Initial bypass of JumpTarget::ComputeEntryFrame for deferred code

entry labels where it is statically safe.

Review URL: http://codereview.chromium.org/115296

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@1943 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/arm/jump-target-arm.cc

@@ -52,6 +52,8 @@ void JumpTarget::DoJump() {
     cgen_->DeleteFrame();
     __ jmp(&entry_label_);
   } else {
+    // Preconfigured entry frame is not used on ARM.
+    ASSERT(entry_frame_ == NULL);
     // Forward jump.  The current frame is added to the end of the list
     // of frames reaching the target block and a jump to the merge code
     // is emitted.
@@ -115,6 +117,8 @@ void JumpTarget::DoBranch(Condition cc, Hint ignored) {
     __ bind(&original_fall_through);
 
   } else {
+    // Preconfigured entry frame is not used on ARM.
+    ASSERT(entry_frame_ == NULL);
     // Forward branch.  A copy of the current frame is added to the end
     // of the list of frames reaching the target block and a branch to
     // the merge code is emitted.
@@ -141,6 +145,8 @@ void JumpTarget::Call() {
   cgen_->frame()->SpillAll();
   VirtualFrame* target_frame = new VirtualFrame(cgen_->frame());
   target_frame->Adjust(1);
+  // We do not expect a call with a preconfigured entry frame.
+  ASSERT(entry_frame_ == NULL);
   AddReachingFrame(target_frame);
   __ bl(&merge_labels_.last());
 
@@ -205,13 +211,15 @@ void JumpTarget::DoBind(int mergable_elements) {
   bool had_fall_through = false;
   if (cgen_->has_valid_frame()) {
     had_fall_through = true;
-    AddReachingFrame(cgen_->frame());
+    AddReachingFrame(cgen_->frame());  // Return value ignored.
     RegisterFile empty;
     cgen_->SetFrame(NULL, &empty);
   }
 
   // Compute the frame to use for entry to the block.
-  ComputeEntryFrame(mergable_elements);
+  if (entry_frame_ == NULL) {
+    ComputeEntryFrame(mergable_elements);
+  }
 
   // Some moves required to merge to an expected frame require purely
   // frame state changes, and do not require any code generation.

src/codegen-inl.h

@@ -30,10 +30,19 @@
 #define V8_CODEGEN_INL_H_
 
 #include "codegen.h"
+#include "register-allocator-inl.h"
 
 namespace v8 { namespace internal {
 
 
+void DeferredCode::SetEntryFrame(Result* arg) {
+  ASSERT(generator()->has_valid_frame());
+  generator()->frame()->Push(arg);
+  enter()->set_entry_frame(new VirtualFrame(generator()->frame()));
+  *arg = generator()->frame()->Pop();
+}
+
+
 // -----------------------------------------------------------------------------
 // Support for "structured" code comments.
 //

src/codegen.h

@@ -117,7 +117,14 @@ class DeferredCode: public ZoneObject {
   MacroAssembler* masm() const { return masm_; }
   CodeGenerator* generator() const { return generator_; }
 
+  // Set the virtual frame for entry to the deferred code as a
+  // snapshot of the code generator's current frame (plus additional
+  // results).  This is optional, but should be done before branching
+  // or jumping to the deferred code.
+  inline void SetEntryFrame(Result* arg);
+
   JumpTarget* enter() { return &enter_; }
+
   void BindExit() { exit_.Bind(0); }
   void BindExit(Result* result) { exit_.Bind(result, 1); }
   void BindExit(Result* result0, Result* result1) {

src/ia32/codegen-ia32.cc

@@ -113,6 +113,8 @@ void CodeGenerator::GenCode(FunctionLiteral* fun) {
   // Adjust for function-level loop nesting.
   loop_nesting_ += fun->loop_nesting();
 
+  JumpTarget::set_compiling_deferred_code(false);
+
   {
     CodeGenState state(this);
 
@@ -316,7 +318,9 @@ void CodeGenerator::GenCode(FunctionLiteral* fun) {
   if (HasStackOverflow()) {
     ClearDeferred();
   } else {
+    JumpTarget::set_compiling_deferred_code(true);
     ProcessDeferred();
+    JumpTarget::set_compiling_deferred_code(false);
   }
 
   // There is no need to delete the register allocator, it is a
@@ -1247,6 +1251,10 @@ void CodeGenerator::ConstantSmiBinaryOperation(Token::Value op,
 
