[llvm-commits] CVS: llvm/lib/CodeGen/RegAllocLinearScan.cpp
Chris Lattner
lattner at cs.uiuc.edu
Wed Nov 17 19:49:42 PST 2004
Changes in directory llvm/lib/CodeGen:
RegAllocLinearScan.cpp updated: 1.99 -> 1.100
---
Log message:
Add a counter for the number of times linscan has to backtrack. Start using
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.
---
Diffs of the changes: (+36 -22)
Index: llvm/lib/CodeGen/RegAllocLinearScan.cpp
diff -u llvm/lib/CodeGen/RegAllocLinearScan.cpp:1.99 llvm/lib/CodeGen/RegAllocLinearScan.cpp:1.100
--- llvm/lib/CodeGen/RegAllocLinearScan.cpp:1.99 Wed Nov 17 20:42:27 2004
+++ llvm/lib/CodeGen/RegAllocLinearScan.cpp Wed Nov 17 21:49:30 2004
@@ -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 @@
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 @@
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 @@
// 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 @@
}
}
- // 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 @@
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 @@
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 @@
// 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 @@
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 @@
}
}
+ // 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)
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