Date: Wed, 13 Mar 2019 08:05:49 -0700 From: Steve Kargl <sgk@troutmask.apl.washington.edu> To: freebsd-toolchain@freebsd.org, freebsd-current@freebsd.org Subject: Re: Optimization bug with floating-point? Message-ID: <20190313150548.GA34658@troutmask.apl.washington.edu> In-Reply-To: <20190313024506.GA31746@troutmask.apl.washington.edu> References: <20190313024506.GA31746@troutmask.apl.washington.edu>
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On Tue, Mar 12, 2019 at 07:45:41PM -0700, Steve Kargl wrote: > All, > > There seems to an optimization bug with clang on > > % uname -a > FreeBSD mobile 13.0-CURRENT FreeBSD 13.0-CURRENT r344653 MOBILE i386 > > IOW, if you do numerica work on i386, you may want to check your > results. > > The program demonstrating the issue is at the end of this email. > > gcc8 --version > gcc8 (FreeBSD Ports Collection) 8.3.0 > > gcc8 -fno-builtin -o z a.c -lm && ./z > gcc8 -O -fno-builtin -o z a.c -lm && ./z > gcc8 -O2 -fno-builtin -o z a.c -lm && ./z > gcc8 -O3 -fno-builtin -o z a.c -lm && ./z > > Max ULP: 2.297073 > Count: 0 (# of ULP that exceed 21) > The above results do not change if one add -ffloat-store to the command line. > cc -O -fno-builtin -o z a.c -lm && ./z > cc -O2 -fno-builtin -o z a.c -lm && ./z > cc -O3 -fno-builtin -o z a.c -lm && ./z > > Max ULP: 23.061242 > Count: 39 (# of ULP that exceeds 21) Clang doesn't support -ffloat-store, so the above does not change. -- Steve
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