1 files changed, 410 insertions, 0 deletions
diff --git a/js/src/frontend/SwitchEmitter.cpp b/js/src/frontend/SwitchEmitter.cpp
new file mode 100644
index 0000000000..c7282fb1e5
--- /dev/null
+++ b/js/src/frontend/SwitchEmitter.cpp
@@ -0,0 +1,410 @@
+/* -*- 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/SwitchEmitter.h"
+
+#include "mozilla/Assertions.h"  // MOZ_ASSERT
+#include "mozilla/Span.h"        // mozilla::Span
+
+#include <algorithm>  // std::min, std::max
+
+#include "jstypes.h"  // JS_BIT
+
+#include "frontend/BytecodeEmitter.h"  // BytecodeEmitter
+#include "frontend/SharedContext.h"    // StatementKind
+#include "js/friend/ErrorMessages.h"   // JSMSG_*
+#include "js/TypeDecls.h"              // jsbytecode
+#include "util/BitArray.h"
+#include "vm/BytecodeUtil.h"  // SET_JUMP_OFFSET, JUMP_OFFSET_LEN, SET_RESUMEINDEX
+#include "vm/Opcodes.h"       // JSOp, JSOpLength_TableSwitch
+#include "vm/Runtime.h"       // ReportOutOfMemory
+
+using namespace js;
+using namespace js::frontend;
+
+using mozilla::Maybe;
+
+bool SwitchEmitter::TableGenerator::addNumber(int32_t caseValue) {
+  if (isInvalid()) {
+    return true;
+  }
+
+  if (unsigned(caseValue + int(Bit(15))) >= unsigned(Bit(16))) {
+    setInvalid();
+    return true;
+  }
+
+  if (intmap_.isNothing()) {
+    intmap_.emplace();
+  }
+
+  low_ = std::min(low_, caseValue);
+  high_ = std::max(high_, caseValue);
+
+  // Check for duplicates, which are not supported in a table switch.
+  // We bias caseValue by 65536 if it's negative, and hope that's a rare case
+  // (because it requires a malloc'd bitmap).
+  if (caseValue < 0) {
+    caseValue += Bit(16);
+  }
+  if (caseValue >= intmapBitLength_) {
+    size_t newLength = NumWordsForBitArrayOfLength(caseValue + 1);
+    if (!intmap_->resize(newLength)) {
+      ReportOutOfMemory(bce_->cx);
+      return false;
+    }
+    intmapBitLength_ = newLength * BitArrayElementBits;
+  }
+  if (IsBitArrayElementSet(intmap_->begin(), intmap_->length(), caseValue)) {
+    // Duplicate entry is not supported in table switch.
+    setInvalid();
+    return true;
+  }
+  SetBitArrayElement(intmap_->begin(), intmap_->length(), caseValue);
+  return true;
+}
+
+void SwitchEmitter::TableGenerator::finish(uint32_t caseCount) {
+  intmap_.reset();
+
+#ifdef DEBUG
+  finished_ = true;
+#endif
+
+  if (isInvalid()) {
+    return;
+  }
+
+  if (caseCount == 0) {
+    low_ = 0;
+    high_ = -1;
+    return;
+  }
+
+  // Compute table length. Don't use table switch if overlarge or more than
+  // half-sparse.
+  tableLength_ = uint32_t(high_ - low_ + 1);
+  if (tableLength_ >= Bit(16) || tableLength_ > 2 * caseCount) {
+    setInvalid();
+  }
+}
+
+uint32_t SwitchEmitter::TableGenerator::toCaseIndex(int32_t caseValue) const {
+  MOZ_ASSERT(finished_);
+  MOZ_ASSERT(isValid());
+  uint32_t caseIndex = uint32_t(caseValue - low_);
+  MOZ_ASSERT(caseIndex < tableLength_);
+  return caseIndex;
+}
+
+uint32_t SwitchEmitter::TableGenerator::tableLength() const {
+  MOZ_ASSERT(finished_);
+  MOZ_ASSERT(isValid());
+  return tableLength_;
+}
+
+SwitchEmitter::SwitchEmitter(BytecodeEmitter* bce) : bce_(bce) {}
+
+bool SwitchEmitter::emitDiscriminant(const Maybe<uint32_t>& switchPos) {
+  MOZ_ASSERT(state_ == State::Start);
+  switchPos_ = switchPos;
+
+  if (switchPos_) {
+    // Ensure that the column of the switch statement is set properly.
