Why doesn't GCC show vectorization information?

Question

I\'m using Codeblocks for a C program on Windows 7. The program is using the OMP library. GCC version is 4.9.2. Mingw x86_64-w64-mingw32-gcc-4.9.2.exe.

Flags used are: <

Answer 1

In GCC-9.0.0,Messages are now prefixed with optimizaed,missed,or note,rather than the old behavior of all being preixed with note. If want to get exhaustive log of all decisions made by the vectorizer via new -internals suboption of -fopt-info.

Answer 2

CodeBlocks is an IDE. It doesn't compile anything. GCC does. The -ftree-vectorizer-verbose used to work in previous versions. Now there's -fopt-info, which allows to retrieve information about optimizations (vectorization too); you can find the relevant documentation here.

It is even shown how to actually retrieve the vectorizer output to stderr: and this one:

gcc -O2 -ftree-vectorize -fopt-info-vec-missed 

prints information about missed optimization opportunities from vectorization passes on stderr. Note that -fopt-info-vec-missed is equivalent to -fopt-info-missed-vec.

You can change missed to e.g. optimized, all and so on as listed.