gcc-help-owner@xxxxxxxxxxx wrote on 03/12/2009 17:16:42: > Fahimeh Yazdanpanah <fahim_yazdan@xxxxxxxxx> > Sent by: gcc-help-owner@xxxxxxxxxxx > > 03/12/2009 17:16 > > To > > gcc-help@xxxxxxxxxxx > > cc > > Subject > > Auto-vectorization of if-conversion > > Hello, > > I am trying to vectorize this loop with gcc-4.4.2 under 64-bit linuxubuntu : > > for (i = 0; i < 1024; i++) > d[i] = (a[i] > 0 ? b[i] : c[i]); > > but it is not vectorized. For compiling that, I use these flags: > gcc -O3 -fprefetch-loop-arrays -lstdc++ -ftree-vectorize -ftree- > vectorizer-verbose=2 -ffast-math -mfpmath=sse -march=core2 > > according to http://gcc.gnu.org/projects/tree-ssa/vectorization.html > , it must be vectorized. Would you please tell me what I do wrong? The if-conversion pass fails here because of speculative loads of b and c. Taking the loads outside of condition allows if-conversion and makes the loop vectorizable: for (i = 0; i < 1024; i++) { bb = b[i]; cc = c[i]; d[i] = (a[i] > 0 ? bb : cc); } Ira > > Thanks in advance, > Best regards, > Fahimeh > > > >
