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Try schedule def + use closer whne Sethi-Ullman numbers are the same.

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e.g.
t1 = op t2, c1
t3 = op t4, c2
and the following instructions are both ready.
t2 = op c3
t4 = op c4

Then schedule t2 = op first.
i.e.
t4 = op c4
t2 = op c3
t1 = op t2, c1
t3 = op t4, c2

This creates more short live intervals which work better with the register
allocator.

llvm-svn: 35089
This commit is contained in:
Evan Cheng 2007-03-13 23:25:11 +00:00
parent 7cbde8351a
commit 399f56eac2
1 changed files with 38 additions and 6 deletions
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44
lib/CodeGen/SelectionDAG/ScheduleDAGRRList.cpp
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@ -576,6 +576,15 @@ namespace {
};
}
static unsigned closestSucc(const SUnit *SU) {
unsigned MaxCycle = 0;
for (SUnit::const_succ_iterator I = SU->Succs.begin(), E = SU->Succs.end();
I != E; ++I)
if (I->first->Cycle > MaxCycle)
MaxCycle = I->first->Cycle;
return MaxCycle;
}
// Bottom up
bool bu_ls_rr_sort::operator()(const SUnit *left, const SUnit *right) const {
bool LIsTarget = left->Node->isTargetOpcode();
@ -596,15 +605,38 @@ bool bu_ls_rr_sort::operator()(const SUnit *left, const SUnit *right) const {
unsigned RPriority = SPQ->getNodePriority(right);
if (LPriority > RPriority)
return true;
else if (LPriority == RPriority)
if (left->Height > right->Height)
else if (LPriority == RPriority) {
// Try schedule def + use closer whne Sethi-Ullman numbers are the same.
// e.g.
// t1 = op t2, c1
// t3 = op t4, c2
//
// and the following instructions are both ready.
// t2 = op c3
// t4 = op c4
//
// Then schedule t2 = op first.
// i.e.
// t4 = op c4
// t2 = op c3
// t1 = op t2, c1
// t3 = op t4, c2
//
// This creates more short live intervals.
unsigned LDist = closestSucc(left);
unsigned RDist = closestSucc(right);
if (LDist < RDist)
return true;
else if (left->Height == right->Height)
if (left->Depth < right->Depth)
else if (LDist == RDist)
if (left->Height > right->Height)
return true;
else if (left->Depth == right->Depth)
if (left->CycleBound > right->CycleBound)
else if (left->Height == right->Height)
if (left->Depth < right->Depth)
return true;
else if (left->Depth == right->Depth)
if (left->CycleBound > right->CycleBound)
return true;
}
return false;
}