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Re-write the address propagation code for pre-indexed loads/stores to take into account some previously misssed cases (PRE_DEC addressing mode, the offset and base address are swapped, etc). This should fix PR15581.

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llvm-svn: 180609
This commit is contained in:
Silviu Baranga 2013-04-26 15:52:24 +00:00
parent edc2de8f08
commit 4e4dc8ed27
1 changed files with 29 additions and 14 deletions
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43
lib/CodeGen/SelectionDAG/DAGCombiner.cpp
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@ -7152,25 +7152,40 @@ bool DAGCombiner::CombineToPreIndexedLoadStore(SDNode *N) {
assert(OtherUses[i]->getOperand(!OffsetIdx).getNode() ==
BasePtr.getNode() && "Expected BasePtr operand");
APInt OV =
cast<ConstantSDNode>(Offset)->getAPIntValue();
if (AM == ISD::PRE_DEC)
OV = -OV;
// We need to replace ptr0 in the following expression:
// x0 * offset0 + y0 * ptr0 = t0
// knowing that
// x1 * offset1 + y1 * ptr0 = t1 (the indexed load/store)
//
// where x0, x1, y0 and y1 in {-1, 1} are given by the types of the
// indexed load/store and the expresion that needs to be re-written.
//
// Therefore, we have:
// t0 = (x0 * offset0 - x1 * y0 * y1 *offset1) + (y0 * y1) * t1
ConstantSDNode *CN =
cast<ConstantSDNode>(OtherUses[i]->getOperand(OffsetIdx));
APInt CNV = CN->getAPIntValue();
if (OtherUses[i]->getOpcode() == ISD::SUB && OffsetIdx == 1)
CNV += OV;
else
CNV -= OV;
int X0, X1, Y0, Y1;
APInt Offset0 = CN->getAPIntValue();
APInt Offset1 = cast<ConstantSDNode>(Offset)->getAPIntValue();
SDValue NewOp1 = Result.getValue(isLoad ? 1 : 0);
SDValue NewOp2 = DAG.getConstant(CNV, CN->getValueType(0));
if (OffsetIdx == 0)
std::swap(NewOp1, NewOp2);
X0 = (OtherUses[i]->getOpcode() == ISD::SUB && OffsetIdx == 1) ? -1 : 1;
Y0 = (OtherUses[i]->getOpcode() == ISD::SUB && OffsetIdx == 0) ? -1 : 1;
X1 = (AM == ISD::PRE_DEC && !Swapped) ? -1 : 1;
Y1 = (AM == ISD::PRE_DEC && Swapped) ? -1 : 1;
SDValue NewUse = DAG.getNode(OtherUses[i]->getOpcode(),
unsigned Opcode = (Y0 * Y1 < 0) ? ISD::SUB : ISD::ADD;
APInt CNV = Offset0;
if (X0 < 0) CNV = -CNV;
if (X1 * Y0 * Y1 < 0) CNV = CNV + Offset1;
else CNV = CNV - Offset1;
// We can now generate the new expression.
SDValue NewOp1 = DAG.getConstant(CNV, CN->getValueType(0));
SDValue NewOp2 = Result.getValue(isLoad ? 1 : 0);
SDValue NewUse = DAG.getNode(Opcode,
OtherUses[i]->getDebugLoc(),
OtherUses[i]->getValueType(0), NewOp1, NewOp2);
DAG.ReplaceAllUsesOfValueWith(SDValue(OtherUses[i], 0), NewUse);