[cfe-commits] r78765 - /cfe/trunk/lib/CodeGen/CGExprScalar.cpp

[Chris Lattner]

On Aug 11, 2009, at 6:16 PM, Dan Gohman wrote:

> Author: djg
> Date: Tue Aug 11 20:16:29 2009
> New Revision: 78765
>
> URL: http://llvm.org/viewvc/llvm-project?rev=78765&view=rev
> Log:
> Use the new nsw form of add for signed integer addition.

Daniel, does the driver currently eat the -fwrapv option?  We should  
start forwarding it to clang and use it to turn off NSW adds.

-Chris

>
> Modified:
>    cfe/trunk/lib/CodeGen/CGExprScalar.cpp
>
> Modified: cfe/trunk/lib/CodeGen/CGExprScalar.cpp
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CGExprScalar.cpp?rev=78765&r1=78764&r2=78765&view=diff
>
> = 
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> ======================================================================
> --- cfe/trunk/lib/CodeGen/CGExprScalar.cpp (original)
> +++ cfe/trunk/lib/CodeGen/CGExprScalar.cpp Tue Aug 11 20:16:29 2009
> @@ -741,7 +741,12 @@
>     NextVal = llvm::ConstantInt::getTrue(VMContext);
>   } else if (isa<llvm::IntegerType>(InVal->getType())) {
>     NextVal = llvm::ConstantInt::get(InVal->getType(), AmountVal);
> -    NextVal = Builder.CreateAdd(InVal, NextVal, isInc ? "inc" :  
> "dec");
> +
> +    // Signed integer overflow is undefined behavior.
> +    if (ValTy->isSignedIntegerType())
> +      NextVal = Builder.CreateNSWAdd(InVal, NextVal, isInc ?  
> "inc" : "dec");
> +    else
> +      NextVal = Builder.CreateAdd(InVal, NextVal, isInc ? "inc" :  
> "dec");
>   } else {
>     // Add the inc/dec to the real part.
>     if (InVal->getType() == llvm::Type::FloatTy)
> @@ -1033,7 +1038,11 @@
>
>     if (Ops.LHS->getType()->isFPOrFPVector())
>       return Builder.CreateFAdd(Ops.LHS, Ops.RHS, "add");
> -
> +
> +    // Signed integer overflow is undefined behavior.
> +    if (Ops.Ty->isSignedIntegerType())
> +      return Builder.CreateNSWAdd(Ops.LHS, Ops.RHS, "add");
> +
>     return Builder.CreateAdd(Ops.LHS, Ops.RHS, "add");
>   }
>
>
>
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