   switch (op) {
     case Token::ADD: {
+      operand->ToRegister();
+      frame_->Spill(operand->reg());
+      __ add(Operand(operand->reg()), Immediate(value));
+
       DeferredCode* deferred = NULL;
       if (reversed) {
         deferred = new DeferredInlineSmiAddReversed(this, smi_value,
@@ -1254,9 +1262,7 @@ void CodeGenerator::ConstantSmiBinaryOperation(Token::Value op,
       } else {
         deferred = new DeferredInlineSmiAdd(this, smi_value, overwrite_mode);
       }
-      operand->ToRegister();
-      frame_->Spill(operand->reg());
-      __ add(Operand(operand->reg()), Immediate(value));
+      deferred->SetEntryFrame(operand);
       deferred->enter()->Branch(overflow, operand, not_taken);
       __ test(operand->reg(), Immediate(kSmiTagMask));
       deferred->enter()->Branch(not_zero, operand, not_taken);
@@ -1271,8 +1277,7 @@ void CodeGenerator::ConstantSmiBinaryOperation(Token::Value op,
       if (reversed) {
         answer = allocator()->Allocate();
         ASSERT(answer.is_valid());
-        deferred = new DeferredInlineSmiSubReversed(this,
-                                                    smi_value,
+        deferred = new DeferredInlineSmiSubReversed(this, smi_value,
                                                     overwrite_mode);
         __ Set(answer.reg(), Immediate(value));
         // We are in the reversed case so they can't both be Smi constants.
@@ -1281,12 +1286,11 @@ void CodeGenerator::ConstantSmiBinaryOperation(Token::Value op,
       } else {
         operand->ToRegister();
         frame_->Spill(operand->reg());
-        deferred = new DeferredInlineSmiSub(this,
-                                            smi_value,
-                                            overwrite_mode);
+        deferred = new DeferredInlineSmiSub(this, smi_value, overwrite_mode);
         __ sub(Operand(operand->reg()), Immediate(value));
         answer = *operand;
       }
+      deferred->SetEntryFrame(operand);
       deferred->enter()->Branch(overflow, operand, not_taken);
       __ test(answer.reg(), Immediate(kSmiTagMask));
       deferred->enter()->Branch(not_zero, operand, not_taken);
@@ -5413,19 +5417,24 @@ void Reference::GetValue(TypeofState typeof_state) {
       } else {
         // Inline the inobject property case.
         Comment cmnt(masm, "[ Inlined named property load");
-        DeferredReferenceGetNamedValue* deferred =
-            new DeferredReferenceGetNamedValue(cgen_, GetName());
         Result receiver = cgen_->frame()->Pop();
         receiver.ToRegister();
-        // Check that the receiver is a heap object.
-        __ test(receiver.reg(), Immediate(kSmiTagMask));
-        deferred->enter()->Branch(zero, &receiver, not_taken);
 
         // Preallocate the value register to ensure that there is no
         // spill emitted between the patch site label and the offset in
-        // the load instruction.
+        // the load instruction and that all frames reaching the
+        // deferred code are identical.
         Result value = cgen_->allocator()->Allocate();
         ASSERT(value.is_valid());
+
+        // Check that the receiver is a heap object.
+        __ test(receiver.reg(), Immediate(kSmiTagMask));
+
+        DeferredReferenceGetNamedValue* deferred =
+            new DeferredReferenceGetNamedValue(cgen_, GetName());
+        deferred->SetEntryFrame(&receiver);
+        deferred->enter()->Branch(zero, &receiver, not_taken);
+
         __ bind(deferred->patch_site());
         // This is the map check instruction that will be patched (so we can't
         // use the double underscore macro that may insert instructions).

src/ia32/jump-target-ia32.cc

@@ -51,10 +51,15 @@ void JumpTarget::DoJump() {
     cgen_->frame()->MergeTo(entry_frame_);
     cgen_->DeleteFrame();
     __ jmp(&entry_label_);
+  } else if (entry_frame_ != NULL) {
+    // Forward jump with a preconfigured entry frame.  Assert the
+    // current frame matches the expected one and jump to the block.
+    ASSERT(cgen_->frame()->Equals(entry_frame_));
+    cgen_->DeleteFrame();
+    __ jmp(&entry_label_);
   } else {
-    // Forward jump.  The current frame is added to the end of the list
-    // of frames reaching the target block and a jump to the merge code
-    // is emitted.
+    // Forward jump.  Remember the current frame and emit a jump to
+    // its merge code.
     AddReachingFrame(cgen_->frame());
     RegisterFile empty;
     cgen_->SetFrame(NULL, &empty);
@@ -114,12 +119,19 @@ void JumpTarget::DoBranch(Condition cc, Hint hint) {
     cgen_->SetFrame(fall_through_frame, &non_frame_registers);
     __ bind(&original_fall_through);
 
+  } else if (entry_frame_ != NULL) {
+    // Forward branch with a preconfigured entry frame.  Assert the
+    // current frame matches the expected one and branch to the block.
+    ASSERT(cgen_->frame()->Equals(entry_frame_));
+    // Use masm_-> instead of __ as forward branches are expected to
+    // be a fixed size (no inserted coverage-checking instructions
+    // please).  This is used in Reference::GetValue.
+    masm_->j(cc, &entry_label_, hint);
+    is_linked_ = true;
+
   } else {
-    // Forward branch.  A copy of the current frame is added to the end of the
-    // list of frames reaching the target block and a branch to the merge code
-    // is emitted.  Use masm_-> instead of __ as forward branches are expected
-    // to be a fixed size (no inserted coverage-checking instructions please).
-    // This is used in Reference::GetValue.
+    // Forward branch.  A copy of the current frame is remembered and
+    // a branch to the merge code is emitted.
     AddReachingFrame(new VirtualFrame(cgen_->frame()));
     masm_->j(cc, &merge_labels_.last(), hint);
     is_linked_ = true;
@@ -143,6 +155,8 @@ void JumpTarget::Call() {
   cgen_->frame()->SpillAll();
   VirtualFrame* target_frame = new VirtualFrame(cgen_->frame());
   target_frame->Adjust(1);
+  // We do not expect a call with a preconfigured entry frame.
+  ASSERT(entry_frame_ == NULL);
   AddReachingFrame(target_frame);
   __ call(&merge_labels_.last());
 
