExtent();
+    BCEScriptStencil stencil(*bce_, std::move(immutableScriptData));
+
+    RootedScript script(cx,
+                        stencil.intoScript(cx, bce_->compilationInfo, extent));
     if (!script) {
       return false;
     }
-  }
 
-  if (!JSScript::fullyInitFromStencil(bce_->cx, bce_->compilationInfo, script,
-                                      stencil)) {
-    return false;
+    bce_->outputScript = script;
   }
-  MOZ_ASSERT(!bce_->outputScript);
-  bce_->outputScript = script;
 
 #ifdef DEBUG
   state_ = State::End;

js/src/frontend/Stencil.cpp

@@ -6,6 +6,7 @@
 
 #include "frontend/Stencil.h"
 
+#include "frontend/CompilationInfo.h"
 #include "frontend/SharedContext.h"
 #include "js/TracingAPI.h"
 #include "vm/EnvironmentObject.h"
@@ -214,3 +215,29 @@ void ScriptStencilBase::trace(JSTracer* trc) {
     }
   }
 }
+
+JSScript* ScriptStencil::intoScript(JSContext* cx,
+                                    CompilationInfo& compilationInfo,
+                                    SourceExtent extent) {
+  MOZ_ASSERT(immutableScriptData,
+             "Need generated bytecode to use ScriptStencil::intoScript");
+
+  RootedObject functionOrGlobal(cx, cx->global());
+  if (functionIndex) {
+    functionOrGlobal =
+        compilationInfo.funcData[*functionIndex].as<JSFunction*>();
+  }
+
+  RootedScript script(
+      cx, JSScript::Create(cx, functionOrGlobal, compilationInfo.sourceObject,
+                           extent, immutableFlags));
+  if (!script) {
+    return nullptr;
+  }
+
+  if (!JSScript::fullyInitFromStencil(cx, compilationInfo, script, *this)) {
+    return nullptr;
+  }
+
+  return script;
+}

js/src/frontend/Stencil.h

@@ -376,6 +376,11 @@ class ScriptStencil : public ScriptStencilBase {
     return immutableFlags.hasFlag(ImmutableFlags::IsFunction);
   }
 
+  // Allocate a JSScript and initialize it with bytecode. This consumes
+  // allocations within this stencil.
+  JSScript* intoScript(JSContext* cx, CompilationInfo& compilationInfo,
+                       SourceExtent extent);
+
   // Store all atoms into `atoms`
   // `atoms` is the pointer to `this.natoms`-length array of `GCPtrAtom`.
   virtual void initAtomMap(GCPtrAtom* atoms) const = 0;