Re: Extreme memory demand compiling not-too-complicated expression: gcc bug?
|[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]|
On 11 April 2012 12:00, Bob McKay wrote: > Dear gcc-ers, > I need to compile fairly complex (automatically generated) > expressions using gcc. An example is attached. To allow the code to > run reasonably fast, I assumed it would be reasonable to macro-ise the > functions where possible (most operators need to be protected against > overflow, since I can't control the expressions that are generated), > and inline the rest. Inlining works fine (the code compiles in a > fraction of a second), but macro-ising doesn't. This version of the > code ran up to 14GB of (real) memory and ~15 minutes compilation time > before I killed it. While it doesn't matter much to me (the inlined > version is still a huge speed-up on the interpreter I was using till > now), it does seem a little surprising that compiling a relatively > simple expression should generate such overheads. I could understand > it, I guess, if I were using aggressive optimisations; but the same > overheads appeared even under minimum optimisation. So back to the > question: does this look like a bug to you? Should I be reporting it? Impossible to know, as you haven't provided the most basic information such as which version you're using. if you're using GCC 3.1 and it works OK with a recent version, no, definitely don't report it. In any case, running that through the preprocessor expands to 200MB so it's not really surprising the compiler struggles with it. > Even better, can anyone suggest a combination of switches that will > allow it to compile in a reasonable time and memory? Are you sure the version using inline functions isn't just better in every way?