1 //===-- LegalizeVectorOps.cpp - Implement SelectionDAG::LegalizeVectors ---===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file implements the SelectionDAG::LegalizeVectors method.
12 // The vector legalizer looks for vector operations which might need to be
13 // unrolled and legalizes them. This is a separate step from Legalize because
14 // unrolling can introduce illegal types. For example, suppose we have an
15 // ISD::SDIV of type v2i64 on x86-32. The type is legal (for example, addition
16 // on a v2i64 is legal), but ISD::SDIV isn't legal, so we have to unroll the
17 // operation, which introduces nodes with the illegal type i64 which must be
18 // expanded. Similarly, suppose we have an ISD::SRA of type v16i8 on PowerPC;
19 // the operation must be unrolled, which introduces nodes with the illegal
20 // type i8 which must be promoted.
22 // This does not legalize vector manipulations like ISD::BUILD_VECTOR,
23 // or operations that happen to take a vector which are custom-lowered like
24 // ISD::CALL; the legalization for such operations never produces nodes
25 // with illegal types, so it's okay to put off legalizing them until
26 // SelectionDAG::Legalize runs.
28 //===----------------------------------------------------------------------===//
30 #include "llvm/CodeGen/SelectionDAG.h"
31 #include "llvm/Target/TargetLowering.h"
35 class VectorLegalizer {
38 bool Changed; // Keep track of whether anything changed
40 /// LegalizedNodes - For nodes that are of legal width, and that have more
41 /// than one use, this map indicates what regularized operand to use. This
42 /// allows us to avoid legalizing the same thing more than once.
43 DenseMap<SDValue, SDValue> LegalizedNodes;
45 // Adds a node to the translation cache
46 void AddLegalizedOperand(SDValue From, SDValue To) {
47 LegalizedNodes.insert(std::make_pair(From, To));
48 // If someone requests legalization of the new node, return itself.
50 LegalizedNodes.insert(std::make_pair(To, To));
53 // Legalizes the given node
54 SDValue LegalizeOp(SDValue Op);
55 // Assuming the node is legal, "legalize" the results
56 SDValue TranslateLegalizeResults(SDValue Op, SDValue Result);
57 // Implements unrolling a generic vector operation, i.e. turning it into
59 SDValue UnrollVectorOp(SDValue Op);
60 // Implements unrolling a VSETCC.
61 SDValue UnrollVSETCC(SDValue Op);
62 // Implements expansion for FNEG; falls back to UnrollVectorOp if FSUB
64 SDValue ExpandFNEG(SDValue Op);
65 // Implements vector promotion; this is essentially just bitcasting the
66 // operands to a different type and bitcasting the result back to the
68 SDValue PromoteVectorOp(SDValue Op);
72 VectorLegalizer(SelectionDAG& dag) :
73 DAG(dag), TLI(dag.getTargetLoweringInfo()), Changed(false) {}
76 bool VectorLegalizer::Run() {
77 // The legalize process is inherently a bottom-up recursive process (users
78 // legalize their uses before themselves). Given infinite stack space, we
79 // could just start legalizing on the root and traverse the whole graph. In
80 // practice however, this causes us to run out of stack space on large basic
81 // blocks. To avoid this problem, compute an ordering of the nodes where each
82 // node is only legalized after all of its operands are legalized.
83 DAG.AssignTopologicalOrder();
84 for (SelectionDAG::allnodes_iterator I = DAG.allnodes_begin(),
85 E = prior(DAG.allnodes_end()); I != next(E); ++I)
86 LegalizeOp(SDValue(I, 0));
88 // Finally, it's possible the root changed. Get the new root.
89 SDValue OldRoot = DAG.getRoot();
90 assert(LegalizedNodes.count(OldRoot) && "Root didn't get legalized?");
91 DAG.setRoot(LegalizedNodes[OldRoot]);
93 LegalizedNodes.clear();
95 // Remove dead nodes now.
