Reviewers: Vyacheslav Egorov,
Description:
Do not transform a/b into a * (1/b) in the parser for integer constants.
Strength reduction should be performed at a later stage. This
change avoid going to a double representation the case of
integer division.
Please review this at http://codereview.chromium.org/6044010/
SVN Base: http://v8.googlecode.com/svn/branches/bleeding_edge/
Affected files:
M src/parser.cc
Index: src/parser.cc
===================================================================
--- src/parser.cc (revision 6162)
+++ src/parser.cc (working copy)
@@ -2323,26 +2323,6 @@
}
}
- // Convert constant divisions to multiplications for speed.
- if (op == Token::DIV &&
- y && y->AsLiteral() && y->AsLiteral()->handle()->IsNumber()) {
- double y_val = y->AsLiteral()->handle()->Number();
- int64_t y_int = static_cast<int64_t>(y_val);
- // There are rounding issues with this optimization, but they don't
- // apply if the number to be divided with has a reciprocal that
can be
- // precisely represented as a floating point number. This is the
case
- // if the number is an integer power of 2. Negative integer
powers of
- // 2 work too, but for -2, -1, 1 and 2 we don't do the strength
- // reduction because the inlined optimistic idiv has a reasonable
- // chance of succeeding by producing a Smi answer with no
remainder.
- if (static_cast<double>(y_int) == y_val &&
- (IsPowerOf2(y_int) || IsPowerOf2(-y_int)) &&
- (y_int > 2 || y_int < -2)) {
- y = NewNumberLiteral(1 / y_val);
- op = Token::MUL;
- }
- }
-
// For now we distinguish between comparisons and other binary
// operations. (We could combine the two and get rid of this
// code and AST node eventually.)
--
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