[llvm-dev] Confused on how to do a machinefunction pass
fateme Hoseini via llvm-dev
llvm-dev at lists.llvm.org
Tue Nov 17 08:29:22 PST 2015
Yes, I have done exactly the same. The wawanalyzer is the same. I changed
ARM.h and ARMTargetMachine.cpp in the tager/arm folder. then I make
tool/llc and lib folder.
On Tue, Nov 17, 2015 at 10:55 AM, John Criswell <jtcriswel at gmail.com> wrote:
> On 11/17/15 12:16 AM, fateme Hoseini via llvm-dev wrote:
>
> Hi,
> So, I run my pass in X86 target with llc command and it printed out
> "hello****". Now I am trying to do the same pass for ARM target. So I did
> exactly what I did for X86 as mentioned in my previous posts. When I run
> the following command:
>
>
> Have you modified the ARM code generator to run your pass (the same way
> that you modified the X86 code generator to run your pass)?
>
> Each backend has code that configures the set of MachineFunctionPass'es to
> run when that code generator is used. For each backend, you must modify
> that code to run your MachineFunctionPass.
>
> Regards,
>
> John Criswell
>
>
> llc -march=arm test.ll -o test
> nothing prints out. I did the same for MIPS target too and I got no
> result. Can anyone tell me what I'm doing wrong. Is there any difference
> between writing machinefunction passes in x86 and other targets?
> Thank you,
> Fami
>
> On Fri, Nov 6, 2015 at 10:56 AM, fateme Hoseini <hoseini.f at gmail.com>
> wrote:
>
>> Hi
>> So I m trying to write my first backend pass. I created a file in
>> target\x86\wawanalyzer.cpp based on hexagonHardwareLoops.cpp file. Now it's
>> just a simple file that prints hello to the output. I have attached the
>> file to this post.
>>
>> Then I did the following:
>>
>> 1. add "FunctionPass *createwawAnalyzer();" line to x86.h
>> 2. add file name to CMakelist.txt.
>> 3. This is going to run after postRAscheduler and before code emission so
>> I changed the x86TrgetMachine.cpp as follow:
>> void X86PassConfig::addPreEmitPass() {
>> /////////////add mypass here///////
>> addPass(createwawAnalyzer());
>> //////////////////////////////////
>> if (getOptLevel() != CodeGenOpt::None)
>> addPass(createExecutionDependencyFixPass(&X86::VR128RegClass));
>>
>> if (UseVZeroUpper)
>> addPass(createX86IssueVZeroUpperPass());
>>
>> if (getOptLevel() != CodeGenOpt::None) {
>> addPass(createX86PadShortFunctions());
>> addPass(createX86FixupLEAs());
>> }
>> then I run make on mypass and remake llvm3.7\lib and llvm3.7\tool\llc.
>> but when I run llc -help it doesn't show my pass. Did I miss some steps
>> or did something wrong? What's the correct way to run the pass with llc
>> command?
>>
>> I appreciate any help,
>> Regards
>> Fami
>>
>> On Wed, Nov 4, 2015 at 1:02 PM, fateme Hoseini < <hoseini.f at gmail.com>
>> hoseini.f at gmail.com> wrote:
>>
>>> Thank you so much.
>>> That helped alot.
>>>
>>> Fami
>>>
>>> On Wed, Nov 4, 2015 at 9:40 AM, John Criswell < <jtcriswel at gmail.com>
>>> jtcriswel at gmail.com> wrote:
>>>
>>>> On 11/3/15 7:54 PM, fateme Hoseini wrote:
>>>>
>>>> Dear John,
>>>> Thank you so much for your help. I looked at those documents. Could you
>>>> kindly answer the following questions:
>>>>
>>>> Does it mean that I have to make my own backend target in order to
>>>> write a machine pass even if I want to run a simple machinefunction pass?
>>>> for example,if I want my pass to get MIPS instructions as an input, I have
>>>> to copy all the files from mips target and add a file to it which
>>>> implements my pass. and there should be a way to connect the pass to other
>>>> MIPS backend files?
>>>>
>>>>
>>>> No, you do not need to create a new backend. All you need to do is to
>>>> add your pass to the list of passes that are run when the MIPS code
>>>> generator is used.
>>>>
>>>> In LLVM 3.3, there was a file in the X86 backend that had code to
>>>> schedule all the MachineFunctionPass'es when the X86 code generator was
>>>> used. That was in lib/Target/X86/X86TargetMachine.cpp. You can probably
>>>> find a similar file for LLVM 3.7 for the MIPS backend.
>>>>
>>>> So, to summarize, you'll add your source file to the MIPS backend, add
>>>> a line somewhere to run your pass when the MIPS code generator is used, and
>>>> then recompile llvm/lib and llvm/tools/llc.
>>>>
>>>>
>>>>
>>>> As a result, is the way that I described in my first post completely
>>>> wrong because I cannot run a stand alone machine function pass like a
>>>> frontend function pass?
>>>>
>>>>
>>>> As far as I know, there is no way to load a MachineFunctionPass and run
>>>> it using llc, opt, or clang. I believe you need to compile it into the
>>>> MIPS backend code.
