Add generated code for ascii string comparison

Careted a stub for string comparison and used part of the code from that to inline string comparison in the compare stub.
Review URL: http://codereview.chromium.org/525115

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@3569 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/arm/codegen-arm.cc

@@ -3464,6 +3464,17 @@ void CodeGenerator::GenerateSubString(ZoneList<Expression*>* args) {
 }
 
 
+void CodeGenerator::GenerateStringCompare(ZoneList<Expression*>* args) {
+  ASSERT_EQ(2, args->length());
+
+  Load(args->at(0));
+  Load(args->at(1));
+
+  frame_->CallRuntime(Runtime::kStringCompare, 2);
+  frame_->EmitPush(r0);
+}
+
+
 void CodeGenerator::GenerateRegExpExec(ZoneList<Expression*>* args) {
   ASSERT_EQ(4, args->length());
 

src/arm/codegen-arm.h

@@ -366,6 +366,9 @@ class CodeGenerator: public AstVisitor {
   // Fast support for SubString.
   void GenerateSubString(ZoneList<Expression*>* args);
 
+  // Fast support for StringCompare.
+  void GenerateStringCompare(ZoneList<Expression*>* args);
+
   // Support for direct calls from JavaScript to native RegExp code.
   void GenerateRegExpExec(ZoneList<Expression*>* args);
 

src/code-stubs.h

@@ -38,6 +38,7 @@ namespace internal {
   V(GenericBinaryOp)                     \
   V(StringAdd)                           \
   V(SubString)                           \
+  V(StringCompare)                       \
   V(SmiOp)                               \
   V(Compare)                             \
   V(RecordWrite)                         \

src/codegen.cc

@@ -346,6 +346,7 @@ CodeGenerator::InlineRuntimeLUT CodeGenerator::kInlineRuntimeLUT[] = {
   {&CodeGenerator::GenerateIsFunction, "_IsFunction"},
   {&CodeGenerator::GenerateStringAdd, "_StringAdd"},
   {&CodeGenerator::GenerateSubString, "_SubString"},
+  {&CodeGenerator::GenerateStringCompare, "_StringCompare"},
   {&CodeGenerator::GenerateRegExpExec, "_RegExpExec"},
 };
 

src/ia32/assembler-ia32.cc

@@ -1207,6 +1207,14 @@ void Assembler::sub(Register dst, const Operand& src) {
 }
 
 
+void Assembler::subb(Register dst, const Operand& src) {
+  EnsureSpace ensure_space(this);
+  last_pc_ = pc_;
+  EMIT(0x2A);
+  emit_operand(dst, src);
+}
+
+
 void Assembler::sub(const Operand& dst, Register src) {
   EnsureSpace ensure_space(this);
   last_pc_ = pc_;
@@ -1592,6 +1600,18 @@ void Assembler::j(Condition cc, Handle<Code> code, Hint hint) {
 }
 
 
+void Assembler::loope(Label* L) {
+  EnsureSpace ensure_space(this);
+  last_pc_ = pc_;
+  // Only short backward jumps.
+  ASSERT(L->is_bound());
+  int offs = L->pos() - pc_offset();
+  const int kLoopInstructionSize = 2;
+  ASSERT(is_int8(offs - kLoopInstructionSize));
+  EMIT(0xE1);
+  EMIT((offs - kLoopInstructionSize) & 0xFF);
+}
+
 // FPU instructions
 
 

src/ia32/assembler-ia32.h

@@ -540,7 +540,7 @@ class Assembler : public Malloced {
   void cmov(Condition cc, Register dst, Handle<Object> handle);
   void cmov(Condition cc, Register dst, const Operand& src);
 
-  // Repetitive moves.
+  // Repetitive string instructions.
   void rep_movs();
 
   // Exchange two registers
@@ -617,6 +617,7 @@ class Assembler : public Malloced {
   void shr_cl(Register dst);
 
   void subb(const Operand& dst, int8_t imm8);
+  void subb(Register dst, const Operand& src);
   void sub(const Operand& dst, const Immediate& x);
   void sub(Register dst, const Operand& src);
   void sub(const Operand& dst, Register src);
@@ -675,6 +676,9 @@ class Assembler : public Malloced {
   void j(Condition cc, byte* entry, RelocInfo::Mode rmode, Hint hint = no_hint);
   void j(Condition cc, Handle<Code> code, Hint hint = no_hint);
 
+  // Loop instruction using ecx as counter.
+  void loope(Label* L);
+
   // Floating-point operations
   void fld(int i);
 

src/ia32/codegen-ia32.cc

@@ -5447,6 +5447,18 @@ void CodeGenerator::GenerateSubString(ZoneList<Expression*>* args) {
 }
 
