[llvm-commits] [gcc-plugin] r83276 - /gcc-plugin/trunk/llvm-backend.cpp

[Török Edwin]

On 2009-10-04 15:23, Duncan Sands wrote:
> Author: baldrick
> Date: Sun Oct  4 07:23:48 2009
> New Revision: 83276
>
> URL: http://llvm.org/viewvc/llvm-project?rev=83276&view=rev
> Log:
> Don't bother running the garbage collector.  The original idea was that once
> functions are converted to LLVM IR, they can be discarded.  This was done by
> estimating the amount of memory that could be recovered, and running the garbage
> collector if that seemed beneficial.  However even on huge testcases this never
> saved more than a megabyte or three, while it increased compile time considerably.
>   

This seems to suggest that turning off the garbage collector makes it
faster.

> In fact, if the garbage collector isn't run at all then gcc-4.5 with the plugin
> uses up less memory than gcc-4.5 (presumably because RTL is fat), and about the
> same or less than llvm-gcc (on insn-attrtab.c a bit more than 5% less).  Turning
> off the garbage collector almost doubles -O0 compile times, making them about the
> same as llvm-gcc.
>   

However this suggests that turning it off slows it down.
Did you mean "compile time" or "speed"?
If it doubles compile time, why turn it off?

Best regards,
--Edwin