Why doesn't only with '-xP -ipo' flag, icpc display vectorization message?

Why doesn't only with '-xP -ipo' flag, icpc display vectorization message?

On Linux, I usually use '-xP -ipo (and -O3)' w/o -ipo_obj. Then duruing compiling, no remark messages on vectorization are displayed; instead they are displayed on linking, and some vectorization messages are missing which should be displayed with -ipo_obj option.

Will anyone tell me why and is it ok? And if possible, how can I display vectorization remarks on compiling (at least -rec_report(n) doesn't work w/o -ipo_obj.)

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For more complete information about compiler optimizations, see our Optimization Notice.

Under the default compilation mode, source files compile directly into object files, which eventually are linked into an executable. Here you will see the vectorization message when each source file is compiled, as illustrated below(here joho.c contains a vectorizable loop):

[abik@worf tmp]$ icc -xP -c main.c
[abik@worf tmp]$ icc -xP -c joho.c
joho.c(7) : (col. 2) remark: LOOP WAS VECTORIZED.
[abik@worf tmp]$ icc -xP main.o joho.o

Under ipo compilation, each source file first maps to some form of intermediate representation. The actual compilation is done during the linking step (somewhat of a misnomer now), and vectorization messages only appear during this last step, as shown below (note that vectorization now also occurs after inlining, so the call site in main.c is reported instead):

[abik@worf tmp]$ icc -xP -ipo -c main.c
[abik@worf tmp]$ icc -xP -ipo -c joho.c
[abik@worf tmp]$ icc -xP -ipo main.o joho.o
IPO: performing multi-file optimizations
IPO: generating object file /tmp/ipo_iccSOEnWv.o
main.c(5) : (col. 8) remark: LOOP WAS VECTORIZED.

Hope this clarifies things.

Aart Bik

Thank you very much!!

Yes, indeed it clarified. Probably in my case, apparently "missing" vectorization remarks should appear with other source files. In my case this happens with so many vectorization messages that I can't notice it.

It's very interesting.

Thank you very much!

Message Edited by maverick6664 on 06-07-2005 10:14 PM

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