On Wed, Mar 13, 2019 at 09:32:57AM -0700, John Baldwin wrote: > On 3/13/19 8:16 AM, Steve Kargl wrote: > > On Tue, Mar 12, 2019 at 07:45:41PM -0700, Steve Kargl wrote: > >> > >> 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) > >> > > > > clang agrees with gcc8 if one changes ... > > > >> int > >> main(void) > >> { > >> double re, im, u, ur, ui; > >> float complex f; > >> float x, y; > > > > this line to "volatile float x, y". > > So it seems to be a regression in clang 7 vs clang 6? > /usr/local/bin/clang60 has the same problem. % /usr/local/bin/clang60 -o z -O2 a.c -lm && ./z Maximum ULP: 23.061242 # of ULP > 21: 39 Adding volatile as in the above "fixes" the problem. AFAICT, this a i386/387 code generation problem. Perhaps, an alignment issue? -- Steve 20170425 https://www.youtube.com/watch?v=VWUpyCsUKR4 20161221 https://www.youtube.com/watch?v=IbCHE-hONowReceived on Wed Mar 13 2019 - 15:40:42 UTC
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