2012/9/8 Sisyphus <[email protected]>: > Hi, > > Attached is a small demo program (demo.c). > > With 32-bit mingw compilers (both mingw.org's 4.5.2 and mingw64's 4.6.3) the > output of that program differs, depending upon whether I build it with > -ffloat-store or not. > I've no problem with that - I think I understand what's going on. > To get the output I desire I build *with* -ffloat-store. > > When I switch to 64-bit mingw64 compilers (I've tried both 4.6.3 and 4.7.0) > I get the desired output *without* having to invoke -ffloat-store. > And if I do invoke -ffloat-store, I still get the same output. > > Why the different behaviour with the 64-bit compilers ?
This is caused by x64 ABI and used optimization. I tested your demo by x64 compiler with option -O2 and I noticed a code difference with option -ffloat-store -O2 vs -fno-float-store -O2 (default). > And a second question: > Is -fno-float-store a valid option ? Yes, it is. > I can find no documentation for it - yet using it on the command line does > not produce the "unrecognized command line option" error that I would expect > from an invalid option. It is a valid option and documented by gcc's documentation. See for more details either invoke.texi or 'gcc info'. > Cheers, > Rob Cheers, Kai ------------------------------------------------------------------------------ Live Security Virtual Conference Exclusive live event will cover all the ways today's security and threat landscape has changed and how IT managers can respond. Discussions will include endpoint security, mobile security and the latest in malware threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ _______________________________________________ Mingw-w64-public mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/mingw-w64-public
