| 1 | Features, caveats and tricks
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| 2 | ----------------------------
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| 3 |
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| 4 | _Optlink
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| 5 | --------
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| 6 |
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| 7 | The _Optlink implementation differs from VACPP implementation in the
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| 8 | following ways:
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| 9 |
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| 10 | o _Optlink is not enabled unless you enable optimization (-O).
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| 11 |
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| 12 | o The floating-point parameters are always passed on stack, never in
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| 13 | FPU registers.
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| 14 |
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| 15 | Use _Optlink for VACPP compatibility only. If you want performance,
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| 16 | use the __attribute__((regparm=x)), where x is the number of parameters
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| 17 | to be passed in registers (_Optlink uses three). The 'regparm' calling
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| 18 | convention is much more optimal than _Optlink: it does not allocate
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| 19 | stack for parameters passed in registers (and does not store registers
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