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Add a counter for the number of times linscan has to backtrack. Start using

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the iterator hints we have to speed up overlaps().  This speeds linscan up
by about .2s (out of 8.7) on 175.vpr for PPC.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@17935 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2004-11-18 03:49:30 +00:00
parent bae74d9192
commit 19828d46f6
1 changed files with 36 additions and 22 deletions
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58
lib/CodeGen/RegAllocLinearScan.cpp
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@ -29,13 +29,13 @@
#include <cmath>
#include <set>
#include <queue>
using namespace llvm;
namespace {
Statistic<double> efficiency
("regalloc", "Ratio of intervals processed over total intervals");
Statistic<> NumBacktracks("regalloc", "Number of times we had to backtrack");
static unsigned numIterations = 0;
static unsigned numIntervals = 0;
@ -196,8 +196,8 @@ void RA::linearScan()
handled_.push_back(cur);
} else {
// otherwise we are allocating a virtual register. try to find a free
// physical register or spill an interval in order to assign it one (we
// could spill the current though).
// physical register or spill an interval (possibly this one) in order to
// assign it one.
assignRegOrStackSlotAtInterval(cur);
}
@ -342,6 +342,15 @@ static RA::IntervalPtrs::iterator FindIntervalInVector(RA::IntervalPtrs &IP,
return IP.end();
}
static void RevertVectorIteratorsTo(RA::IntervalPtrs &V, unsigned Point) {
for (unsigned i = 0, e = V.size(); i != e; ++i) {
RA::IntervalPtr &IP = V[i];
LiveInterval::iterator I = std::upper_bound(IP.first->begin(),
IP.second, Point);
if (I != IP.first->begin()) --I;
IP.second = I;
}
}
/// assignRegOrStackSlotAtInterval - assign a register if one is available, or
@ -367,7 +376,7 @@ void RA::assignRegOrStackSlotAtInterval(LiveInterval* cur)
// register as not free and update spill weights
for (IntervalPtrs::const_iterator i = inactive_.begin(),
e = inactive_.end(); i != e; ++i) {
if (cur->overlaps(*i->first)) {
if (cur->overlapsFrom(*i->first, i->second-1)) {
unsigned reg = i->first->reg;
if (MRegisterInfo::isVirtualRegister(reg))
reg = vrm_->getPhys(reg);
@ -376,16 +385,15 @@ void RA::assignRegOrStackSlotAtInterval(LiveInterval* cur)
}
}
// for every interval in fixed we overlap with,
// mark the register as not free and update spill weights
// For every interval in fixed we overlap with, mark the register as not free
// and update spill weights.
for (IntervalPtrs::const_iterator i = fixed_.begin(),
e = fixed_.end(); i != e; ++i) {
if (cur->overlaps(*i->first)) {
e = fixed_.end(); i != e; ++i)
if (cur->overlapsFrom(*i->first, i->second)) {
unsigned reg = i->first->reg;
prt_->addRegUse(reg);
updateSpillWeights(reg, i->first->weight);
}
}
unsigned physReg = getFreePhysReg(cur);
// restore the physical register tracker
@ -438,6 +446,8 @@ void RA::assignRegOrStackSlotAtInterval(LiveInterval* cur)
return;
}
++NumBacktracks;
// push the current interval back to unhandled since we are going
// to re-run at least this iteration. Since we didn't modify it it
// should go back right in the front of the list
@ -450,7 +460,8 @@ void RA::assignRegOrStackSlotAtInterval(LiveInterval* cur)
assert(MRegisterInfo::isPhysicalRegister(minReg) &&
"did not choose a register to spill?");
std::vector<bool> toSpill(mri_->getNumRegs(), false);
// we are going to spill minReg and all its aliases
// We are going to spill minReg and all its aliases.
toSpill[minReg] = true;
for (const unsigned* as = mri_->getAliasSet(minReg); *as; ++as)
toSpill[*as] = true;
@ -462,18 +473,16 @@ void RA::assignRegOrStackSlotAtInterval(LiveInterval* cur)
// set of spilled vregs (used later to rollback properly)
std::set<unsigned> spilled;
// spill live intervals of virtual regs mapped to the physical
// register we want to clear (and its aliases). we only spill
// those that overlap with the current interval as the rest do not
// affect its allocation. we also keep track of the earliest start
// of all spilled live intervals since this will mark our rollback
// point
for (IntervalPtrs::iterator
i = active_.begin(); i != active_.end(); ++i) {
// spill live intervals of virtual regs mapped to the physical register we
// want to clear (and its aliases). We only spill those that overlap with the
// current interval as the rest do not affect its allocation. we also keep
// track of the earliest start of all spilled live intervals since this will
// mark our rollback point.
for (IntervalPtrs::iterator i = active_.begin(); i != active_.end(); ++i) {
unsigned reg = i->first->reg;
if (MRegisterInfo::isVirtualRegister(reg) &&
toSpill[vrm_->getPhys(reg)] &&
cur->overlaps(*i->first)) {
cur->overlapsFrom(*i->first, i->second)) {
DEBUG(std::cerr << "\t\t\tspilling(a): " << *i->first << '\n');
earliestStart = std::min(earliestStart, i->first->beginNumber());
int slot = vrm_->assignVirt2StackSlot(i->first->reg);
@ -483,12 +492,11 @@ void RA::assignRegOrStackSlotAtInterval(LiveInterval* cur)
spilled.insert(reg);
}
}
for (IntervalPtrs::iterator
i = inactive_.begin(); i != inactive_.end(); ++i) {
for (IntervalPtrs::iterator i = inactive_.begin(); i != inactive_.end(); ++i){
unsigned reg = i->first->reg;
if (MRegisterInfo::isVirtualRegister(reg) &&
toSpill[vrm_->getPhys(reg)] &&
cur->overlaps(*i->first)) {
cur->overlapsFrom(*i->first, i->second-1)) {
DEBUG(std::cerr << "\t\t\tspilling(i): " << *i->first << '\n');
earliestStart = std::min(earliestStart, i->first->beginNumber());
int slot = vrm_->assignVirt2StackSlot(reg);
@ -543,6 +551,12 @@ void RA::assignRegOrStackSlotAtInterval(LiveInterval* cur)
}
}
// Rewind the iterators in the active, inactive, and fixed lists back to the
// point we reverted to.
RevertVectorIteratorsTo(active_, earliestStart);
RevertVectorIteratorsTo(inactive_, earliestStart);
RevertVectorIteratorsTo(fixed_, earliestStart);
// scan the rest and undo each interval that expired after t and
// insert it in active (the next iteration of the algorithm will
// put it in inactive if required)