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Bring back a burr scheduling heuristic that's still needed.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@45252 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Evan Cheng 2007-12-20 02:22:36 +00:00
parent 32e4c7c486
commit d6c0758944
1 changed files with 34 additions and 5 deletions
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39
lib/CodeGen/SelectionDAG/ScheduleDAGRRList.cpp
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@ -1198,6 +1198,26 @@ static unsigned closestSucc(const SUnit *SU) {
return MaxCycle; return MaxCycle;
} }
/// calcMaxScratches - Returns an cost estimate of the worse case requirement
/// for scratch registers. Live-in operands and live-out results don't count
/// since they are "fixed".
static unsigned calcMaxScratches(const SUnit *SU) {
unsigned Scratches = 0;
for (SUnit::const_pred_iterator I = SU->Preds.begin(), E = SU->Preds.end();
I != E; ++I) {
if (I->isCtrl) continue; // ignore chain preds
if (I->Dep->Node->getOpcode() != ISD::CopyFromReg)
Scratches++;
}
for (SUnit::const_succ_iterator I = SU->Succs.begin(), E = SU->Succs.end();
I != E; ++I) {
if (I->isCtrl) continue; // ignore chain succs
if (I->Dep->Node->getOpcode() != ISD::CopyToReg)
Scratches += 10;
}
return Scratches;
}
// Bottom up // Bottom up
bool bu_ls_rr_sort::operator()(const SUnit *left, const SUnit *right) const { bool bu_ls_rr_sort::operator()(const SUnit *left, const SUnit *right) const {
// There used to be a special tie breaker here that looked for // There used to be a special tie breaker here that looked for
@ -1240,14 +1260,23 @@ bool bu_ls_rr_sort::operator()(const SUnit *left, const SUnit *right) const {
if (LDist < RDist) if (LDist < RDist)
return true; return true;
else if (LDist == RDist) { else if (LDist == RDist) {
if (left->Height > right->Height) // Intuitively, it's good to push down instructions whose results are
// liveout so their long live ranges won't conflict with other values
// which are needed inside the BB. Further prioritize liveout instructions
// by the number of operands which are calculated within the BB.
unsigned LScratch = calcMaxScratches(left);
unsigned RScratch = calcMaxScratches(right);
if (LScratch > RScratch)
return true; return true;
else if (left->Height == right->Height) else if (LScratch == RScratch)
if (left->Depth < right->Depth) if (left->Height > right->Height)
return true; return true;
else if (left->Depth == right->Depth) else if (left->Height == right->Height)
if (left->CycleBound > right->CycleBound) if (left->Depth < right->Depth)
return true; return true;
else if (left->Depth == right->Depth)
if (left->CycleBound > right->CycleBound)
return true;
} }
} }
return false; return false;