On Mon, Jan 13, 2014 at 2:53 PM, Robert O'Callahan <[email protected]>wrote:
> On Mon, Jan 13, 2014 at 2:22 PM, Daniel Micay <[email protected]>wrote: > >> -fsanitize=signed-integer-overflow: Signed integer overflow, including >> all the checks added by -ftrapv, and checking for overflow in signed >> division (INT_MIN / -1). >> >> Why not measure the impact of this on Firefox performance? We'll have >> a concrete answer about half of the picture (but not about the cost >> for unsigned or checks on overlong shifts and for division by zero). >> > > That would give us neither an upper bound on overhead (due to excluding > unsigned), nor a lower bound (due to no range analysis or LLVM changes). > But it might be interesting... > Just for fun I did a Firefox build with -ftrapv. The most surprising thing is that the browser actually worked, on Linux64 at least. Not so much on Linux32 and Mac. https://tbpl.mozilla.org/?tree=Try&rev=45b9932ca819 The Talos performance results aren't exactly science, but it looks like the performance impact is negligible. For example, tp5o (page load time test) reported 285, central is around 280 (lower is better). Dromaeo-CSS reported 5408, whereas central is around 5500 (but noisy) (higher is better). Like I said, I don't really know what this means, but it sounds hopeful to me. Rob -- Jtehsauts tshaei dS,o n" Wohfy Mdaon yhoaus eanuttehrotraiitny eovni le atrhtohu gthot sf oirng iyvoeu rs ihnesa.r"t sS?o Whhei csha iids teoa stiheer :p atroa lsyazye,d 'mYaonu,r "sGients uapr,e tfaokreg iyvoeunr, 'm aotr atnod sgaoy ,h o'mGee.t" uTph eann dt hwea lmka'n? gBoutt uIp waanndt wyeonut thoo mken.o w
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