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Two changes:

Browse Source 
#1 is to unconditionally strip constantpointerrefs out of
instruction operands where they are absolutely pointless and inhibit
optimization.  GRRR!

#2 is to implement InstCombine/getelementptr_const.ll


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@12519 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2004-03-25 22:59:29 +00:00
parent f6e59410ee
commit ebd985cb87
1 changed files with 40 additions and 16 deletions
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56
lib/Transforms/Scalar/InstructionCombining.cpp
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@ -2260,23 +2260,32 @@ Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) {
// is a getelementptr instruction, combine the indices of the two
// getelementptr instructions into a single instruction.
//
std::vector<Value*> SrcGEPOperands;
if (GetElementPtrInst *Src = dyn_cast<GetElementPtrInst>(GEP.getOperand(0))) {
SrcGEPOperands.assign(Src->op_begin(), Src->op_end());
} else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(GEP.getOperand(0))) {
if (CE->getOpcode() == Instruction::GetElementPtr)
SrcGEPOperands.assign(CE->op_begin(), CE->op_end());
}
if (!SrcGEPOperands.empty()) {
std::vector<Value *> Indices;
// Can we combine the two pointer arithmetics offsets?
if (Src->getNumOperands() == 2 && isa<Constant>(Src->getOperand(1)) &&
if (SrcGEPOperands.size() == 2 && isa<Constant>(SrcGEPOperands[1]) &&
isa<Constant>(GEP.getOperand(1))) {
// Replace: gep (gep %P, long C1), long C2, ...
// With: gep %P, long (C1+C2), ...
Value *Sum = ConstantExpr::get(Instruction::Add,
cast<Constant>(Src->getOperand(1)),
cast<Constant>(SrcGEPOperands[1]),
cast<Constant>(GEP.getOperand(1)));
assert(Sum && "Constant folding of longs failed!?");
GEP.setOperand(0, Src->getOperand(0));
GEP.setOperand(0, SrcGEPOperands[0]);
GEP.setOperand(1, Sum);
AddUsersToWorkList(*Src); // Reduce use count of Src
if (Instruction *I = dyn_cast<Instruction>(GEP.getOperand(0)))
AddUsersToWorkList(*I); // Reduce use count of Src
return &GEP;
} else if (Src->getNumOperands() == 2) {
} else if (SrcGEPOperands.size() == 2) {
// Replace: gep (gep %P, long B), long A, ...
// With: T = long A+B; gep %P, T, ...
//
@ -2284,32 +2293,37 @@ Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) {
// chain to be resolved before we perform this transformation. This
// avoids us creating a TON of code in some cases.
//
if (isa<GetElementPtrInst>(Src->getOperand(0)) &&
cast<Instruction>(Src->getOperand(0))->getNumOperands() == 2)
if (isa<GetElementPtrInst>(SrcGEPOperands[0]) &&
cast<Instruction>(SrcGEPOperands[0])->getNumOperands() == 2)
return 0; // Wait until our source is folded to completion.
Value *Sum = BinaryOperator::create(Instruction::Add, Src->getOperand(1),
Value *Sum = BinaryOperator::create(Instruction::Add, SrcGEPOperands[1],
GEP.getOperand(1),
Src->getName()+".sum", &GEP);
GEP.setOperand(0, Src->getOperand(0));
GEP.getOperand(0)->getName()+".sum",
&GEP);
GEP.setOperand(0, SrcGEPOperands[0]);
GEP.setOperand(1, Sum);
WorkList.push_back(cast<Instruction>(Sum));
return &GEP;
} else if (*GEP.idx_begin() == Constant::getNullValue(Type::LongTy) &&
Src->getNumOperands() != 1) {
SrcGEPOperands.size() != 1) {
// Otherwise we can do the fold if the first index of the GEP is a zero
Indices.insert(Indices.end(), Src->idx_begin(), Src->idx_end());
Indices.insert(Indices.end(), SrcGEPOperands.begin()+1,
SrcGEPOperands.end());
Indices.insert(Indices.end(), GEP.idx_begin()+1, GEP.idx_end());
} else if (Src->getOperand(Src->getNumOperands()-1) ==
Constant::getNullValue(Type::LongTy)) {
} else if (SrcGEPOperands.back() == Constant::getNullValue(Type::LongTy)) {
// FIXME: when we allow indices to be non-long values, support this for
// other types!
// 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(), Src->idx_begin(), Src->idx_end()-1);
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(Src->getOperand(0), Indices, GEP.getName());
return new GetElementPtrInst(SrcGEPOperands[0], Indices, GEP.getName());
} else if (GlobalValue *GV = dyn_cast<GlobalValue>(GEP.getOperand(0))) {
// GEP of global variable. If all of the indices for this GEP are
@ -2548,6 +2562,16 @@ bool InstCombiner::runOnFunction(Function &F) {
continue;
}
// Check to see if any of the operands of this instruction are a
// ConstantPointerRef. Since they sneak in all over the place and inhibit
// optimization, we want to strip them out unconditionally!
for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
if (ConstantPointerRef *CPR =
dyn_cast<ConstantPointerRef>(I->getOperand(i))) {
I->setOperand(i, CPR->getValue());
Changed = true;
}
// Now that we have an instruction, try combining it to simplify it...
if (Instruction *Result = visit(*I)) {
++NumCombined;