1 files changed, 179 insertions, 0 deletions
diff --git a/js/src/frontend/CForEmitter.cpp b/js/src/frontend/CForEmitter.cpp
new file mode 100644
index 0000000000..4fccde0e88
--- /dev/null
+++ b/js/src/frontend/CForEmitter.cpp
@@ -0,0 +1,179 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: set ts=8 sts=2 et sw=2 tw=80:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "frontend/CForEmitter.h"
+
+#include "frontend/BytecodeEmitter.h"  // BytecodeEmitter
+#include "frontend/EmitterScope.h"     // EmitterScope
+#include "vm/Opcodes.h"                // JSOp
+#include "vm/ScopeKind.h"              // ScopeKind
+#include "vm/StencilEnums.h"           // TryNoteKind
+
+using namespace js;
+using namespace js::frontend;
+
+using mozilla::Maybe;
+
+CForEmitter::CForEmitter(BytecodeEmitter* bce,
+                         const EmitterScope* headLexicalEmitterScopeForLet)
+    : bce_(bce),
+      headLexicalEmitterScopeForLet_(headLexicalEmitterScopeForLet) {}
+
+bool CForEmitter::emitInit(const Maybe<uint32_t>& initPos) {
+  MOZ_ASSERT(state_ == State::Start);
+
+  loopInfo_.emplace(bce_, StatementKind::ForLoop);
+
+  if (initPos) {
+    if (!bce_->updateSourceCoordNotes(*initPos)) {
+      return false;
+    }
+  }
+
+#ifdef DEBUG
+  state_ = State::Init;
+#endif
+  return true;
+}
+
+bool CForEmitter::emitCond(const Maybe<uint32_t>& condPos) {
+  MOZ_ASSERT(state_ == State::Init);
+
+  // ES 13.7.4.8 step 2. The initial freshening.
+  //
+  // If an initializer let-declaration may be captured during loop
+  // iteration, the current scope has an environment.  If so, freshen the
+  // current environment to expose distinct bindings for each loop
+  // iteration.
+  if (headLexicalEmitterScopeForLet_) {
+    // The environment chain only includes an environment for the
+    // for(;;) loop head's let-declaration *if* a scope binding is
+    // captured, thus requiring a fresh environment each iteration. If
+    // a lexical scope exists for the head, it must be the innermost
+    // one. If that scope has closed-over bindings inducing an
+    // environment, recreate the current environment.
+    MOZ_ASSERT(headLexicalEmitterScopeForLet_ == bce_->innermostEmitterScope());
+    MOZ_ASSERT(headLexicalEmitterScopeForLet_->scope(bce_).kind() ==
+               ScopeKind::Lexical);
+
+    if (headLexicalEmitterScopeForLet_->hasEnvironment()) {
+      if (!bce_->emitInternedScopeOp(headLexicalEmitterScopeForLet_->index(),
+                                     JSOp::FreshenLexicalEnv)) {
+        return false;
+      }
+    }
+  }
+
+  if (!loopInfo_->emitLoopHead(bce_, condPos)) {
+    //              [stack]
+    return false;
+  }
+
+#ifdef DEBUG
+  state_ = State::Cond;
+#endif
+  return true;
+}
+
+bool CForEmitter::emitBody(Cond cond) {
+  MOZ_ASSERT(state_ == State::Cond);
+  cond_ = cond;
+
+  if (cond_ == Cond::Present) {
+    if (!bce_->emitJump(JSOp::JumpIfFalse, &loopInfo_->breaks)) {
+      return false;
+    }
+  }
+
+  tdzCache_.emplace(bce_);
+
+#ifdef DEBUG
+  state_ = State::Body;
+#endif
+  return true;
+}
+
+bool CForEmitter::emitUpdate(Update update, const Maybe<uint32_t>& updatePos) {
+  MOZ_ASSERT(state_ == State::Body);
+  update_ = update;
+  tdzCache_.reset();
+
+  // Set loop and enclosing "update" offsets, for continue.  Note that we
+  // continue to immediately *before* the block-freshening: continuing must
+  // refresh the block.
+  if (!loopInfo_->emitContinueTarget(bce_)) {
+    return false;
+  }
+
+  // ES 13.7.4.8 step 3.e. The per-iteration freshening.
+  if (headLexicalEmitterScopeForLet_) {
+    MOZ_ASSERT(headLexicalEmitterScopeForLet_ == bce_->innermostEmitterScope());
+    MOZ_ASSERT(headLexicalEmitterScopeForLet_->scope(bce_).kind() ==
+               ScopeKind::Lexical);
+
+    if (headLexicalEmitterScopeForLet_->hasEnvironment()) {
+      if (!bce_->emitInternedScopeOp(headLexicalEmitterScopeForLet_->index(),
+                                     JSOp::FreshenLexicalEnv)) {
+        return false;
+      }
+    }
+  }
+
+  // The update code may not be executed at all; it needs its own TDZ
+  // cache.
+  if (update_ == Update::Present) {
+    tdzCache_.emplace(bce_);
+
+    if (updatePos) {
+      if (!bce_->updateSourceCoordNotes(*updatePos)) {
+        return false;
+      }
+    }
+  }
+
+#ifdef DEBUG
+  state_ = State::Update;
+#endif
+  return true;
+}
+
+bool CForEmitter::emitEnd(uint32_t forPos) {
+  MOZ_ASSERT(state_ == State::Update);
+
+  if (update_ == Update::Present) {
+    tdzCache_.reset();
+
+    //              [stack] UPDATE
+
+    if (!bce_->emit1(JSOp::Pop)) {
+      //            [stack]
+      return false;
+    }
+  }
+
+  if (cond_ == Cond::Missing && update_ == Update::Missing) {
+    // If there is no condition clause and no update clause, mark
+    // the loop-ending "goto" with the location of the "for".
+    // This ensures that the debugger will stop on each loop
+    // iteration.
+    if (!bce_->updateSourceCoordNotes(forPos)) {
+      return false;
+    }
+  }
+
+  // Emit the loop-closing jump.
+  if (!loopInfo_->emitLoopEnd(bce_, JSOp::Goto, TryNoteKind::Loop)) {
+    //              [stack]
+    return false;
+  }
+
+  loopInfo_.reset();
+
+#ifdef DEBUG
+  state_ = State::End;
+#endif
+  return true;
+}