+    if (!bce_->updateSourceCoordNotes(*switchPos_)) {
+      return false;
+    }
+  }
+
+  state_ = State::Discriminant;
+  return true;
+}
+
+bool SwitchEmitter::emitLexical(LexicalScope::ParserData* bindings) {
+  MOZ_ASSERT(state_ == State::Discriminant);
+  MOZ_ASSERT(bindings);
+
+  tdzCacheLexical_.emplace(bce_);
+  emitterScope_.emplace(bce_);
+  if (!emitterScope_->enterLexical(bce_, ScopeKind::Lexical, bindings)) {
+    return false;
+  }
+
+  state_ = State::Lexical;
+  return true;
+}
+
+bool SwitchEmitter::validateCaseCount(uint32_t caseCount) {
+  MOZ_ASSERT(state_ == State::Discriminant || state_ == State::Lexical);
+  if (caseCount > Bit(16)) {
+    bce_->reportError(switchPos_, JSMSG_TOO_MANY_CASES);
+    return false;
+  }
+  caseCount_ = caseCount;
+
+  state_ = State::CaseCount;
+  return true;
+}
+
+bool SwitchEmitter::emitCond() {
+  MOZ_ASSERT(state_ == State::CaseCount);
+
+  kind_ = Kind::Cond;
+
+  // After entering the scope if necessary, push the switch control.
+  controlInfo_.emplace(bce_, StatementKind::Switch);
+  top_ = bce_->bytecodeSection().offset();
+
+  if (!caseOffsets_.resize(caseCount_)) {
+    ReportOutOfMemory(bce_->cx);
+    return false;
+  }
+
+  MOZ_ASSERT(top_ == bce_->bytecodeSection().offset());
+
+  tdzCacheCaseAndBody_.emplace(bce_);
+
+  state_ = State::Cond;
+  return true;
+}
+
+bool SwitchEmitter::emitTable(const TableGenerator& tableGen) {
+  MOZ_ASSERT(state_ == State::CaseCount);
+  kind_ = Kind::Table;
+
+  // After entering the scope if necessary, push the switch control.
+  controlInfo_.emplace(bce_, StatementKind::Switch);
+  top_ = bce_->bytecodeSection().offset();
+
+  if (!caseOffsets_.resize(tableGen.tableLength())) {
+    ReportOutOfMemory(bce_->cx);
+    return false;
+  }
+
+  MOZ_ASSERT(top_ == bce_->bytecodeSection().offset());
+  if (!bce_->emitN(JSOp::TableSwitch,
+                   JSOpLength_TableSwitch - sizeof(jsbytecode))) {
+    return false;
+  }
+
+  // Skip default offset.
+  jsbytecode* pc =
+      bce_->bytecodeSection().code(top_ + BytecodeOffsetDiff(JUMP_OFFSET_LEN));
+
+  // Fill in switch bounds, which we know fit in 16-bit offsets.
+  SET_JUMP_OFFSET(pc, tableGen.low());
+  SET_JUMP_OFFSET(pc + JUMP_OFFSET_LEN, tableGen.high());
+
+  state_ = State::Table;
+  return true;
+}
+
+bool SwitchEmitter::emitCaseOrDefaultJump(uint32_t caseIndex, bool isDefault) {
+  MOZ_ASSERT(kind_ == Kind::Cond);
+
+  if (isDefault) {
+    if (!bce_->emitJump(JSOp::Default, &condSwitchDefaultOffset_)) {
+      return false;
+    }
+    return true;
+  }
+
+  JumpList caseJump;
+  if (!bce_->emitJump(JSOp::Case, &caseJump)) {
+    return false;
+  }
+  caseOffsets_[caseIndex] = caseJump.offset;
+  lastCaseOffset_ = caseJump.offset;
+
+  return true;
+}
+
+bool SwitchEmitter::prepareForCaseValue() {
+  MOZ_ASSERT(kind_ == Kind::Cond);
+  MOZ_ASSERT(state_ == State::Cond || state_ == State::Case);
+
+  if (!bce_->emit1(JSOp::Dup)) {
+    return false;
+  }
+
+  state_ = State::CaseValue;
+  return true;
+}
+
+bool SwitchEmitter::emitCaseJump() {
+  MOZ_ASSERT(kind_ == Kind::Cond);
+  MOZ_ASSERT(state_ == State::CaseValue);
+
+  if (!bce_->emit1(JSOp::StrictEq)) {
+    return false;
+  }
+
+  if (!emitCaseOrDefaultJump(caseIndex_, false)) {
+    return false;
+  }
+  caseIndex_++;
+
+  state_ = State::Case;
+  return true;
+}
+
+bool SwitchEmitter::emitImplicitDefault() {
+  MOZ_ASSERT(kind_ == Kind::Cond);
+  MOZ_ASSERT(state_ == State::Cond || state_ == State::Case);
+  if (!emitCaseOrDefaultJump(0, true)) {
+    return false;
+  }
+
+  caseIndex_ = 0;
+
+  // No internal state after emitting default jump.
+  return true;
+}
+
+bool SwitchEmitter::emitCaseBody() {
+  MOZ_ASSERT(kind_ == Kind::Cond);
+  MOZ_ASSERT(state_ == State::Cond || state_ == State::Case ||
+             state_ == State::CaseBody || state_ == State::DefaultBody);
+
+  tdzCacheCaseAndBody_.reset();
+
+  if (state_ == State::Cond || state_ == State::Case) {
+    // For cond switch, JSOp::Default is always emitted.
