[llvm] r275357 - [SCCP] Generalize tryToReplaceInstWithConstant to work also with arguments.

[Davide Italiano via llvm-commits]

Are you still seeing problems?

On Thu, Jul 14, 2016 at 1:34 PM, Davide Italiano <davide at freebsd.org> wrote:
> On Thu, Jul 14, 2016 at 12:27 PM, Matthew Simpson
> <mssimpso at codeaurora.org> wrote:
>> Hi Davide,
>>
>> We're seeing large compile-time regressions with this change and LTO when
>> compiling spec2000/2006. For example, the compile-time of spec2000/crafty
>> roughly doubles. Would you mind taking a look? We're compiling with "-Ofast
>> -flto -fuse-ld=gold -mcpu=kryo". Please let me know if you're unable to
>> reproduce. Thanks!
>>
>
> Sorry about that, r275468 should help, please let me know if you still
> have trouble!
>
>> -- Matt
>>
>>
>>
>> On Wed, Jul 13, 2016 at 10:34 PM, Davide Italiano via llvm-commits
>> <llvm-commits at lists.llvm.org> wrote:
>>>
>>> On Wed, Jul 13, 2016 at 6:51 PM, Eli Friedman <eli.friedman at gmail.com>
>>> wrote:
>>> > On Wed, Jul 13, 2016 at 6:27 PM, Davide Italiano via llvm-commits
>>> > <llvm-commits at lists.llvm.org> wrote:
>>> >>
>>> >> Author: davide
>>> >> Date: Wed Jul 13 20:27:29 2016
>>> >> New Revision: 275357
>>> >>
>>> >> URL: http://llvm.org/viewvc/llvm-project?rev=275357&view=rev
>>> >> Log:
>>> >> [SCCP] Generalize tryToReplaceInstWithConstant to work also with
>>> >> arguments.
>>> >>
>>> >> Modified:
>>> >>     llvm/trunk/lib/Transforms/Scalar/SCCP.cpp
>>> >>
>>> >> Modified: llvm/trunk/lib/Transforms/Scalar/SCCP.cpp
>>> >> URL:
>>> >>
>>> >> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/SCCP.cpp?rev=275357&r1=275356&r2=275357&view=diff
>>> >>
>>> >>
>>> >> ==============================================================================
>>> >> --- llvm/trunk/lib/Transforms/Scalar/SCCP.cpp (original)
>>> >> +++ llvm/trunk/lib/Transforms/Scalar/SCCP.cpp Wed Jul 13 20:27:29 2016
>>> >> @@ -1510,16 +1510,16 @@ bool SCCPSolver::ResolvedUndefsIn(Functi
>>> >>    return false;
>>> >>  }
>>> >>
>>> >> -static bool tryToReplaceInstWithConstant(SCCPSolver Solver,
>>> >> Instruction
>>> >> *Inst,
>>> >> -                                         bool shouldEraseFromParent) {
>>> >> +template <typename ArgOrInst>
>>> >> +static bool tryToReplaceWithConstant(SCCPSolver Solver, ArgOrInst *AI)
>>> >> {
>>> >
>>> >
>>> > Can you just use a Value* here?
>>> >
>>>
>>> Sure, I'll change that.
>>>
>>> >>
>>> >>    Constant *Const = nullptr;
>>> >> -  if (Inst->getType()->isStructTy()) {
>>> >> -    std::vector<LatticeVal> IVs =
>>> >> Solver.getStructLatticeValueFor(Inst);
>>> >> +  if (AI->getType()->isStructTy()) {
>>> >> +    std::vector<LatticeVal> IVs = Solver.getStructLatticeValueFor(AI);
>>> >>      if (std::any_of(IVs.begin(), IVs.end(),
>>> >>                      [](LatticeVal &LV) { return LV.isOverdefined();
>>> >> }))
>>> >>        return false;
>>> >>      std::vector<Constant *> ConstVals;
>>> >> -    StructType *ST = dyn_cast<StructType>(Inst->getType());
>>> >> +    StructType *ST = dyn_cast<StructType>(AI->getType());
>>> >>      for (unsigned i = 0, e = ST->getNumElements(); i != e; ++i) {
>>> >>        LatticeVal V = IVs[i];
