[PATCH] Fix a performance problem in gep(gep ...) merging

[Quentin Colombet]

The thing with the "both constants" approach is that we may miss some cases where an addressing mode may apply. In particular, on x86, when one argument of the add is a constant, we would be able to match reg1 + reg2 + displacement.

That being said, your numbers imply this is not a problem in practice, and most targets do not support reg1 + reg2 + reg3/imm addressing mode. Anyway, we could recover from that later on if needed.

So LGTM.

Thanks Wei!
-Quentin


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http://reviews.llvm.org/D8911

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