http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58134
--- Comment #3 from Sharad Singhai <singhai at gcc dot gnu.org> ---
I think this is the intended behavior. While working on the new dump
infrastructure, I modified the behavior of -ftree-vectorizer-verbose.
Thus right now
-ftree-vectorizer-verbose=1 : dump info about optimized loops
...=2 : dump info about missed loops
...>2 : dump info about optimized _and_ missed loops
Thus at 3 and greater, you are again seeing info available at 1. But really,
only 1 and 2 are meaningful. Anything higher is a combination of these two
kinds of information. This was a way to preserve compatibility with old
scripts, while deprecating this flag. I didn't see any tests relying on the old
behavior.
Here is the current documentation about this flag in gcc.info:
`-ftree-vectorizer-verbose=N'
This option is deprecated and is implemented in terms of
`-fopt-info'. Please use `-fopt-info-KIND' form instead, where
KIND is one of the valid opt-info options. It prints additional
optimization information. For N=0 no diagnostic information is
reported. If N=1 the vectorizer reports each loop that got
vectorized, and the total number of loops that got vectorized. If
N=2 the vectorizer reports locations which could not be vectorized
and the reasons for those. For any higher verbosity levels all the
analysis and transformation information from the vectorizer is
reported.
