Optimize the slow case implementations of bit operations by

avoiding excessive ToNumber calls and by dealing with NaNs
in BIT_AND and SAR.
Review URL: http://codereview.chromium.org/125118

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@2163 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/runtime.js

@@ -97,12 +97,12 @@ function STRICT_EQUALS(x) {
   if (IS_STRING(this)) {
     if (!IS_STRING(x)) return 1;  // not equal
     return %StringEquals(this, x);
-  } 
+  }
 
   if (IS_NUMBER(this)) {
     if (!IS_NUMBER(x)) return 1;  // not equal
     return %NumberEquals(this, x);
-  } 
+  }
 
   // If anything else gets here, we just do simple identity check.
   // Objects (including functions), null, undefined and booleans were
@@ -148,7 +148,7 @@ function ADD(x) {
   // Default implementation.
   var a = %ToPrimitive(this, NO_HINT);
   var b = %ToPrimitive(x, NO_HINT);
-  
+
   if (IS_STRING(a)) {
     return %StringAdd(a, %ToString(b));
   } else if (IS_STRING(b)) {
@@ -160,40 +160,48 @@ function ADD(x) {
 
 
 // Left operand (this) is already a string.
-function STRING_ADD_LEFT(x) {
-  x = %ToString(%ToPrimitive(x, NO_HINT));
-  return %StringAdd(this, x);
+function STRING_ADD_LEFT(y) {
+  if (!IS_STRING(y)) y = %ToString(%ToPrimitive(y, NO_HINT));
+  return %StringAdd(this, y);
 }
 
 
-// Right operand (x) is already a string.
-function STRING_ADD_RIGHT(x) {
-  var a = %ToString(%ToPrimitive(this, NO_HINT));
-  return %StringAdd(a, x);
+// Right operand (y) is already a string.
+function STRING_ADD_RIGHT(y) {
+  var x = IS_STRING(this) ? this : %ToString(%ToPrimitive(this, NO_HINT));
+  return %StringAdd(x, y);
 }
 
 
 // ECMA-262, section 11.6.2, page 50.
-function SUB(x) {
-  return %NumberSub(%ToNumber(this), %ToNumber(x));
+function SUB(y) {
+  var x = IS_NUMBER(this) ? this : %ToNumber(this);
+  if (!IS_NUMBER(y)) y = %ToNumber(y);
+  return %NumberSub(x, y);
 }
 
 
 // ECMA-262, section 11.5.1, page 48.
-function MUL(x) {
-  return %NumberMul(%ToNumber(this), %ToNumber(x));
+function MUL(y) {
+  var x = IS_NUMBER(this) ? this : %ToNumber(this);
+  if (!IS_NUMBER(y)) y = %ToNumber(y);
+  return %NumberMul(x, y);
 }
 
 
 // ECMA-262, section 11.5.2, page 49.
-function DIV(x) {
-  return %NumberDiv(%ToNumber(this), %ToNumber(x));
+function DIV(y) {
+  var x = IS_NUMBER(this) ? this : %ToNumber(this);
+  if (!IS_NUMBER(y)) y = %ToNumber(y);
+  return %NumberDiv(x, y);
 }
 
 
 // ECMA-262, section 11.5.3, page 49.
-function MOD(x) {
-  return %NumberMod(%ToNumber(this), %ToNumber(x));
+function MOD(y) {
+  var x = IS_NUMBER(this) ? this : %ToNumber(this);
+  if (!IS_NUMBER(y)) y = %ToNumber(y);
+  return %NumberMod(x, y);
 }
 
 
@@ -204,50 +212,82 @@ function MOD(x) {
 */
 
 // ECMA-262, section 11.10, page 57.
-function BIT_OR(x) {
-  return %NumberOr(%ToNumber(this), %ToNumber(x));
+function BIT_OR(y) {
+  var x = IS_NUMBER(this) ? this : %ToNumber(this);
+  if (!IS_NUMBER(y)) y = %ToNumber(y);
+  return %NumberOr(x, y);
 }
 
 
 // ECMA-262, section 11.10, page 57.
-function BIT_AND(x) {
-  return %NumberAnd(%ToNumber(this), %ToNumber(x));
+function BIT_AND(y) {
+  var x;
+  if (IS_NUMBER(this)) {
+    x = this;
+  } else {
+    x = %ToNumber(this);
+    // Optimize for the case where we end up AND'ing a value
+    // that doesn't convert to a number. This is common in
+    // certain benchmarks.
+    if (NUMBER_IS_NAN(x)) return 0;
+  }
+  if (!IS_NUMBER(y)) y = %ToNumber(y);
+  return %NumberAnd(x, y);
 }
 
 
 // ECMA-262, section 11.10, page 57.
-function BIT_XOR(x) {
-  return %NumberXor(%ToNumber(this), %ToNumber(x));
+function BIT_XOR(y) {
+  var x = IS_NUMBER(this) ? this : %ToNumber(this);
+  if (!IS_NUMBER(y)) y = %ToNumber(y);
+  return %NumberXor(x, y);
 }
 
 
 // ECMA-262, section 11.4.7, page 47.
 function UNARY_MINUS() {
-  return %NumberUnaryMinus(%ToNumber(this));
+  var x = IS_NUMBER(this) ? this : %ToNumber(this);
+  return %NumberUnaryMinus(x);
 }
 
 
 // ECMA-262, section 11.4.8, page 48.
 function BIT_NOT() {
-  return %NumberNot(%ToNumber(this));
+  var x = IS_NUMBER(this) ? this : %ToNumber(this);
+  return %NumberNot(x);
 }
 
 
 // ECMA-262, section 11.7.1, page 51.
-function SHL(x) {
-  return %NumberShl(%ToNumber(this), %ToNumber(x));
+function SHL(y) {
+  var x = IS_NUMBER(this) ? this : %ToNumber(this);
+  if (!IS_NUMBER(y)) y = %ToNumber(y);
+  return %NumberShl(x, y);
 }
 
 
 // ECMA-262, section 11.7.2, page 51.
-function SAR(x) {
-  return %NumberSar(%ToNumber(this), %ToNumber(x));
+function SAR(y) {
+  var x;
+  if (IS_NUMBER(this)) {
+    x = this;
+  } else {
+    x = %ToNumber(this);
+    // Optimize for the case where we end up shifting a value
+    // that doesn't convert to a number. This is common in
+    // certain benchmarks.
+    if (NUMBER_IS_NAN(x)) return 0;
+  }
+  if (!IS_NUMBER(y)) y = %ToNumber(y);
+  return %NumberSar(x, y);
 }
 
 
 // ECMA-262, section 11.7.3, page 52.
-function SHR(x) {
-  return %NumberShr(%ToNumber(this), %ToNumber(x));
+function SHR(y) {
+  var x = IS_NUMBER(this) ? this : %ToNumber(this);
+  if (!IS_NUMBER(y)) y = %ToNumber(y);
+  return %NumberShr(x, y);
 }