[llvm-dev] Opt plugin linkage
John Brawn via llvm-dev
llvm-dev at lists.llvm.org
Thu Apr 18 10:38:16 PDT 2019
The fundamental problem here is that opt doesn’t use ExecutionEngine (because it has no need to), so trying
to use ExecutionEngine (or any other bit of llvm that opt doesn’t use for that matter) in an opt plugin isn’t
going to work.
The solution I’d go with would be to build llvm with shared libraries (use –DBUILD_SHARED_LIBS=ON on the
cmake command) then link the plugin against ExecutionEngine. That shouldn’t require any changes anywhere
(when I gave it a quick try it seemed to work).
John
From: llvm-dev [mailto:llvm-dev-bounces at lists.llvm.org] On Behalf Of Zhang via llvm-dev
Sent: 16 April 2019 22:04
To: Viktor Was BSc; llvm-dev
Subject: Re: [llvm-dev] Opt plugin linkage
Just another follow-up, seems like ExecutionEngine is still not usable without editing CMakeLists, on my setup I had to edit CMakeLists.txt as well to get the example working.
Below is the modifications I made:
Modified Hello.cpp for testing:
```
bool runOnFunction(Function &F) override {
++HelloCounter;
std::string errStr;
EngineBuilder eb;
eb.setErrorStr(&errStr);
eb.setEngineKind(EngineKind::Kind::JIT);
ExecutionEngine* ee=eb.create();
errs()<<"ExecutionEngine:"<<ee<<" Error:"<<errStr<<"\n";
delete ee;
errs() << "Hello: ";
errs().write_escaped(F.getName()) << '\n';
return false;
}
```
Modified opt's CMakeLists.txt:
```
set(LLVM_LINK_COMPONENTS
${LLVM_TARGETS_TO_BUILD}
AggressiveInstCombine
Analysis
BitWriter
CodeGen
Core
MC
MCJIT
Object
OrcJIT
Interpreter
RuntimeDyld
Coroutines
IPO
IRReader
InstCombine
Instrumentation
MC
ObjCARCOpts
ScalarOpts
Support
Target
TransformUtils
Vectorize
Passes
ExecutionEngine
)
# Support plugins.
set(LLVM_NO_DEAD_STRIP 1)
add_llvm_tool(opt
AnalysisWrappers.cpp
BreakpointPrinter.cpp
Debugify.cpp
GraphPrinters.cpp
NewPMDriver.cpp
PassPrinters.cpp
PrintSCC.cpp
opt.cpp
DEPENDS
intrinsics_gen
)
export_executable_symbols(opt)
if(WITH_POLLY AND LINK_POLLY_INTO_TOOLS)
target_link_libraries(opt PRIVATE Polly)
endif(WITH_POLLY AND LINK_POLLY_INTO_TOOLS)
target_link_libraries(opt PUBLIC LLVMExecutionEngine)
```
Modified opt's LLVMBuild.txt:
```
;===- ./tools/opt/LLVMBuild.txt --------------------------------*- Conf -*--===;
;
; The LLVM Compiler Infrastructure
;
; This file is distributed under the University of Illinois Open Source
; License. See LICENSE.TXT for details.
;
;===------------------------------------------------------------------------===;
;
; This is an LLVMBuild description file for the components in this subdirectory.
;
; For more information on the LLVMBuild system, please see:
;
; http://llvm.org/docs/LLVMBuild.html
;
;===------------------------------------------------------------------------===;
[component_0]
type = Tool
name = opt
parent = Tools
required_libraries =
AsmParser
BitReader
BitWriter
CodeGen
IRReader
IPO
Instrumentation
Scalar
ObjCARC
Passes
ExecutionEngine
Interpreter
MCJIT
Native
NativeCodeGen
all-targets
```
On top of that I also added these lines to the beginning of main function in opt.cpp to force linking ExecutionEngine:
```
if(argc==-1){
EngineBuilder eb;
ExecutionEngine* ee=eb.create();
delete ee;
}
```
as well as force linking MCJIT and Interpreter by including headers in opt:
```
#include "llvm/ExecutionEngine/ExecutionEngine.h"
#include "llvm/ExecutionEngine/Interpreter.h"
#include "llvm/ExecutionEngine/MCJIT.h"
```
Moving cl::parseCommandLineOptions doesn't seem to be related to the issue, my previous assumption was wrong.
