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Implement folding of GEP's like: 

%tmp.0 = getelementptr [50 x sbyte]* %ar, uint 0, int 5         ; <sbyte*> [#uses=2]
        %tmp.7 = getelementptr sbyte* %tmp.0, int 8             ; <sbyte*> [#uses=1]

together.  This patch actually allows us to simplify and generalize the code.

llvm-svn: 13415
This commit is contained in:
Chris Lattner 2004-05-07 22:09:22 +00:00
parent 9a7b9d07f0
commit 5f667a6f58
1 changed files with 43 additions and 53 deletions
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96
llvm/lib/Transforms/Scalar/InstructionCombining.cpp
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@ -2535,17 +2535,18 @@ static Value *InsertSignExtendToPtrTy(Value *V, const Type *DTy,
Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) {
Value *PtrOp = GEP.getOperand(0);
// Is it 'getelementptr %P, long 0' or 'getelementptr %P'
// If so, eliminate the noop.
if (GEP.getNumOperands() == 1)
return ReplaceInstUsesWith(GEP, GEP.getOperand(0));
return ReplaceInstUsesWith(GEP, PtrOp);
bool HasZeroPointerIndex = false;
if (Constant *C = dyn_cast<Constant>(GEP.getOperand(1)))
HasZeroPointerIndex = C->isNullValue();
if (GEP.getNumOperands() == 2 && HasZeroPointerIndex)
return ReplaceInstUsesWith(GEP, GEP.getOperand(0));
return ReplaceInstUsesWith(GEP, PtrOp);
// Eliminate unneeded casts for indices.
bool MadeChange = false;
@ -2601,46 +2602,37 @@ Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) {
// getelementptr instructions into a single instruction.
//
std::vector<Value*> SrcGEPOperands;
if (GetElementPtrInst *Src = dyn_cast<GetElementPtrInst>(GEP.getOperand(0))) {
if (GetElementPtrInst *Src = dyn_cast<GetElementPtrInst>(PtrOp)) {
SrcGEPOperands.assign(Src->op_begin(), Src->op_end());
} else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(GEP.getOperand(0))) {
} else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(PtrOp)) {
if (CE->getOpcode() == Instruction::GetElementPtr)
SrcGEPOperands.assign(CE->op_begin(), CE->op_end());
}
if (!SrcGEPOperands.empty()) {
// Note that if our source is a gep chain itself that we wait for that
// chain to be resolved before we perform this transformation. This
// avoids us creating a TON of code in some cases.
//
if (isa<GetElementPtrInst>(SrcGEPOperands[0]) &&
cast<Instruction>(SrcGEPOperands[0])->getNumOperands() == 2)
return 0; // Wait until our source is folded to completion.
std::vector<Value *> Indices;
// Find out whether the last index in the source GEP is a sequential idx.
bool EndsWithSequential = false;
for (gep_type_iterator I = gep_type_begin(*cast<User>(PtrOp)),
E = gep_type_end(*cast<User>(PtrOp)); I != E; ++I)
if (!isa<StructType>(*I))
EndsWithSequential = true;
// Can we combine the two pointer arithmetics offsets?
if (SrcGEPOperands.size() == 2 && isa<Constant>(SrcGEPOperands[1]) &&
isa<Constant>(GEP.getOperand(1))) {
Constant *SGC = cast<Constant>(SrcGEPOperands[1]);
Constant *GC = cast<Constant>(GEP.getOperand(1));
if (SGC->getType() != GC->getType()) {
SGC = ConstantExpr::getSignExtend(SGC, Type::LongTy);
GC = ConstantExpr::getSignExtend(GC, Type::LongTy);
}
// Replace: gep (gep %P, long C1), long C2, ...
// With: gep %P, long (C1+C2), ...
GEP.setOperand(0, SrcGEPOperands[0]);
GEP.setOperand(1, ConstantExpr::getAdd(SGC, GC));
if (Instruction *I = dyn_cast<Instruction>(GEP.getOperand(0)))
AddUsersToWorkList(*I); // Reduce use count of Src
return &GEP;
} else if (SrcGEPOperands.size() == 2) {
if (EndsWithSequential) {
