(Also CCing #571572) Dear Denis,
On Sat, Feb 27, 2010 at 05:44:45PM +0100, Denis Barbier wrote: > Hi, > > I played with the example provided by Kumar Appaiah, and narrowed the > problem down to zdrot; after copying zdrot.f into the same directory > as zgesvd_ex.f: > $ gfortran -O2 -c zgesvd_ex.f > $ gfortran -O2 -c zdrot.f > $ gfortran -o zgesvd_ex zgesvd_ex.o zdrot.o -llapack > $ ./zgesvd_ex > gives the expected result (with libblas3gf 1.2-4), but > $ gfortran -O2 -ftree-vectorize -c zdrot.f > $ gfortran -o zgesvd_ex zgesvd_ex.o zdrot.o -llapack > $ ./zgesvd_ex > gives the wrong result. > This looks like a bug in the gcc vectorizer, and it cannot be > reproduced with gcc 4.5 from experimental. This was fantastic analysis. I actually would like to know how you zeroed in onto zdrot to find the problem. I shall now try to play around with zdrot to see if I can create a test case which reproduces the bug, so that I can file a bug report with GCC. Thanks so much! Kumar -- In this playhouse of infinite forms I have had my play, and here have I caught sight of him that is formless. - Rabindranath Tagore (Gitanjali, 1912)
signature.asc
Description: Digital signature
