[llvm-commits] [llvm] r122265 - /llvm/trunk/lib/Transforms/Utils/SimplifyInstructions.cpp

[Frits van Bommel]

On Mon, Dec 20, 2010 at 10:07 PM, Duncan Sands <baldrick at free.fr> wrote:
> +    bool runOnFunction(Function &F) {
> +      bool Changed = false;
> +      const TargetData *TD = getAnalysisIfAvailable<TargetData>();
> +      const DominatorTree *DT = getAnalysisIfAvailable<DominatorTree>();
> +      for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
> +        for (BasicBlock::iterator BI = BB->begin(), BE = BB->end(); BI != BE;) {
> +          Instruction *I = BI++;
> +          if (Value *V = SimplifyInstruction(I, TD, DT)) {
> +            I->replaceAllUsesWith(V);
> +            I->eraseFromParent();
> +            Changed = true;
> +            ++NumSimplified;
> +          }
> +        }
> +      return Changed;
> +    }

I know this is intended primarily for testing, but maybe this should
iterate until no changes were made just to be thorough? Or use a
worklist so users of replaced values are re-examined later?
Currently this pass depends on basic blocks order; IIRC
SimplifyInstruction assumes the operands have already been simplified,
which currently isn't necessarily the case if blocks don't happen to
be topologically sorted (with respect to domination).