[turbofan] Optimize certain chains of Branch into a Switch.

src/compiler/x64/code-generator-x64.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/compiler/code-generator-impl.h"
 #include "src/compiler/gap-resolver.h"
 #include "src/compiler/node-matchers.h"
 #include "src/scopes.h"
@@ skipping 514 matching lines @@
         __ cmpp(rsi, FieldOperand(func, JSFunction::kContextOffset));
         __ Assert(equal, kWrongFunctionContext);
       }
       __ Call(FieldOperand(func, JSFunction::kCodeEntryOffset));
       AddSafepointAndDeopt(instr);
       break;
     }
     case kArchJmp:
       AssembleArchJump(i.InputRpo(0));
       break;
-    case kArchSwitch:
-      AssembleArchSwitch(instr);
+    case kArchLookupSwitch:
+      AssembleArchLookupSwitch(instr);
+      break;
+    case kArchTableSwitch:
+      AssembleArchTableSwitch(instr);
       break;
     case kArchNop:
       // don't emit code for nops.
       break;
     case kArchRet:
       AssembleReturn();
       break;
     case kArchStackPointer:
       __ movq(i.OutputRegister(), rsp);
       break;
@@ skipping 516 matching lines @@
   }
   if (!branch->fallthru) __ jmp(flabel, flabel_distance);
 }
 
 
 void CodeGenerator::AssembleArchJump(BasicBlock::RpoNumber target) {
   if (!IsNextInAssemblyOrder(target)) __ jmp(GetLabel(target));
 }
 
 
-void CodeGenerator::AssembleArchSwitch(Instruction* instr) {
-  X64OperandConverter i(this, instr);
-  size_t const label_count = instr->InputCount() - 1;
-  Label** labels = zone()->NewArray<Label*>(label_count);
-  for (size_t index = 0; index < label_count; ++index) {
-    labels[index] = GetLabel(i.InputRpo(static_cast<int>(index + 1)));
-  }
-  Label* const table = AddJumpTable(labels, label_count);
-  __ leaq(kScratchRegister, Operand(table));
-  __ jmp(Operand(kScratchRegister, i.InputRegister(0), times_8, 0));
-}
-
-
 // Assembles boolean materializations after this instruction.
 void CodeGenerator::AssembleArchBoolean(Instruction* instr,
                                         FlagsCondition condition) {
   X64OperandConverter i(this, instr);
   Label done;
 
   // Materialize a full 64-bit 1 or 0 value. The result register is always the
   // last output of the instruction.
   Label check;
   DCHECK_NE(0, static_cast<int>(instr->OutputCount()));
@@ skipping 47 matching lines @@
       cc = no_overflow;
       break;
   }
   __ bind(&check);
   __ setcc(cc, reg);
   __ movzxbl(reg, reg);
   __ bind(&done);
 }
 
 
+void CodeGenerator::AssembleArchLookupSwitch(Instruction* instr) {
+  X64OperandConverter i(this, instr);
+  Register input = i.InputRegister(0);
+  for (size_t index = 2; index < instr->InputCount(); index += 2) {
+    __ cmpl(input, Immediate(i.InputInt32(static_cast<int>(index + 0))));
+    __ j(equal, GetLabel(i.InputRpo(static_cast<int>(index + 1))));
+  }
+  AssembleArchJump(i.InputRpo(1));
+}
+
+
+void CodeGenerator::AssembleArchTableSwitch(Instruction* instr) {
+  X64OperandConverter i(this, instr);
+  Register input = i.InputRegister(0);
+  int32_t const case_count = static_cast<int32_t>(instr->InputCount() - 2);
+  Label** cases = zone()->NewArray<Label*>(case_count);
+  for (int32_t index = 0; index < case_count; ++index) {
+    cases[index] = GetLabel(i.InputRpo(index + 2));
+  }
+  Label* const table = AddJumpTable(cases, case_count);
+  __ cmpl(input, Immediate(case_count));
+  __ j(above_equal, GetLabel(i.InputRpo(1)));
+  __ leaq(kScratchRegister, Operand(table));
+  __ jmp(Operand(kScratchRegister, input, times_8, 0));
+}
+
+
 void CodeGenerator::AssembleDeoptimizerCall(int deoptimization_id) {
   Address deopt_entry = Deoptimizer::GetDeoptimizationEntry(
       isolate(), deoptimization_id, Deoptimizer::LAZY);
   __ call(deopt_entry, RelocInfo::RUNTIME_ENTRY);
 }
 
 
 void CodeGenerator::AssemblePrologue() {
   CallDescriptor* descriptor = linkage()->GetIncomingDescriptor();
   int stack_slots = frame()->GetSpillSlotCount();
@@ skipping 257 matching lines @@
     }
   }
   MarkLazyDeoptSite();
 }
 
 #undef __
 
 }  // namespace internal
 }  // namespace compiler
 }  // namespace v8