[turbofan] Relax dependencies due to deopt during instruction scheduling.

src/compiler/instruction-scheduler.h

 // Copyright 2015 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.
 
 #ifndef V8_COMPILER_INSTRUCTION_SCHEDULER_H_
 #define V8_COMPILER_INSTRUCTION_SCHEDULER_H_
 
 #include "src/compiler/instruction.h"
 #include "src/zone/zone-containers.h"
 
 namespace v8 {
 namespace internal {
 namespace compiler {
 
 // A set of flags describing properties of the instructions so that the
 // scheduler is aware of dependencies between instructions.
 enum ArchOpcodeFlags {
   kNoOpcodeFlags = 0,
   kIsBlockTerminator = 1,  // The instruction marks the end of a basic block
                            // e.g.: jump and return instructions.
   kHasSideEffect = 2,      // The instruction has some side effects (memory
                            // store, function call...)
   kIsLoadOperation = 4,    // The instruction is a memory load.
+  kMayNeedDeoptCheck = 8,  // The instruction might be associated with a deopt
+                           // check. This is the case of instruction which can
+                           // blow up with particular inputs (e.g.: division by
+                           // zero on Intel platforms).
 };
 
-
 class InstructionScheduler final : public ZoneObject {
  public:
   InstructionScheduler(Zone* zone, InstructionSequence* sequence);
 
   void StartBlock(RpoNumber rpo);
   void EndBlock(RpoNumber rpo);
 
   void AddInstruction(Instruction* instr);
 
   static bool SchedulerSupported();
@@ skipping 111 matching lines @@
   // Return the scheduling properties of the given instruction.
   int GetInstructionFlags(const Instruction* instr) const;
   int GetTargetInstructionFlags(const Instruction* instr) const;
 
   // Return true if the instruction is a basic block terminator.
   bool IsBlockTerminator(const Instruction* instr) const;
 
   // Check whether the given instruction has side effects (e.g. function call,
   // memory store).
   bool HasSideEffect(const Instruction* instr) const {
-    return GetInstructionFlags(instr) & kHasSideEffect;
+    return (GetInstructionFlags(instr) & kHasSideEffect) != 0;
   }
 
   // Return true if the instruction is a memory load.
   bool IsLoadOperation(const Instruction* instr) const {
-    return GetInstructionFlags(instr) & kIsLoadOperation;
+    return (GetInstructionFlags(instr) & kIsLoadOperation) != 0;
+  }
+
+  // Return true if this instruction is usually associated with a deopt check
+  // to validate its input.
+  bool MayNeedDeoptCheck(const Instruction* instr) const {
+    return (GetInstructionFlags(instr) & kMayNeedDeoptCheck) != 0;
+  }
+
+  // Return true if the instruction cannot be moved before the last deopt
+  // point we encountered.
+  bool DependsOnDeoptimization(const Instruction* instr) const {
+    return MayNeedDeoptCheck(instr) || instr->IsDeoptimizeCall() ||
+           HasSideEffect(instr) || IsLoadOperation(instr);
   }
 
   // Identify nops used as a definition point for live-in registers at
   // function entry.
   bool IsFixedRegisterParameter(const Instruction* instr) const {
     return (instr->arch_opcode() == kArchNop) && (instr->OutputCount() == 1) &&
            (instr->OutputAt(0)->IsUnallocated()) &&
            (UnallocatedOperand::cast(instr->OutputAt(0))
                 ->HasFixedRegisterPolicy() ||
             UnallocatedOperand::cast(instr->OutputAt(0))
@@ skipping 33 matching lines @@
   // Keep track of definition points for virtual registers. This is used to
   // record operand dependencies in the scheduling graph.
   ZoneMap<int32_t, ScheduleGraphNode*> operands_map_;
 };
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_COMPILER_INSTRUCTION_SCHEDULER_H_