On 09/05/2014, at 10:50 AM, Doug Baskins wrote:
> John:
>
> Yes, I have seen the problem with Judy1 64Bit using apt-get from ubuntu. I
> have also found it only happens with the GCC-4.8 compiler with -O2 and -O3.
>
No, it happens with -O1 as well I think. Two flags fix this:
-fno-strict-aliasing
which is required for ALL compilers including clang and all versions
of gcc. And
-fno-aggressive-loop-optimizations
I think it is spelled which is specific to gcc-4.8.*. Unfortunately due to the
bad design of the gcc CLI you cannot give this flag on pre 4.8 gcc without
the compiler bugging out. It is safe to give wrong flags to clang, it complains
but continues anyhow.
With these flags I think -O2 will actually work. I don't know that -O3 makes
much
difference on any compiler, except slowing the compile down. For clang,
the -O1 switch sometimes produces *faster* code than -O2 and -O3 is absurdly
slow to compile for little gain. WIth clang -O2 is a lot slower than -O1.
gcc without at least -O1 produces unusably slow code, don't even think
about it.
--
john skaller
skal...@users.sourceforge.net
http://felix-lang.org
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