Fwd: Assembler code with useless instructions

[Diego Caballero]

Hello,

I get 10% lower performance due to an assemble instruction that seems
to be useless.
I have a lot of blocks like the following (exactly the same) in my code:

 callq     400a50 <expf@plt>
 movaps %xmm0,%xmm4
 movss   (%r15),%xmm0
 movss   %xmm4,0x40(%rsp)
 callq     400a50 <expf@plt>
 ...

and at the end of them:

 movss   0x40(%rsp),%xmm4

%xmm4 is not read in the middle, so I don't understand why gcc generates
the second instruction, instead of something like that:

 movss  %xmm0,0x40(%rsp)
 movss  (%r15),%xmm0
 callq  400a50 <expf@plt>
 ...
 movss  0x40(%rsp),%xmm4

Thank you in advance.
Best regards.

--
Diego Caballero