[llvm-dev] How to optimize a large project in llvm pass?

[Mehdi AMINI via llvm-dev]

Hi,

` -Xclang -load -Xclang path/to/.../libmypass.so` is gonna load the pass
inside clang, however clang will invoke the linker separately and it won't
have your pass. I don't know if gold or lld can load dynamically passes
like this?
An alternative it to link your pass statically with the gold plugin or with
lld.

Best,

-- 
Mehdi


On Sun, Apr 19, 2020 at 11:53 PM y liu via llvm-dev <llvm-dev at lists.llvm.org>
wrote:

> Hi,
> I have written MyPass.cpp and I use "EP_FullLinkTimeOptimizationLast".
> I compile it and get libMypass.so.
> MyPass.so rely on some other code, such as，Init.c and Helper.c.
> So, I  use following commands to get a static library libmypass-rt.a.
> "
> $ clang -fsanitize=safe-stack -c -emit-llvm -fpic -Wall -Wextra -O2 -I
> ../include -o obj/helpers.o helpers.c
> $ clang -fsanitize=safe-stack -c -emit-llvm -fpic -Wall -Wextra -O2 -I
> ../include -o obj/init.o init.c
> $ ar rcs obj/libmypass-rt.a obj/helpers.o obj/init.o
> ."
> When mypass optimizes the target program, it reles on libmypass-rt.a
> library. So I need to link libmypass-rt.a to the target program, then
> optimize after link.
> So, I need LTO.
> I use following commands:
> $ export CC=clang
> $ export CXX=clang++
> $ export RANLIB=llvm-ranlib
> $ export  LIBS="path/to/.../libmypass-rt.a"
>
> $ export CFLAGS=" -fsanitize=safe-stack -Wall -Wextra -fpic -flto -Xclang -load -Xclang path/to/.../libmypass.so"
> $ export LDFLAGS=" -flto -fuse-ld=gold"
> $ ./configure
> $ make
> But, errors occurred. I check out config.log
> /usr/bin/ld.gold: error: path/to/.../libmemsentry-rt.a
> : no archive symbol table (run ranlib)
> clang-10: error: linker command failed with exit code 1
>  (use -v to see invocation)
>
> What shuold I do?
> If this problem is solved, please tell me whether my method can achieve my
> goal？
>
> Thansk!
>
>
>
>    -
>
>
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