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Do not transform a/b into a * (1/b) in the parser for integer constants.

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Strength reduction should be performed at a later stage. This
change avoid going to a double representation the case of
integer division.


Review URL: http://codereview.chromium.org/6044010

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@6174 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
This commit is contained in:
fschneider@chromium.org 2011-01-05 11:25:42 +00:00
parent 7311e10fdb
commit 83c7c699eb
1 changed files with 0 additions and 20 deletions
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20
src/parser.cc
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@ -2323,26 +2323,6 @@ Expression* Parser::ParseBinaryExpression(int prec, bool accept_IN, bool* ok) {
}
}
// 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.)