Comment #2 on issue 2513 by [email protected]: life benchmark slowness
http://code.google.com/p/v8/issues/detail?id=2513
The reason for the bad performance is that in the code generated by
Emscripten boolean values are used as integers, e.g. in expressions
like 'i7 & (i2 | 0) > 0'. We basically fall back to a generic runtime
function to perform the bitwise AND (including the implicit conversion).
Mechanically replacing all such expressions by an equivalent ternary,
e.g. 'i7 & ((i2 | 0) > 0 ? 1 : 0)' for the expression above, reduces the
time for the benchmark by a factor of 4, see attached diff.
Perhaps we can generate better code for such expressions, but doing it in a
way that doesn't hurt "good" JavaScript code is a bit tricky, so this won't
happen soon. Therefore, it would be nice if Emscripten could be changed to
generate the boolean->int conversion explicitly.
Attachments:
life.diff 856 bytes
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