From c0f6402a9415b091555c9b84a5ad62de085e4266 Mon Sep 17 00:00:00 2001 From: Chris Lattner Date: Tue, 22 Dec 2009 19:33:28 +0000 Subject: Fix the Convert to scalar to not insert dead loads in the store case. The load is needed when we have a small store into a large alloca (at which point we get a load/insert/store sequence), but when you do a full-sized store, this load ends up being dead. This dead load is bad in really large nasty testcases where the load ends up causing mem2reg to insert large chains of dependent phi nodes which only ADCE can delete. Instead of doing this, just don't insert the dead load. This fixes rdar://6864035 llvm-svn: 91917 --- llvm/lib/Transforms/Scalar/ScalarReplAggregates.cpp | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-) (limited to 'llvm/lib/Transforms/Scalar/ScalarReplAggregates.cpp') diff --git a/llvm/lib/Transforms/Scalar/ScalarReplAggregates.cpp b/llvm/lib/Transforms/Scalar/ScalarReplAggregates.cpp index 884345d4a97..79bb7c547ca 100644 --- a/llvm/lib/Transforms/Scalar/ScalarReplAggregates.cpp +++ b/llvm/lib/Transforms/Scalar/ScalarReplAggregates.cpp @@ -1373,11 +1373,16 @@ void SROA::ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI, uint64_t Offset) { if (StoreInst *SI = dyn_cast(User)) { assert(SI->getOperand(0) != Ptr && "Consistency error!"); - Value *Old = Builder.CreateLoad(NewAI, NewAI->getName()+".in"); + Instruction *Old = Builder.CreateLoad(NewAI, NewAI->getName()+".in"); Value *New = ConvertScalar_InsertValue(SI->getOperand(0), Old, Offset, Builder); Builder.CreateStore(New, NewAI); SI->eraseFromParent(); + + // If the load we just inserted is now dead, then the inserted store + // overwrote the entire thing. + if (Old->use_empty()) + Old->eraseFromParent(); continue; } @@ -1397,11 +1402,16 @@ void SROA::ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI, uint64_t Offset) { for (unsigned i = 1; i != NumBytes; ++i) APVal |= APVal << 8; - Value *Old = Builder.CreateLoad(NewAI, NewAI->getName()+".in"); + Instruction *Old = Builder.CreateLoad(NewAI, NewAI->getName()+".in"); Value *New = ConvertScalar_InsertValue( ConstantInt::get(User->getContext(), APVal), Old, Offset, Builder); Builder.CreateStore(New, NewAI); + + // If the load we just inserted is now dead, then the memset overwrote + // the entire thing. + if (Old->use_empty()) + Old->eraseFromParent(); } MSI->eraseFromParent(); continue; -- cgit v1.2.3