[X64] replace far jump by near jump

Code size in snapshot can be reduced ~41KB

Contributed by kanghua.yu@intel.com

Bug: None
Cq-Include-Trybots: master.tryserver.chromium.linux:linux_chromium_rel_ng
Change-Id: Ib73af39fe97cd38728affea40c593236f15bf6e5
Reviewed-on: https://chromium-review.googlesource.com/588751
Commit-Queue: Pan Deng <pan.deng@intel.com>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47531}

src/assembler.cc

@@ -159,7 +159,8 @@ AssemblerBase::AssemblerBase(IsolateData isolate_data, void* buffer,
       enabled_cpu_features_(0),
       emit_debug_code_(FLAG_debug_code),
       predictable_code_size_(false),
-      constant_pool_available_(false) {
+      constant_pool_available_(false),
+      jump_optimization_info_(nullptr) {
   own_buffer_ = buffer == NULL;
   if (buffer_size == 0) buffer_size = kMinimalBufferSize;
   DCHECK(buffer_size > 0);

src/assembler.h

@@ -65,6 +65,26 @@ void SetUpJSCallerSavedCodeData();
 // Return the code of the n-th saved register available to JavaScript.
 int JSCallerSavedCode(int n);
 
+// -----------------------------------------------------------------------------
+// Optimization for far-jmp like instructions that can be replaced by shorter.
+
+class JumpOptimizationInfo {
+ public:
+  bool is_collecting() const { return stage_ == kCollection; }
+  bool is_optimizing() const { return stage_ == kOptimization; }
+  void set_optimizing() { stage_ = kOptimization; }
+
+  bool is_optimizable() const { return optimizable_; }
+  void set_optimizable() { optimizable_ = true; }
+
+  std::vector<uint32_t>& farjmp_bitmap() { return farjmp_bitmap_; }
+
+ private:
+  enum { kCollection, kOptimization } stage_ = kCollection;
+  bool optimizable_ = false;
+  std::vector<uint32_t> farjmp_bitmap_;
+};
+
 // -----------------------------------------------------------------------------
 // Platform independent assembler base class.
 
@@ -119,6 +139,13 @@ class AssemblerBase: public Malloced {
     }
   }
 
+  JumpOptimizationInfo* jump_optimization_info() {
+    return jump_optimization_info_;
+  }
+  void set_jump_optimization_info(JumpOptimizationInfo* jump_opt) {
+    jump_optimization_info_ = jump_opt;
+  }
+
   // Overwrite a host NaN with a quiet target NaN.  Used by mksnapshot for
   // cross-snapshotting.
   static void QuietNaN(HeapObject* nan) { }
@@ -165,6 +192,8 @@ class AssemblerBase: public Malloced {
   // if the pp register points to the current code object's constant pool.
   bool constant_pool_available_;
 
+  JumpOptimizationInfo* jump_optimization_info_;
+
   // Constant pool.
   friend class FrameAndConstantPoolScope;
   friend class ConstantPoolUnavailableScope;

src/compiler/code-assembler.cc

@@ -154,9 +154,21 @@ Handle<Code> CodeAssembler::GenerateCode(CodeAssemblerState* state) {
 
   RawMachineAssembler* rasm = state->raw_assembler_.get();
   Schedule* schedule = rasm->Export();
+  JumpOptimizationInfo jump_opt;
+
   Handle<Code> code = Pipeline::GenerateCodeForCodeStub(
       rasm->isolate(), rasm->call_descriptor(), rasm->graph(), schedule,
-      state->flags_, state->name_);
+      state->flags_, state->name_,
+      rasm->isolate()->serializer_enabled() ? &jump_opt : nullptr);
+
+  if (jump_opt.is_optimizable()) {
+    jump_opt.set_optimizing();
+
+    // Regenerate machine code
+    code = Pipeline::GenerateCodeForCodeStub(
+        rasm->isolate(), rasm->call_descriptor(), rasm->graph(), schedule,
+        state->flags_, state->name_, &jump_opt);
+  }
 
