llvm dev - Apr 2016 - JIT compiler - showing generated machine code

When using LLVM as a JIT compiler, you can use module.dump() to show the
generated intermediate code, which is good.

Is there similarly a programmatic way to show the generated x64 machine
code in assembly format?
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I'm not sure if there is a ready-made solution, but you can consider using
the MC component of LLVM to easily write
yourself a disassembler (easily == 100 to 200 LOC, if I recall correctly).  For
inspiration, take a look at how "llvm-mc
  --disassemble" works.

-- Sanjoy

Russell Wallace via llvm-dev wrote:
> When using LLVM as a JIT compiler, you can use module.dump() to show the
generated intermediate code, which is good.
>
> Is there similarly a programmatic way to show the generated x64 machine
code in assembly format?
>
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev

On 6 Apr 2016, at 05:14, Russell Wallace via llvm-dev <llvm-dev at
lists.llvm.org> wrote:
> 
> When using LLVM as a JIT compiler, you can use module.dump() to show the
generated intermediate code, which is good.
> 
> Is there similarly a programmatic way to show the generated x64 machine
code in assembly format?
If you want to do this solely for debugging, the easiest way is to print it out
as hex bytes (“0xhhx”, byte) and then either pipe or redirect that output to
llvm-mc.

David

> From: llvm-dev [mailto:llvm-dev-bounces at lists.llvm.org] 
> On Behalf Of Sanjoy Das via llvm-dev
> Subject: Re: [llvm-dev] JIT compiler - showing generated machine code
> Russell Wallace via llvm-dev wrote:
> > When using LLVM as a JIT compiler, you can use module.dump() to show
the generated
> > intermediate code, which is good.
> >
> > Is there similarly a programmatic way to show the generated x64
machine code in
> > assembly format?
> I'm not sure if there is a ready-made solution, but you can consider
using the MC
> component of LLVM to easily write yourself a disassembler (easily == 100 to
200 LOC,
> if I recall correctly).  For inspiration, take a look at how "llvm-mc
--disassemble"
> works.
After generating code for the module, we use something like this to run an
additional pass to display the assembly in the log:

    legacy::PassManager* pMPasses = new legacy::PassManager();
    target_machine->Options.MCOptions.AsmVerbose = true;
    if (target_machine->addPassesToEmitFile(*pMPasses, *llvm_log,
                                            TargetMachine::CGFT_AssemblyFile)) {
        llvm_log->flush();
        delete pMPasses;
        sysLogger("** could not add emit file pass **");
    } else {
        pMPasses->run(*pMod);
        delete pMPasses;
    }

We found that setting AsmVerbose early would often display different x86 code
than was actually in the final functions.  There might well be better ways to do
this these days.

 - Chuck