[hydrogen] optimize switch with string clauses

src/ia32/lithium-codegen-ia32.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 1698 matching lines @@
   int false_block = chunk_->LookupDestination(instr->false_block_id());
   Label* true_label = chunk_->GetAssemblyLabel(true_block);
   Label* false_label = chunk_->GetAssemblyLabel(false_block);
 
   Condition true_cond = EmitIsObject(reg, temp, false_label, true_label);
 
   EmitBranch(true_block, false_block, true_cond);
 }
 
 
+Condition LCodeGen::EmitIsString(Register input,
+                                 Register temp1,
+                                 Label* is_not_string,
+                                 Label* is_string) {
+  __ JumpIfSmi(input, is_not_string);
+
+  Condition cond = masm_->IsObjectStringType(input, temp1, temp1);
+
+  return cond;
+}
+
+
+void LCodeGen::DoIsStringAndBranch(LIsStringAndBranch* instr) {
+  Register reg = ToRegister(instr->InputAt(0));
+  Register temp = ToRegister(instr->TempAt(0));
+
+  int true_block = chunk_->LookupDestination(instr->true_block_id());
+  int false_block = chunk_->LookupDestination(instr->false_block_id());
+  Label* true_label = chunk_->GetAssemblyLabel(true_block);
+  Label* false_label = chunk_->GetAssemblyLabel(false_block);
+
+  Condition true_cond = EmitIsString(reg, temp, false_label, true_label);
+
+  EmitBranch(true_block, false_block, true_cond);
+}
+
+
 void LCodeGen::DoIsSmiAndBranch(LIsSmiAndBranch* instr) {
   Operand input = ToOperand(instr->InputAt(0));
 
   int true_block = chunk_->LookupDestination(instr->true_block_id());
   int false_block = chunk_->LookupDestination(instr->false_block_id());
 
   __ test(input, Immediate(kSmiTagMask));
   EmitBranch(true_block, false_block, zero);
 }
 
 
 void LCodeGen::DoIsUndetectableAndBranch(LIsUndetectableAndBranch* instr) {
   Register input = ToRegister(instr->InputAt(0));
   Register temp = ToRegister(instr->TempAt(0));
 
   int true_block = chunk_->LookupDestination(instr->true_block_id());
   int false_block = chunk_->LookupDestination(instr->false_block_id());
 
   STATIC_ASSERT(kSmiTag == 0);
   __ JumpIfSmi(input, chunk_->GetAssemblyLabel(false_block));
   __ mov(temp, FieldOperand(input, HeapObject::kMapOffset));
   __ test_b(FieldOperand(temp, Map::kBitFieldOffset),
             1 << Map::kIsUndetectable);
   EmitBranch(true_block, false_block, not_zero);
 }
 
 
+static Condition ComputeCompareCondition(Token::Value op) {
+  switch (op) {
+    case Token::EQ_STRICT:
+    case Token::EQ:
+      return equal;
+    case Token::LT:
+      return less;
+    case Token::GT:
+      return greater;
+    case Token::LTE:
+      return less_equal;
+    case Token::GTE:
+      return greater_equal;
+    default:
+      UNREACHABLE();
+      return no_condition;
+  }
+}
+
+
+void LCodeGen::DoCompareGenericAndBranch(LCompareGenericAndBranch* instr) {
+  Token::Value op = instr->op();
+  int true_block = chunk_->LookupDestination(instr->true_block_id());
+  int false_block = chunk_->LookupDestination(instr->false_block_id());
+
+  Handle<Code> ic = CompareIC::GetUninitialized(op);

[fschneider, 2011/11/07 08:27:18]

Use StringCompareStub instead. StringCompareStub should also be fast for
symbols, so maybe it would be fine performance-wise to just do 1 pass of
comparisons using this stub.

[indutny, 2011/11/07 11:49:28]

Just benchmarked it, and found that StringCompareStub is slower for
string-to-string comparisons.

[fschneider, 2011/11/07 15:34:00]

Ok, thanks for trying out. Stick to the faster version then.
It turns out that CompareIC has a couple of fast checks before going to
slow-compare like string length.

+  CallCode(ic, RelocInfo::CODE_TARGET, instr);
+
+  Condition condition = ComputeCompareCondition(op);
+  __ test(eax, Operand(eax));
+
+  EmitBranch(true_block, false_block, condition);
+}
+
+
 static InstanceType TestType(HHasInstanceTypeAndBranch* instr) {
   InstanceType from = instr->from();
   InstanceType to = instr->to();
   if (from == FIRST_TYPE) return to;
   ASSERT(from == to || to == LAST_TYPE);
   return from;
 }
 
 
 static Condition BranchCondition(HHasInstanceTypeAndBranch* instr) {
@@ skipping 253 matching lines @@
   __ StoreToSafepointRegisterSlot(temp, temp);
   CallCodeGeneric(stub.GetCode(),
                   RelocInfo::CODE_TARGET,
                   instr,
                   RECORD_SAFEPOINT_WITH_REGISTERS_AND_NO_ARGUMENTS);
   // Put the result value into the eax slot and restore all registers.
   __ StoreToSafepointRegisterSlot(eax, eax);
 }
 
 
-static Condition ComputeCompareCondition(Token::Value op) {
-  switch (op) {
-    case Token::EQ_STRICT:
-    case Token::EQ:
-      return equal;
-    case Token::LT:
-      return less;
-    case Token::GT:
-      return greater;
-    case Token::LTE:
-      return less_equal;
-    case Token::GTE:
-      return greater_equal;
-    default:
-      UNREACHABLE();
-      return no_condition;
-  }
-}
-
-
 void LCodeGen::DoCmpT(LCmpT* instr) {
   Token::Value op = instr->op();
 
   Handle<Code> ic = CompareIC::GetUninitialized(op);
   CallCode(ic, RelocInfo::CODE_TARGET, instr);
 
   Condition condition = ComputeCompareCondition(op);
   Label true_value, done;
   __ test(eax, Operand(eax));
   __ j(condition, &true_value, Label::kNear);
@@ skipping 2534 matching lines @@
                                          env->deoptimization_index());
   __ InvokeBuiltin(Builtins::IN, CALL_FUNCTION, safepoint_generator);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_IA32