// Copyright 2009 the V8 project authors. All rights reserved.
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following
// disclaimer in the documentation and/or other materials provided
// with the distribution.
// * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived
// from this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#include "v8.h"
#include "codegen-inl.h"
#include "jump-target-inl.h"
#include "register-allocator-inl.h"
namespace v8 {
namespace internal {
// -------------------------------------------------------------------------
// JumpTarget implementation.
bool JumpTarget::compiling_deferred_code_ = false;
void JumpTarget::Unuse() {
reaching_frames_.Clear();
merge_labels_.Clear();
entry_frame_ = NULL;
entry_label_.Unuse();
}
void JumpTarget::ComputeEntryFrame() {
// Given: a collection of frames reaching by forward CFG edges and
// the directionality of the block. Compute: an entry frame for the
// block.
Counters::compute_entry_frame.Increment();
#ifdef DEBUG
if (compiling_deferred_code_) {
ASSERT(reaching_frames_.length() > 1);
VirtualFrame* frame = reaching_frames_[0];
bool all_identical = true;
for (int i = 1; i < reaching_frames_.length(); i++) {
if (!frame->Equals(reaching_frames_[i])) {
all_identical = false;
break;
}
}
ASSERT(!all_identical || all_identical);
}
#endif
// Choose an initial frame.
VirtualFrame* initial_frame = reaching_frames_[0];
// A list of pointers to frame elements in the entry frame. NULL
// indicates that the element has not yet been determined.
int length = initial_frame->element_count();
ZoneList<FrameElement*> elements(length);
// Initially populate the list of elements based on the initial
// frame.
for (int i = 0; i < length; i++) {
FrameElement element = initial_frame->elements_[i];
// We do not allow copies or constants in bidirectional frames.
if (direction_ == BIDIRECTIONAL) {
if (element.is_constant() || element.is_copy()) {
elements.Add(NULL);
continue;
}
}
elements.Add(&initial_frame->elements_[i]);
}
// Compute elements based on the other reaching frames.
if (reaching_frames_.length() > 1) {
for (int i = 0; i < length; i++) {
FrameElement* element = elements[i];
for (int j = 1; j < reaching_frames_.length(); j++) {
// Element computation is monotonic: new information will not
// change our decision about undetermined or invalid elements.
if (element == NULL || !element->is_valid()) break;
element = element->Combine(&reaching_frames_[j]->elements_[i]);
FrameElement* other = &reaching_frames_[j]->elements_[i];
if (element != NULL && !element->is_copy()) {
ASSERT(other != NULL);
// We overwrite the number information of one of the incoming frames.
// This is safe because we only use the frame for emitting merge code.
// The number information of incoming frames is not used anymore.
element->set_number_info(NumberInfo::Combine(element->number_info(),
other->number_info()));
}
}
elements[i] = element;
}
}
// Build the new frame. A freshly allocated frame has memory elements
// for the parameters and some platform-dependent elements (e.g.,
// return address). Replace those first.
entry_frame_ = new VirtualFrame();
int index = 0;
for (; index < entry_frame_->element_count(); index++) {
FrameElement* target = elements[index];
// If the element is determined, set it now. Count registers. Mark
// elements as copied exactly when they have a copy. Undetermined
// elements are initially recorded as if in memory.
if (target != NULL) {
entry_frame_->elements_[index] = *target;
InitializeEntryElement(index, target);
}
}
// Then fill in the rest of the frame with new elements.
for (; index < length; index++) {
FrameElement* target = elements[index];
if (target == NULL) {
entry_frame_->elements_.Add(
FrameElement::MemoryElement(NumberInfo::kUninitialized));
} else {
entry_frame_->elements_.Add(*target);
InitializeEntryElement(index, target);
}
}
// Allocate any still-undetermined frame elements to registers or
// memory, from the top down.
for (int i = length - 1; i >= 0; i--) {
if (elements[i] == NULL) {
// Loop over all the reaching frames to check whether the element
// is synced on all frames and to count the registers it occupies.