96 DAG.RemoveDeadNodes();
101 SDValue VectorLegalizer::TranslateLegalizeResults(SDValue Op, SDValue Result) {
102 // Generic legalization: just pass the operand through.
103 for (unsigned i = 0, e = Op.getNode()->getNumValues(); i != e; ++i)
104 AddLegalizedOperand(Op.getValue(i), Result.getValue(i));
105 return Result.getValue(Op.getResNo());
108 SDValue VectorLegalizer::LegalizeOp(SDValue Op) {
109 // Note that LegalizeOp may be reentered even from single-use nodes, which
110 // means that we always must cache transformed nodes.
111 DenseMap<SDValue, SDValue>::iterator I = LegalizedNodes.find(Op);
112 if (I != LegalizedNodes.end()) return I->second;
114 SDNode* Node = Op.getNode();
116 // Legalize the operands
117 SmallVector<SDValue, 8> Ops;
118 for (unsigned i = 0, e = Node->getNumOperands(); i != e; ++i)
119 Ops.push_back(LegalizeOp(Node->getOperand(i)));
122 DAG.UpdateNodeOperands(Op.getValue(0), Ops.data(), Ops.size());
124 bool HasVectorValue = false;
125 for (SDNode::value_iterator J = Node->value_begin(), E = Node->value_end();
128 HasVectorValue |= J->isVector();
130 return TranslateLegalizeResults(Op, Result);
132 switch (Op.getOpcode()) {
134 return TranslateLegalizeResults(Op, Result);
161 case ISD::ZERO_EXTEND:
162 case ISD::ANY_EXTEND:
164 case ISD::SIGN_EXTEND:
165 case ISD::SINT_TO_FP:
166 case ISD::UINT_TO_FP:
167 case ISD::FP_TO_SINT:
168 case ISD::FP_TO_UINT:
184 case ISD::FNEARBYINT:
189 switch (TLI.getOperationAction(Node->getOpcode(), Node->getValueType(0))) {
190 case TargetLowering::Promote:
191 // "Promote" the operation by bitcasting
192 Result = PromoteVectorOp(Op);
195 case TargetLowering::Legal: break;
196 case TargetLowering::Custom: {
197 SDValue Tmp1 = TLI.LowerOperation(Op, DAG);
198 if (Tmp1.getNode()) {
204 case TargetLowering::Expand:
205 if (Node->getOpcode() == ISD::FNEG)
206 Result = ExpandFNEG(Op);
207 else if (Node->getOpcode() == ISD::VSETCC)
208 Result = UnrollVSETCC(Op);
210 Result = UnrollVectorOp(Op);
214 // Make sure that the generated code is itself legal.
216 Result = LegalizeOp(Result);
220 // Note that LegalizeOp may be reentered even from single-use nodes, which
221 // means that we always must cache transformed nodes.
