This provides minor simulation performance benefit, but can provide
large C++ compilation time improvement, notably with Clang (4x).
This patch implements #2366 .
This adds the flag --generate-waivefile <filename>. This will generate
a verilator config file with the proper lint_off statemens to turn off
warnings emitted during this particular run.
This feature can be used to start with using Verilator as linter and
systematically capture all known lint warning for further
elimination. It hopefully helps people turning of -Wno-fatal or
-Wno-lint and gradually improve their code base.
Signed-off-by: Stefan Wallentowitz <stefan.wallentowitz@hm.edu>
The build is now by default configured to link performance critical
libraries (libgcc, libstdc++, libtcmalloc) statically. This improves
Verilation speed by between 4.5-7% based on my measurements as it
eliminates approx 20% of the mispredicted branches from the execution.
With partial static linking, the size of the .text section in
verilator_bin is increased by about 14%, and the binary is itself only
about 800KB bigger on disk, so hopefully this is not a big issue in
exchange for the faster compilation speed. A configure option
"--disable-partial-static" is provided to restore the old behaviour of
linking everything dynamically.
Note: This patch also changes to use libtcmalloc_minimal, which is all
we really need and itself has fewer dependencies.
As Verilator continuously allocates and releases small objects (e.g.:
AstNode, V3GraphVertex, V3GraphEdge), it spends a significant amount of
time in malloc/free and friends. This patch adds the --enable-tcmalloc
configure option to link Verilator against the high performance malloc
implementation library libtcmalloc. The default is to use libtcmalloc if
available on the system. Note that there are no source code change, we
are simply replacing the standard library memory allocation functions.
Measured major compilation speed improvement of 27% when running
Verilator with -O3 on a large design.
Geza Lore
Maciej Sobkowski
Maarten De Braekeleer
Stefan Wallentowitz
Wilson Snyder
Pieter Kapsenberg
Patrick Stewart
Todd Strader
Gianfranco Costamagna
John Coiner
Johan Bjork