bool is_synced = true;
RegisterFile candidate_registers;
int best_count = kMinInt;
int best_reg_num = RegisterAllocator::kInvalidRegister;
NumberInfo::Type info = NumberInfo::kUninitialized;
for (int j = 0; j < reaching_frames_.length(); j++) {
FrameElement element = reaching_frames_[j]->elements_[i];
if (direction_ == BIDIRECTIONAL) {
info = NumberInfo::kUnknown;
} else if (!element.is_copy()) {
info = NumberInfo::Combine(info, element.number_info());
} else {
// New elements will not be copies, so get number information from
// backing element in the reaching frame.
info = NumberInfo::Combine(info,
reaching_frames_[j]->elements_[element.index()].number_info());
}
is_synced = is_synced && element.is_synced();
if (element.is_register() && !entry_frame_->is_used(element.reg())) {
// Count the register occurrence and remember it if better
// than the previous best.
int num = RegisterAllocator::ToNumber(element.reg());
candidate_registers.Use(num);
if (candidate_registers.count(num) > best_count) {
best_count = candidate_registers.count(num);
best_reg_num = num;
}
}
}
// We must have a number type information now (not for copied elements).
ASSERT(entry_frame_->elements_[i].is_copy()
|| info != NumberInfo::kUninitialized);
// If the value is synced on all frames, put it in memory. This
// costs nothing at the merge code but will incur a
// memory-to-register move when the value is needed later.
if (is_synced) {
// Already recorded as a memory element.
// Set combined number info.
entry_frame_->elements_[i].set_number_info(info);
continue;
}
// Try to put it in a register. If there was no best choice
// consider any free register.
if (best_reg_num == RegisterAllocator::kInvalidRegister) {
for (int j = 0; j < RegisterAllocator::kNumRegisters; j++) {
if (!entry_frame_->is_used(j)) {
best_reg_num = j;
break;
}
}
}
if (best_reg_num != RegisterAllocator::kInvalidRegister) {
// If there was a register choice, use it. Preserve the copied
// flag on the element.
bool is_copied = entry_frame_->elements_[i].is_copied();
Register reg = RegisterAllocator::ToRegister(best_reg_num);
entry_frame_->elements_[i] =
FrameElement::RegisterElement(reg, FrameElement::NOT_SYNCED,
NumberInfo::kUninitialized);
if (is_copied) entry_frame_->elements_[i].set_copied();
entry_frame_->set_register_location(reg, i);
}
// Set combined number info.
entry_frame_->elements_[i].set_number_info(info);
}
}
// If we have incoming backward edges assert we forget all number information.
#ifdef DEBUG
if (direction_ == BIDIRECTIONAL) {
for (int i = 0; i < length; ++i) {
if (!entry_frame_->elements_[i].is_copy()) {
ASSERT(entry_frame_->elements_[i].number_info() ==
NumberInfo::kUnknown);
}
}
}
#endif
// The stack pointer is at the highest synced element or the base of
// the expression stack.
int stack_pointer = length - 1;
while (stack_pointer >= entry_frame_->expression_base_index() &&
!entry_frame_->elements_[stack_pointer].is_synced()) {
stack_pointer--;
}
entry_frame_->stack_pointer_ = stack_pointer;
}
void JumpTarget::Jump() {
DoJump();
}
void JumpTarget::Jump(Result* arg) {
ASSERT(cgen()->has_valid_frame());
cgen()->frame()->Push(arg);
DoJump();
}
void JumpTarget::Branch(Condition cc, Hint hint) {
DoBranch(cc, hint);
}
#ifdef DEBUG
#define DECLARE_ARGCHECK_VARS(name) \
Result::Type name##_type = name->type(); \
Register name##_reg = name->is_register() ? name->reg() : no_reg
#define ASSERT_ARGCHECK(name) \
ASSERT(name->type() == name##_type); \
ASSERT(!name->is_register() || name->reg().is(name##_reg))
#else
#define DECLARE_ARGCHECK_VARS(name) do {} while (false)
#define ASSERT_ARGCHECK(name) do {} while (false)
#endif
void JumpTarget::Branch(Condition cc, Result* arg, Hint hint) {
ASSERT(cgen()->has_valid_frame());
// We want to check that non-frame registers at the call site stay in
// the same registers on the fall-through branch.
