[llvm] r270892 - [MemCpyOpt] Don't perform callslot optimization across may-throw calls
Eli Friedman via llvm-commits
llvm-commits at lists.llvm.org
Thu May 26 13:21:40 PDT 2016
On Thu, May 26, 2016 at 12:24 PM, David Majnemer via llvm-commits <
llvm-commits at lists.llvm.org> wrote:
> Author: majnemer
> Date: Thu May 26 14:24:24 2016
> New Revision: 270892
>
> URL: http://llvm.org/viewvc/llvm-project?rev=270892&view=rev
> Log:
> [MemCpyOpt] Don't perform callslot optimization across may-throw calls
>
> An exception could prevent a store from occurring but MemCpyOpt's
> callslot optimization would fire anyway, causing the store to occur.
>
> This fixes PR27849.
>
> Added:
> llvm/trunk/test/Transforms/MemCpyOpt/callslot_throw.ll
> Modified:
> llvm/trunk/lib/Transforms/Scalar/MemCpyOptimizer.cpp
> llvm/trunk/test/Transforms/MemCpyOpt/loadstore-sret.ll
>
> Modified: llvm/trunk/lib/Transforms/Scalar/MemCpyOptimizer.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/MemCpyOptimizer.cpp?rev=270892&r1=270891&r2=270892&view=diff
>
> ==============================================================================
> --- llvm/trunk/lib/Transforms/Scalar/MemCpyOptimizer.cpp (original)
> +++ llvm/trunk/lib/Transforms/Scalar/MemCpyOptimizer.cpp Thu May 26
> 14:24:24 2016
> @@ -496,7 +496,7 @@ static unsigned findCommonAlignment(cons
>
> // This method try to lift a store instruction before position P.
> // It will lift the store and its argument + that anything that
> -// lay alias with these.
> +// may alias with these.
> // The method returns true if it was successful.
> static bool moveUp(AliasAnalysis &AA, StoreInst *SI, Instruction *P) {
> // If the store alias this position, early bail out.
> @@ -675,6 +675,8 @@ bool MemCpyOpt::processStore(StoreInst *
> if (C) {
> // Check that nothing touches the dest of the "copy" between
> // the call and the store.
> + Value *CpyDest = SI->getPointerOperand()->stripPointerCasts();
> + bool CpyDestIsLocal = isa<AllocaInst>(CpyDest);
> AliasAnalysis &AA =
> getAnalysis<AAResultsWrapperPass>().getAAResults();
> MemoryLocation StoreLoc = MemoryLocation::get(SI);
> for (BasicBlock::iterator I = --SI->getIterator(), E =
> C->getIterator();
> @@ -683,6 +685,12 @@ bool MemCpyOpt::processStore(StoreInst *
> C = nullptr;
> break;
> }
> + // The store to dest may never happen if an exception can be
> thrown
> + // between the load and the store.
> + if (I->mayThrow() && !CpyDestIsLocal) {
> + C = nullptr;
> + break;
> + }
> }
> }
>
> @@ -815,6 +823,10 @@ bool MemCpyOpt::performCallSlotOptzn(Ins
> if (destSize < srcSize)
> return false;
> } else if (Argument *A = dyn_cast<Argument>(cpyDest)) {
> + // The store to dest may never happen if the call can throw.
> + if (C->mayThrow())
> + return false;
>
I'm not sure mayThrow is sufficient; it doesn't cover longjmp. Maybe not
worth worrying about, though.
-Eli
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