[LLVMdev] GC infrastructure checked in
gordonhenriksen at mac.com
Mon Jan 7 09:39:08 PST 2008
On Jan 7, 2008, at 10:54, Carl Friedrich Bolz wrote:
> Gordon Henriksen wrote:
>> That said, the PyPy group has llvmgcroot support on a branch; you
>> could ask Armin Rigo <arigo at tunes dot org> for details about
>> accessing it.
>> On his benchmarks, Armin saw an 8% speedup vs. a shadow stack.
>> Their gcc backend still outperforms the LLVM backend, though—and
>> llvm-gcc outperforms that further still.
> The second part of this is not correct. I don't think we ever even
> tried llvm-gcc on the output of our C backend. What we see on x86
> machines is that LLVM's own code generators produce slower code than
> using LLVM's C backend and then running GCC on this. This however is
> then faster than our own C backend using GCC.
Thanks for the clarification, Carl.
> Hm, summary:
> pypy-llvm-backend with llvm's codegen
> < pypy-c-backend with GCC
> < pypy-llvm-backend using llvm's C backend and then GCC
I wonder what the impact of using llvm-gcc instead of GCC is in this
final pipeline. If that actually works, you could indeed eliminate the
shadow stack here as well, since llvm-gcc has extensions to emit
gcroot intrinsic calls. It's currently hardwired to the shadow-stack
codegen, but that's very fixable.
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