[turbofan] Remove obsolete {BlockCodeTargetSharingScope}.

By now we no longer emit calls with {RelocInfo::CODE_TARGET} as part of
WebAssembly code. Hence the requirement to block sharing of code targets
disappeared and the support can be dropped.

R=jarin@chromium.org

Change-Id: I6df026cd05769ddaa6ea8df5a7b17b62e8a7c373
Reviewed-on: https://chromium-review.googlesource.com/1100889Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
Commit-Queue: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53782}

src/arm/assembler-arm.cc

@@ -541,7 +541,6 @@ Assembler::Assembler(IsolateData isolate_data, void* buffer, int buffer_size)
   pending_64_bit_constants_.reserve(kMinNumPendingConstants);
   reloc_info_writer.Reposition(buffer_ + buffer_size_, pc_);
   next_buffer_check_ = 0;
-  code_target_sharing_blocked_nesting_ = 0;
   const_pool_blocked_nesting_ = 0;
   no_const_pool_before_ = 0;
   first_const_pool_32_use_ = -1;
@@ -564,7 +563,6 @@ Assembler::Assembler(IsolateData isolate_data, void* buffer, int buffer_size)
 
 Assembler::~Assembler() {
   DCHECK_EQ(const_pool_blocked_nesting_, 0);
-  DCHECK_EQ(code_target_sharing_blocked_nesting_, 0);
 }
 
 void Assembler::GetCode(Isolate* isolate, CodeDesc* desc) {
@@ -5153,10 +5151,8 @@ void Assembler::ConstantPoolAddEntry(int position, RelocInfo::Mode rmode,
   if (pending_32_bit_constants_.empty()) {
     first_const_pool_32_use_ = position;
   }
-  ConstantPoolEntry entry(position, value,
-                          sharing_ok || (rmode == RelocInfo::CODE_TARGET &&
-                                         IsCodeTargetSharingAllowed()),
-                          rmode);
+  ConstantPoolEntry entry(
+      position, value, sharing_ok || (rmode == RelocInfo::CODE_TARGET), rmode);
 
   bool shared = false;
   if (sharing_ok) {
@@ -5175,8 +5171,7 @@ void Assembler::ConstantPoolAddEntry(int position, RelocInfo::Mode rmode,
 
   // Share entries if allowed and possible.
   // Null-values are placeholders and must be ignored.
-  if (rmode == RelocInfo::CODE_TARGET && IsCodeTargetSharingAllowed() &&
-      value != 0) {
+  if (rmode == RelocInfo::CODE_TARGET && value != 0) {
     // Sharing entries here relies on canonicalized handles - without them, we
     // will miss the optimisation opportunity.
     Address handle_address = static_cast<Address>(value);

src/arm/assembler-arm.h

@@ -1427,36 +1427,6 @@ class Assembler : public AssemblerBase {
     DISALLOW_IMPLICIT_CONSTRUCTORS(BlockConstPoolScope);
   };
 
-  // Class for blocking sharing of code targets in constant pool.
-  class BlockCodeTargetSharingScope {
-   public:
-    explicit BlockCodeTargetSharingScope(Assembler* assem) : assem_(nullptr) {
-      Open(assem);
-    }
-    // This constructor does not initialize the scope. The user needs to
-    // explicitly call Open() before using it.
-    BlockCodeTargetSharingScope() : assem_(nullptr) {}
-    ~BlockCodeTargetSharingScope() {
-      Close();
-    }
-    void Open(Assembler* assem) {
-      DCHECK_NULL(assem_);
-      DCHECK_NOT_NULL(assem);
-      assem_ = assem;
-      assem_->StartBlockCodeTargetSharing();
-    }
-
-   private:
-    void Close() {
-      if (assem_ != nullptr) {
-        assem_->EndBlockCodeTargetSharing();
-      }
-    }
-    Assembler* assem_;
-
-    DISALLOW_COPY_AND_ASSIGN(BlockCodeTargetSharingScope);
-  };
-
   // Record a comment relocation entry that can be used by a disassembler.
   // Use --code-comments to enable.
   void RecordComment(const char* msg);
@@ -1588,20 +1558,6 @@ class Assembler : public AssemblerBase {
   // Patch branch instruction at pos to branch to given branch target pos
   void target_at_put(int pos, int target_pos);
 
-  // Prevent sharing of code target constant pool entries until
-  // EndBlockCodeTargetSharing is called. Calls to this function can be nested
-  // but must be followed by an equal number of call to
-  // EndBlockCodeTargetSharing.
-  void StartBlockCodeTargetSharing() {
-    ++code_target_sharing_blocked_nesting_;
-  }
-
-  // Resume sharing of constant pool code target entries. Needs to be called
-  // as many times as StartBlockCodeTargetSharing to have an effect.
-  void EndBlockCodeTargetSharing() {
-    --code_target_sharing_blocked_nesting_;
-  }
-
   // Prevent contant pool emission until EndBlockConstPool is called.
   // Calls to this function can be nested but must be followed by an equal
   // number of call to EndBlockConstpool.
@@ -1709,12 +1665,6 @@ class Assembler : public AssemblerBase {
   static constexpr int kCheckPoolIntervalInst = 32;
   static constexpr int kCheckPoolInterval = kCheckPoolIntervalInst * kInstrSize;
 
