Messages in this thread | | | Date | Sun, 30 Jan 2000 13:22:02 -0800 | From | "Jeffrey B. Siegal" <> | Subject | Re: Code optimization <LEA Instruction> |
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Jamie Lokier wrote: > Not necessarily. The smallest instructions tend to be more complicated > and expand to more basic operations, so decoding cost _may_ be reduced, > but the next step in translation, and the area used in the cache, and > the execution time, may be longer.
-Os doesn't just use the smallest instructions (and note my use of the phrase "or something like it"; it also indicates to the compiler that it should generate *fewer* instructions. Fewer instructions means faster translation and it also means more of the program can fit into the translation cache.
I'm suspicious that that (gcc's) code generation in fact "matters" quite a lot for an architecture like Crusoe. There is a cooperative relationship between high level code generation and low level translation. Currently gcc is optimized to generate code for conventional processors, and Crusoe is optimized to translate code generated for conventional processors, so the two are roughly in sync. But I suspect there is a much better equilibrium that has not yet been identified.
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