 
+void CodeGenerator::GenerateStringCompare(ZoneList<Expression*>* args) {
+  ASSERT_EQ(2, args->length());
+
+  Load(args->at(0));
+  Load(args->at(1));
+
+  StringCompareStub stub;
+  Result answer = frame_->CallStub(&stub, 2);
+  frame_->Push(&answer);
+}
+
+
 void CodeGenerator::GenerateRegExpExec(ZoneList<Expression*>* args) {
   ASSERT_EQ(args->length(), 4);
 
@@ -8562,9 +8574,10 @@ void CompareStub::Generate(MacroAssembler* masm) {
 
   // Fast negative check for symbol-to-symbol equality.
   __ bind(&check_for_symbols);
+  Label check_for_strings;
   if (cc_ == equal) {
-    BranchIfNonSymbol(masm, &call_builtin, eax, ecx);
-    BranchIfNonSymbol(masm, &call_builtin, edx, ecx);
+    BranchIfNonSymbol(masm, &check_for_strings, eax, ecx);
+    BranchIfNonSymbol(masm, &check_for_strings, edx, ecx);
 
     // We've already checked for object identity, so if both operands
     // are symbols they aren't equal. Register eax already holds a
@@ -8572,6 +8585,44 @@ void CompareStub::Generate(MacroAssembler* masm) {
     __ ret(2 * kPointerSize);
   }
 
+  __ bind(&check_for_strings);
+
+  // Check that both objects are not smis.
+  ASSERT_EQ(0, kSmiTag);
+  __ mov(ebx, Operand(edx));
+  __ and_(ebx, Operand(eax));
+  __ test(ebx, Immediate(kSmiTagMask));
+  __ j(zero, &call_builtin);
+
+  // Load instance type for both objects.
+  __ mov(ecx, FieldOperand(edx, HeapObject::kMapOffset));
+  __ mov(ebx, FieldOperand(eax, HeapObject::kMapOffset));
+  __ movzx_b(ecx, FieldOperand(ecx, Map::kInstanceTypeOffset));
+  __ movzx_b(ebx, FieldOperand(ebx, Map::kInstanceTypeOffset));
+
+  // Check that both are flat ascii strings.
+  Label non_ascii_flat;
+  ASSERT(kNotStringTag != 0);
+  const int kFlatAsciiString =
+      kIsNotStringMask | kStringRepresentationMask | kStringEncodingMask;
+  __ and_(ecx, kFlatAsciiString);
+  __ cmp(ecx, kStringTag | kSeqStringTag | kAsciiStringTag);
+  __ j(not_equal, &call_builtin);
+  __ and_(ebx, kFlatAsciiString);
+  __ cmp(ebx, kStringTag | kSeqStringTag | kAsciiStringTag);
+  __ j(not_equal, &call_builtin);
+
+  // Inline comparison of ascii strings.
+  StringCompareStub::GenerateCompareFlatAsciiStrings(masm,
+                                                     edx,
+                                                     eax,
+                                                     ecx,
+                                                     ebx,
+                                                     edi);
+#ifdef DEBUG
+  __ Abort("Unexpected fall-through from string comparison");
+#endif
+
   __ bind(&call_builtin);
   // must swap argument order
   __ pop(ecx);
@@ -9579,6 +9630,144 @@ void SubStringStub::Generate(MacroAssembler* masm) {
   __ TailCallRuntime(ExternalReference(Runtime::kSubString), 3, 1);
 }
 
