[turbofan] Frame elision for code stubs

src/compiler/code-generator.cc

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/compiler/code-generator.h"
 
 #include "src/address-map.h"
 #include "src/compiler/code-generator-impl.h"
 #include "src/compiler/linkage.h"
 #include "src/compiler/pipeline.h"
@@ skipping 38 matching lines @@
       deoptimization_literals_(code->zone()),
       inlined_function_count_(0),
       translations_(code->zone()),
       last_lazy_deopt_pc_(0),
       jump_tables_(nullptr),
       ools_(nullptr),
       osr_pc_offset_(-1) {
   for (int i = 0; i < code->InstructionBlockCount(); ++i) {
     new (&labels_[i]) Label;
   }
-  if (code->ContainsCall()) {
-    frame->MarkNeedsFrame();
-  }
 }
 
-
 Handle<Code> CodeGenerator::GenerateCode() {
   CompilationInfo* info = this->info();
 
   // Open a frame scope to indicate that there is a frame on the stack.  The
   // MANUAL indicates that the scope shouldn't actually generate code to set up
   // the frame (that is done in AssemblePrologue).
   FrameScope frame_scope(masm(), StackFrame::MANUAL);
 
   // Emit a code line info recording start event.
   PositionsRecorder* recorder = masm()->positions_recorder();
   LOG_CODE_EVENT(isolate(), CodeStartLinePosInfoRecordEvent(recorder));
 
   // Place function entry hook if requested to do so.
   if (linkage()->GetIncomingDescriptor()->IsJSFunctionCall()) {
     ProfileEntryHookStub::MaybeCallEntryHook(masm());
   }
   // Architecture-specific, linkage-specific prologue.
   info->set_prologue_offset(masm()->pc_offset());
-  AssemblePrologue();
-  if (linkage()->GetIncomingDescriptor()->InitializeRootRegister()) {
-    masm()->InitializeRootRegister();
-  }
 
   // Define deoptimization literals for all inlined functions.
   DCHECK_EQ(0u, deoptimization_literals_.size());
   for (const CompilationInfo::InlinedFunctionHolder& inlined :
        info->inlined_functions()) {
     if (!inlined.shared_info.is_identical_to(info->shared_info())) {
       DefineDeoptimizationLiteral(inlined.shared_info);
     }
   }
   inlined_function_count_ = deoptimization_literals_.size();
 
   // Define deoptimization literals for all unoptimized code objects of inlined
   // functions. This ensures unoptimized code is kept alive by optimized code.
   for (const CompilationInfo::InlinedFunctionHolder& inlined :
        info->inlined_functions()) {
     if (!inlined.shared_info.is_identical_to(info->shared_info())) {
       DefineDeoptimizationLiteral(inlined.inlined_code_object_root);
     }
   }
-
+  // Finish the Frame
+  frame()->AlignFrame(kFrameAlignmentInBytes);
+  AssembleSetupStackPointer();
   // Assemble all non-deferred blocks, followed by deferred ones.
   for (int deferred = 0; deferred < 2; ++deferred) {
     for (const InstructionBlock* block : code()->instruction_blocks()) {
       if (block->IsDeferred() == (deferred == 0)) {
         continue;
       }
       // Align loop headers on 16-byte boundaries.
       if (block->IsLoopHeader()) masm()->Align(16);
       // Ensure lazy deopt doesn't patch handler entry points.
       if (block->IsHandler()) EnsureSpaceForLazyDeopt();
@@ skipping 19 matching lines @@
           buffer = buffer.SubVector(next, buffer.length());
         }
         if (block->loop_header().IsValid()) {
           next =
               SNPrintF(buffer, " (in loop %d)", block->loop_header().ToInt());
           buffer = buffer.SubVector(next, buffer.length());
         }
         SNPrintF(buffer, " --");
         masm()->RecordComment(buffer_start);
       }
+
+      frame_access_state()->MarkHasFrame(block->needs_frame());
+
       masm()->bind(GetLabel(current_block_));
+      if (block->must_construct_frame()) {
+        AssemblePrologue();
+        // TODO(mtrofin): investigate why moving this back to function
+        // prologue upsets the ARM simulator.
+        if (linkage()->GetIncomingDescriptor()->InitializeRootRegister()) {
+          masm()->InitializeRootRegister();

[danno, 2016/03/29 15:04:28]

I'd really like to know why this doesn't work when it's in AssemblePrologue. It
makes me a bit nervous that this special handling needs to be in here and we
don't understand exactly why, and ideally I would like to have it fixed before
landing this.

