Add dummy lowering for shifts
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@70715 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/MSP430/MSP430ISelLowering.cpp b/lib/Target/MSP430/MSP430ISelLowering.cpp
index 8427fc7..9817202 100644
--- a/lib/Target/MSP430/MSP430ISelLowering.cpp
+++ b/lib/Target/MSP430/MSP430ISelLowering.cpp
@@ -49,6 +49,12 @@
// Division is expensive
setIntDivIsCheap(false);
+ // Even if we have only 1 bit shift here, we can perform
+ // shifts of the whole bitwidth 1 bit per step.
+ setShiftAmountType(MVT::i8);
+
+ setOperationAction(ISD::SRA, MVT::i16, Custom);
+
setOperationAction(ISD::RET, MVT::Other, Custom);
}
@@ -56,6 +62,7 @@
LowerOperation(SDValue Op, SelectionDAG &DAG) {
switch (Op.getOpcode()) {
case ISD::FORMAL_ARGUMENTS: return LowerFORMAL_ARGUMENTS(Op, DAG);
+ case ISD::SRA: return LowerShifts(Op, DAG);
case ISD::RET: return LowerRET(Op, DAG);
default:
assert(0 && "unimplemented operand");
@@ -210,10 +217,34 @@
return DAG.getNode(MSP430ISD::RET_FLAG, dl, MVT::Other, Chain);
}
+SDValue MSP430TargetLowering::LowerShifts(SDValue Op,
+ SelectionDAG &DAG) {
+ assert(Op.getOpcode() == ISD::SRA && "Only SRA is currently supported.");
+ SDNode* N = Op.getNode();
+ MVT VT = Op.getValueType();
+ DebugLoc dl = N->getDebugLoc();
+
+ // We currently only lower SRA of constant argument.
+ if (!isa<ConstantSDNode>(N->getOperand(1)))
+ return SDValue();
+
+ uint64_t ShiftAmount = cast<ConstantSDNode>(N->getOperand(1))->getZExtValue();
+
+ // Expand the stuff into sequence of shifts.
+ // FIXME: for some shift amounts this might be done better!
+ // E.g.: foo >> (8 + N) => sxt(swpb(foo)) >> N
+ SDValue Victim = N->getOperand(0);
+ while (ShiftAmount--)
+ Victim = DAG.getNode(MSP430ISD::RRA, dl, VT, Victim);
+
+ return Victim;
+}
+
const char *MSP430TargetLowering::getTargetNodeName(unsigned Opcode) const {
switch (Opcode) {
default: return NULL;
case MSP430ISD::RET_FLAG: return "MSP430ISD::RET_FLAG";
+ case MSP430ISD::RRA: return "MSP430ISD::RRA";
}
}