Use methods to determine if a LiveInterval is spillable.
Don't accidentally produce unspillable intervals for deeply nested loops.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@97496 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/LiveIntervalAnalysis.cpp b/lib/CodeGen/LiveIntervalAnalysis.cpp
index ebcfd60..ccda66f 100644
--- a/lib/CodeGen/LiveIntervalAnalysis.cpp
+++ b/lib/CodeGen/LiveIntervalAnalysis.cpp
@@ -1340,11 +1340,9 @@
MachineBasicBlock *MBB = MI->getParent();
if (ImpUse && MI != ReMatDefMI) {
- // Re-matting an instruction with virtual register use. Update the
- // register interval's spill weight to HUGE_VALF to prevent it from
- // being spilled.
- LiveInterval &ImpLi = getInterval(ImpUse);
- ImpLi.weight = HUGE_VALF;
+ // Re-matting an instruction with virtual register use. Prevent interval
+ // from being spilled.
+ getInterval(ImpUse).markNotSpillable();
}
unsigned MBBId = MBB->getNumber();
@@ -1396,7 +1394,7 @@
LiveInterval &nI = getOrCreateInterval(NewVReg);
if (!TrySplit) {
// The spill weight is now infinity as it cannot be spilled again.
- nI.weight = HUGE_VALF;
+ nI.markNotSpillable();
continue;
}
@@ -1544,6 +1542,22 @@
}
}
+float
+LiveIntervals::getSpillWeight(bool isDef, bool isUse, unsigned loopDepth) {
+ // Limit the loop depth ridiculousness.
+ if (loopDepth > 200)
+ loopDepth = 200;
+
+ // The loop depth is used to roughly estimate the number of times the
+ // instruction is executed. Something like 10^d is simple, but will quickly
+ // overflow a float. This expression behaves like 10^d for small d, but is
+ // more tempered for large d. At d=200 we get 6.7e33 which leaves a bit of
+ // headroom before overflow.
+ float lc = powf(1 + (100.0f / (loopDepth+10)), (float)loopDepth);
+
+ return (isDef + isUse) * lc;
+}
+
void
LiveIntervals::normalizeSpillWeights(std::vector<LiveInterval*> &NewLIs) {
for (unsigned i = 0, e = NewLIs.size(); i != e; ++i)
@@ -1558,8 +1572,7 @@
std::vector<LiveInterval*> added;
- assert(li.weight != HUGE_VALF &&
- "attempt to spill already spilled interval!");
+ assert(li.isSpillable() && "attempt to spill already spilled interval!");
DEBUG({
dbgs() << "\t\t\t\tadding intervals for spills for interval: ";
@@ -1595,10 +1608,7 @@
// create a new register for this spill
LiveInterval &nI = getOrCreateInterval(NewVReg);
-
- // the spill weight is now infinity as it
- // cannot be spilled again
- nI.weight = HUGE_VALF;
+ nI.markNotSpillable();
// Rewrite register operands to use the new vreg.
for (SmallVectorImpl<unsigned>::iterator I = Indices.begin(),
@@ -1652,8 +1662,7 @@
if (EnableFastSpilling)
return addIntervalsForSpillsFast(li, loopInfo, vrm);
- assert(li.weight != HUGE_VALF &&
- "attempt to spill already spilled interval!");
+ assert(li.isSpillable() && "attempt to spill already spilled interval!");
DEBUG({
dbgs() << "\t\t\t\tadding intervals for spills for interval: ";
@@ -1920,11 +1929,10 @@
unsigned ImpUse = getReMatImplicitUse(li, ReMatDefMI);
if (ImpUse) {
// Re-matting an instruction with virtual register use. Add the
- // register as an implicit use on the use MI and update the register
- // interval's spill weight to HUGE_VALF to prevent it from being
- // spilled.
+ // register as an implicit use on the use MI and mark the register
+ // interval as unspillable.
LiveInterval &ImpLi = getInterval(ImpUse);
- ImpLi.weight = HUGE_VALF;
+ ImpLi.markNotSpillable();
MI->addOperand(MachineOperand::CreateReg(ImpUse, false, true));
}
}