   state->code_generated_ = true;
   return code;

src/compiler/code-generator.cc

@@ -38,7 +38,8 @@ class CodeGenerator::JumpTable final : public ZoneObject {
 CodeGenerator::CodeGenerator(Zone* codegen_zone, Frame* frame, Linkage* linkage,
                              InstructionSequence* code, CompilationInfo* info,
                              base::Optional<OsrHelper> osr_helper,
-                             int start_source_position)
+                             int start_source_position,
+                             JumpOptimizationInfo* jump_opt)
     : zone_(codegen_zone),
       frame_access_state_(nullptr),
       linkage_(linkage),
@@ -72,6 +73,7 @@ CodeGenerator::CodeGenerator(Zone* codegen_zone, Frame* frame, Linkage* linkage,
   }
   CreateFrameAccessState(frame);
   CHECK_EQ(info->is_osr(), osr_helper_.has_value());
+  tasm_.set_jump_optimization_info(jump_opt);
 }
 
 Isolate* CodeGenerator::isolate() const { return info_->isolate(); }
@@ -152,8 +154,11 @@ void CodeGenerator::AssembleCode() {
       if (block->IsDeferred() == (deferred == 0)) {
         continue;
       }
+
       // Align loop headers on 16-byte boundaries.
-      if (block->IsLoopHeader()) tasm()->Align(16);
+      if (block->IsLoopHeader() && !tasm()->jump_optimization_info()) {
+        tasm()->Align(16);
+      }
       // Bind a label for a block.
       current_block_ = block->rpo_number();
       unwinding_info_writer_.BeginInstructionBlock(tasm()->pc_offset(), block);

src/compiler/code-generator.h

@@ -82,7 +82,8 @@ class CodeGenerator final : public GapResolver::Assembler {
   explicit CodeGenerator(Zone* codegen_zone, Frame* frame, Linkage* linkage,
                          InstructionSequence* code, CompilationInfo* info,
                          base::Optional<OsrHelper> osr_helper,
-                         int start_source_position);
+                         int start_source_position,
+                         JumpOptimizationInfo* jump_opt);
 
   // Generate native code. After calling AssembleCode, call FinalizeCode to
   // produce the actual code object. If an error occurs during either phase,

src/compiler/pipeline.cc

@@ -142,7 +142,8 @@ class PipelineData {
 
   // For machine graph testing entry point.
   PipelineData(ZoneStats* zone_stats, CompilationInfo* info, Graph* graph,
-               Schedule* schedule, SourcePositionTable* source_positions)
+               Schedule* schedule, SourcePositionTable* source_positions,
+               JumpOptimizationInfo* jump_opt)
       : isolate_(info->isolate()),
         info_(info),
         debug_name_(info_->GetDebugName()),
@@ -156,8 +157,8 @@ class PipelineData {
         codegen_zone_scope_(zone_stats_, ZONE_NAME),
         codegen_zone_(codegen_zone_scope_.zone()),
         register_allocation_zone_scope_(zone_stats_, ZONE_NAME),
-        register_allocation_zone_(register_allocation_zone_scope_.zone()) {
-  }
+        register_allocation_zone_(register_allocation_zone_scope_.zone()),
+        jump_optimization_info_(jump_opt) {}
   // For register allocation testing entry point.
   PipelineData(ZoneStats* zone_stats, CompilationInfo* info,
                InstructionSequence* sequence)
@@ -254,6 +255,10 @@ class PipelineData {
     return protected_instructions_;
   }
 
