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Eliminate reachability matrix. It has to be calculated before any instruction

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selection is done. That's rather expensive especially in situations where it
isn't really needed.
Move back to a searching the predecessors, but make use of topological order
to trim the search space.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@29559 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Evan Cheng 2006-08-08 00:31:00 +00:00
parent 080e187dfb
commit f4b4c416d3
1 changed files with 34 additions and 57 deletions
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91
lib/Target/X86/X86ISelDAGToDAG.cpp
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@ -99,8 +99,7 @@ namespace {
X86DAGToDAGISel(X86TargetMachine &TM)
: SelectionDAGISel(X86Lowering),
X86Lowering(*TM.getTargetLowering()),
Subtarget(&TM.getSubtarget<X86Subtarget>()),
ReachabilityMatrix(NULL) {}
Subtarget(&TM.getSubtarget<X86Subtarget>()) {}
virtual bool runOnFunction(Function &Fn) {
// Make sure we re-emit a set of the global base reg if necessary
@ -124,8 +123,6 @@ namespace {
#include "X86GenDAGISel.inc"
private:
void DetermineReachability();
void Select(SDOperand &Result, SDOperand N);
bool MatchAddress(SDOperand N, X86ISelAddressMode &AM, bool isRoot = true);
@ -142,10 +139,6 @@ namespace {
unsigned NumBytes = (DAGSize + 7) / 8;
UnfoldableSet = new unsigned char[NumBytes];
memset(UnfoldableSet, 0, NumBytes);
unsigned RMSize = (DAGSize * DAGSize + 7) / 8;
ReachabilityMatrix = new unsigned char[RMSize];
memset(ReachabilityMatrix, 0, RMSize);
DetermineReachability();
}
/// SelectInlineAsmMemoryOperand - Implement addressing mode selection for
@ -192,20 +185,6 @@ namespace {
/// base register. Return the virtual register that holds this value.
SDOperand getGlobalBaseReg();
/// ReachabilityMatrix - A N x N matrix representing all pairs reachability
/// information. One bit per potential edge.
unsigned char *ReachabilityMatrix;
inline void setReachable(SDNode *f, SDNode *t) {
unsigned Idx = f->getNodeId() * DAGSize + t->getNodeId();
ReachabilityMatrix[Idx / 8] |= 1 << (Idx % 8);
}
inline bool isReachable(SDNode *f, SDNode *t) {
unsigned Idx = f->getNodeId() * DAGSize + t->getNodeId();
return ReachabilityMatrix[Idx / 8] & (1 << (Idx % 8));
}
/// UnfoldableSet - An boolean array representing nodes which have been
/// folded into addressing modes and therefore should not be folded in
/// another operation.
@ -227,6 +206,38 @@ namespace {
};
}
static void findNonImmUse(SDNode* Use, SDNode* Def, bool &found,
std::set<SDNode *> &Visited) {
if (found ||
Use->getNodeId() > Def->getNodeId() ||
!Visited.insert(Use).second)
return;
for (unsigned i = 0, e = Use->getNumOperands(); i != e; ++i) {
SDNode *N = Use->getOperand(i).Val;
if (N != Def) {
findNonImmUse(N, Def, found, Visited);
} else {
found = true;
break;
}
}
}
static inline bool isNonImmUse(SDNode* Use, SDNode* Def) {
std::set<SDNode *> Visited;
bool found = false;
for (unsigned i = 0, e = Use->getNumOperands(); i != e; ++i) {
SDNode *N = Use->getOperand(i).Val;
if (N != Def) {
findNonImmUse(N, Def, found, Visited);
if (found) break;
}
}
return found;
}
bool X86DAGToDAGISel::CanBeFoldedBy(SDNode *N, SDNode *U) {
// Is it already folded by SelectAddr / SelectLEAAddr?
if (isUnfoldable(N))
@ -244,38 +255,7 @@ bool X86DAGToDAGISel::CanBeFoldedBy(SDNode *N, SDNode *U) {
// / [X]
// | ^
// [U]--------|
assert(isReachable(U, N) && "Attempting to fold a non-operand node?");
for (SDNode::op_iterator I = U->op_begin(), E = U->op_end(); I != E; ++I) {
SDNode *P = I->Val;
if (P != N && isReachable(P, N))
return false;
}
return true;
}
/// DetermineReachability - Determine reachability between all pairs of nodes
/// between f and t in topological order.
void X86DAGToDAGISel::DetermineReachability() {
for (unsigned i = 0; i < DAGSize; ++i) {
SDNode *N = TopOrder[i];
setReachable(N, N);
// If N is a leaf node, there is nothing more to do.
if (N->getNumOperands() == 0)
continue;
for (unsigned i2 = 0; ; ++i2) {
SDNode *M = TopOrder[i2];
if (isReachable(M, N)) {
// Update reachability from M to N's operands.
for (SDNode::op_iterator I = N->op_begin(),E = N->op_end(); I != E;++I){
SDNode *P = I->Val;
if (P->getNodeId() >= 0)
setReachable(M, P);
}
}
if (M == N) break;
}
}
return !isNonImmUse(U, N);
}
/// InstructionSelectBasicBlock - This callback is invoked by SelectionDAGISel
@ -294,9 +274,6 @@ void X86DAGToDAGISel::InstructionSelectBasicBlock(SelectionDAG &DAG) {
DEBUG(std::cerr << "===== Instruction selection ends:\n");
#endif
delete[] ReachabilityMatrix;
delete[] UnfoldableSet;
ReachabilityMatrix = NULL;
UnfoldableSet = NULL;
DAG.RemoveDeadNodes();