[llvm-commits] [llvm] r40809 - /llvm/trunk/lib/Transforms/Utils/PromoteMemoryToRegister.cpp

[Reid Spencer]

On Sat, 2007-08-04 at 02:15 +0000, Chris Lattner wrote:
> Author: lattner
> Date: Fri Aug  3 21:15:24 2007
> New Revision: 40809
> 
> URL: http://llvm.org/viewvc/llvm-project?rev=40809&view=rev
> Log:
> In mem2reg, when handling the single-store case, make sure to remove
> a using block from the list if we handle it.  Not doing this caused us
> to not be able to promote (with the fast path) allocas which have uses (whoops).
> 
> This increases the # allocas hitting this fastpath from 4042 to 8935 on the
> testcase in PR1432, speeding up mem2reg by 2.6x

Whoa! Nice!

Reid.

> 
> 
> Modified:
>     llvm/trunk/lib/Transforms/Utils/PromoteMemoryToRegister.cpp
> 
> Modified: llvm/trunk/lib/Transforms/Utils/PromoteMemoryToRegister.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/PromoteMemoryToRegister.cpp?rev=40809&r1=40808&r2=40809&view=diff
> 
> ==============================================================================
> --- llvm/trunk/lib/Transforms/Utils/PromoteMemoryToRegister.cpp (original)
> +++ llvm/trunk/lib/Transforms/Utils/PromoteMemoryToRegister.cpp Fri Aug  3 21:15:24 2007
> @@ -531,28 +531,29 @@
>  /// the value stored.
>  void PromoteMem2Reg::RewriteSingleStoreAlloca(AllocaInst *AI,
>                                                AllocaInfo &Info) {
> +  StoreInst *OnlyStore = Info.OnlyStore;
> +  
>    // Be aware of loads before the store.
>    std::set<BasicBlock*> ProcessedBlocks;
>    for (unsigned i = 0, e = Info.UsingBlocks.size(); i != e; ++i) {
>      // If the store dominates the block and if we haven't processed it yet,
>      // do so now.
> -    if (!dominates(Info.OnlyStore->getParent(), Info.UsingBlocks[i]))
> -      continue;
> -    
> -    if (!ProcessedBlocks.insert(Info.UsingBlocks[i]).second)
> +    if (!dominates(OnlyStore->getParent(), Info.UsingBlocks[i]))
>        continue;
>      
>      BasicBlock *UseBlock = Info.UsingBlocks[i];
> +    if (!ProcessedBlocks.insert(UseBlock).second)
> +      continue;
>      
>      // If the use and store are in the same block, do a quick scan to
>      // verify that there are no uses before the store.
> -    if (UseBlock == Info.OnlyStore->getParent()) {
> +    if (UseBlock == OnlyStore->getParent()) {
>        BasicBlock::iterator I = UseBlock->begin();
> -      for (; &*I != Info.OnlyStore; ++I) { // scan block for store.
> +      for (; &*I != OnlyStore; ++I) { // scan block for store.
>          if (isa<LoadInst>(I) && I->getOperand(0) == AI)
>            break;
>        }
> -      if (&*I != Info.OnlyStore) break;  // Do not handle this case.
> +      if (&*I != OnlyStore) break;  // Do not handle this case.
>      }
>      
>      // Otherwise, if this is a different block or if all uses happen
> @@ -562,7 +563,7 @@
>           I != E; ) {
>        if (LoadInst *LI = dyn_cast<LoadInst>(I++)) {
>          if (LI->getOperand(0) == AI) {
> -          LI->replaceAllUsesWith(Info.OnlyStore->getOperand(0));
> +          LI->replaceAllUsesWith(OnlyStore->getOperand(0));
>            if (AST && isa<PointerType>(LI->getType()))
>              AST->deleteValue(LI);
>            LI->eraseFromParent();
> @@ -572,6 +573,7 @@
>      
>      // Finally, remove this block from the UsingBlock set.
>      Info.UsingBlocks[i] = Info.UsingBlocks.back();
> +    Info.UsingBlocks.pop_back();
>      --i; --e;
>    }
>  }
> 
> 
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