Port optimized comparison of a string to a constant single character string t...

src/ia32/codegen-ia32.cc

 // Copyright 2010 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 2414 matching lines @@
   // If either side is a constant of some sort, we can probably optimize the
   // comparison.
   bool left_side_constant_smi = false;
   bool left_side_constant_null = false;
   bool left_side_constant_1_char_string = false;
   if (left_side.is_constant()) {
     left_side_constant_smi = left_side.handle()->IsSmi();
     left_side_constant_null = left_side.handle()->IsNull();
     left_side_constant_1_char_string =
         (left_side.handle()->IsString() &&
-         (String::cast(*left_side.handle())->length() == 1));
+         String::cast(*left_side.handle())->length() == 1 &&
+         String::cast(*left_side.handle())->IsAsciiRepresentation());
   }
   bool right_side_constant_smi = false;
   bool right_side_constant_null = false;
   bool right_side_constant_1_char_string = false;
   if (right_side.is_constant()) {
     right_side_constant_smi = right_side.handle()->IsSmi();
     right_side_constant_null = right_side.handle()->IsNull();
     right_side_constant_1_char_string =
         (right_side.handle()->IsString() &&
-         (String::cast(*right_side.handle())->length() == 1));
+         String::cast(*right_side.handle())->length() == 1 &&
+         String::cast(*right_side.handle())->IsAsciiRepresentation());
   }
 
   if (left_side_constant_smi || right_side_constant_smi) {
     if (left_side_constant_smi && right_side_constant_smi) {
       // Trivial case, comparing two constants.
       int left_value = Smi::cast(*left_side.handle())->value();
       int right_value = Smi::cast(*right_side.handle())->value();
       switch (cc) {
         case less:
           dest->Goto(left_value < right_value);
@@ skipping 168 matching lines @@
       left_side.ToRegister();
 
       // Here we split control flow to the stub call and inlined cases
       // before finally splitting it to the control destination.  We use
       // a jump target and branching to duplicate the virtual frame at
       // the first split.  We manually handle the off-frame references
       // by reconstituting them on the non-fall-through path.
       JumpTarget is_not_string, is_string;
       Register left_reg = left_side.reg();
       Handle<Object> right_val = right_side.handle();
+      ASSERT(StringShape(String::cast(*right_val)).IsSymbol());
       __ test(left_side.reg(), Immediate(kSmiTagMask));
       is_not_string.Branch(zero, &left_side);
       Result temp = allocator_->Allocate();
       ASSERT(temp.is_valid());
       __ mov(temp.reg(),
              FieldOperand(left_side.reg(), HeapObject::kMapOffset));
       __ movzx_b(temp.reg(),
                  FieldOperand(temp.reg(), Map::kInstanceTypeOffset));
       // If we are testing for equality then make use of the symbol shortcut.
       // Check if the right left hand side has the same type as the left hand
       // side (which is always a symbol).
       if (cc == equal) {
         Label not_a_symbol;
         ASSERT(kSymbolTag != 0);
         // Ensure that no non-strings have the symbol bit set.
         ASSERT(kNotStringTag + kIsSymbolMask > LAST_TYPE);
         __ test(temp.reg(), Immediate(kIsSymbolMask));  // Test the symbol bit.
         __ j(zero, &not_a_symbol);
         // They are symbols, so do identity compare.
         __ cmp(left_side.reg(), right_side.handle());
         dest->true_target()->Branch(equal);
         dest->false_target()->Branch(not_equal);
         __ bind(&not_a_symbol);
       }
-      // If the receiver is not a string of the type we handle call the stub.
+      // Call the compare stub if the left side is not a flat ascii string.
       __ and_(temp.reg(),
           kIsNotStringMask | kStringRepresentationMask | kStringEncodingMask);
       __ cmp(temp.reg(), kStringTag | kSeqStringTag | kAsciiStringTag);
       temp.Unuse();
       is_string.Branch(equal, &left_side);
 
       // Setup and call the compare stub.
       is_not_string.Bind(&left_side);
       CompareStub stub(cc, strict, kCantBothBeNaN);
       Result result = frame_->CallStub(&stub, &left_side, &right_side);
       result.ToRegister();
       __ cmp(result.reg(), 0);
       result.Unuse();
       dest->true_target()->Branch(cc);
       dest->false_target()->Jump();
 
       is_string.Bind(&left_side);
-      // Here we know we have a sequential ASCII string.
+      // left_side is a sequential ASCII string.
       left_side = Result(left_reg);
       right_side = Result(right_val);
       Result temp2 = allocator_->Allocate();
       ASSERT(temp2.is_valid());
       // Test string equality and comparison.
       if (cc == equal) {
         Label comparison_done;
         __ cmp(FieldOperand(left_side.reg(), String::kLengthOffset),
                Immediate(1));
         __ j(not_equal, &comparison_done);
         uint8_t char_value =
-            static_cast<uint8_t>(String::cast(*right_side.handle())->Get(0));
+            static_cast<uint8_t>(String::cast(*right_val)->Get(0));
         __ cmpb(FieldOperand(left_side.reg(), SeqAsciiString::kHeaderSize),
                 char_value);
         __ bind(&comparison_done);
       } else {
         __ mov(temp2.reg(),
                FieldOperand(left_side.reg(), String::kLengthOffset));
         __ sub(Operand(temp2.reg()), Immediate(1));
         Label comparison;
-        // If the length is 0 then our subtraction gave -1 which compares less
+        // If the length is 0 then the subtraction gave -1 which compares less
         // than any character.
         __ j(negative, &comparison);
         // Otherwise load the first character.
         __ movzx_b(temp2.reg(),
                    FieldOperand(left_side.reg(), SeqAsciiString::kHeaderSize));
         __ bind(&comparison);
-        // Compare the first character of the string with out constant
-        // 1-character string.
+        // Compare the first character of the string with the
+        // constant 1-character string.
         uint8_t char_value =
-            static_cast<uint8_t>(String::cast(*right_side.handle())->Get(0));
+            static_cast<uint8_t>(String::cast(*right_val)->Get(0));
         __ cmp(Operand(temp2.reg()), Immediate(char_value));
         Label characters_were_different;
         __ j(not_equal, &characters_were_different);
         // If the first character is the same then the long string sorts after
         // the short one.
         __ cmp(FieldOperand(left_side.reg(), String::kLengthOffset),
                Immediate(1));
         __ bind(&characters_were_different);
       }
       temp2.Unuse();
@@ skipping 10082 matching lines @@
 
   // Call the runtime; it returns -1 (less), 0 (equal), or 1 (greater)
   // tagged as a small integer.
   __ bind(&runtime);
   __ TailCallRuntime(Runtime::kStringCompare, 2, 1);
 }
 
 #undef __
 
 } }  // namespace v8::internal