-  // Sharing of code target entries may be blocked in some code sequences.
-  int code_target_sharing_blocked_nesting_;
-  bool IsCodeTargetSharingAllowed() const {
-    return code_target_sharing_blocked_nesting_ == 0;
-  }
-
   // Emission of the constant pool may be blocked in some code sequences.
   int const_pool_blocked_nesting_;  // Block emission if this is not zero.
   int no_const_pool_before_;  // Block emission before this pc offset.
@@ -1761,7 +1711,6 @@ class Assembler : public AssemblerBase {
 
   friend class RelocInfo;
   friend class BlockConstPoolScope;
-  friend class BlockCodeTargetSharingScope;
   friend class EnsureSpace;
   friend class UseScratchRegisterScope;
 };

src/arm64/assembler-arm64.cc

@@ -338,8 +338,7 @@ bool ConstPool::RecordEntry(intptr_t data, RelocInfo::Mode mode) {
 
   if (CanBeShared(mode)) {
     write_reloc_info = AddSharedEntry(shared_entries_, raw_data, offset);
-  } else if (mode == RelocInfo::CODE_TARGET &&
-             assm_->IsCodeTargetSharingAllowed() && raw_data != 0) {
+  } else if (mode == RelocInfo::CODE_TARGET && raw_data != 0) {
     // A zero data value is a placeholder and must not be shared.
     write_reloc_info = AddSharedEntry(handle_to_index_map_, raw_data, offset);
   } else {
@@ -548,7 +547,6 @@ Assembler::Assembler(IsolateData isolate_data, void* buffer, int buffer_size)
       unresolved_branches_() {
   const_pool_blocked_nesting_ = 0;
   veneer_pool_blocked_nesting_ = 0;
-  code_target_sharing_blocked_nesting_ = 0;
   Reset();
 }
 
@@ -557,7 +555,6 @@ Assembler::~Assembler() {
   DCHECK(constpool_.IsEmpty());
   DCHECK_EQ(const_pool_blocked_nesting_, 0);
   DCHECK_EQ(veneer_pool_blocked_nesting_, 0);
-  DCHECK_EQ(code_target_sharing_blocked_nesting_, 0);
 }
 
 
@@ -566,7 +563,6 @@ void Assembler::Reset() {
   DCHECK((pc_ >= buffer_) && (pc_ < buffer_ + buffer_size_));
   DCHECK_EQ(const_pool_blocked_nesting_, 0);
   DCHECK_EQ(veneer_pool_blocked_nesting_, 0);
-  DCHECK_EQ(code_target_sharing_blocked_nesting_, 0);
   DCHECK(unresolved_branches_.empty());
   memset(buffer_, 0, pc_ - buffer_);
 #endif

src/arm64/assembler-arm64.h

@@ -3229,34 +3229,6 @@ class Assembler : public AssemblerBase {
     DISALLOW_IMPLICIT_CONSTRUCTORS(BlockPoolsScope);
   };
 
-  // Class for blocking sharing of code targets in constant pool.
-  class BlockCodeTargetSharingScope {
-   public:
-    explicit BlockCodeTargetSharingScope(Assembler* assem) : assem_(nullptr) {
-      Open(assem);
-    }
-    // This constructor does not initialize the scope. The user needs to
-    // explicitly call Open() before using it.
-    BlockCodeTargetSharingScope() : assem_(nullptr) {}
-    ~BlockCodeTargetSharingScope() { Close(); }
-    void Open(Assembler* assem) {
-      DCHECK_NULL(assem_);
-      DCHECK_NOT_NULL(assem);
-      assem_ = assem;
-      assem_->StartBlockCodeTargetSharing();
-    }
-
-   private:
-    void Close() {
-      if (assem_ != nullptr) {
-        assem_->EndBlockCodeTargetSharing();
-      }
-    }
-    Assembler* assem_;
-
-    DISALLOW_COPY_AND_ASSIGN(BlockCodeTargetSharingScope);
-  };
-
  protected:
   inline const Register& AppropriateZeroRegFor(const CPURegister& reg) const;
 
@@ -3341,16 +3313,6 @@ class Assembler : public AssemblerBase {
   void RemoveBranchFromLabelLinkChain(Instruction* branch, Label* label,
                                       Instruction* label_veneer = nullptr);
 
-  // Prevent sharing of code target constant pool entries until
-  // EndBlockCodeTargetSharing is called. Calls to this function can be nested
-  // but must be followed by an equal number of call to
-  // EndBlockCodeTargetSharing.
-  void StartBlockCodeTargetSharing() { ++code_target_sharing_blocked_nesting_; }
-
-  // Resume sharing of constant pool code target entries. Needs to be called
-  // as many times as StartBlockCodeTargetSharing to have an effect.
-  void EndBlockCodeTargetSharing() { --code_target_sharing_blocked_nesting_; }
-
  private:
   static uint32_t FPToImm8(double imm);
 
@@ -3530,12 +3492,6 @@ class Assembler : public AssemblerBase {
   // Emission of the veneer pools may be blocked in some code sequences.
   int veneer_pool_blocked_nesting_;  // Block emission if this is not zero.
 
