[LLVMdev] Possible missed optimization?

[Jakob Stoklund Olesen]

On Sep 4, 2010, at 11:21 AM, Borja Ferrer wrote:

> I've noticed this pattern happening with other operators aswell, but used xor in this example. As i said before, i tried with different register allocation orders, but it will produce always the same result. GCC is emitting longer code, but since LLVM is so nearer to the optimal code sequence i wanted to reach it.

In LLVM, copies are coalesced away as much as possible before registers are allocated, so the allocation order wouldn't affect it.

Try looking at the output of -debug-only=regcoalescing to see what is going wrong.

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