// Replace: gep (gep %P, long B), long A, ...
// With: T = long A+B; gep %P, T, ...
//
// Note that if our source is a gep chain itself that we wait for that
// chain to be resolved before we perform this transformation. This
// avoids us creating a TON of code in some cases.
//
if (isa<GetElementPtrInst>(SrcGEPOperands[0]) &&
cast<Instruction>(SrcGEPOperands[0])->getNumOperands() == 2)
return 0; // Wait until our source is folded to completion.
Value *Sum, *SO1 = SrcGEPOperands[1], *GO1 = GEP.getOperand(1);
Value *Sum, *SO1 = SrcGEPOperands.back(), *GO1 = GEP.getOperand(1);
if (SO1 == Constant::getNullValue(SO1->getType())) {
Sum = GO1;
} else if (GO1 == Constant::getNullValue(GO1->getType())) {
@ -2670,13 +2662,26 @@ Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) {
}
}
}
Sum = BinaryOperator::create(Instruction::Add, SO1, GO1,
GEP.getOperand(0)->getName()+".sum", &GEP);
WorkList.push_back(cast<Instruction>(Sum));
if (isa<Constant>(SO1) && isa<Constant>(GO1))
Sum = ConstantExpr::getAdd(cast<Constant>(SO1), cast<Constant>(GO1));
else {
Sum = BinaryOperator::create(Instruction::Add, SO1, GO1,
PtrOp->getName()+".sum", &GEP);
WorkList.push_back(cast<Instruction>(Sum));
}
}
// Recycle the GEP we already have if possible.
if (SrcGEPOperands.size() == 2) {
GEP.setOperand(0, SrcGEPOperands[0]);
GEP.setOperand(1, Sum);
return &GEP;
} else {
Indices.insert(Indices.end(), SrcGEPOperands.begin()+1,
SrcGEPOperands.end()-1);
Indices.push_back(Sum);
Indices.insert(Indices.end(), GEP.op_begin()+2, GEP.op_end());
}
GEP.setOperand(0, SrcGEPOperands[0]);
GEP.setOperand(1, Sum);
return &GEP;
} else if (isa<Constant>(*GEP.idx_begin()) &&
cast<Constant>(*GEP.idx_begin())->isNullValue() &&
SrcGEPOperands.size() != 1) {
@ -2684,27 +2689,12 @@ Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) {
Indices.insert(Indices.end(), SrcGEPOperands.begin()+1,
SrcGEPOperands.end());
Indices.insert(Indices.end(), GEP.idx_begin()+1, GEP.idx_end());
} else if (SrcGEPOperands.back() ==
Constant::getNullValue(SrcGEPOperands.back()->getType())) {
// We have to check to make sure this really is an ARRAY index we are
// ending up with, not a struct index.
generic_gep_type_iterator<std::vector<Value*>::iterator>
GTI = gep_type_begin(SrcGEPOperands[0]->getType(),
SrcGEPOperands.begin()+1, SrcGEPOperands.end());
std::advance(GTI, SrcGEPOperands.size()-2);
if (isa<SequentialType>(*GTI)) {
// If the src gep ends with a constant array index, merge this get into
// it, even if we have a non-zero array index.
Indices.insert(Indices.end(), SrcGEPOperands.begin()+1,
SrcGEPOperands.end()-1);
Indices.insert(Indices.end(), GEP.idx_begin(), GEP.idx_end());
}
}
if (!Indices.empty())
return new GetElementPtrInst(SrcGEPOperands[0], Indices, GEP.getName());
} else if (GlobalValue *GV = dyn_cast<GlobalValue>(GEP.getOperand(0))) {
} else if (GlobalValue *GV = dyn_cast<GlobalValue>(PtrOp)) {
// GEP of global variable. If all of the indices for this GEP are
// constants, we can promote this to a constexpr instead of an instruction.
@ -2721,7 +2711,7 @@ Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) {
// Replace all uses of the GEP with the new constexpr...
return ReplaceInstUsesWith(GEP, CE);
}
} else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(GEP.getOperand(0))) {
} else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(PtrOp)) {
if (CE->getOpcode() == Instruction::Cast) {
if (HasZeroPointerIndex) {
// transform: GEP (cast [10 x ubyte]* X to [0 x ubyte]*), long 0, ...