-  // Sharing of code target entries may be blocked in some code sequences.
-  int code_target_sharing_blocked_nesting_;
-  bool IsCodeTargetSharingAllowed() const {
-    return code_target_sharing_blocked_nesting_ == 0;
-  }
-
   // Relocation info generation
   // Each relocation is encoded as a variable size value
   static constexpr int kMaxRelocSize = RelocInfoWriter::kMaxSize;

src/compiler/arm/code-generator-arm.cc

@@ -669,11 +669,6 @@ CodeGenerator::CodeGenResult CodeGenerator::AssembleArchInstruction(
   ArchOpcode arch_opcode = ArchOpcodeField::decode(opcode);
   switch (arch_opcode) {
     case kArchCallCodeObject: {
-      // We must not share code targets for calls to builtins for wasm code, as
-      // they might need to be patched individually.
-      internal::Assembler::BlockCodeTargetSharingScope scope;
-      if (info()->IsWasm()) scope.Open(tasm());
-
       if (instr->InputAt(0)->IsImmediate()) {
         __ Call(i.InputCode(0), RelocInfo::CODE_TARGET);
       } else {
@@ -690,11 +685,6 @@ CodeGenerator::CodeGenResult CodeGenerator::AssembleArchInstruction(
       break;
     }
     case kArchCallWasmFunction: {
-      // We must not share code targets for calls to builtins for wasm code, as
-      // they might need to be patched individually.
-      internal::Assembler::BlockCodeTargetSharingScope scope;
-      if (info()->IsWasm()) scope.Open(tasm());
-
       if (instr->InputAt(0)->IsImmediate()) {
         Constant constant = i.ToConstant(instr->InputAt(0));
         Address wasm_code = static_cast<Address>(constant.ToInt32());
@@ -709,11 +699,6 @@ CodeGenerator::CodeGenResult CodeGenerator::AssembleArchInstruction(
     }
     case kArchTailCallCodeObjectFromJSFunction:
     case kArchTailCallCodeObject: {
-      // We must not share code targets for calls to builtins for wasm code, as
-      // they might need to be patched individually.
-      internal::Assembler::BlockCodeTargetSharingScope scope;
-      if (info()->IsWasm()) scope.Open(tasm());
-
       if (arch_opcode == kArchTailCallCodeObjectFromJSFunction) {
         AssemblePopArgumentsAdaptorFrame(kJavaScriptCallArgCountRegister,
                                          i.TempRegister(0), i.TempRegister(1),
@@ -736,11 +721,6 @@ CodeGenerator::CodeGenResult CodeGenerator::AssembleArchInstruction(
       break;
     }
     case kArchTailCallWasm: {
-      // We must not share code targets for calls to builtins for wasm code, as
-      // they might need to be patched individually.
-      internal::Assembler::BlockCodeTargetSharingScope scope;
-      if (info()->IsWasm()) scope.Open(tasm());
-
       if (instr->InputAt(0)->IsImmediate()) {
         Constant constant = i.ToConstant(instr->InputAt(0));
         Address wasm_code = static_cast<Address>(constant.ToInt32());

src/compiler/arm64/code-generator-arm64.cc

@@ -601,11 +601,6 @@ CodeGenerator::CodeGenResult CodeGenerator::AssembleArchInstruction(
   ArchOpcode arch_opcode = ArchOpcodeField::decode(opcode);
   switch (arch_opcode) {
     case kArchCallCodeObject: {
-      // We must not share code targets for calls to builtins for wasm code, as
-      // they might need to be patched individually.
-      internal::Assembler::BlockCodeTargetSharingScope scope;
-      if (info()->IsWasm()) scope.Open(tasm());
-
       if (instr->InputAt(0)->IsImmediate()) {
         __ Call(i.InputCode(0), RelocInfo::CODE_TARGET);
       } else {
@@ -635,11 +630,6 @@ CodeGenerator::CodeGenResult CodeGenerator::AssembleArchInstruction(
     }
     case kArchTailCallCodeObjectFromJSFunction:
     case kArchTailCallCodeObject: {
-      // We must not share code targets for calls to builtins for wasm code, as
-      // they might need to be patched individually.
-      internal::Assembler::BlockCodeTargetSharingScope scope;
-      if (info()->IsWasm()) scope.Open(tasm());
-
       if (arch_opcode == kArchTailCallCodeObjectFromJSFunction) {
         AssemblePopArgumentsAdaptorFrame(kJavaScriptCallArgCountRegister,
                                          i.TempRegister(0), i.TempRegister(1),