[llvm-bugs] [Bug 37464] New: Clang 6.0 takes extremely long time to compile a specific file.

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=37464

            Bug ID: 37464
           Summary: Clang 6.0 takes extremely long time to compile a
                    specific file.
           Product: clang
           Version: 6.0
          Hardware: PC
                OS: FreeBSD
            Status: NEW
          Severity: normal
          Priority: P
         Component: LLVM Codegen
          Assignee: unassignedclangbugs at nondot.org
          Reporter: FreeBSD at Shaneware.biz
                CC: llvm-bugs at lists.llvm.org

Using clang 6.0 to compile a specific file from the godot project is
excessively long.

clang 5.0 compiles this file in around 4 seconds
clang 6.0 compiles the same file in 5842 seconds (yes over 1.5 hours, the
entire project can normally be built in under 700 seconds)

I am using FreeBSD 11-stable, this issue was first noticed on 12-current after
clang6 was added as the base compiler. I see the same issue on FreeBSD 11 using
clang6 from ports.

clang++ --version
FreeBSD clang version 5.0.1 (tags/RELEASE_501/final 320880) (based on LLVM
5.0.1)

clang++60 --version
clang version 6.0.0 (tags/RELEASE_600/final)

This happens with an amd64 target, adding -m32 allows clang6 to compile the
file in a few seconds.

The issue appears to be in the optimisation, using -O0 compiles in a few
seconds while -O1 or higher takes thousands of seconds.

The godot project is a game engine, it can be built as a runtime only or as an
IDE. Building with the IDE enabled bypasses this issue, it only happens with a
runtime only build.

Within the godot project the file is servers/physics/collision_solver_sat.cpp
https://github.com/godotengine/godot/blob/master/servers/physics/collision_solver_sat.cpp

I haven't had any luck compiling this one file outside of the main project, so
the best I can recommend is to start building the port on FreeBSD, stop the
build once the first couple of files have compiled and then manually compile
the specific file.

cd /usr/ports/devel/godot
make
Ctrl-C
cd work/godot-3.0.2-stable
time clang++60 -o servers/physics/collision_solver_sat.x11.opt.64.llvm.o -c
-pipe -g1 -O3 -ffast-math -fstack-protector -fno-strict-aliasing
-DRTAUDIO_ENABLED -pthread -w -DNDEBUG -DZSTD_STATIC_LINKING_ONLY
-DFREETYPE_ENABLED -DRECAST_ENABLED -DSVG_ENABLED -DTYPED_METHOD_BIND
-DTOUCH_ENABLED -DALSA_ENABLED -DOSS_ENABLED -DPULSEAUDIO_ENABLED -DX11_ENABLED
-DUNIX_ENABLED -DOPENGL_ENABLED -DGLES_ENABLED -DPTRCALL_ENABLED
-DGDSCRIPT_ENABLED -DMINIZIP_ENABLED -DXML_ENABLED -DGLAD_ENABLED
-DGLES_OVER_GL -D_THREAD_SAFE -D_REENTRANT -Icore -Icore/math -Ieditor
-Idrivers -I. -I/usr/local/include -I/usr/local/include/freetype2
-I/usr/local/include/libpng16 -Iplatform/x11 -Ithirdparty/zstd
-Ithirdparty/zstd/common -Ithirdparty/rtaudio -Ithirdparty/glad
-Ithirdparty/recastnavigation/Recast
-Ithirdparty/recastnavigation/Recast/Include -Ithirdparty/nanosvg
servers/physics/collision_solver_sat.cpp

-- 
You are receiving this mail because:
You are on the CC list for the bug.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-bugs/attachments/20180515/d84be04b/attachment.html>