Those modifications works at least on my setup with the following output:
```
λ : >>> bin/opt -load lib/LLVMHello.dylib hw.ll -hello
WARNING: You're attempting to print out a bitcode file.
This is inadvisable as it may cause display problems. If
you REALLY want to taste LLVM bitcode first-hand, you
can force output with the `-f' option.
Assertion failed: (M && "Module is null?"), function Init, file /Users/naville/Development/Hikari/lib/ExecutionEngine/ExecutionEngine.cpp, line 80.
```
Which is due to i didn't initialize the EEBuilder properly, but at least the pass now loads and executes properly
Zhang
------------------ Original ------------------
From: "Zhang via llvm-dev"<llvm-dev at lists.llvm.org>;
Date: Wed, Apr 17, 2019 04:35 AM
To: "Viktor Was BSc"<gs15m015 at technikum-wien.at>; "llvm-dev"<llvm-dev at lists.llvm.org>;
Subject: Re: [llvm-dev] Opt plugin linkage
Hey:
I spent sometime debugging this, it seems like editing ``llvm/tools/opt.cpp`` and move ``cl::ParseCommandLineOptions(argc, argv,
"llvm .bc -> .bc modular optimizer and analysis printer\n");`` to the beginning of main() solved it for me. I'm not sure if this is a bug on LLVM side
Zhang
------------------ Original ------------------
From: "Viktor Was BSc via llvm-dev"<llvm-dev at lists.llvm.org>;
Date: Wed, Apr 17, 2019 03:09 AM
To: "llvm-dev"<llvm-dev at lists.llvm.org>;
Subject: Re: [llvm-dev] Opt plugin linkage
How come the hello pass example is so totally useless as a starting point? Why is this not using any library/compontent which could conflict with opt or clang and showing how to handle this? I have no clue as to how I have to setup llvm to get this to work or why it doesn't work in the first place with the setup described in "Getting started" and "writing an llvm pass" pages etc.
Also there is basically no documentation for the custom cmake commands.
Can please somebody help me with this issue? How do I get dynamically loaded llvm pass plugins to work? Am I the only one ever having this issue?
Thanks
Viktor
On Apr 16, 2019, at 05:38, Viktor Was BSc via llvm-dev <llvm-dev at lists.llvm.org<mailto:llvm-dev at lists.llvm.org>> wrote:
Hi,
I have a dynamically loaded llvm pass built in-tree with ninja (generated with cmake, basically a copy of the hallo pass plugin, linux, llvm/clang version 6.0.1).
It uses the ExecutionEngine.
Building it without linking against LLVMExecutionEngine library results in an undefined symbol to the vtable of the EngineBuilder when loaded to opt. Linking the plugin with LLVMExecutionEngine results in the pass simply not being executable with giving "opt: Unkown command line argument '-passArg'."
For a minimal example add set(LLVM_LINK_COMPONENTS Core) to the CMakeLists.txt of the Hello llvm pass.
There is no error or warning at any point when linking or loading a plugin linked against some libs.
How do I find out which llvm libs I can't link with a dynamically loaded plugin?
How can I use the EngineBuilder in my plugin with proper symbol resolution?
For reproductivity:
cmake -G "Sublime Text 2 - Ninja" -DCMAKE_EXPORT_COMPILE_COMMANDS=ON -DLLVM_EXPORT_SYMBOLS_FOR_PLUGINS=ON -DLLVM_BUILD_TESTS=ON -DLLVM_BUILD_EXAMPLES=ON -DLLVM_ENABLE_PROJECTS="clang;clang-tools-extra" -DLLVM_TOOL_CLANG_BUILD=ON -DLLVM_TOOL_CLANG_TOOLS_EXTRA=ON -DLLVM_OPTIMIZED_TABLEGEN=ON -DCLANG_BUILD_EXAMPLES=ON -DCLANG_PLUGIN_SUPPORT=ON
Hope someone can help me out.
Viktor
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