[PATCH] MCObjectSymbolizer

[Stephen Checkoway]

On Oct 14, 2013, at 7:59 PM, Sean Silva <silvas at purdue.edu> wrote:

> 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?

I was using -symbolize.

>> 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).


llvm-objdump -disassemble -cfg -symbolize ninja

-- 
Stephen Checkoway