[Webkit-unassigned] [Bug 72878] Strength reduction for Mul and Mod operations for known constants in DFG

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=72878





--- Comment #10 from Filip Pizlo <fpizlo at apple.com>  2011-11-22 20:04:13 PST ---
(In reply to comment #9)
> Created an attachment (id=116309)
 --> (https://bugs.webkit.org/attachment.cgi?id=116309&action=review) [details]
> simple test case
> 
> Filip, thanks for the comments!
> 
> Here's a very simple test case for constant power of two mul and mod.
> 
> Tested on 64bit:
> 
> ToT -
> constant multiply result: 9999999900000000, in 878 ms
> constant modulo result: 50000000, in 784 ms
> 
> Patched -
> constant multiply result: 9999999900000000, in 721 ms
> constant modulo result: 50000000, in 721 ms

That's great!  Note that 'i' and 'iter' are global variables in your test, so probably you could get even better performance by making 'iter' an argument to the test functions (so it's local) or maybe loading it into a local 'var' at the top of those functions, and then declaring 'i' as a var.

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