222 AddLegalizedOperand(Op, Result);
226 SDValue VectorLegalizer::PromoteVectorOp(SDValue Op) {
227 MVT VT = Op.getValueType();
228 assert(Op.getNode()->getNumValues() == 1 &&
229 "Can't promote a vector with multiple results!");
230 MVT NVT = TLI.getTypeToPromoteTo(Op.getOpcode(), VT);
231 DebugLoc dl = Op.getDebugLoc();
232 SmallVector<SDValue, 4> Operands(Op.getNumOperands());
234 for (unsigned j = 0; j != Op.getNumOperands(); ++j) {
235 if (Op.getOperand(j).getValueType().isVector())
236 Operands[j] = DAG.getNode(ISD::BIT_CONVERT, dl, NVT, Op.getOperand(j));
238 Operands[j] = Op.getOperand(j);
241 Op = DAG.getNode(Op.getOpcode(), dl, NVT, &Operands[0], Operands.size());
243 return DAG.getNode(ISD::BIT_CONVERT, dl, VT, Op);
246 SDValue VectorLegalizer::ExpandFNEG(SDValue Op) {
247 if (TLI.isOperationLegalOrCustom(ISD::FSUB, Op.getValueType())) {
248 SDValue Zero = DAG.getConstantFP(-0.0, Op.getValueType());
249 return DAG.getNode(ISD::FSUB, Op.getDebugLoc(), Op.getValueType(),
250 Zero, Op.getOperand(0));
252 return UnrollVectorOp(Op);
255 SDValue VectorLegalizer::UnrollVSETCC(SDValue Op) {
256 MVT VT = Op.getValueType();
257 unsigned NumElems = VT.getVectorNumElements();
258 MVT EltVT = VT.getVectorElementType();
259 SDValue LHS = Op.getOperand(0), RHS = Op.getOperand(1), CC = Op.getOperand(2);
260 MVT TmpEltVT = LHS.getValueType().getVectorElementType();
261 DebugLoc dl = Op.getDebugLoc();
262 SmallVector<SDValue, 8> Ops(NumElems);
263 for (unsigned i = 0; i < NumElems; ++i) {
264 SDValue LHSElem = DAG.getNode(ISD::EXTRACT_VECTOR_ELT, dl, TmpEltVT, LHS,
265 DAG.getIntPtrConstant(i));
266 SDValue RHSElem = DAG.getNode(ISD::EXTRACT_VECTOR_ELT, dl, TmpEltVT, RHS,
267 DAG.getIntPtrConstant(i));
268 Ops[i] = DAG.getNode(ISD::SETCC, dl, TLI.getSetCCResultType(TmpEltVT),
269 LHSElem, RHSElem, CC);
270 Ops[i] = DAG.getNode(ISD::SELECT, dl, EltVT, Ops[i],
271 DAG.getConstant(APInt::getAllOnesValue
272 (EltVT.getSizeInBits()), EltVT),
273 DAG.getConstant(0, EltVT));
275 return DAG.getNode(ISD::BUILD_VECTOR, dl, VT, &Ops[0], NumElems);
278 /// UnrollVectorOp - We know that the given vector has a legal type, however
279 /// the operation it performs is not legal, and the target has requested that
280 /// the operation be expanded. "Unroll" the vector, splitting out the scalars
281 /// and operating on each element individually.
282 SDValue VectorLegalizer::UnrollVectorOp(SDValue Op) {
283 MVT VT = Op.getValueType();
284 assert(Op.getNode()->getNumValues() == 1 &&
285 "Can't unroll a vector with multiple results!");
286 unsigned NE = VT.getVectorNumElements();
287 MVT EltVT = VT.getVectorElementType();
288 DebugLoc dl = Op.getDebugLoc();
290 SmallVector<SDValue, 8> Scalars;
291 SmallVector<SDValue, 4> Operands(Op.getNumOperands());
292 for (unsigned i = 0; i != NE; ++i) {
293 for (unsigned j = 0; j != Op.getNumOperands(); ++j) {
294 SDValue Operand = Op.getOperand(j);
295 MVT OperandVT = Operand.getValueType();
296 if (OperandVT.isVector()) {
297 // A vector operand; extract a single element.
298 MVT OperandEltVT = OperandVT.getVectorElementType();
299 Operands[j] = DAG.getNode(ISD::EXTRACT_VECTOR_ELT, dl,
302 DAG.getConstant(i, MVT::i32));
304 // A scalar operand; just use it as is.
305 Operands[j] = Operand;
309 switch (Op.getOpcode()) {
311 Scalars.push_back(DAG.getNode(Op.getOpcode(), dl, EltVT,
312 &Operands[0], Operands.size()));
319 Scalars.push_back(DAG.getNode(Op.getOpcode(), dl, EltVT, Operands[0],
320 DAG.getShiftAmountOperand(Operands[1])));
325 return DAG.getNode(ISD::BUILD_VECTOR, dl, VT, &Scalars[0], Scalars.size());
330 bool SelectionDAG::LegalizeVectors() {
331 return VectorLegalizer(*this).Run();