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

src/compiler/ia32/code-generator-ia32.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/ia32/assembler-ia32.h"
@@ skipping 292 matching lines @@
         __ cmp(esi, 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:
       __ mov(i.OutputRegister(), esp);
       break;
@@ skipping 429 matching lines @@
   // Add a jump if not falling through to the next block.
   if (!branch->fallthru) __ jmp(flabel);
 }
 
 
 void CodeGenerator::AssembleArchJump(BasicBlock::RpoNumber target) {
   if (!IsNextInAssemblyOrder(target)) __ jmp(GetLabel(target));
 }
 
 
-void CodeGenerator::AssembleArchSwitch(Instruction* instr) {
-  IA32OperandConverter 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(index + 1));
-  }
-  Label* const table = AddJumpTable(labels, label_count);
-  __ jmp(Operand::JumpTable(i.InputRegister(0), times_4, table));
-}
-
-
 // Assembles boolean materializations after an instruction.
 void CodeGenerator::AssembleArchBoolean(Instruction* instr,
                                         FlagsCondition condition) {
   IA32OperandConverter i(this, instr);
   Label done;
 
   // Materialize a full 32-bit 1 or 0 value. The result register is always the
   // last output of the instruction.
   Label check;
   DCHECK_NE(0u, instr->OutputCount());
@@ skipping 58 matching lines @@
     __ j(cc, &set, Label::kNear);
     __ Move(reg, Immediate(0));
     __ jmp(&done, Label::kNear);
     __ bind(&set);
     __ mov(reg, Immediate(1));
   }
   __ bind(&done);
 }
 
 
+void CodeGenerator::AssembleArchLookupSwitch(Instruction* instr) {
+  IA32OperandConverter i(this, instr);
+  Register input = i.InputRegister(0);
+  for (size_t index = 2; index < instr->InputCount(); index += 2) {
+    __ cmp(input, Immediate(i.InputInt32(index + 0)));
+    __ j(equal, GetLabel(i.InputRpo(index + 1)));
+  }
+  AssembleArchJump(i.InputRpo(1));
+}
+
+
+void CodeGenerator::AssembleArchTableSwitch(Instruction* instr) {
+  IA32OperandConverter i(this, instr);
+  Register input = i.InputRegister(0);
+  size_t const case_count = instr->InputCount() - 2;
+  Label** cases = zone()->NewArray<Label*>(case_count);
+  for (size_t index = 0; index < case_count; ++index) {
+    cases[index] = GetLabel(i.InputRpo(index + 2));
+  }
+  Label* const table = AddJumpTable(cases, case_count);
+  __ cmp(input, Immediate(case_count));
+  __ j(above_equal, GetLabel(i.InputRpo(1)));
+  __ jmp(Operand::JumpTable(input, times_4, table));
+}
+
+
 void CodeGenerator::AssembleDeoptimizerCall(int deoptimization_id) {
   Address deopt_entry = Deoptimizer::GetDeoptimizationEntry(
       isolate(), deoptimization_id, Deoptimizer::LAZY);
   __ call(deopt_entry, RelocInfo::RUNTIME_ENTRY);
 }
 
 
 // The calling convention for JSFunctions on IA32 passes arguments on the
 // stack and the JSFunction and context in EDI and ESI, respectively, thus
 // the steps of the call look as follows:
@@ skipping 389 matching lines @@
     }
   }
   MarkLazyDeoptSite();
 }
 
 #undef __
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8