+
+void StringCompareStub::GenerateCompareFlatAsciiStrings(MacroAssembler* masm,
+                                                        Register left,
+                                                        Register right,
+                                                        Register counter,
+                                                        Register scratch1,
+                                                        Register scratch2) {
+  ASSERT(counter.is(ecx));
+  Label compare_lengths, compare_lengths_1;
+
+  // Find minimum length. If either length is zero just compare lengths.
+  __ mov(counter, FieldOperand(left, String::kLengthOffset));
+  __ test(counter, Operand(counter));
+  __ j(zero, &compare_lengths_1);
+  __ mov(scratch1, FieldOperand(right, String::kLengthOffset));
+  __ test(scratch1, Operand(scratch1));
+  __ j(zero, &compare_lengths_1);
+  __ cmp(counter, Operand(scratch1));
+  if (CpuFeatures::IsSupported(CMOV)) {
+    CpuFeatures::Scope use_cmov(CMOV);
+    __ cmov(less, counter, Operand(scratch1));
+  } else {
+    Label l;
+    __ j(less, &l);
+    __ mov(counter, scratch1);
+    __ bind(&l);
+  }
+
+  Label result_greater, result_less;
+  Label loop;
+  // Compare next character.
+  __ mov(scratch2, Immediate(-1));  // Index into strings.
+  __ bind(&loop);
+  // Compare characters.
+  __ add(Operand(scratch2), Immediate(1));
+  __ mov_b(scratch1, Operand(left,
+                             scratch2,
+                             times_1,
+                             SeqAsciiString::kHeaderSize - kHeapObjectTag));
+  __ subb(scratch1, Operand(right,
+                            scratch2,
+                            times_1,
+                            SeqAsciiString::kHeaderSize - kHeapObjectTag));
+  __ loope(&loop);
+  // If min length characters match compare lengths otherwise last character
+  // compare is the result.
+  __ j(equal, &compare_lengths);
+  __ j(less, &result_less);
+  __ jmp(&result_greater);
+
+  // Compare lengths.
+  Label result_not_equal;
+  __ bind(&compare_lengths);
+  __ mov(counter, FieldOperand(left, String::kLengthOffset));
+  __ bind(&compare_lengths_1);
+  __ sub(counter, FieldOperand(right, String::kLengthOffset));
+  __ j(not_zero, &result_not_equal);
+
+  // Result is EQUAL.
+  ASSERT_EQ(0, EQUAL);
+  ASSERT_EQ(0, kSmiTag);
+  __ xor_(eax, Operand(eax));
+  __ IncrementCounter(&Counters::string_compare_native, 1);
+  __ ret(2 * kPointerSize);
+  __ bind(&result_not_equal);
+  __ j(greater, &result_greater);
+
+  // Result is LESS.
+  __ bind(&result_less);
+  __ mov(eax, Immediate(Smi::FromInt(LESS)->value()));
+  __ IncrementCounter(&Counters::string_compare_native, 1);
+  __ ret(2 * kPointerSize);
+
+  // Result is GREATER.
+  __ bind(&result_greater);
+  __ mov(eax, Immediate(Smi::FromInt(GREATER)->value()));
+  __ IncrementCounter(&Counters::string_compare_native, 1);
+  __ ret(2 * kPointerSize);
+}
+
+
+void StringCompareStub::Generate(MacroAssembler* masm) {
+  Label runtime;
+
+  // Stack frame on entry.
+  //  esp[0]: return address
+  //  esp[4]: right string
+  //  esp[8]: left string
+
+  __ mov(edx, Operand(esp, 2 * kPointerSize));  // left
+  __ mov(eax, Operand(esp, 1 * kPointerSize));  // right
+
+  Label not_same;
+  __ cmp(edx, Operand(eax));
+  __ j(not_equal, &not_same);
+  ASSERT_EQ(0, EQUAL);
+  ASSERT_EQ(0, kSmiTag);
+  __ xor_(eax, Operand(eax));
+  __ IncrementCounter(&Counters::string_compare_native, 1);
+  __ ret(2 * kPointerSize);
+
+  __ bind(&not_same);
+
+  // Check that both objects are not smis.
+  ASSERT_EQ(0, kSmiTag);
+  __ mov(ebx, Operand(edx));
+  __ and_(ebx, Operand(eax));
+  __ test(ebx, Immediate(kSmiTagMask));
+  __ j(zero, &runtime);
+
+  // Load instance type for both strings.
+  __ mov(ecx, FieldOperand(edx, HeapObject::kMapOffset));
+  __ mov(ebx, FieldOperand(eax, HeapObject::kMapOffset));
+  __ movzx_b(ecx, FieldOperand(ecx, Map::kInstanceTypeOffset));
+  __ movzx_b(ebx, FieldOperand(ebx, Map::kInstanceTypeOffset));
+
+  // Check that both are flat ascii strings.
+  Label non_ascii_flat;
+  __ and_(ecx, kStringRepresentationMask | kStringEncodingMask);
+  __ cmp(ecx, kSeqStringTag | kAsciiStringTag);
+  __ j(not_equal, &non_ascii_flat);
+  const int kFlatAsciiString =
+      kIsNotStringMask | kStringRepresentationMask | kStringEncodingMask;
+  __ and_(ebx, kFlatAsciiString);
+  __ cmp(ebx, kStringTag | kSeqStringTag | kAsciiStringTag);
+  __ j(not_equal, &non_ascii_flat);
+
+  // Compare flat ascii strings.
+  GenerateCompareFlatAsciiStrings(masm, edx, eax, ecx, ebx, edi);
+
+  __ bind(&non_ascii_flat);
+
+  // Call the runtime; it returns -1 (less), 0 (equal), or 1 (greater)
+  // tagged as a small integer.
+  __ bind(&runtime);
+  __ TailCallRuntime(ExternalReference(Runtime::kStringCompare), 2, 1);
+}
+
 #undef __
 
 } }  // namespace v8::internal

src/ia32/codegen-ia32.h

@@ -547,6 +547,9 @@ class CodeGenerator: public AstVisitor {
   // Fast support for SubString.
   void GenerateSubString(ZoneList<Expression*>* args);
 
