[LLVMdev] Spilled variables using unaligned moves
Chris Lattner
clattner at apple.com
Mon Jul 14 11:37:04 PDT 2008
On Jul 14, 2008, at 7:43 AM, Nicolas Capens wrote:
> Hi all,
>
> It looks like vector spills don’t use aligned moves even though the
> stack is aligned. This seems like an optimization opportunity.
What target is this? Linux doesn't have a 16-byte aligned stack.
-Chris
>
> The attached replacement of fibonacci.cpp generates x86 code like
> this:
>
> 03A70010 push ebp
> 03A70011 mov ebp,esp
> 03A70013 and esp,0FFFFFFF0h
> 03A70019 sub esp,1A0h
> ...
> 03A7006C movups xmmword ptr [esp+180h],xmm7
> ...
> 03A70229 mulps xmm1,xmmword ptr [esp+180h]
> ...
> 03A70682 movups xmm0,xmmword ptr [esp+180h]
>
> Note how stores and loads use unaligned moves while it could use
> aligned moves. It’s also interesting that the multiply does
> correctly assume the stack to be 16-byte aligned.
>
> Is there something I’m doing wrong (again), or is this already known?
>
> Thanks a lot,
>
> Nicolas Capens
>
> <fibonacci.cpp>
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20080714/42b5ecb0/attachment.html>
More information about the llvm-dev
mailing list