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Teach SROA how to promote an array index that is variable, if the dimension

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of the array is just two.  This occurs 8 times in gcc, 6 times in crafty, and
12 times in 099.go.

This implements ScalarRepl/sroa_two.ll


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@17727 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2004-11-14 05:00:19 +00:00
parent 6c84e795ea
commit d878ecd904
1 changed files with 97 additions and 39 deletions
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136
lib/Transforms/Scalar/ScalarReplAggregates.cpp
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@ -181,39 +181,35 @@ bool SROA::performScalarRepl(Function &F) {
//
while (!AI->use_empty()) {
Instruction *User = cast<Instruction>(AI->use_back());
if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User)) {
// We now know that the GEP is of the form: GEP <ptr>, 0, <cst>
uint64_t Idx = cast<ConstantInt>(GEPI->getOperand(2))->getRawValue();
assert(Idx < ElementAllocas.size() && "Index out of range?");
AllocaInst *AllocaToUse = ElementAllocas[Idx];
Value *RepValue;
if (GEPI->getNumOperands() == 3) {
// Do not insert a new getelementptr instruction with zero indices,
// only to have it optimized out later.
RepValue = AllocaToUse;
} else {
// We are indexing deeply into the structure, so we still need a
// getelement ptr instruction to finish the indexing. This may be
// expanded itself once the worklist is rerun.
//
std::string OldName = GEPI->getName(); // Steal the old name...
std::vector<Value*> NewArgs;
NewArgs.push_back(Constant::getNullValue(Type::IntTy));
NewArgs.insert(NewArgs.end(), GEPI->op_begin()+3, GEPI->op_end());
GEPI->setName("");
RepValue =
new GetElementPtrInst(AllocaToUse, NewArgs, OldName, GEPI);
}
// Move all of the users over to the new GEP.
GEPI->replaceAllUsesWith(RepValue);
// Delete the old GEP
GEPI->getParent()->getInstList().erase(GEPI);
GetElementPtrInst *GEPI = cast<GetElementPtrInst>(User);
// We now know that the GEP is of the form: GEP <ptr>, 0, <cst>
uint64_t Idx = cast<ConstantInt>(GEPI->getOperand(2))->getRawValue();
assert(Idx < ElementAllocas.size() && "Index out of range?");
AllocaInst *AllocaToUse = ElementAllocas[Idx];
Value *RepValue;
if (GEPI->getNumOperands() == 3) {
// Do not insert a new getelementptr instruction with zero indices, only
// to have it optimized out later.
RepValue = AllocaToUse;
} else {
assert(0 && "Unexpected instruction type!");
// We are indexing deeply into the structure, so we still need a
// getelement ptr instruction to finish the indexing. This may be
// expanded itself once the worklist is rerun.
//
std::string OldName = GEPI->getName(); // Steal the old name.
std::vector<Value*> NewArgs;
NewArgs.push_back(Constant::getNullValue(Type::IntTy));
NewArgs.insert(NewArgs.end(), GEPI->op_begin()+3, GEPI->op_end());
GEPI->setName("");
RepValue = new GetElementPtrInst(AllocaToUse, NewArgs, OldName, GEPI);
}
// Move all of the users over to the new GEP.
GEPI->replaceAllUsesWith(RepValue);
// Delete the old GEP
GEPI->eraseFromParent();
}
// Finally, delete the Alloca instruction
@ -256,6 +252,15 @@ int SROA::isSafeElementUse(Value *Ptr) {
return 3; // All users look ok :)
}
/// AllUsersAreLoads - Return true if all users of this value are loads.
static bool AllUsersAreLoads(Value *Ptr) {
for (Value::use_iterator I = Ptr->use_begin(), E = Ptr->use_end();
I != E; ++I)
if (cast<Instruction>(*I)->getOpcode() != Instruction::Load)