+  JumpOptimizationInfo* jump_optimization_info() const {
+    return jump_optimization_info_;
+  }
+
   void DeleteGraphZone() {
     if (graph_zone_ == nullptr) return;
     graph_zone_scope_.Destroy();
@@ -333,9 +338,9 @@ class PipelineData {
 
   void InitializeCodeGenerator(Linkage* linkage) {
     DCHECK_NULL(code_generator_);
-    code_generator_ =
-        new CodeGenerator(codegen_zone(), frame(), linkage, sequence(), info(),
-                          osr_helper_, start_source_position_);
+    code_generator_ = new CodeGenerator(
+        codegen_zone(), frame(), linkage, sequence(), info(), osr_helper_,
+        start_source_position_, jump_optimization_info_);
   }
 
   void BeginPhaseKind(const char* phase_kind_name) {
@@ -409,6 +414,8 @@ class PipelineData {
   ZoneVector<trap_handler::ProtectedInstructionData>* protected_instructions_ =
       nullptr;
 
+  JumpOptimizationInfo* jump_optimization_info_ = nullptr;
+
   DISALLOW_COPY_AND_ASSIGN(PipelineData);
 };
 
@@ -1752,14 +1759,16 @@ Handle<Code> Pipeline::GenerateCodeForCodeStub(Isolate* isolate,
                                                CallDescriptor* call_descriptor,
                                                Graph* graph, Schedule* schedule,
                                                Code::Flags flags,
-                                               const char* debug_name) {
+                                               const char* debug_name,
+                                               JumpOptimizationInfo* jump_opt) {
   CompilationInfo info(CStrVector(debug_name), isolate, graph->zone(), flags);
   if (isolate->serializer_enabled()) info.MarkAsSerializing();
 
   // Construct a pipeline for scheduling and code generation.
   ZoneStats zone_stats(isolate->allocator());
   SourcePositionTable source_positions(graph);
-  PipelineData data(&zone_stats, &info, graph, schedule, &source_positions);
+  PipelineData data(&zone_stats, &info, graph, schedule, &source_positions,
+                    jump_opt);
   data.set_verify_graph(FLAG_verify_csa);
   std::unique_ptr<PipelineStatistics> pipeline_statistics;
   if (FLAG_turbo_stats || FLAG_turbo_stats_nvp) {
@@ -1824,7 +1833,8 @@ Handle<Code> Pipeline::GenerateCodeForTesting(
   // table, then remove this conditional allocation.
   if (!source_positions)
     source_positions = new (info->zone()) SourcePositionTable(graph);
-  PipelineData data(&zone_stats, info, graph, schedule, source_positions);
+  PipelineData data(&zone_stats, info, graph, schedule, source_positions,
+                    nullptr);
   std::unique_ptr<PipelineStatistics> pipeline_statistics;
   if (FLAG_turbo_stats || FLAG_turbo_stats_nvp) {
     pipeline_statistics.reset(new PipelineStatistics(info, &zone_stats));
@@ -1901,6 +1911,14 @@ bool PipelineImpl::ScheduleAndSelectInstructions(Linkage* linkage,
   }
 
   bool verify_stub_graph = data->verify_graph();
+  // Jump optimization runs instruction selection twice, but the instruction
+  // selector mutates nodes like swapping the inputs of a load, which can
+  // violate the machine graph verification rules. So we skip the second
+  // verification on a graph that already verified before.
+  auto jump_opt = data->jump_optimization_info();
+  if (jump_opt && jump_opt->is_optimizing()) {
+    verify_stub_graph = false;
+  }
   if (verify_stub_graph ||
       (FLAG_turbo_verify_machine_graph != nullptr &&
        (!strcmp(FLAG_turbo_verify_machine_graph, "*") ||

src/compiler/pipeline.h

@@ -17,6 +17,7 @@ namespace internal {
 class CompilationInfo;
 class CompilationJob;
 class RegisterConfiguration;
+class JumpOptimizationInfo;
 
 namespace trap_handler {
 struct ProtectedInstructionData;
@@ -55,7 +56,8 @@ class Pipeline : public AllStatic {
                                               CallDescriptor* call_descriptor,
                                               Graph* graph, Schedule* schedule,
                                               Code::Flags flags,
-                                              const char* debug_name);
+                                              const char* debug_name,
+                                              JumpOptimizationInfo* jump_opt);
 
   // Run the entire pipeline and generate a handle to a code object suitable for
   // testing.