>>>>
>>>>
>>>> Also another question, I'm a PhD student and I'm completely new to the
>>>> llvm backend process. I want to estimate my project time. How long
>>>> approximately do you think it will take to be get familiar with backend and
>>>> be able to write machinefunction pass? for further steps I have to
>>>> implement a register allocation algorithm.
>>>>
>>>>
>>>> It's difficult to estimate (especially since I haven't implemented
>>>> anything as complicated as a register allocator). Your profiling pass may
>>>> take anywhere from 1 week to 1 month depending on how complicated it is. I
>>>> think a register allocator would take anywhere from 1 month up to 6 months
>>>> depending on how robust you need it to be, but since I've never built one,
>>>> I can't say for certain.
>>>>
>>>> Regards,
>>>>
>>>> John Criswell
>>>>
>>>>
>>>>
>>>> Regards,
>>>> Fami
>>>>
>>>>
>>>> On Tue, Nov 3, 2015 at 3:52 PM, John Criswell < <jtcriswel at gmail.com>
>>>> jtcriswel at gmail.com> wrote:
>>>>
>>>>> Dear Fami,
>>>>>
>>>>> A MachineFunctionPass is run by the code generator, so you can only
>>>>> use it in tools like llc, clang, and libLTO. The opt program only
>>>>> manipulates LLVM IR and therefore does not run MachineFunctionPass'es.
>>>>>
>>>>> Regarding documentation, have you looked at the following?
>>>>>
>>>>> <http://llvm.org/docs/WritingAnLLVMBackend.html>
>>>>> http://llvm.org/docs/WritingAnLLVMBackend.html
>>>>> <http://llvm.org/docs/CodeGenerator.html>
>>>>> http://llvm.org/docs/CodeGenerator.html
>>>>> <http://llvm.org/docs/MIRLangRef.html>
>>>>> http://llvm.org/docs/MIRLangRef.html
>>>>>
>>>>> Regards,
>>>>>
>>>>> John Criswell
>>>>>
>>>>>
>>>>> On 11/3/15 3:47 PM, fateme Hoseini via llvm-dev wrote:
>>>>>
>>>>> Hi everyone,
>>>>> I am a LLVM newbie. I need to write a machinefunction pass for my
>>>>> project. This should be an analyzer of the machine code to do some
>>>>> profiling. I have written a couple of function passes for front end, but it
>>>>> seems they are completely different. I searched through forum and llvm
>>>>> documents, but couldn't find anything useful or questions were unanswered.
>>>>> Can anyone reference me to any material on how to do that or help me with
>>>>> my roblem.
>>>>>
>>>>> I have created a folder in: lib/Transform and put my pass in it.
>>>>> I am writing a simple pass like this:
>>>>>
>>>>> using namespace llvm;
>>>>>
>>>>> namespace {
>>>>> struct analyzer : public MachineFunctionPass {
>>>>> static char ID;
>>>>> analyzer() : MachineFunctionPass(ID) {}
>>>>> virtual bool runOnMachineFunction(MachineFunction &MF) {
>>>>> errs() << "hello " ;
>>>>> return false;
>>>>> }
>>>>> };
>>>>> }
>>>>> char analyzer::ID = 0;
>>>>> static RegisterPass<analyzer> X("analyzer", "WAW analyzer");
>>>>>
>>>>> I make it successfully. But when I load it for my test code I get this
>>>>> error:
>>>>>
>>>>> Pass 'WAW analyzer' is not initialized.
>>>>> Verify if there is a pass dependency cycle.
>>>>> Required Passes:
>>>>> opt: /llvm/llvm-3.7/lib/IR/LegacyPassManager.cpp:635: void
>>>>> llvm::PMTopLevelManager::schedulePass(llvm::Pass*): Assertion `PI &&
>>>>> "Expected required passes to be initialized"' failed.
>>>>> .....
>>>>>
>>>>> I don't know how to solve it? Do we have to run machinefunction passes
>>>>> with OPT command? Is this correct to put machinefunction pass in an
>>>>> external folder or do we have to change some llvm built-in files?
>>>>>
>>>>> Regards,
>>>>> Fami
>>>>>
>>>>>
>>>>>
>>>>> _______________________________________________
>>>>> LLVM Developers mailing listllvm-dev at lists.llvm.orghttp://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>>>>
>>>>>
>>>>>
>>>>> --
>>>>> John Criswell
>>>>> Assistant Professor
>>>>> Department of Computer Science, University of Rochesterhttp://www.cs.rochester.edu/u/criswell
>>>>>
>>>>>
>>>>
>>>>
>>>> --
>>>> John Criswell
>>>> Assistant Professor
>>>> Department of Computer Science, University of Rochesterhttp://www.cs.rochester.edu/u/criswell
>>>>
>>>>
>>>
>>
>
>
> _______________________________________________
> LLVM Developers mailing listllvm-dev at lists.llvm.orghttp://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
>
>
> --
> John Criswell
> Assistant Professor
> Department of Computer Science, University of Rochesterhttp://www.cs.rochester.edu/u/criswell
>
>
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