[DAGCombiner] Factor out distributeTruncateThroughAnd
Currently this code is duplicated across visitSHL, visitSRA and visitSRL. The
plan is to add rotates as clients to this new function.
There is no functional change intended here.
llvm-svn: 202908
diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 7f1900d..8650154 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -348,6 +348,14 @@
/// \return True if some memory operations were changed.
bool MergeConsecutiveStores(StoreSDNode *N);
+ /// \brief Try to transform a truncation where C is a constant:
+ /// (trunc (and X, C)) -> (and (trunc X), (trunc C))
+ ///
+ /// \p N needs to be a truncation and its first operand an AND. Other
+ /// requirements are checked by the function (e.g. that trunc is
+ /// single-use) and if missed an empty SDValue is returned.
+ SDValue distributeTruncateThroughAnd(SDNode *N);
+
public:
DAGCombiner(SelectionDAG &D, AliasAnalysis &A, CodeGenOpt::Level OL)
: DAG(D), TLI(D.getTargetLoweringInfo()), Level(BeforeLegalizeTypes),
@@ -3806,6 +3814,28 @@
return DAG.getNode(LHS->getOpcode(), SDLoc(N), VT, NewShift, NewRHS);
}
+SDValue DAGCombiner::distributeTruncateThroughAnd(SDNode *N) {
+ assert(N->getOpcode() == ISD::TRUNCATE);
+ assert(N->getOperand(0).getOpcode() == ISD::AND);
+
+ // (truncate:TruncVT (and N00, N01C)) -> (and (truncate:TruncVT N00), TruncC)
+ if (N->hasOneUse() && N->getOperand(0).hasOneUse()) {
+ SDValue N01 = N->getOperand(0).getOperand(1);
+
+ if (ConstantSDNode *N01C = dyn_cast<ConstantSDNode>(N01)) {
+ EVT TruncVT = N->getValueType(0);
+ SDValue N00 = N->getOperand(0).getOperand(0);
+ APInt TruncC = N01C->getAPIntValue();
+ TruncC = TruncC.trunc(TruncVT.getScalarType().getSizeInBits());
+
+ return DAG.getNode(ISD::AND, SDLoc(N), TruncVT,
+ DAG.getNode(ISD::TRUNCATE, SDLoc(N), TruncVT, N00),
+ DAG.getConstant(TruncC, TruncVT));
+ }
+ }
+
+ return SDValue();
+}
SDValue DAGCombiner::visitSHL(SDNode *N) {
SDValue N0 = N->getOperand(0);
SDValue N1 = N->getOperand(1);
@@ -3859,21 +3889,10 @@
return DAG.getConstant(0, VT);
// fold (shl x, (trunc (and y, c))) -> (shl x, (and (trunc y), (trunc c))).
if (N1.getOpcode() == ISD::TRUNCATE &&
- N1.getOperand(0).getOpcode() == ISD::AND &&
- N1.hasOneUse() && N1.getOperand(0).hasOneUse()) {
- SDValue N101 = N1.getOperand(0).getOperand(1);
- if (ConstantSDNode *N101C = dyn_cast<ConstantSDNode>(N101)) {
- EVT TruncVT = N1.getValueType();
- SDValue N100 = N1.getOperand(0).getOperand(0);
- APInt TruncC = N101C->getAPIntValue();
- TruncC = TruncC.trunc(TruncVT.getSizeInBits());
- return DAG.getNode(ISD::SHL, SDLoc(N), VT, N0,
- DAG.getNode(ISD::AND, SDLoc(N), TruncVT,
- DAG.getNode(ISD::TRUNCATE,
- SDLoc(N),
- TruncVT, N100),
- DAG.getConstant(TruncC, TruncVT)));
- }
+ N1.getOperand(0).getOpcode() == ISD::AND) {
+ SDValue NewOp1 = distributeTruncateThroughAnd(N1.getNode());
+ if (NewOp1.getNode())
+ return DAG.getNode(ISD::SHL, SDLoc(N), VT, N0, NewOp1);
}
if (N1C && SimplifyDemandedBits(SDValue(N, 0)))
@@ -4073,22 +4092,10 @@
// fold (sra x, (trunc (and y, c))) -> (sra x, (and (trunc y), (trunc c))).
if (N1.getOpcode() == ISD::TRUNCATE &&
- N1.getOperand(0).getOpcode() == ISD::AND &&
- N1.hasOneUse() && N1.getOperand(0).hasOneUse()) {
- SDValue N101 = N1.getOperand(0).getOperand(1);
- if (ConstantSDNode *N101C = dyn_cast<ConstantSDNode>(N101)) {
- EVT TruncVT = N1.getValueType();
- SDValue N100 = N1.getOperand(0).getOperand(0);
- APInt TruncC = N101C->getAPIntValue();
- TruncC = TruncC.trunc(TruncVT.getScalarType().getSizeInBits());
- return DAG.getNode(ISD::SRA, SDLoc(N), VT, N0,
- DAG.getNode(ISD::AND, SDLoc(N),
- TruncVT,
- DAG.getNode(ISD::TRUNCATE,
- SDLoc(N),
- TruncVT, N100),
- DAG.getConstant(TruncC, TruncVT)));
- }
+ N1.getOperand(0).getOpcode() == ISD::AND) {
+ SDValue NewOp1 = distributeTruncateThroughAnd(N1.getNode());
+ if (NewOp1.getNode())
+ return DAG.getNode(ISD::SRA, SDLoc(N), VT, N0, NewOp1);
}
// fold (sra (trunc (sr x, c1)), c2) -> (trunc (sra x, c1+c2))
@@ -4267,22 +4274,10 @@
// fold (srl x, (trunc (and y, c))) -> (srl x, (and (trunc y), (trunc c))).
if (N1.getOpcode() == ISD::TRUNCATE &&
- N1.getOperand(0).getOpcode() == ISD::AND &&
- N1.hasOneUse() && N1.getOperand(0).hasOneUse()) {
- SDValue N101 = N1.getOperand(0).getOperand(1);
- if (ConstantSDNode *N101C = dyn_cast<ConstantSDNode>(N101)) {
- EVT TruncVT = N1.getValueType();
- SDValue N100 = N1.getOperand(0).getOperand(0);
- APInt TruncC = N101C->getAPIntValue();
- TruncC = TruncC.trunc(TruncVT.getSizeInBits());
- return DAG.getNode(ISD::SRL, SDLoc(N), VT, N0,
- DAG.getNode(ISD::AND, SDLoc(N),
- TruncVT,
- DAG.getNode(ISD::TRUNCATE,
- SDLoc(N),
- TruncVT, N100),
- DAG.getConstant(TruncC, TruncVT)));
- }
+ N1.getOperand(0).getOpcode() == ISD::AND) {
+ SDValue NewOp1 = distributeTruncateThroughAnd(N1.getNode());
+ if (NewOp1.getNode())
+ return DAG.getNode(ISD::SRL, SDLoc(N), VT, N0, NewOp1);
}
// fold operands of srl based on knowledge that the low bits are not