[PATCH] MCObjectSymbolizer

[Sean Silva]

On Mon, Oct 14, 2013 at 6:49 PM, Stephen Checkoway <s at pahtak.org> wrote:

> MCObjectSymbolizer currently iterates through each symbol every time it is
> asked to tryAddingSymbolicOperand. With many symbols, this takes a very
> long time.
>

I ran into an issue this summer where `llvm-objdump -symbolize` took like
10,000 times longer than without. Is this related to that?


>
> The attached patch iterates through the symbols the first time this is
> needed and puts them in a sorted vector. Subsequent lookups use
> std::upper_bound() to find the symbol in log(n) time.
>
> Without the patch, calling MCObjectDisassembler::buildModule(/* withCFG */
> false) on an unstripped build of Chromium took more than 2 hours (which is
> when I gave up on it). With the patch, it takes 24 seconds.
>
> My particular build of Chromium has 474,222 symbols (as counted with nm
> chrome|wc -l) and is 2.1 GB.
>
> It is difficult to test the speedup with llvm-objdump because passing true
> for withCFG uses more than my available 32 GB of RAM when run on a 7.3 MB
> file and on smaller files, e.g., my 3 MB ninja binary, the difference in
> speed is in the noise. And even then, it's using about 6 GB of RAM.
>

What command line for llvm-objdump uses 6GB of RAM on the ninja binary?
That seems bug-worthy; the ninja executable is like <200K of code (the rest
is debug info, which ninja builds with by default).

-- Sean Silva


>
> --
> Stephen Checkoway
>
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