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[SelectionDAG] Force cycle detection in AssignTopologicalOrder before aborting

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DAG cycle detection is only enabled with ENABLE_EXPENSIVE_CHECKS.  However we
can run it just before we would crash in order to provide more informative
diagnostics.

Now in addition to the "Overran sorted position" message we also get the Node
printed if a cycle was detected.

Tested by building several configs: Debug+Assert, Debug+Assert+Check (this is
ENABLE_EXPENSIVE_CHECKS), Release+Assert and Release.  Also tried that the
AssignTopologicalOrder assert produces the expected results.

llvm-svn: 209977
This commit is contained in:
Adam Nemet 2014-05-31 16:23:20 +00:00
parent 267d4048ff
commit 807861a7b6
3 changed files with 21 additions and 11 deletions
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2
include/llvm/CodeGen/SelectionDAG.h
View File

@ -151,7 +151,7 @@ public:
};
class SelectionDAG;
void checkForCycles(const SelectionDAG *DAG);
void checkForCycles(const SelectionDAG *DAG, bool force = false);
/// SelectionDAG class - This is used to represent a portion of an LLVM function
/// in a low-level Data Dependence DAG representation suitable for instruction

3
include/llvm/CodeGen/SelectionDAGNodes.h
View File

@ -49,7 +49,8 @@ template <typename T> struct DenseMapInfo;
template <typename T> struct simplify_type;
template <typename T> struct ilist_traits;
void checkForCycles(const SDNode *N, const SelectionDAG *DAG = nullptr);
void checkForCycles(const SDNode *N, const SelectionDAG *DAG = nullptr,
bool force = false);
/// SDVTList - This represents a list of ValueType's that has been intern'd by
/// a SelectionDAG. Instances of this simple value class are returned by

27
lib/CodeGen/SelectionDAG/SelectionDAG.cpp
View File

@ -6002,6 +6002,8 @@ unsigned SelectionDAG::AssignTopologicalOrder() {
SDNode *S = ++I;
dbgs() << "Overran sorted position:\n";
S->dumprFull(this); dbgs() << "\n";
dbgs() << "Checking if this is due to cycles\n";
checkForCycles(this, true);
#endif
llvm_unreachable(nullptr);
}
@ -6587,7 +6589,7 @@ bool ShuffleVectorSDNode::isSplatMask(const int *Mask, EVT VT) {
return true;
}
#ifdef XDEBUG
#ifndef NDEBUG
static void checkForCyclesHelper(const SDNode *N,
SmallPtrSet<const SDNode*, 32> &Visited,
SmallPtrSet<const SDNode*, 32> &Checked,
@ -6614,15 +6616,22 @@ static void checkForCyclesHelper(const SDNode *N,
#endif
void llvm::checkForCycles(const llvm::SDNode *N,
const llvm::SelectionDAG *DAG) {
const llvm::SelectionDAG *DAG,
bool force) {
#ifndef NDEBUG
bool check = force;
#ifdef XDEBUG
assert(N && "Checking nonexistent SDNode");
SmallPtrSet<const SDNode*, 32> visited;
SmallPtrSet<const SDNode*, 32> checked;
checkForCyclesHelper(N, visited, checked, DAG);
#endif
check = true;
#endif // XDEBUG
if (check) {
assert(N && "Checking nonexistent SDNode");
SmallPtrSet<const SDNode*, 32> visited;
SmallPtrSet<const SDNode*, 32> checked;
checkForCyclesHelper(N, visited, checked, DAG);
}
#endif // !NDEBUG
}
void llvm::checkForCycles(const llvm::SelectionDAG *DAG) {
checkForCycles(DAG->getRoot().getNode(), DAG);
void llvm::checkForCycles(const llvm::SelectionDAG *DAG, bool force) {
checkForCycles(DAG->getRoot().getNode(), DAG, force);
}