From 730a570c8c1b84f650ae92bacd61c88cfef9c6a4 Mon Sep 17 00:00:00 2001 From: Silviu Baranga Date: Fri, 26 Apr 2013 15:52:24 +0000 Subject: 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. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@180609 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/CodeGen/SelectionDAG/DAGCombiner.cpp | 43 +++++++++++++++++++++----------- 1 file changed, 29 insertions(+), 14 deletions(-) diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp index 05a58b1c1b..310da09edf 100644 --- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp +++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp @@ -7152,25 +7152,40 @@ bool DAGCombiner::CombineToPreIndexedLoadStore(SDNode *N) { assert(OtherUses[i]->getOperand(!OffsetIdx).getNode() == BasePtr.getNode() && "Expected BasePtr operand"); - APInt OV = - cast(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(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(Offset)->getAPIntValue(); + + 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; + + 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; - SDValue NewOp1 = Result.getValue(isLoad ? 1 : 0); - SDValue NewOp2 = DAG.getConstant(CNV, CN->getValueType(0)); - if (OffsetIdx == 0) - std::swap(NewOp1, NewOp2); + // 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(OtherUses[i]->getOpcode(), + SDValue NewUse = DAG.getNode(Opcode, OtherUses[i]->getDebugLoc(), OtherUses[i]->getValueType(0), NewOp1, NewOp2); DAG.ReplaceAllUsesOfValueWith(SDValue(OtherUses[i], 0), NewUse); -- cgit v1.2.3