return false;
return true;
}
/// isSafeUseOfAllocation - Check to see if this user is an allowed use for an
/// aggregate allocation.
///
@ -271,18 +276,28 @@ int SROA::isSafeUseOfAllocation(Instruction *User) {
return 0;
++I;
if (I == E || !isa<ConstantInt>(I.getOperand()))
return 0;
if (I == E) return 0; // ran out of GEP indices??
// If this is a use of an array allocation, do a bit more checking for sanity.
if (const ArrayType *AT = dyn_cast<ArrayType>(*I)) {
uint64_t NumElements = AT->getNumElements();
// Check to make sure that index falls within the array. If not,
// something funny is going on, so we won't do the optimization.
//
if (cast<ConstantInt>(GEPI->getOperand(2))->getRawValue() >= NumElements)
if (ConstantInt *CI = dyn_cast<ConstantInt>(I.getOperand())) {
// Check to make sure that index falls within the array. If not,
// something funny is going on, so we won't do the optimization.
//
if (cast<ConstantInt>(GEPI->getOperand(2))->getRawValue() >= NumElements)
return 0;
} else {
// If this is an array index and the index is not constant, we cannot
// promote... that is unless the array has exactly one or two elements in
// it, in which case we CAN promote it, but we have to canonicalize this
// out if this is the only problem.
if (NumElements == 1 || NumElements == 2)
return AllUsersAreLoads(GEPI) ? 1 : 0; // Canonicalization required!
return 0;
}
}
// If there are any non-simple uses of this getelementptr, make sure to reject
@ -315,6 +330,49 @@ int SROA::isSafeAllocaToScalarRepl(AllocationInst *AI) {
/// CanonicalizeAllocaUsers - If SROA reported that it can promote the specified
/// allocation, but only if cleaned up, perform the cleanups required.
void SROA::CanonicalizeAllocaUsers(AllocationInst *AI) {
// At this point, we know that the end result will be SROA'd and promoted, so
// we can insert ugly code if required so long as sroa+mem2reg will clean it
// up.
for (Value::use_iterator UI = AI->use_begin(), E = AI->use_end();
UI != E; ) {
GetElementPtrInst *GEPI = cast<GetElementPtrInst>(*UI++);
gep_type_iterator I = gep_type_begin(GEPI), E = gep_type_end(GEPI);
++I;
if (const ArrayType *AT = dyn_cast<ArrayType>(*I)) {
uint64_t NumElements = AT->getNumElements();
if (!isa<ConstantInt>(I.getOperand())) {
if (NumElements == 1) {
GEPI->setOperand(2, Constant::getNullValue(Type::IntTy));
} else {
assert(NumElements == 2 && "Unhandled case!");
// All users of the GEP must be loads. At each use of the GEP, insert
// two loads of the appropriate indexed GEP and select between them.
Value *IsOne = BinaryOperator::createSetNE(I.getOperand(),
Constant::getNullValue(I.getOperand()->getType()),
"isone", GEPI);
// Insert the new GEP instructions, which are properly indexed.
std::vector<Value*> Indices(GEPI->op_begin()+1, GEPI->op_end());
Indices[1] = Constant::getNullValue(Type::IntTy);
Value *ZeroIdx = new GetElementPtrInst(GEPI->getOperand(0), Indices,
GEPI->getName()+".0", GEPI);
Indices[1] = ConstantInt::get(Type::IntTy, 1);
Value *OneIdx = new GetElementPtrInst(GEPI->getOperand(0), Indices,
GEPI->getName()+".1", GEPI);
// Replace all loads of the variable index GEP with loads from both
// indexes and a select.
while (!GEPI->use_empty()) {
LoadInst *LI = cast<LoadInst>(GEPI->use_back());
Value *Zero = new LoadInst(ZeroIdx, LI->getName()+".0", LI);
Value *One = new LoadInst(OneIdx , LI->getName()+".1", LI);
Value *R = new SelectInst(IsOne, One, Zero, LI->getName(), LI);
LI->replaceAllUsesWith(R);
LI->eraseFromParent();
}
GEPI->eraseFromParent();
}
}
}
}
}