>>> >>        ConstVals.push_back(V.isConstant()
>>> >> @@ -1528,18 +1528,23 @@ static bool tryToReplaceInstWithConstant
>>> >>      }
>>> >>      Const = ConstantStruct::get(ST, ConstVals);
>>> >>    } else {
>>> >> -    LatticeVal IV = Solver.getLatticeValueFor(Inst);
>>> >> +    LatticeVal IV = Solver.getLatticeValueFor(AI);
>>> >>      if (IV.isOverdefined())
>>> >>        return false;
>>> >> -
>>> >> -    Const =
>>> >> -        IV.isConstant() ? IV.getConstant() :
>>> >> UndefValue::get(Inst->getType());
>>> >> +    Const = IV.isConstant() ? IV.getConstant() :
>>> >> UndefValue::get(AI->getType());
>>> >>    }
>>> >>    assert(Const && "Constant is nullptr here!");
>>> >> -  DEBUG(dbgs() << "  Constant: " << *Const << " = " << *Inst << '\n');
>>> >> +  DEBUG(dbgs() << "  Constant: " << *Const << " = " << *AI << '\n');
>>> >>
>>> >>    // Replaces all of the uses of a variable with uses of the constant.
>>> >> -  Inst->replaceAllUsesWith(Const);
>>> >> +  AI->replaceAllUsesWith(Const);
>>> >> +  return true;
>>> >> +}
>>> >> +
>>> >> +static bool tryToReplaceInstWithConstant(SCCPSolver Solver,
>>> >> Instruction
>>> >> *Inst,
>>> >> +                                         bool shouldEraseFromParent) {
>>> >> +  if (!tryToReplaceWithConstant(Solver, Inst))
>>> >> +    return false;
>>> >>
>>> >>    // Delete the instruction.
>>> >>    if (shouldEraseFromParent)
>>> >> @@ -1766,17 +1771,8 @@ static bool runIPSCCP(Module &M, const D
>>> >>          // TODO: Could use getStructLatticeValueFor to find out if the
>>> >> entire
>>> >>          // result is a constant and replace it entirely if so.
>>> >>
>>> >> -        LatticeVal IV = Solver.getLatticeValueFor(&*AI);
>>> >> -        if (IV.isOverdefined()) continue;
>>> >> -
>>> >> -        Constant *CST = IV.isConstant() ?
>>> >> -        IV.getConstant() : UndefValue::get(AI->getType());
>>> >> -        DEBUG(dbgs() << "***  Arg " << *AI << " = " << *CST <<"\n");
>>> >> -
>>> >> -        // Replaces all of the uses of a variable with uses of the
>>> >> -        // constant.
>>> >> -        AI->replaceAllUsesWith(CST);
>>> >> -        ++IPNumArgsElimed;
>>> >> +        if (tryToReplaceWithConstant(Solver, &*AI))
>>> >> +          ++IPNumArgsElimed;
>>> >>        }
>>> >>      }
>>> >
>>> >
>>> > Testcase?
>>> >
>>>
>>> Sorry if I failed to mention on this commit, but this is NFC as we
>>> skip the replacement phase if the argument is of struct type (unless
>>> I'm missing something).
>>> My next patch, http://reviews.llvm.org/D22329 , changes the behaviour
>>> and add test cases.
>>>
>>>
>>> Thanks for your review!
>>>
>>> --
>>> Davide
>>>
>>> "There are no solved problems; there are only problems that are more
>>> or less solved" -- Henri Poincare
>>> _______________________________________________
>>> llvm-commits mailing list
>>> llvm-commits at lists.llvm.org
>>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-commits
>>
>>
>
>
>
> --
> Davide
>
> "There are no solved problems; there are only problems that are more
> or less solved" -- Henri Poincare



-- 
Davide

"There are no solved problems; there are only problems that are more
or less solved" -- Henri Poincare