+        }
+      }
+
       for (int i = block->code_start(); i < block->code_end(); ++i) {
-        AssembleInstruction(code()->InstructionAt(i));
+        Instruction* instr = code()->InstructionAt(i);
+        AssembleGaps(instr);
+        if (block->must_deconstruct_frame() &&

[danno, 2016/03/29 15:04:28]

Can you add a predicate to block called MustDeconstructFrameAfterInstruction()
that takes index i and encapsulates this test?

[Mircea Trofin, 2016/03/30 04:13:27]

I think the main problem here is this !instr->IsRet(). Without it, the rest
would look pretty clean and straight forward. I'd prefer refactoring (subsequent
to this CL) AssembleReturn, so it won't disassemble the frame 
by itself.

Or were you talking about just the first 2 conditions?

+            i == block->last_instruction_index() && !instr->IsRet()) {
+          DCHECK(instr->IsJump());
+          AssembleDeconstructFrame();
+        }
+        AssembleInstruction(instr);
       }
     }
   }
 
   // Assemble all out-of-line code.
   if (ools_) {
     masm()->RecordComment("-- Out of line code --");
     for (OutOfLineCode* ool = ools_; ool; ool = ool->next()) {
       masm()->bind(ool->entry());
       ool->Generate();
@@ skipping 124 matching lines @@
     RootIndexMap map(isolate());
     int root_index = map.Lookup(*object);
     if (root_index != RootIndexMap::kInvalidRootIndex) {
       *index_return = static_cast<Heap::RootListIndex>(root_index);
       return true;
     }
   }
   return false;
 }
 
-
 void CodeGenerator::AssembleInstruction(Instruction* instr) {
-  AssembleGaps(instr);
   AssembleSourcePosition(instr);
   // Assemble architecture-specific code for the instruction.
   AssembleArchInstruction(instr);
 
   FlagsMode mode = FlagsModeField::decode(instr->opcode());
   FlagsCondition condition = FlagsConditionField::decode(instr->opcode());
   switch (mode) {
     case kFlags_branch: {
       // Assemble a branch after this instruction.
       InstructionOperandConverter i(this, instr);
@@ skipping 448 matching lines @@
     Instruction* instr, size_t frame_state_offset) {
   int const deoptimization_id = BuildTranslation(
       instr, -1, frame_state_offset, OutputFrameStateCombine::Ignore());
   DeoptimizationExit* const exit =
       new (zone()) DeoptimizationExit(deoptimization_id);
   deoptimization_exits_.push_back(exit);
   return exit;
 }
 
 int CodeGenerator::TailCallFrameStackSlotDelta(int stack_param_delta) {
-  CallDescriptor* descriptor = linkage()->GetIncomingDescriptor();
-  int spill_slots = frame()->GetSpillSlotCount();
-  bool has_frame = descriptor->IsJSFunctionCall() || spill_slots > 0;
   // Leave the PC on the stack on platforms that have that as part of their ABI
   int pc_slots = V8_TARGET_ARCH_STORES_RETURN_ADDRESS_ON_STACK ? 1 : 0;
-  int sp_slot_delta =
-      has_frame ? (frame()->GetTotalFrameSlotCount() - pc_slots) : 0;
+  int sp_slot_delta = frame_access_state()->has_frame()
+                          ? (frame()->GetTotalFrameSlotCount() - pc_slots)
+                          : 0;
   // Discard only slots that won't be used by new parameters.
   sp_slot_delta += stack_param_delta;
   return sp_slot_delta;
 }
 
-
 OutOfLineCode::OutOfLineCode(CodeGenerator* gen)
     : frame_(gen->frame()), masm_(gen->masm()), next_(gen->ools_) {
   gen->ools_ = this;
 }
 
 
 OutOfLineCode::~OutOfLineCode() {}
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8