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On Wed, 14 Jan 2015 21:59:37 +0100 |
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"Andreas K. Huettel" <dilfridge@g.o> wrote: |
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> That said, long time ago I was taught that "instruction set |
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> use-flags" should be avoided as much as possible. I don't remember |
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> the source for that anymore. |
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> |
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> Question to all, is that documented anywhere, and what are the |
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> specifics? I suspect "use flags that only switch CFLAGS etc" are |
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> forbidden, "useflags that enable assembler code etc" are allowed? |
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> |
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I don't think this is documented besides the fact that forcing cflags |
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is forbidden. |
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For asm code you don't have much choice: either your package compiles |
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all asm and has some kind of cpu detection so that it choses the best |
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implementation at runtime (wasting a bit of resources), either if you |
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enable something your cpu doesn't support then your program gets killed |
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by SIGILL. |
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Also, this is not the case for x86* but iirc on arm, if your cflags |
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have some -march or -mcpu then gcc forwards it to as which in turns |
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refuses any instruction not supported by your cpu: you must disable |
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forbidden instructions in order to build your package. |
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Alexis. |
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