On 2011-05-31 11:57, Alexander Best wrote:
...
however i've often read messages - mostly by bruce evans - claiming that
anything greater than -O will in fact decrease a kernel's ability to be
debugged just as well as a kernel with -O.
The critical option when -O2 is used is -fno-omit-frame-pointers, since removing
frame pointers makes debugging impossible (on i386). With -O2 code is moved
around and
removed, so debugging is more difficult, but can still provide useful
information.
any reason we cannot use -O2 -fno-omit-frame-pointers -fno-strict-aliasing as
standard COPTFLAGS with debugging enabled for *all* archs?
Most likely, the performance gain from -O2 is rather small, except for
special cases, but the pain during debugging is increased a great deal.
Even if you add frame pointers, with -O2 large pieces of code can be
transformed, variables or even entire functions can be completely
eliminated, and so on, making debugging much more difficult.
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