+    if (!emitImplicitDefault()) {
+      return false;
+    }
+  }
+
+  JumpList caseJump;
+  caseJump.offset = caseOffsets_[caseIndex_];
+  if (!bce_->emitJumpTargetAndPatch(caseJump)) {
+    return false;
+  }
+
+  JumpTarget here;
+  if (!bce_->emitJumpTarget(&here)) {
+    return false;
+  }
+  caseIndex_++;
+
+  tdzCacheCaseAndBody_.emplace(bce_);
+
+  state_ = State::CaseBody;
+  return true;
+}
+
+bool SwitchEmitter::emitCaseBody(int32_t caseValue,
+                                 const TableGenerator& tableGen) {
+  MOZ_ASSERT(kind_ == Kind::Table);
+  MOZ_ASSERT(state_ == State::Table || state_ == State::CaseBody ||
+             state_ == State::DefaultBody);
+
+  tdzCacheCaseAndBody_.reset();
+
+  JumpTarget here;
+  if (!bce_->emitJumpTarget(&here)) {
+    return false;
+  }
+  caseOffsets_[tableGen.toCaseIndex(caseValue)] = here.offset;
+
+  tdzCacheCaseAndBody_.emplace(bce_);
+
+  state_ = State::CaseBody;
+  return true;
+}
+
+bool SwitchEmitter::emitDefaultBody() {
+  MOZ_ASSERT(state_ == State::Cond || state_ == State::Table ||
+             state_ == State::Case || state_ == State::CaseBody);
+  MOZ_ASSERT(!hasDefault_);
+
+  tdzCacheCaseAndBody_.reset();
+
+  if (state_ == State::Cond || state_ == State::Case) {
+    // For cond switch, JSOp::Default is always emitted.
+    if (!emitImplicitDefault()) {
+      return false;
+    }
+  }
+  JumpTarget here;
+  if (!bce_->emitJumpTarget(&here)) {
+    return false;
+  }
+  defaultJumpTargetOffset_ = here;
+
+  tdzCacheCaseAndBody_.emplace(bce_);
+
+  hasDefault_ = true;
+  state_ = State::DefaultBody;
+  return true;
+}
+
+bool SwitchEmitter::emitEnd() {
+  MOZ_ASSERT(state_ == State::Cond || state_ == State::Table ||
+             state_ == State::CaseBody || state_ == State::DefaultBody);
+
+  tdzCacheCaseAndBody_.reset();
+
+  if (!hasDefault_) {
+    // If no default case, offset for default is to end of switch.
+    if (!bce_->emitJumpTarget(&defaultJumpTargetOffset_)) {
+      return false;
+    }
+  }
+  MOZ_ASSERT(defaultJumpTargetOffset_.offset.valid());
+
+  // Set the default offset (to end of switch if no default).
+  jsbytecode* pc;
+  if (kind_ == Kind::Cond) {
+    pc = nullptr;
+    bce_->patchJumpsToTarget(condSwitchDefaultOffset_,
+                             defaultJumpTargetOffset_);
+  } else {
+    // Fill in the default jump target.
+    pc = bce_->bytecodeSection().code(top_);
+    SET_JUMP_OFFSET(pc, (defaultJumpTargetOffset_.offset - top_).value());
+    pc += JUMP_OFFSET_LEN;
+  }
+
+  if (kind_ == Kind::Table) {
+    // Skip over the already-initialized switch bounds.
+    pc += 2 * JUMP_OFFSET_LEN;
+
+    // Use the 'default' offset for missing cases.
+    for (uint32_t i = 0, length = caseOffsets_.length(); i < length; i++) {
+      if (caseOffsets_[i].value() == 0) {
+        caseOffsets_[i] = defaultJumpTargetOffset_.offset;
+      }
+    }
+
+    // Allocate resume index range.
+    uint32_t firstResumeIndex = 0;
+    mozilla::Span<BytecodeOffset> offsets =
+        mozilla::Span(caseOffsets_.begin(), caseOffsets_.end());
+    if (!bce_->allocateResumeIndexRange(offsets, &firstResumeIndex)) {
+      return false;
+    }
+    SET_RESUMEINDEX(pc, firstResumeIndex);
+  }
+
+  // Patch breaks before leaving the scope, as all breaks are under the
+  // lexical scope if it exists.
+  if (!controlInfo_->patchBreaks(bce_)) {
+    return false;
+  }
+
+  if (emitterScope_ && !emitterScope_->leave(bce_)) {
+    return false;
+  }
+
+  emitterScope_.reset();
+  tdzCacheLexical_.reset();
+
+  controlInfo_.reset();
+
+  state_ = State::End;
+  return true;
+}