[rfc] removing -mpreferred-stack-boundary=2 flag for i386?
matthias.andree at gmx.de
Sat Dec 24 10:18:36 UTC 2011
Am 24.12.2011 00:56, schrieb Alexander Best:
> hi there,
> is -mpreferred-stack-boundary=2 really necessary for i386 builds any longer?
> i built GENERIC (including modules) with and without that flag. the results
> 1654496 bytes with the flag set
> 1654952 bytes with the flag unset
> the gcc(1) man page states the following:
> This extra alignment does consume extra stack space, and generally
> increases code size. Code that is sensitive to stack space usage,
> such as embedded systems and operating system kernels, may want to
> reduce the preferred alignment to -mpreferred-stack-boundary=2.
What do the numbers above have to do with *stack* alignment or size
(which is a run-time figure, and cannot be statically determined if any
variable-depth recursion takes place).
What are those 16... numbers, anyways? How did you obtain them?
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