Split the virtual frame into heavy and light versions....

src/jump-target-heavy.cc

+// Copyright 2010 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 {
+
+
+void JumpTarget::Jump(Result* arg) {
+  ASSERT(cgen()->has_valid_frame());
+
+  cgen()->frame()->Push(arg);
+  DoJump();
+}
+
+
+#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(Result* arg) {
+  if (cgen()->has_valid_frame()) {
+    cgen()->frame()->Push(arg);
+  }
+  DoBind();
+  *arg = cgen()->frame()->Pop();
+}
+
+
+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;
+
+        FrameElement* other = &reaching_frames_[j]->elements_[i];
+        element = element->Combine(other);
+        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::Uninitialized()));
+    } 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 info = NumberInfo::Uninitialized();
+
+      for (int j = 0; j < reaching_frames_.length(); j++) {
+        FrameElement element = reaching_frames_[j]->elements_[i];
+        if (direction_ == BIDIRECTIONAL) {
+          info = NumberInfo::Unknown();
+        } 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.IsUninitialized());
+
+      // 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::Uninitialized());
+        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().IsUnknown());
+      }
+    }
+  }
+#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;
+}
+
+
+DeferredCode::DeferredCode()
+    : masm_(CodeGeneratorScope::Current()->masm()),
+      statement_position_(masm_->current_statement_position()),
+      position_(masm_->current_position()) {
+  ASSERT(statement_position_ != RelocInfo::kNoPosition);
+  ASSERT(position_ != RelocInfo::kNoPosition);
+
+  CodeGeneratorScope::Current()->AddDeferred(this);
+#ifdef DEBUG
+  comment_ = "";
+#endif
+
+  // Copy the register locations from the code generator's frame.
+  // These are the registers that will be spilled on entry to the
+  // deferred code and restored on exit.
+  VirtualFrame* frame = CodeGeneratorScope::Current()->frame();
+  int sp_offset = frame->fp_relative(frame->stack_pointer_);
+  for (int i = 0; i < RegisterAllocator::kNumRegisters; i++) {
+    int loc = frame->register_location(i);
+    if (loc == VirtualFrame::kIllegalIndex) {
+      registers_[i] = kIgnore;
+    } else if (frame->elements_[loc].is_synced()) {
+      // Needs to be restored on exit but not saved on entry.
+      registers_[i] = frame->fp_relative(loc) | kSyncedFlag;
+    } else {
+      int offset = frame->fp_relative(loc);
+      registers_[i] = (offset < sp_offset) ? kPush : offset;
+    }
+  }
+}
+
+} }  // namespace v8::internal