@@ -158,6 +172,29 @@ void JumpTarget::DoBind(int mergable_elements) {
   // block.
   ASSERT(!cgen_->has_valid_frame() || cgen_->HasValidEntryRegisters());
 
+  // Fast case: the jump target was manually configured with an entry
+  // frame to use.
+  if (entry_frame_ != NULL) {
+    // Assert no reaching frames to deal with.
+    ASSERT(reaching_frames_.is_empty());
+    ASSERT(!cgen_->has_valid_frame());
+
+    RegisterFile reserved = RegisterAllocator::Reserved();
+    if (direction_ == BIDIRECTIONAL) {
+      // Copy the entry frame so the original can be used for a
+      // possible backward jump.
+      cgen_->SetFrame(new VirtualFrame(entry_frame_), &reserved);
+    } else {
+      // Take ownership of the entry frame.
+      cgen_->SetFrame(entry_frame_, &reserved);
+      entry_frame_ = NULL;
+    }
+    __ bind(&entry_label_);
+    is_linked_ = false;
+    is_bound_ = true;
+    return;
+  }
+
   if (direction_ == FORWARD_ONLY) {
     // A simple case: no forward jumps and no possible backward jumps.
     if (!is_linked()) {
@@ -207,13 +244,15 @@ void JumpTarget::DoBind(int mergable_elements) {
   bool had_fall_through = false;
   if (cgen_->has_valid_frame()) {
     had_fall_through = true;
-    AddReachingFrame(cgen_->frame());
+    AddReachingFrame(cgen_->frame());  // Return value ignored.
     RegisterFile empty;
     cgen_->SetFrame(NULL, &empty);
   }
 
   // Compute the frame to use for entry to the block.
-  ComputeEntryFrame(mergable_elements);
+  if (entry_frame_ == NULL) {
+    ComputeEntryFrame(mergable_elements);
+  }
 
   // Some moves required to merge to an expected frame require purely
   // frame state changes, and do not require any code generation.

src/jump-target.cc

@@ -35,6 +35,9 @@ namespace v8 { namespace internal {
 // -------------------------------------------------------------------------
 // JumpTarget implementation.
 
+bool JumpTarget::compiling_deferred_code_ = false;
+
+
 JumpTarget::JumpTarget(CodeGenerator* cgen, Directionality direction)
     : cgen_(cgen),
       direction_(direction),
@@ -97,6 +100,22 @@ void JumpTarget::ComputeEntryFrame(int mergable_elements) {
   // 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];
 
@@ -509,6 +528,7 @@ void JumpTarget::Bind(Result* arg0,
 
 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);

src/jump-target.h

@@ -161,6 +161,10 @@ class JumpTarget : public Malloced {  // Shadows are dynamically allocated.
 
   static const int kAllElements = -1;  // Not a valid number of elements.
 
+  static void set_compiling_deferred_code(bool flag) {
+    compiling_deferred_code_ = flag;
+  }
+
  protected:
   // The code generator gives access to its current frame.
   CodeGenerator* cgen_;
@@ -198,12 +202,14 @@ class JumpTarget : public Malloced {  // Shadows are dynamically allocated.
   void DoBind(int mergable_elements);
 
  private:
-  // Add a virtual frame reaching this labeled block via a forward
-  // jump, and a fresh label for its merge code.
+  static bool compiling_deferred_code_;
+
+  // Add a virtual frame reaching this labeled block via a forward jump,
+  // and a corresponding merge code label.
   void AddReachingFrame(VirtualFrame* frame);
 
-  // Compute a frame to use for entry to this block.  Mergable
-  // elements is as described for the Bind function.
+  // Compute a frame to use for entry to this block.  Mergable elements
+  // is as described for the Bind function.
   void ComputeEntryFrame(int mergable_elements);
 
   DISALLOW_COPY_AND_ASSIGN(JumpTarget);

src/v8-counters.h

@@ -124,7 +124,8 @@ namespace v8 { namespace internal {
   SC(enum_cache_misses, V8.EnumCacheMisses)                         \
   SC(reloc_info_count, V8.RelocInfoCount)                           \
   SC(reloc_info_size, V8.RelocInfoSize)                             \
-  SC(zone_segment_bytes, V8.ZoneSegmentBytes)
+  SC(zone_segment_bytes, V8.ZoneSegmentBytes)                       \
+  SC(compute_entry_frame, V8.ComputeEntryFrame)
 
 
 // This file contains all the v8 counters that are in use.