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Factor out cycle-finder code and make it generic.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@71241 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Anton Korobeynikov 2009-05-08 18:51:58 +00:00
parent d34167a4ab
commit c1c6ef8f74
3 changed files with 120 additions and 110 deletions
include/llvm/CodeGen
SelectionDAGISel.h
lib
CodeGen/SelectionDAG
SelectionDAGISel.cpp
Target/X86
X86ISelDAGToDAG.cpp

6
include/llvm/CodeGen/SelectionDAGISel.h

@ -88,10 +88,8 @@ public:
/// U can be folded during instruction selection that starts at Root and
/// folding N is profitable.
virtual
bool IsLegalAndProfitableToFold(SDNode *N, SDNode *U, SDNode *Root) const {
return true;
}
bool IsLegalAndProfitableToFold(SDNode *N, SDNode *U, SDNode *Root) const;
/// CreateTargetHazardRecognizer - Return a newly allocated hazard recognizer
/// to use for this target when scheduling the DAG.
virtual ScheduleHazardRecognizer *CreateTargetHazardRecognizer();

116
lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp

@ -1203,4 +1203,120 @@ SelectInlineAsmMemoryOperands(std::vector<SDValue> &Ops) {
Ops.push_back(InOps.back());
}
/// findFlagUse - Return use of MVT::Flag value produced by the specified
/// SDNode.
///
static SDNode *findFlagUse(SDNode *N) {
unsigned FlagResNo = N->getNumValues()-1;
for (SDNode::use_iterator I = N->use_begin(), E = N->use_end(); I != E; ++I) {
SDUse &Use = I.getUse();
if (Use.getResNo() == FlagResNo)
return Use.getUser();
}
return NULL;
}
/// findNonImmUse - Return true if "Use" is a non-immediate use of "Def".
/// This function recursively traverses up the operand chain, ignoring
/// certain nodes.
static bool findNonImmUse(SDNode *Use, SDNode* Def, SDNode *ImmedUse,
SDNode *Root,
SmallPtrSet<SDNode*, 16> &Visited) {
if (Use->getNodeId() < Def->getNodeId() ||
!Visited.insert(Use))
return false;
for (unsigned i = 0, e = Use->getNumOperands(); i != e; ++i) {
SDNode *N = Use->getOperand(i).getNode();
if (N == Def) {
if (Use == ImmedUse || Use == Root)
continue; // We are not looking for immediate use.
assert(N != Root);
return true;
}
// Traverse up the operand chain.
if (findNonImmUse(N, Def, ImmedUse, Root, Visited))
return true;
}
return false;
}
/// isNonImmUse - Start searching from Root up the DAG to check is Def can
/// be reached. Return true if that's the case. However, ignore direct uses
/// by ImmedUse (which would be U in the example illustrated in
/// IsLegalAndProfitableToFold) and by Root (which can happen in the store
/// case).
/// FIXME: to be really generic, we should allow direct use by any node
/// that is being folded. But realisticly since we only fold loads which
/// have one non-chain use, we only need to watch out for load/op/store
/// and load/op/cmp case where the root (store / cmp) may reach the load via
/// its chain operand.
static inline bool isNonImmUse(SDNode *Root, SDNode *Def, SDNode *ImmedUse) {
SmallPtrSet<SDNode*, 16> Visited;
return findNonImmUse(Root, Def, ImmedUse, Root, Visited);
}
/// IsLegalAndProfitableToFold - Returns true if the specific operand node N of
/// U can be folded during instruction selection that starts at Root and
/// folding N is profitable.
bool SelectionDAGISel::IsLegalAndProfitableToFold(SDNode *N, SDNode *U,
SDNode *Root) const {
if (OptLevel == CodeGenOpt::None) return false;
// If Root use can somehow reach N through a path that that doesn't contain
// U then folding N would create a cycle. e.g. In the following
// diagram, Root can reach N through X. If N is folded into into Root, then
// X is both a predecessor and a successor of U.
//
// [N*] //
// ^ ^ //
// / \ //
// [U*] [X]? //
// ^ ^ //
// \ / //
// \ / //
// [Root*] //
//
// * indicates nodes to be folded together.
//
// If Root produces a flag, then it gets (even more) interesting. Since it
// will be "glued" together with its flag use in the scheduler, we need to
// check if it might reach N.
//
// [N*] //
// ^ ^ //
// / \ //
// [U*] [X]? //
// ^ ^ //
// \ \ //
// \ | //
// [Root*] | //
// ^ | //
// f | //
// | / //
// [Y] / //
// ^ / //
// f / //
// | / //
// [FU] //
//
// If FU (flag use) indirectly reaches N (the load), and Root folds N
// (call it Fold), then X is a predecessor of FU and a successor of
// Fold. But since Fold and FU are flagged together, this will create
// a cycle in the scheduling graph.
MVT VT = Root->getValueType(Root->getNumValues()-1);
while (VT == MVT::Flag) {
SDNode *FU = findFlagUse(Root);
if (FU == NULL)
break;
Root = FU;
VT = Root->getValueType(Root->getNumValues()-1);
}
return !isNonImmUse(Root, N, U);
}
char SelectionDAGISel::ID = 0;

