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Fix a potential bug with two combine-to's back to back that chris pointed

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out, where after the first CombineTo() call, the node the second CombineTo
wishes to replace may no longer exist.

Fix a very real bug with the truncated load optimization on little endian
targets, which do not need a byte offset added to the load.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@23704 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Nate Begeman 2005-10-12 23:18:53 +00:00
parent 3df4d525c5
commit 765784ad76
1 changed files with 14 additions and 4 deletions
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18
lib/CodeGen/SelectionDAG/DAGCombiner.cpp
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@ -1194,13 +1194,17 @@ SDOperand DAGCombiner::visitSIGN_EXTEND(SDNode *N) {
// fold (sext (sext x)) -> (sext x)
if (N0.getOpcode() == ISD::SIGN_EXTEND)
return DAG.getNode(ISD::SIGN_EXTEND, VT, N0.getOperand(0));
// fold (sext (sextload x)) -> (sextload x)
if (N0.getOpcode() == ISD::SEXTLOAD && VT == N0.getValueType())
return N0;
// fold (sext (load x)) -> (sextload x)
if (N0.getOpcode() == ISD::LOAD && N0.Val->hasNUsesOfValue(1, 0)) {
SDOperand ExtLoad = DAG.getExtLoad(ISD::SEXTLOAD, VT, N0.getOperand(0),
N0.getOperand(1), N0.getOperand(2),
N0.getValueType());
CombineTo(N0.Val, ExtLoad, ExtLoad.getOperand(0));
return CombineTo(N, ExtLoad);
WorkList.push_back(N);
return SDOperand();
}
return SDOperand();
}
@ -1303,13 +1307,19 @@ SDOperand DAGCombiner::visitTRUNCATE(SDNode *N) {
assert(MVT::getSizeInBits(N0.getValueType()) > MVT::getSizeInBits(VT) &&
"Cannot truncate to larger type!");
MVT::ValueType PtrType = N0.getOperand(1).getValueType();
// For big endian targets, we need to add an offset to the pointer to load
// the correct bytes. For little endian systems, we merely need to read
// fewer bytes from the same pointer.
uint64_t PtrOff =
(MVT::getSizeInBits(N0.getValueType()) - MVT::getSizeInBits(VT)) / 8;
SDOperand NewPtr = DAG.getNode(ISD::ADD, PtrType, N0.getOperand(1),
DAG.getConstant(PtrOff, PtrType));
SDOperand NewPtr = TLI.isLittleEndian() ? N0.getOperand(1) :
DAG.getNode(ISD::ADD, PtrType, N0.getOperand(1),
DAG.getConstant(PtrOff, PtrType));
WorkList.push_back(NewPtr.Val);
SDOperand Load = DAG.getLoad(VT, N0.getOperand(0), NewPtr,N0.getOperand(2));
CombineTo(N0.Val, Load, Load.getOperand(0));
return CombineTo(N, Load);
WorkList.push_back(N);
return SDOperand();
}
return SDOperand();
}