[llvm-commits] CVS: llvm/lib/Transforms/Scalar/LoopUnswitch.cpp

[Chris Lattner]

> If a condition is not inside a loop then the condition is suitable
> to loop unswitch candidate for the loop.

I don't understand, why reject unswitching on these values?

cases like this should be unswitched:

int foo(int arg) {
   for (..)
     if (arg)
       ...
}

-Chris

>
> ---
> Diffs of the changes:  (+7 -0)
>
>  LoopUnswitch.cpp |    7 +++++++
>  1 files changed, 7 insertions(+)
>
>
> Index: llvm/lib/Transforms/Scalar/LoopUnswitch.cpp
> diff -u llvm/lib/Transforms/Scalar/LoopUnswitch.cpp:1.70 llvm/lib/ 
> Transforms/Scalar/LoopUnswitch.cpp:1.71
> --- llvm/lib/Transforms/Scalar/LoopUnswitch.cpp:1.70	Tue Jun  5  
> 19:21:03 2007
> +++ llvm/lib/Transforms/Scalar/LoopUnswitch.cpp	Wed Jun 27 19:44:10  
> 2007
> @@ -128,6 +128,13 @@
>  static Value *FindLIVLoopCondition(Value *Cond, Loop *L, bool  
> &Changed) {
>    // Constants should be folded, not unswitched on!
>    if (isa<Constant>(Cond)) return false;
> +
> +  // If cond is not in loop then it is not suitable.
> +  if (Instruction *I = dyn_cast<Instruction>(Cond))
> +    if (!L->contains(I->getParent()))
> +      return 0;
> +  if (isa<Argument>(Cond))
> +    return 0;
>
>    // TODO: Handle: br (VARIANT|INVARIANT).
>    // TODO: Hoist simple expressions out of loops.
>
>
>
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