On 12/01/2009 02:28 AM, Ira Rosen wrote:
Benjamin Redelings<benjamin_redelings@xxxxxxxx> wrote on 01/12/2009
01:24:15:
Also, perhaps the documentation should explicitly say somewhere that
vectorization can depend on flags like this. "unhandled use in
statement" certainly doesn't point the user to an idea of how to fix
this :-P
The vectorizer prints:
"unsafe fp math optimization: sum_18 = D.2721_17 + sum_26;"
But you are right, the bottom line printing:
"not vectorized: unsupported use in stmt."
doesn't help much.
Ira
Hi Ira,
1. That's actually quite helpful :-) And thank you for all your work
on this! I can't wait to go make sure my actual code is autovectorized.
Anyway, I didn't see this because I didn't use
-ftree-vectorizer-verbose=9. Would it be possible to mention this at
verbosity levels less than 9? Ideally, level 2, which tells me which
loops aren't vectorized without mentioning all the cost model parameters.
( BTW the gcc man pages indicate that 7 is the highest value for
tree-vectorizer-verbose, although it seems that now 9 is the highest value.)
2. Interestingly, the following is recognized WITHOUT -ffast-math:
for(i=0;i<argc;i++)
f4[i] += f1[i]*f2[i]*f3[i];
If I change this to the following, then it needs -ffast-math:
for(i=0;i<argc;i++)
sum += f1[i]*f2[i]*f3[i];
This is essentially doing the first thing, plus also summing the f4[i].
I guess that is the problem?
3. Finally, the following loop does not even receive a mention as being
not vectorized (that I could find!)
for(i=0;i<argc;i++)
sum += d1[i]*d2[i]*d3[i]*d4[i];
Here d1, d2, d3, and d4 are double*. However, the loop is recognized if
they are float * OR of they are double* but there are only three of
them. I presume this is intended... can you explain why?
Thanks for all your help!
-BenRI
