[LLVMdev] Spilled variables using unaligned moves

[Nicolas Capens]

Hi all,

 

It looks like vector spills don't use aligned moves even though the stack is
aligned. This seems like an optimization opportunity.

 

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

 

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