On Wed, 2018-01-17 at 14:53 -0800, Andi Kleen wrote: > From: Andi Kleen <[email protected]> > > I was looking at the generated assembler for the C fill RSB > inline asm operations, and noticed several issues: > > - The C code sets up the loop register, which > is then immediately overwritten in __FILL_RETURN_BUFFER > with the same value again. > > - The C code also passes in the iteration count > in another register, which is not used at all. > > Remove these two unnecessary operations. Just rely on > the single constant passed to the macro for the iterations. > > This eliminates several instructions and avoids unnecessarily > clobbering a register. > > Signed-off-by: Andi Kleen <[email protected]>
We still clobber the register, but you're right it's now filled in the __FILL_RETURN_BUFFER macro itself. It was a previous iteration which had the loop count passed in. Acked-by: David Woodhouse <[email protected]>
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