[llvm-commits] [llvm] r53167 - /llvm/trunk/lib/Analysis/ScalarEvolution.cpp

[Chris Lattner]

On Jul 6, 2008, at 11:15 PM, Nick Lewycky wrote:

> Author: nicholas
> Date: Mon Jul  7 01:15:49 2008
> New Revision: 53167
>
> URL: http://llvm.org/viewvc/llvm-project?rev=53167&view=rev
> Log:
> Handle 'lshr' instruction with SCEVUDiv object.
> Comment the xor %x, -1 case.

Does the scev expander currently handle these cases?

-Chris

>
>
> Modified:
>    llvm/trunk/lib/Analysis/ScalarEvolution.cpp
>
> Modified: llvm/trunk/lib/Analysis/ScalarEvolution.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/ScalarEvolution.cpp?rev=53167&r1=53166&r2=53167&view=diff
>
> =
> =
> =
> =
> =
> =
> =
> =
> ======================================================================
> --- llvm/trunk/lib/Analysis/ScalarEvolution.cpp (original)
> +++ llvm/trunk/lib/Analysis/ScalarEvolution.cpp Mon Jul  7 01:15:49  
> 2008
> @@ -1742,12 +1742,14 @@
>     }
>     break;
>   case Instruction::Xor:
> -    // If the RHS of the xor is a signbit, then this is just an add.
> -    // Instcombine turns add of signbit into xor as a strength  
> reduction step.
>     if (ConstantInt *CI = dyn_cast<ConstantInt>(U->getOperand(1))) {
> +      // If the RHS of the xor is a signbit, then this is just an  
> add.
> +      // Instcombine turns add of signbit into xor as a strength  
> reduction step.
>       if (CI->getValue().isSignBit())
>         return SE.getAddExpr(getSCEV(U->getOperand(0)),
>                              getSCEV(U->getOperand(1)));
> +
> +      // If the RHS of xor is -1, then this is a not operation.
>       else if (CI->isAllOnesValue())
>         return SE.getNotSCEV(getSCEV(U->getOperand(0)));
>     }
> @@ -1763,6 +1765,16 @@
>     }
>     break;
>
> +  case Instruction::LShr:
> +    // Turn logical shift right of a constant into a unsigned divide.
> +    if (ConstantInt *SA = dyn_cast<ConstantInt>(U->getOperand(1))) {
> +      uint32_t BitWidth = cast<IntegerType>(V->getType())- 
> >getBitWidth();
> +      Constant *X = ConstantInt::get(
> +        APInt(BitWidth, 1).shl(SA->getLimitedValue(BitWidth)));
> +      return SE.getUDivExpr(getSCEV(U->getOperand(0)), getSCEV(X));
> +    }
> +    break;
> +
>   case Instruction::Trunc:
>     return SE.getTruncateExpr(getSCEV(U->getOperand(0)), U- 
> >getType());
>
>
>
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