Am 31.07.2014 23:59, schrieb Walter Bright:
On 7/31/2014 10:40 AM, Daniel Gibson wrote:
It's a major PITA to debug problems that only happen in release builds.
Debugging optimized code was a well known problem even back in the 70's.
Nobody has solved it, and nobody wants unoptimized code.
Yeah, and because of this I'd like optimizations not to cause different
behavior if at all possible to keep these kind of bugs as low as possible.
And I agree with your stance on those fine-grained optimization switches
from your other post. GCC currently has 191 flags the influence
optimization[1] (+ a version that negates them for most), and I don't
understand what most of them do, so it would be hard for me to decide
which optimizations I want and which I don't want.
However, what about an extra flag for "unsafe" optimizations?
I'd like the compiler to do inlining, replacing int multiplications with
powers of two with shifts and other "safe" optimizations that don't
change the semantics of my program (see the examples in the post you
quoted), but I *don't* want it to e.g. remove writes to memory that
isn't read afterwards or make assumptions based on assertions (that are
disabled in the current compile mode).
And maybe a warning mode that tells me about "dead"/"superfluous" code
that would be eliminated in an optimized build so I can check if that
would break anything for me in that respect without trying to understand
the asm output would be helpful.
Cheers,
Daniel
[1] according to $ gcc-4.8 --help=optimizer | grep "^ -" | wc -l
