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

[Eli Friedman via llvm-commits]

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?


>    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?

-Eli
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