Optimize implementation of Math.floor a little by special casing...

src/ia32/codegen-ia32.cc

 // Copyright 2006-2009 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 5979 matching lines @@
 
 
 void CodeGenerator::VisitThisFunction(ThisFunction* node) {
   frame_->PushFunction();
 }
 
 
 void CodeGenerator::VisitCompareOperation(CompareOperation* node) {
   Comment cmnt(masm_, "[ CompareOperation");
 
+  bool left_already_loaded = false;
+
   // Get the expressions from the node.
   Expression* left = node->left();
   Expression* right = node->right();
   Token::Value op = node->op();
   // To make typeof testing for natives implemented in JavaScript really
   // efficient, we generate special code for expressions of the form:
   // 'typeof <expression> == <string>'.
   UnaryOperation* operation = left->AsUnaryOperation();
   if ((op == Token::EQ || op == Token::EQ_STRICT) &&
       (operation != NULL && operation->op() == Token::TYPEOF) &&
@@ skipping 60 matching lines @@
     } else if (check->Equals(Heap::function_symbol())) {
       __ test(answer.reg(), Immediate(kSmiTagMask));
       destination()->false_target()->Branch(zero);
       frame_->Spill(answer.reg());
       __ CmpObjectType(answer.reg(), JS_FUNCTION_TYPE, answer.reg());
       destination()->true_target()->Branch(equal);
       // Regular expressions are callable so typeof == 'function'.
       __ CmpInstanceType(answer.reg(), JS_REGEXP_TYPE);
       answer.Unuse();
       destination()->Split(equal);
-
     } else if (check->Equals(Heap::object_symbol())) {
       __ test(answer.reg(), Immediate(kSmiTagMask));
       destination()->false_target()->Branch(zero);
       __ cmp(answer.reg(), Factory::null_value());
       destination()->true_target()->Branch(equal);
 
       Result map = allocator()->Allocate();
       ASSERT(map.is_valid());
       // Regular expressions are typeof == 'function', not 'object'.
       __ CmpObjectType(answer.reg(), JS_REGEXP_TYPE, map.reg());
@@ skipping 11 matching lines @@
       answer.Unuse();
       map.Unuse();
       destination()->Split(less_equal);
     } else {
       // Uncommon case: typeof testing against a string literal that is
       // never returned from the typeof operator.
       answer.Unuse();
       destination()->Goto(false);
     }
     return;
+  } else if (op == Token::LT &&
+             right->AsLiteral() != NULL &&
+             right->AsLiteral()->handle()->IsHeapNumber()) {
+    Handle<HeapNumber> check(HeapNumber::cast(*right->AsLiteral()->handle()));
+    if (check->value() == 2147483648.0) {  // 0x80000000.
+      Load(left);
+      left_already_loaded = true;
+      Result lhs = frame_->Pop();
+      lhs.ToRegister();
+      __ test(lhs.reg(), Immediate(kSmiTagMask));
+      destination()->true_target()->Branch(zero);  // All Smis are less.
+      Result scratch = allocator()->Allocate();
+      ASSERT(scratch.is_valid());
+      __ mov(scratch.reg(), FieldOperand(lhs.reg(), HeapObject::kMapOffset));
+      __ cmp(scratch.reg(), Factory::heap_number_map());
+      JumpTarget not_a_number;
+      not_a_number.Branch(not_equal, &lhs);
+      __ mov(scratch.reg(), FieldOperand(lhs.reg(), HeapNumber::kExponentOffset));

[Søren Thygesen Gjesse, 2009/12/21 14:59:39]

Line longer than 80 chars.

+      __ cmp(Operand(scratch.reg()), Immediate(0xfff00000));
+      not_a_number.Branch(above_equal, &lhs);  // It's a negative NaN or -Infinity.

[Søren Thygesen Gjesse, 2009/12/21 14:59:39]

Ditto.

+      const uint32_t borderline_exponent =
+          (HeapNumber::kExponentBias + 31) << HeapNumber::kExponentShift;
+      __ cmp(Operand(scratch.reg()), Immediate(borderline_exponent));
+      scratch.Unuse();
+      lhs.Unuse();
+      destination()->true_target()->Branch(less);
+      destination()->false_target()->Jump();
+
+      not_a_number.Bind(&lhs);
+      frame_->Push(&lhs);
+    }
   }
 
   Condition cc = no_condition;
   bool strict = false;
   switch (op) {
     case Token::EQ_STRICT:
       strict = true;
       // Fall through
     case Token::EQ:
       cc = equal;
       break;
     case Token::LT:
       cc = less;
       break;
     case Token::GT:
       cc = greater;
       break;
     case Token::LTE:
       cc = less_equal;
       break;
     case Token::GTE:
       cc = greater_equal;
       break;
     case Token::IN: {
-      Load(left);
+      if (!left_already_loaded) Load(left);
       Load(right);
       Result answer = frame_->InvokeBuiltin(Builtins::IN, CALL_FUNCTION, 2);
       frame_->Push(&answer);  // push the result
       return;
     }
     case Token::INSTANCEOF: {
-      Load(left);
+      if (!left_already_loaded) Load(left);
       Load(right);
       InstanceofStub stub;
       Result answer = frame_->CallStub(&stub, 2);
       answer.ToRegister();
       __ test(answer.reg(), Operand(answer.reg()));
       answer.Unuse();
       destination()->Split(zero);
       return;
     }
     default:
       UNREACHABLE();
   }
-  Load(left);
+  if (!left_already_loaded) Load(left);
   Load(right);
   Comparison(node, cc, strict, destination());
 }
 
 
 #ifdef DEBUG
 bool CodeGenerator::HasValidEntryRegisters() {
   return (allocator()->count(eax) == (frame()->is_used(eax) ? 1 : 0))
       && (allocator()->count(ebx) == (frame()->is_used(ebx) ? 1 : 0))
       && (allocator()->count(ecx) == (frame()->is_used(ecx) ? 1 : 0))
@@ skipping 2792 matching lines @@
     __ add(Operand(dest), Immediate(2));
   }
   __ sub(Operand(count), Immediate(1));
   __ j(not_zero, &loop);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal