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More isel time load folding checking for nodes that produce flag values.
See comment in CanBeFoldedBy() for detailed explanation. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@30851 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -213,7 +213,20 @@ namespace {
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};
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}
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static void findNonImmUse(SDNode* Use, SDNode* Def, bool &found,
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static SDNode *findFlagUse(SDNode *N) {
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unsigned FlagResNo = N->getNumValues()-1;
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for (SDNode::use_iterator I = N->use_begin(), E = N->use_end(); I != E; ++I) {
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SDNode *User = *I;
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for (unsigned i = 0, e = User->getNumOperands(); i != e; ++i) {
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SDOperand Op = User->getOperand(i);
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if (Op.ResNo == FlagResNo)
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return User;
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}
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}
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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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std::set<SDNode *> &Visited) {
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if (found ||
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Use->getNodeId() > Def->getNodeId() ||
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@ -222,8 +235,10 @@ static void findNonImmUse(SDNode* Use, SDNode* Def, bool &found,
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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 == Ignore)
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continue;
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if (N != Def) {
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findNonImmUse(N, Def, found, Visited);
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findNonImmUse(N, Def, Ignore, found, Visited);
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} else {
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found = true;
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break;
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@ -231,16 +246,27 @@ static void findNonImmUse(SDNode* Use, SDNode* Def, bool &found,
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}
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}
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static inline bool isNonImmUse(SDNode* Use, SDNode* Def) {
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static inline bool isNonImmUse(SDNode* Use, SDNode* Def, SDNode *Ignore=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) {
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findNonImmUse(N, Def, found, Visited);
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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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return found;
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}
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@ -258,7 +284,32 @@ 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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return !FastISel && !isNonImmUse(U, N);
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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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}
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return true;
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}
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return false;
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}
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/// MoveBelowTokenFactor - Replace TokenFactor operand with load's chain operand
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