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Fix a major source of "type unsafety", where a cast is neccesary, but can

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be put either before or after a load.  We chose to cast the value loaded
instead of the pointer to load from.

Fixes bug: test/Regression/Transforms/LevelRaise/2002-05-10-LoadPeephole.ll

llvm-svn: 2621
This commit is contained in:
Chris Lattner 2002-05-14 05:23:45 +00:00
parent b7688286c1
commit f98fefc1ea
1 changed files with 40 additions and 2 deletions
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42
lib/Transforms/LevelRaise.cpp
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@ -356,7 +356,6 @@ static bool PeepholeOptimize(BasicBlock *BB, BasicBlock::iterator &BI) {
}
#endif
#if 1
} else if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
Value *Val = SI->getOperand(0);
Value *Pointer = SI->getPointerOperand();
@ -396,6 +395,46 @@ static bool PeepholeOptimize(BasicBlock *BB, BasicBlock::iterator &BI) {
return true;
}
} else if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
Value *Pointer = LI->getOperand(0);
const Type *PtrElType =
cast<PointerType>(Pointer->getType())->getElementType();
// Peephole optimize the following instructions:
// %Val = cast <T1>* to <T2>* ;; If T1 is losslessly convertable to T2
// %t = load <T2>* %P
//
// Into:
// %t = load <T1>* %P
// %Val = cast <T1> to <T2>
//
// Note: This is not taken care of by expr conversion because there might
// not be a cast available for the store to convert the incoming value of.
// This code is basically here to make sure that pointers don't have casts
// if possible.
//
if (CastInst *CI = dyn_cast<CastInst>(Pointer))
if (Value *CastSrc = CI->getOperand(0)) // CSPT = CastSrcPointerType
if (PointerType *CSPT = dyn_cast<PointerType>(CastSrc->getType()))
// convertable types?
if (PtrElType->isLosslesslyConvertableTo(CSPT->getElementType()) &&
!LI->hasIndices()) { // No subscripts yet!
PRINT_PEEPHOLE2("load-src-cast:in ", Pointer, LI);
// Create the new load instruction... loading the pre-casted value
LoadInst *NewLI = new LoadInst(CastSrc, LI->getName());
// Insert the new T cast instruction... stealing old T's name
CastInst *NCI = new CastInst(NewLI, LI->getType(), CI->getName());
BI = BB->getInstList().insert(BI, NewLI)+1;
// Replace the old store with a new one!
ReplaceInstWithInst(BB->getInstList(), BI, NCI);
PRINT_PEEPHOLE3("load-src-cast:out", NCI, CastSrc, NewLI);
++NumLoadStorePeepholes;
return true;
}
} else if (I->getOpcode() == Instruction::Add &&
isa<CastInst>(I->getOperand(1))) {
@ -404,7 +443,6 @@ static bool PeepholeOptimize(BasicBlock *BB, BasicBlock::iterator &BI) {
++NumGEPInstFormed;
return true;
}
#endif
}
return false;