src/ia32/assembler-ia32.cc

@@ -352,6 +352,29 @@ void Assembler::GetCode(Isolate* isolate, CodeDesc* desc) {
   desc->constant_pool_size = 0;
   desc->unwinding_info_size = 0;
   desc->unwinding_info = nullptr;
+
+  // Collection stage
+  auto jump_opt = jump_optimization_info();
+  if (jump_opt && jump_opt->is_collecting()) {
+    auto& bitmap = jump_opt->farjmp_bitmap();
+    int num = static_cast<int>(farjmp_positions_.size());
+    if (num && bitmap.empty()) {
+      bool can_opt = false;
+
+      bitmap.resize((num + 31) / 32, 0);
+      for (int i = 0; i < num; i++) {
+        int disp_pos = farjmp_positions_[i];
+        int disp = long_at(disp_pos);
+        if (is_int8(disp)) {
+          bitmap[i / 32] |= 1 << (i & 31);
+          can_opt = true;
+        }
+      }
+      if (can_opt) {
+        jump_opt->set_optimizable();
+      }
+    }
+  }
 }
 
 
@@ -1537,6 +1560,21 @@ void Assembler::bind_to(Label* L, int pos) {
       L->UnuseNear();
     }
   }
+
+  // Optimization stage
+  auto jump_opt = jump_optimization_info();
+  if (jump_opt && jump_opt->is_optimizing()) {
+    auto it = label_farjmp_maps_.find(L);
+    if (it != label_farjmp_maps_.end()) {
+      auto& pos_vector = it->second;
+      for (auto fixup_pos : pos_vector) {
+        int disp = pos - (fixup_pos + sizeof(int8_t));
+        CHECK(is_int8(disp));
+        set_byte_at(fixup_pos, disp);
+      }
+      label_farjmp_maps_.erase(it);
+    }
+  }
   L->bind_to(pos);
 }
 
@@ -1547,6 +1585,21 @@ void Assembler::bind(Label* L) {
   bind_to(L, pc_offset());
 }
 
+void Assembler::record_farjmp_position(Label* L, int pos) {
+  auto& pos_vector = label_farjmp_maps_[L];
+  pos_vector.push_back(pos);
+}
+
+bool Assembler::is_optimizable_farjmp(int idx) {
+  if (predictable_code_size()) return false;
+
+  auto jump_opt = jump_optimization_info();
+  CHECK(jump_opt->is_optimizing());
+
+  auto& bitmap = jump_opt->farjmp_bitmap();
+  CHECK(idx < static_cast<int>(bitmap.size() * 32));
+  return !!(bitmap[idx / 32] & (1 << (idx & 31)));
+}
 
 void Assembler::call(Label* L) {
   EnsureSpace ensure_space(this);
@@ -1628,6 +1681,18 @@ void Assembler::jmp(Label* L, Label::Distance distance) {
     EMIT(0xEB);
     emit_near_disp(L);
   } else {
+    auto jump_opt = jump_optimization_info();
+    if (V8_UNLIKELY(jump_opt)) {
+      if (jump_opt->is_optimizing() && is_optimizable_farjmp(farjmp_num_++)) {
+        EMIT(0xEB);
+        record_farjmp_position(L, pc_offset());
+        EMIT(0);
+        return;
+      }
+      if (jump_opt->is_collecting()) {
+        farjmp_positions_.push_back(pc_offset() + 1);
+      }
+    }
     // 1110 1001 #32-bit disp.
     EMIT(0xE9);
     emit_disp(L, Displacement::UNCONDITIONAL_JUMP);
@@ -1684,6 +1749,19 @@ void Assembler::j(Condition cc, Label* L, Label::Distance distance) {
     EMIT(0x70 | cc);
     emit_near_disp(L);
   } else {
+    auto jump_opt = jump_optimization_info();
+    if (V8_UNLIKELY(jump_opt)) {
+      if (jump_opt->is_optimizing() && is_optimizable_farjmp(farjmp_num_++)) {
+        // 0111 tttn #8-bit disp
+        EMIT(0x70 | cc);
+        record_farjmp_position(L, pc_offset());
+        EMIT(0);
+        return;
+      }
+      if (jump_opt->is_collecting()) {
+        farjmp_positions_.push_back(pc_offset() + 2);
+      }
+    }
     // 0000 1111 1000 tttn #32-bit disp
     // Note: could eliminate cond. jumps to this jump if condition
     //       is the same however, seems to be rather unlikely case.