+  // Fast support for StringCompare.
+  void GenerateStringCompare(ZoneList<Expression*>* args);
+
   // Support for direct calls from JavaScript to native RegExp code.
   void GenerateRegExpExec(ZoneList<Expression*>* args);
 
@@ -804,6 +807,31 @@ class SubStringStub: public StringStubBase {
 };
 
 
+class StringCompareStub: public StringStubBase {
+ public:
+  explicit StringCompareStub() {
+  }
+
+  // Compare two flat ascii strings and returns result in eax after popping two
+  // arguments from the stack. Due to the instructions used there are certain
+  // constraints on the registers that can be passed.
+  //   counter must be ecx
+  //   scratch1 most be one of eax, ebx or edx
+  static void GenerateCompareFlatAsciiStrings(MacroAssembler* masm,
+                                              Register left,
+                                              Register right,
+                                              Register counter,
+                                              Register scratch1,
+                                              Register scratch2);
+
+ private:
+  Major MajorKey() { return StringCompare; }
+  int MinorKey() { return 0; }
+
+  void Generate(MacroAssembler* masm);
+};
+
+
 } }  // namespace v8::internal
 
 #endif  // V8_IA32_CODEGEN_IA32_H_

src/runtime.cc

@@ -1158,6 +1158,7 @@ static Object* Runtime_RegExpExec(Arguments args) {
   RUNTIME_ASSERT(last_match_info->HasFastElements());
   RUNTIME_ASSERT(index >= 0);
   RUNTIME_ASSERT(index <= subject->length());
+  Counters::regexp_entry_runtime.Increment();
   Handle<Object> result = RegExpImpl::Exec(regexp,
                                            subject,
                                            index,
@@ -4216,6 +4217,8 @@ static Object* Runtime_StringCompare(Arguments args) {
   CONVERT_CHECKED(String, x, args[0]);
   CONVERT_CHECKED(String, y, args[1]);
 
+  Counters::string_compare_runtime.Increment();
+
   // A few fast case tests before we flatten.
   if (x == y) return Smi::FromInt(EQUAL);
   if (y->length() == 0) {

src/runtime.js

@@ -118,7 +118,7 @@ function COMPARE(x, ncr) {
 
   // Fast cases for string, numbers and undefined compares.
   if (IS_STRING(this)) {
-    if (IS_STRING(x)) return %StringCompare(this, x);
+    if (IS_STRING(x)) return %_StringCompare(this, x);
     if (IS_UNDEFINED(x)) return ncr;
     left = this;
   } else if (IS_NUMBER(this)) {
@@ -135,7 +135,7 @@ function COMPARE(x, ncr) {
   // Default implementation.
   var right = %ToPrimitive(x, NUMBER_HINT);
   if (IS_STRING(left) && IS_STRING(right)) {
-    return %StringCompare(left, right);
+    return %_StringCompare(left, right);
   } else {
     var left_number = %ToNumber(left);
     var right_number = %ToNumber(right);

src/v8-counters.h

@@ -156,6 +156,8 @@ namespace internal {
   SC(string_add_native, V8.StringAddNative)                         \
   SC(sub_string_runtime, V8.SubStringRuntime)                       \
   SC(sub_string_native, V8.SubStringNative)                         \
+  SC(string_compare_native, V8.StringCompareNative)                 \
+  SC(string_compare_runtime, V8.StringCompareRuntime)               \
   SC(regexp_entry_runtime, V8.RegExpEntryRuntime)                   \
   SC(regexp_entry_native, V8.RegExpEntryNative)
 

src/x64/codegen-x64.cc

@@ -3913,6 +3913,17 @@ void CodeGenerator::GenerateSubString(ZoneList<Expression*>* args) {
 }
 
 
+void CodeGenerator::GenerateStringCompare(ZoneList<Expression*>* args) {
+  ASSERT_EQ(2, args->length());
+
+  Load(args->at(0));
+  Load(args->at(1));
+
+  Result answer = frame_->CallRuntime(Runtime::kStringCompare, 2);
+  frame_->Push(&answer);
+}
+
+
 void CodeGenerator::GenerateClassOf(ZoneList<Expression*>* args) {
   ASSERT(args->length() == 1);
   JumpTarget leave, null, function, non_function_constructor;

src/x64/codegen-x64.h

@@ -544,6 +544,9 @@ class CodeGenerator: public AstVisitor {
   // Fast support for SubString.
   void GenerateSubString(ZoneList<Expression*>* args);
 
+  // Fast support for StringCompare.
+  void GenerateStringCompare(ZoneList<Expression*>* args);
+
   // Support for direct calls from JavaScript to native RegExp code.
   void GenerateRegExpExec(ZoneList<Expression*>* args);