llvm dev - May 2017 - Testing selection dag combines

Hi,

I've written a few target specific dag combine functions, called from
performDAGCombine. The mechanism is great but my testing quite labour
intensive - I search for IR which hits the new function then check the MIR
downstream.

I would like to write tests along the lines of "given this dag, call this
function on that node, then check the result is equivalent to this other
dag". Could you point me at the appropriate API for creating a dag from
scratch, and for performing an equivalence test?

Thanks,

Jon
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I've successfully constructed an instance of a SelectionDAG outside of the
back end. Actually using it segfaults though - I'll paste the code here in
the hope that I'm just missing some setup. Suggestions very welcome.

Thanks!

#include "llvm/Target/OOT/OOTLowering.h"

#include "llvm/CodeGen/SelectionDAG.h"
#include "llvm/MC/SubtargetFeature.h"
#include "llvm/Support/TargetRegistry.h"
#include "llvm/Support/TargetSelect.h"
#include "llvm/Target/TargetLowering.h"
#include "llvm/Target/TargetMachine.h"

namespace llvm {
extern Target TheOOTTarget;
}

const llvm::TargetMachine &get_target_machine() {
  static bool init = false;
  static llvm::TargetMachine *local = nullptr;
  if (!init) {
    init = true;
    llvm::InitializeAllTargets();
    llvm::InitializeAllTargetMCs();
    llvm::InitializeAllAsmPrinters();
    llvm::InitializeAllAsmParsers();

    std::string TripleStr = llvm::sys::getDefaultTargetTriple();
    llvm::Triple Triple(TripleStr);

    std::string errMsg;
    const llvm::Target *march        
llvm::TargetRegistry::lookupTarget(TripleStr, errMsg);
    assert(march);

    local = llvm::TheOOTTarget.createTargetMachine(
        TripleStr, "", "", llvm::TargetOptions(),
llvm::None);
  }
  assert(local);
  return *local;
}

int main() {
  using namespace llvm;
  SelectionDAG DAG(get_target_machine(), CodeGenOpt::Default);

  DAG.dump(); // OK

  auto rt = DAG.getRoot();
  SDLoc dl(rt);

  SDValue aconstant = DAG.getConstant(123, dl, MVT::i32);
  aconstant.dump(); // segv
}

On Thu, May 11, 2017 at 11:48 AM, Jon Chesterfield <
jonathanchesterfield at gmail.com> wrote:
> Hi,
>
> I've written a few target specific dag combine functions, called from
> performDAGCombine. The mechanism is great but my testing quite labour
> intensive - I search for IR which hits the new function then check the MIR
> downstream.
>
> I would like to write tests along the lines of "given this dag, call
this
> function on that node, then check the result is equivalent to this other
> dag". Could you point me at the appropriate API for creating a dag
from
> scratch, and for performing an equivalence test?
>
> Thanks,
>
> Jon
>
>
>
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