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A comment on X86 Register Encoding. Parent comment

Re:X86 Register Encoding by brigade on Tuesday November 01, 2016 @03:39PM (#12849376)
Every time I've looked at a hot function across x86-64 and arm(64), x86 needs more instructions too. Really the only thing x86 does more in one instruction that compilers actually use is memory operands, but they'll readily split them if it reduces the total number of loads. Which is quite often. (probably a bad choice though with modern cores)

Lea too if your arithmetic fits in it... but then that has issue restrictions... Three operand and the various conditional stuff in arm64 is worth more overall.

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Re:X86 Register Encoding by pcwalton on Tuesday November 01, 2016 @03:47PM (#12849438)
Well, to be fair, LEA does allow for more compact encoding than RISC add/shift/add if the operations actually fit the template. But it's not enough to overcome the waste elsewhere. Most of the benefit of LEA is that it's three-address rather than two and that it doesn't clobber the flags, but those are solutions to problems that RISC doesn't have in the first place.

Edit: Ah well, beaten by your edit. :)

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