[llvm-commits] [llvm] r147560 - in /llvm/trunk: include/llvm/Analysis/ValueTracking.h lib/Analysis/ValueTracking.cpp

[Duncan Sands]

Hi Dan,

> Generalize isSafeToSpeculativelyExecute to work on arbitrary
> Values, rather than just Instructions, since it's interesting
> for ConstantExprs too.

since constants are not executed, what does this mean?  I notice that all
constants results in 'false', i.e. not safe to speculatively execute.  Why
is that?

Ciao, Duncan.

>
> Modified:
>      llvm/trunk/include/llvm/Analysis/ValueTracking.h
>      llvm/trunk/lib/Analysis/ValueTracking.cpp
>
> Modified: llvm/trunk/include/llvm/Analysis/ValueTracking.h
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Analysis/ValueTracking.h?rev=147560&r1=147559&r2=147560&view=diff
> ==============================================================================
> --- llvm/trunk/include/llvm/Analysis/ValueTracking.h (original)
> +++ llvm/trunk/include/llvm/Analysis/ValueTracking.h Wed Jan  4 17:01:09 2012
> @@ -174,7 +174,7 @@
>     /// the correct dominance relationships for the operands and users hold.
>     /// However, this method can return true for instructions that read memory;
>     /// for such instructions, moving them may change the resulting value.
> -  bool isSafeToSpeculativelyExecute(const Instruction *Inst,
> +  bool isSafeToSpeculativelyExecute(const Value *V,
>                                       const TargetData *TD = 0);
>
>   } // end namespace llvm
>
> Modified: llvm/trunk/lib/Analysis/ValueTracking.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/ValueTracking.cpp?rev=147560&r1=147559&r2=147560&view=diff
> ==============================================================================
> --- llvm/trunk/lib/Analysis/ValueTracking.cpp (original)
> +++ llvm/trunk/lib/Analysis/ValueTracking.cpp Wed Jan  4 17:01:09 2012
> @@ -1879,8 +1879,12 @@
>     return true;
>   }
>
> -bool llvm::isSafeToSpeculativelyExecute(const Instruction *Inst,
> +bool llvm::isSafeToSpeculativelyExecute(const Value *V,
>                                           const TargetData *TD) {
> +  const Operator *Inst = dyn_cast<Operator>(V);
> +  if (!Inst)
> +    return false;
> +
>     for (unsigned i = 0, e = Inst->getNumOperands(); i != e; ++i)
>       if (Constant *C = dyn_cast<Constant>(Inst->getOperand(i)))
>         if (C->canTrap())
>
>
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