[llvm-commits] [PATCH] Shrink MachineOperand from 40 to 32 bytes

[Bob Wilson]

You could make it marginally less icky by making UnsignedContents into a separate union with RegNo and OffsetLo members.
Besides the speedup you measured, this should also help memory usage, so I agree that it's worth putting up with some ickiness.

On Oct 19, 2010, at 10:20 AM, Jakob Stoklund Olesen wrote:

> Hi,
> 
> The attached patch shrinks MachineOperand from 40 to 32 bytes on 64-bit hosts.
> 
> The Contents union contains pointers, so it becomes 8-byte aligned. That creates padding because the largest member has two pointers and an unsigned.
> 
> The patch moves the unsigned outside the union in a way that makes it pack optimally on both 32-bit and 64-bit hosts.
> 
> It is a bit icky, so I wanted your opinions before committing.
> 
> I measured a (statistically significant) 0.8% speedup of code generation on 64-bit Darwin with the patch applied.
> 
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