src/ia32/assembler-ia32.h

@@ -1807,6 +1807,11 @@ class Assembler : public AssemblerBase {
   // record reloc info for current pc_
   void RecordRelocInfo(RelocInfo::Mode rmode, intptr_t data = 0);
 
+  // record the position of jmp/jcc instruction
+  void record_farjmp_position(Label* L, int pos);
+
+  bool is_optimizable_farjmp(int idx);
+
   friend class CodePatcher;
   friend class EnsureSpace;
 
@@ -1830,6 +1835,11 @@ class Assembler : public AssemblerBase {
   void AllocateAndInstallRequestedHeapObjects(Isolate* isolate);
 
   std::forward_list<HeapObjectRequest> heap_object_requests_;
+
+  // Variables for this instance of assembler
+  int farjmp_num_ = 0;
+  std::deque<int> farjmp_positions_;
+  std::map<Label*, std::vector<int>> label_farjmp_maps_;
 };
 
 

src/x64/assembler-x64.cc

@@ -331,6 +331,29 @@ void Assembler::GetCode(Isolate* isolate, CodeDesc* desc) {
   desc->constant_pool_size = 0;
   desc->unwinding_info_size = 0;
   desc->unwinding_info = nullptr;
+
+  // Collection stage
+  auto jump_opt = jump_optimization_info();
+  if (jump_opt && jump_opt->is_collecting()) {
+    auto& bitmap = jump_opt->farjmp_bitmap();
+    int num = static_cast<int>(farjmp_positions_.size());
+    if (num && bitmap.empty()) {
+      bool can_opt = false;
+
+      bitmap.resize((num + 31) / 32, 0);
+      for (int i = 0; i < num; i++) {
+        int disp_pos = farjmp_positions_[i];
+        int disp = long_at(disp_pos);
+        if (is_int8(disp)) {
+          bitmap[i / 32] |= 1 << (i & 31);
+          can_opt = true;
+        }
+      }
+      if (can_opt) {
+        jump_opt->set_optimizable();
+      }
+    }
+  }
 }
 
 
@@ -401,6 +424,21 @@ void Assembler::bind_to(Label* L, int pos) {
       L->UnuseNear();
     }
   }
+
+  // Optimization stage
+  auto jump_opt = jump_optimization_info();
+  if (jump_opt && jump_opt->is_optimizing()) {
+    auto it = label_farjmp_maps_.find(L);
+    if (it != label_farjmp_maps_.end()) {
+      auto& pos_vector = it->second;
+      for (auto fixup_pos : pos_vector) {
+        int disp = pos - (fixup_pos + sizeof(int8_t));
+        CHECK(is_int8(disp));
+        set_byte_at(fixup_pos, disp);
+      }
+      label_farjmp_maps_.erase(it);
+    }
+  }
   L->bind_to(pos);
 }
 
@@ -409,6 +447,21 @@ void Assembler::bind(Label* L) {
   bind_to(L, pc_offset());
 }
 
