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Corrected load folding check. We need to start from the root of the sub-dag
being matched and ensure there isn't a non-direct path to the load (i.e. a path that goes out of the sub-dag.) git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@30958 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -134,7 +134,7 @@ namespace {
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virtual void EmitFunctionEntryCode(Function &Fn, MachineFunction &MF);
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virtual bool CanBeFoldedBy(SDNode *N, SDNode *U);
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virtual bool CanBeFoldedBy(SDNode *N, SDNode *U, SDNode *Root);
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// Include the pieces autogenerated from the target description.
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#include "X86GenDAGISel.inc"
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@ -227,52 +227,54 @@ static SDNode *findFlagUse(SDNode *N) {
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return NULL;
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}
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static void findNonImmUse(SDNode* Use, SDNode* Def, SDNode *Ignore, bool &found,
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static void findNonImmUse(SDNode *Use, SDNode* Def, SDNode *ImmedUse,
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SDNode *Root, SDNode *Skip, bool &found,
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std::set<SDNode *> &Visited) {
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if (found ||
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Use->getNodeId() > Def->getNodeId() ||
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!Visited.insert(Use).second)
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return;
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for (unsigned i = 0, e = Use->getNumOperands(); i != e; ++i) {
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for (unsigned i = 0, e = Use->getNumOperands(); !found && i != e; ++i) {
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SDNode *N = Use->getOperand(i).Val;
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if (N == Ignore)
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if (N == Skip)
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continue;
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if (N != Def) {
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findNonImmUse(N, Def, Ignore, found, Visited);
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} else {
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if (N == Def) {
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if (Use == ImmedUse)
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continue; // Immediate use is ok.
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if (Use == Root) {
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assert(Use->getOpcode() == ISD::STORE ||
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Use->getOpcode() == X86ISD::CMP);
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continue;
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}
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found = true;
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break;
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}
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findNonImmUse(N, Def, ImmedUse, Root, Skip, found, Visited);
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}
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}
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static inline bool isNonImmUse(SDNode* Use, SDNode* Def, SDNode *Ignore=NULL) {
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/// isNonImmUse - Start searching from Root up the DAG to check is Def can
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/// be reached. Return true if that's the case. However, ignore direct uses
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/// by ImmedUse (which would be U in the example illustrated in
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/// CanBeFoldedBy) and by Root (which can happen in the store case).
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/// FIXME: to be really generic, we should allow direct use by any node
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/// that is being folded. But realisticly since we only fold loads which
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/// have one non-chain use, we only need to watch out for load/op/store
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/// and load/op/cmp case where the root (store / cmp) may reach the load via
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/// its chain operand.
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static inline bool isNonImmUse(SDNode *Root, SDNode *Def, SDNode *ImmedUse,
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SDNode *Skip = NULL) {
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std::set<SDNode *> Visited;
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bool found = false;
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for (unsigned i = 0, e = Use->getNumOperands(); i != e; ++i) {
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SDNode *N = Use->getOperand(i).Val;
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if (N != Def && N != Ignore) {
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findNonImmUse(N, Def, Ignore, found, Visited);
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if (found) break;
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}
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}
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if (!found && Ignore) {
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// We must be checking for reachability between Def and a flag use. Go down
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// recursively if Use also produces a flag.
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MVT::ValueType VT = Use->getValueType(Use->getNumValues()-1);
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if (VT == MVT::Flag && !Use->use_empty()) {
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SDNode *FU = findFlagUse(Use);
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if (FU)
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return !isNonImmUse(FU, Def, Use);
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}
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}
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findNonImmUse(Root, Def, ImmedUse, Root, Skip, found, Visited);
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return found;
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}
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bool X86DAGToDAGISel::CanBeFoldedBy(SDNode *N, SDNode *U) {
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bool X86DAGToDAGISel::CanBeFoldedBy(SDNode *N, SDNode *U, SDNode *Root) {
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if (FastISel) return false;
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// If U use can somehow reach N through another path then U can't fold N or
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// it will create a cycle. e.g. In the following diagram, U can reach N
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// through X. If N is folded into into U, then X is both a predecessor and
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@ -285,32 +287,43 @@ bool X86DAGToDAGISel::CanBeFoldedBy(SDNode *N, SDNode *U) {
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// / [X]
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// | ^
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// [U]--------|
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if (!FastISel && !isNonImmUse(U, N)) {
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// If U produces a flag, then it gets (even more) interesting. Since it
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// would have been "glued" together with its flag use, we need to check if
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// it might reach N:
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//
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// [ N ]
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// ^ ^
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// | |
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// [U] \--
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// ^ [TF]
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// | |
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// \ /
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// [FU]
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//
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// If FU (flag use) indirectly reach N (the load), and U fold N (call it
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// NU), then TF is a predecessor of FU and a successor of NU. But since
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// NU and FU are flagged together, this effectively creates a cycle.
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MVT::ValueType VT = U->getValueType(U->getNumValues()-1);
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if (VT == MVT::Flag && !U->use_empty()) {
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SDNode *FU = findFlagUse(U);
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if (FU)
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return !isNonImmUse(FU, N, U);
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if (isNonImmUse(Root, N, U))
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return false;
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// If U produces a flag, then it gets (even more) interesting. Since it
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// would have been "glued" together with its flag use, we need to check if
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// it might reach N:
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//
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// [ N ]
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// ^ ^
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// | |
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// [U] \--
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// ^ [TF]
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// | ^
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// | |
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// \ /
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// [FU]
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//
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// If FU (flag use) indirectly reach N (the load), and U fold N (call it
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// NU), then TF is a predecessor of FU and a successor of NU. But since
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// NU and FU are flagged together, this effectively creates a cycle.
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bool HasFlagUse = false;
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MVT::ValueType VT = Root->getValueType(Root->getNumValues()-1);
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while ((VT == MVT::Flag && !Root->use_empty())) {
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SDNode *FU = findFlagUse(Root);
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if (FU == NULL)
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break;
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else {
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Root = FU;
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HasFlagUse = true;
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}
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return true;
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VT = Root->getValueType(Root->getNumValues()-1);
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}
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return false;
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if (HasFlagUse)
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return !isNonImmUse(Root, N, Root, U);
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return true;
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}
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/// MoveBelowTokenFactor - Replace TokenFactor operand with load's chain operand
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@ -909,7 +922,7 @@ bool X86DAGToDAGISel::TryFoldLoad(SDOperand P, SDOperand N,
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SDOperand &Index, SDOperand &Disp) {
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if (ISD::isNON_EXTLoad(N.Val) &&
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N.hasOneUse() &&
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CanBeFoldedBy(N.Val, P.Val))
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CanBeFoldedBy(N.Val, P.Val, P.Val))
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return SelectAddr(N.getOperand(1), Base, Scale, Index, Disp);
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return false;
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}
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