[hydrogen] optimize switch with string clauses

src/ia32/lithium-codegen-ia32.cc

Index: src/ia32/lithium-codegen-ia32.cc
diff --git a/src/ia32/lithium-codegen-ia32.cc b/src/ia32/lithium-codegen-ia32.cc
index d4cbbcec8fd609f1029221de88cce9b027e83327..7bc3f0d7471b387527671aab59e19cb1dac9f24c 100644
--- a/src/ia32/lithium-codegen-ia32.cc
+++ b/src/ia32/lithium-codegen-ia32.cc
@@ -1716,6 +1716,33 @@ void LCodeGen::DoIsObjectAndBranch(LIsObjectAndBranch* instr) {
 }
 
 
+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));
 
@@ -1743,6 +1770,41 @@ void LCodeGen::DoIsUndetectableAndBranch(LIsUndetectableAndBranch* instr) {
 }
 
 
+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();
@@ -2016,26 +2078,6 @@ void LCodeGen::DoDeferredLInstanceOfKnownGlobal(LInstanceOfKnownGlobal* instr,
 }
 
 
-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();