+void Assembler::record_farjmp_position(Label* L, int pos) {
+  auto& pos_vector = label_farjmp_maps_[L];
+  pos_vector.push_back(pos);
+}
+
+bool Assembler::is_optimizable_farjmp(int idx) {
+  if (predictable_code_size()) return false;
+
+  auto jump_opt = jump_optimization_info();
+  CHECK(jump_opt->is_optimizing());
+
+  auto& bitmap = jump_opt->farjmp_bitmap();
+  CHECK(idx < static_cast<int>(bitmap.size() * 32));
+  return !!(bitmap[idx / 32] & (1 << (idx & 31)));
+}
 
 void Assembler::GrowBuffer() {
   DCHECK(buffer_overflow());
@@ -1268,7 +1321,21 @@ void Assembler::j(Condition cc, Label* L, Label::Distance distance) {
     }
     L->link_to(pc_offset(), Label::kNear);
     emit(disp);
-  } else if (L->is_linked()) {
+  } else {
+    auto jump_opt = jump_optimization_info();
+    if (V8_UNLIKELY(jump_opt)) {
+      if (jump_opt->is_optimizing() && is_optimizable_farjmp(farjmp_num_++)) {
+        // 0111 tttn #8-bit disp
+        emit(0x70 | cc);
+        record_farjmp_position(L, pc_offset());
+        emit(0);
+        return;
+      }
+      if (jump_opt->is_collecting()) {
+        farjmp_positions_.push_back(pc_offset() + 2);
+      }
+    }
+    if (L->is_linked()) {
       // 0000 1111 1000 tttn #32-bit disp.
       emit(0x0F);
       emit(0x80 | cc);
@@ -1282,6 +1349,7 @@ void Assembler::j(Condition cc, Label* L, Label::Distance distance) {
       emitl(current);
       L->link_to(current);
     }
+  }
 }
 
 
@@ -1333,7 +1401,20 @@ void Assembler::jmp(Label* L, Label::Distance distance) {
     }
     L->link_to(pc_offset(), Label::kNear);
     emit(disp);
-  } else if (L->is_linked()) {
+  } else {
+    auto jump_opt = jump_optimization_info();
+    if (V8_UNLIKELY(jump_opt)) {
+      if (jump_opt->is_optimizing() && is_optimizable_farjmp(farjmp_num_++)) {
+        emit(0xEB);
+        record_farjmp_position(L, pc_offset());
+        emit(0);
+        return;
+      }
+      if (jump_opt->is_collecting()) {
+        farjmp_positions_.push_back(pc_offset() + 1);
+      }
+    }
+    if (L->is_linked()) {
       // 1110 1001 #32-bit disp.
       emit(0xE9);
       emitl(L->pos());
@@ -1346,6 +1427,7 @@ void Assembler::jmp(Label* L, Label::Distance distance) {
       emitl(current);
       L->link_to(current);
     }
+  }
 }
 
 

src/x64/assembler-x64.h

@@ -2494,6 +2494,11 @@ class Assembler : public AssemblerBase {
   void bmi2l(SIMDPrefix pp, byte op, Register reg, Register vreg,
              const Operand& rm);
 
+  // record the position of jmp/jcc instruction
+  void record_farjmp_position(Label* L, int pos);
+
+  bool is_optimizable_farjmp(int idx);
+
   friend class CodePatcher;
   friend class EnsureSpace;
   friend class RegExpMacroAssemblerX64;
@@ -2520,6 +2525,11 @@ class Assembler : public AssemblerBase {
   void AllocateAndInstallRequestedHeapObjects(Isolate* isolate);
 
   std::forward_list<HeapObjectRequest> heap_object_requests_;
+
+  // Variables for this instance of assembler
+  int farjmp_num_ = 0;
+  std::deque<int> farjmp_positions_;
+  std::map<Label*, std::vector<int>> label_farjmp_maps_;
 };
 
 

test/cctest/compiler/test-code-generator.cc

@@ -28,7 +28,7 @@ class CodeGeneratorTester : public InitializedHandleScope {
         sequence_(main_isolate(), &zone_, &blocks_),
         frame_(descriptor_->CalculateFixedFrameSize()),
         generator_(&zone_, &frame_, &linkage_, &sequence_, &info_,
-                   base::Optional<OsrHelper>(), kNoSourcePosition) {
+                   base::Optional<OsrHelper>(), kNoSourcePosition, nullptr) {
     info_.set_prologue_offset(generator_.tasm()->pc_offset());
   }