DECLARE_ARGCHECK_VARS(arg);
cgen()->frame()->Push(arg);
DoBranch(cc, hint);
*arg = cgen()->frame()->Pop();
ASSERT_ARGCHECK(arg);
}
void BreakTarget::Branch(Condition cc, Result* arg, Hint hint) {
ASSERT(cgen()->has_valid_frame());
int count = cgen()->frame()->height() - expected_height_;
if (count > 0) {
// We negate and branch here rather than using DoBranch's negate
// and branch. This gives us a hook to remove statement state
// from the frame.
JumpTarget fall_through;
// Branch to fall through will not negate, because it is a
// forward-only target.
fall_through.Branch(NegateCondition(cc), NegateHint(hint));
Jump(arg); // May emit merge code here.
fall_through.Bind();
} else {
DECLARE_ARGCHECK_VARS(arg);
cgen()->frame()->Push(arg);
DoBranch(cc, hint);
*arg = cgen()->frame()->Pop();
ASSERT_ARGCHECK(arg);
}
}
#undef DECLARE_ARGCHECK_VARS
#undef ASSERT_ARGCHECK
void JumpTarget::Bind() {
DoBind();
}
void JumpTarget::Bind(Result* arg) {
if (cgen()->has_valid_frame()) {
cgen()->frame()->Push(arg);
}
DoBind();
*arg = cgen()->frame()->Pop();
}
void JumpTarget::AddReachingFrame(VirtualFrame* frame) {
ASSERT(reaching_frames_.length() == merge_labels_.length());
ASSERT(entry_frame_ == NULL);
Label fresh;
merge_labels_.Add(fresh);
reaching_frames_.Add(frame);
}
// -------------------------------------------------------------------------
// BreakTarget implementation.
void BreakTarget::set_direction(Directionality direction) {
JumpTarget::set_direction(direction);
ASSERT(cgen()->has_valid_frame());
expected_height_ = cgen()->frame()->height();
}
void BreakTarget::CopyTo(BreakTarget* destination) {
ASSERT(destination != NULL);
destination->direction_ = direction_;
destination->reaching_frames_.Rewind(0);
destination->reaching_frames_.AddAll(reaching_frames_);
destination->merge_labels_.Rewind(0);
destination->merge_labels_.AddAll(merge_labels_);
destination->entry_frame_ = entry_frame_;
destination->entry_label_ = entry_label_;
destination->expected_height_ = expected_height_;
}
void BreakTarget::Branch(Condition cc, Hint hint) {
ASSERT(cgen()->has_valid_frame());
int count = cgen()->frame()->height() - expected_height_;
if (count > 0) {
// We negate and branch here rather than using DoBranch's negate
// and branch. This gives us a hook to remove statement state
// from the frame.
JumpTarget fall_through;
// Branch to fall through will not negate, because it is a
// forward-only target.
fall_through.Branch(NegateCondition(cc), NegateHint(hint));
Jump(); // May emit merge code here.
fall_through.Bind();
} else {
DoBranch(cc, hint);
}
}
// -------------------------------------------------------------------------
// ShadowTarget implementation.
ShadowTarget::ShadowTarget(BreakTarget* shadowed) {
ASSERT(shadowed != NULL);
other_target_ = shadowed;
#ifdef DEBUG
is_shadowing_ = true;
#endif
// While shadowing this shadow target saves the state of the original.
shadowed->CopyTo(this);
// The original's state is reset.
shadowed->Unuse();
ASSERT(cgen()->has_valid_frame());
shadowed->set_expected_height(cgen()->frame()->height());
}
void ShadowTarget::StopShadowing() {
ASSERT(is_shadowing_);
// The states of this target, which was shadowed, and the original
// target, which was shadowing, are swapped.
BreakTarget temp;
other_target_->CopyTo(&temp);
CopyTo(other_target_);
temp.CopyTo(this);
temp.Unuse();
#ifdef DEBUG
is_shadowing_ = false;
#endif
}
} } // namespace v8::internal