108
lib/Target/X86/X86ISelDAGToDAG.cpp

@ -249,60 +249,6 @@ namespace {
};
}
/// findFlagUse - Return use of MVT::Flag value produced by the specified
/// SDNode.
///
static SDNode *findFlagUse(SDNode *N) {
unsigned FlagResNo = N->getNumValues()-1;
for (SDNode::use_iterator I = N->use_begin(), E = N->use_end(); I != E; ++I) {
SDUse &Use = I.getUse();
if (Use.getResNo() == FlagResNo)
return Use.getUser();
}
return NULL;
}
/// findNonImmUse - Return true if "Use" is a non-immediate use of "Def".
/// This function recursively traverses up the operand chain, ignoring
/// certain nodes.
static bool findNonImmUse(SDNode *Use, SDNode* Def, SDNode *ImmedUse,
SDNode *Root,
SmallPtrSet<SDNode*, 16> &Visited) {
if (Use->getNodeId() < Def->getNodeId() ||
!Visited.insert(Use))
return false;
for (unsigned i = 0, e = Use->getNumOperands(); i != e; ++i) {
SDNode *N = Use->getOperand(i).getNode();
if (N == Def) {
if (Use == ImmedUse || Use == Root)
continue; // We are not looking for immediate use.
assert(N != Root);
return true;
}
// Traverse up the operand chain.
if (findNonImmUse(N, Def, ImmedUse, Root, Visited))
return true;
}
return false;
}
/// isNonImmUse - Start searching from Root up the DAG to check is Def can
/// be reached. Return true if that's the case. However, ignore direct uses
/// by ImmedUse (which would be U in the example illustrated in
/// IsLegalAndProfitableToFold) and by Root (which can happen in the store
/// case).
/// FIXME: to be really generic, we should allow direct use by any node
/// that is being folded. But realisticly since we only fold loads which
/// have one non-chain use, we only need to watch out for load/op/store
/// and load/op/cmp case where the root (store / cmp) may reach the load via
/// its chain operand.
static inline bool isNonImmUse(SDNode *Root, SDNode *Def, SDNode *ImmedUse) {
SmallPtrSet<SDNode*, 16> Visited;
return findNonImmUse(Root, Def, ImmedUse, Root, Visited);
}
bool X86DAGToDAGISel::IsLegalAndProfitableToFold(SDNode *N, SDNode *U,
SDNode *Root) const {
@ -351,58 +297,8 @@ bool X86DAGToDAGISel::IsLegalAndProfitableToFold(SDNode *N, SDNode *U,
}
}
// If Root use can somehow reach N through a path that that doesn't contain
// U then folding N would create a cycle. e.g. In the following
// diagram, Root can reach N through X. If N is folded into into Root, then
// X is both a predecessor and a successor of U.
//
// [N*] //
// ^ ^ //
// / \ //
// [U*] [X]? //
// ^ ^ //
// \ / //
// \ / //
// [Root*] //
//
// * indicates nodes to be folded together.
//
// If Root produces a flag, then it gets (even more) interesting. Since it
// will be "glued" together with its flag use in the scheduler, we need to
// check if it might reach N.
//
// [N*] //
// ^ ^ //
// / \ //
// [U*] [X]? //
// ^ ^ //
// \ \ //
// \ | //
// [Root*] | //
// ^ | //
// f | //
// | / //
// [Y] / //
// ^ / //
// f / //
// | / //
// [FU] //
//
// If FU (flag use) indirectly reaches N (the load), and Root folds N
// (call it Fold), then X is a predecessor of FU and a successor of
// Fold. But since Fold and FU are flagged together, this will create
// a cycle in the scheduling graph.
MVT VT = Root->getValueType(Root->getNumValues()-1);
while (VT == MVT::Flag) {
SDNode *FU = findFlagUse(Root);
if (FU == NULL)
break;
Root = FU;
VT = Root->getValueType(Root->getNumValues()-1);
}
return !isNonImmUse(Root, N, U);
// Proceed to 'generic' cycle finder code
return SelectionDAGISel::IsLegalAndProfitableToFold(N, U, Root);
}
/// MoveBelowTokenFactor - Replace TokenFactor operand with load's chain operand