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Compile:

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unsigned foo4(unsigned short *P) { return *P & 255; }
unsigned foo5(short *P) { return *P & 255; }

to:

_foo4:
        lbz r3,1(r3)
        blr
_foo5:
        lbz r3,1(r3)
        blr

not:

_foo4:
        lhz r2, 0(r3)
        rlwinm r3, r2, 0, 24, 31
        blr
_foo5:
        lhz r2, 0(r3)
        rlwinm r3, r2, 0, 24, 31
        blr

llvm-svn: 26419
This commit is contained in:
Chris Lattner 2006-02-28 06:49:37 +00:00
parent 866634d77f
commit 3aa1cd759e
1 changed files with 17 additions and 10 deletions
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27
lib/CodeGen/SelectionDAG/DAGCombiner.cpp
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@ -1043,9 +1043,13 @@ SDOperand DAGCombiner::visitAND(SDNode *N) {
}
}
// fold (and (load x), 255) -> (zextload x)
if (N1C && N0.getOpcode() == ISD::LOAD && N0.hasOneUse()) {
MVT::ValueType EVT;
// fold (and (load x), 255) -> (zextload x, i8)
// fold (and (extload x, i16), 255) -> (zextload x, i8)
if (N1C &&
(N0.getOpcode() == ISD::LOAD || N0.getOpcode() == ISD::EXTLOAD ||
N0.getOpcode() == ISD::ZEXTLOAD) &&
N0.hasOneUse()) {
MVT::ValueType EVT, LoadedVT;
if (N1C->getValue() == 255)
EVT = MVT::i8;
else if (N1C->getValue() == 65535)
@ -1054,17 +1058,20 @@ SDOperand DAGCombiner::visitAND(SDNode *N) {
EVT = MVT::i32;
else
EVT = MVT::Other;
if (EVT != MVT::Other) {
assert(MVT::getSizeInBits(VT) > MVT::getSizeInBits(EVT) &&
"Cannot zext to larger type!");
LoadedVT = N0.getOpcode() == ISD::LOAD ? VT :
cast<VTSDNode>(N0.getOperand(3))->getVT();
if (EVT != MVT::Other && LoadedVT > EVT) {
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(VT) - MVT::getSizeInBits(EVT)) / 8;
SDOperand NewPtr = TLI.isLittleEndian() ? N0.getOperand(1) :
DAG.getNode(ISD::ADD, PtrType, N0.getOperand(1),
DAG.getConstant(PtrOff, PtrType));
unsigned PtrOff =
(MVT::getSizeInBits(LoadedVT) - MVT::getSizeInBits(EVT)) / 8;
SDOperand NewPtr = N0.getOperand(1);
if (!TLI.isLittleEndian())
NewPtr = DAG.getNode(ISD::ADD, PtrType, NewPtr,
DAG.getConstant(PtrOff, PtrType));
WorkList.push_back(NewPtr.Val);
SDOperand Load =
DAG.getExtLoad(ISD::ZEXTLOAD, VT, N0.getOperand(0), NewPtr,