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path: root/lib/CodeGen/CalcSpillWeights.cpp
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Diffstat (limited to 'lib/CodeGen/CalcSpillWeights.cpp')
-rw-r--r--lib/CodeGen/CalcSpillWeights.cpp225
1 files changed, 127 insertions, 98 deletions
diff --git a/lib/CodeGen/CalcSpillWeights.cpp b/lib/CodeGen/CalcSpillWeights.cpp
index 0703d6527d..02adae0edd 100644
--- a/lib/CodeGen/CalcSpillWeights.cpp
+++ b/lib/CodeGen/CalcSpillWeights.cpp
@@ -41,107 +41,136 @@ bool CalculateSpillWeights::runOnMachineFunction(MachineFunction &fn) {
<< "********** Function: "
<< fn.getFunction()->getName() << '\n');
- LiveIntervals *lis = &getAnalysis<LiveIntervals>();
- MachineLoopInfo *loopInfo = &getAnalysis<MachineLoopInfo>();
- MachineRegisterInfo *mri = &fn.getRegInfo();
-
- SmallSet<unsigned, 4> processed;
- for (MachineFunction::iterator mbbi = fn.begin(), mbbe = fn.end();
- mbbi != mbbe; ++mbbi) {
- MachineBasicBlock* mbb = mbbi;
- SlotIndex mbbEnd = lis->getMBBEndIdx(mbb);
- MachineLoop* loop = loopInfo->getLoopFor(mbb);
- unsigned loopDepth = loop ? loop->getLoopDepth() : 0;
- bool isExiting = loop ? loop->isLoopExiting(mbb) : false;
-
- for (MachineBasicBlock::const_iterator mii = mbb->begin(), mie = mbb->end();
- mii != mie; ++mii) {
- const MachineInstr *mi = mii;
- if (mi->isIdentityCopy() || mi->isImplicitDef() || mi->isDebugValue())
- continue;
-
- for (unsigned i = 0, e = mi->getNumOperands(); i != e; ++i) {
- const MachineOperand &mopi = mi->getOperand(i);
- if (!mopi.isReg() || mopi.getReg() == 0)
- continue;
- unsigned reg = mopi.getReg();
- if (!TargetRegisterInfo::isVirtualRegister(mopi.getReg()))
- continue;
- // Multiple uses of reg by the same instruction. It should not
- // contribute to spill weight again.
- if (!processed.insert(reg))
- continue;
-
- bool hasDef = mopi.isDef();
- bool hasUse = !hasDef;
- for (unsigned j = i+1; j != e; ++j) {
- const MachineOperand &mopj = mi->getOperand(j);
- if (!mopj.isReg() || mopj.getReg() != reg)
- continue;
- hasDef |= mopj.isDef();
- hasUse |= mopj.isUse();
- if (hasDef && hasUse)
- break;
- }
-
- LiveInterval &regInt = lis->getInterval(reg);
- float weight = lis->getSpillWeight(hasDef, hasUse, loopDepth);
- if (hasDef && isExiting) {
- // Looks like this is a loop count variable update.
- SlotIndex defIdx = lis->getInstructionIndex(mi).getDefIndex();
- const LiveRange *dlr =
- lis->getInterval(reg).getLiveRangeContaining(defIdx);
- if (dlr->end >= mbbEnd)
- weight *= 3.0F;
- }
- regInt.weight += weight;
- }
- processed.clear();
- }
- }
-
- for (LiveIntervals::iterator I = lis->begin(), E = lis->end(); I != E; ++I) {
+ LiveIntervals &lis = getAnalysis<LiveIntervals>();
+ VirtRegAuxInfo vrai(fn, lis, getAnalysis<MachineLoopInfo>());
+ for (LiveIntervals::iterator I = lis.begin(), E = lis.end(); I != E; ++I) {
LiveInterval &li = *I->second;
- if (TargetRegisterInfo::isVirtualRegister(li.reg)) {
- // If the live interval length is essentially zero, i.e. in every live
- // range the use follows def immediately, it doesn't make sense to spill
- // it and hope it will be easier to allocate for this li.
- if (isZeroLengthInterval(&li)) {
- li.weight = HUGE_VALF;
- continue;
- }
-
- bool isLoad = false;
- SmallVector<LiveInterval*, 4> spillIs;
- if (lis->isReMaterializable(li, spillIs, isLoad)) {
- // If all of the definitions of the interval are re-materializable,
- // it is a preferred candidate for spilling. If none of the defs are
- // loads, then it's potentially very cheap to re-materialize.
- // FIXME: this gets much more complicated once we support non-trivial
- // re-materialization.
- if (isLoad)
- li.weight *= 0.9F;
- else
- li.weight *= 0.5F;
- }
-
- // Slightly prefer live interval that has been assigned a preferred reg.
- std::pair<unsigned, unsigned> Hint = mri->getRegAllocationHint(li.reg);
- if (Hint.first || Hint.second)
- li.weight *= 1.01F;
-
- lis->normalizeSpillWeight(li);
- }
+ if (TargetRegisterInfo::isVirtualRegister(li.reg))
+ vrai.CalculateWeightAndHint(li);
}
-
return false;
}
-/// Returns true if the given live interval is zero length.
-bool CalculateSpillWeights::isZeroLengthInterval(LiveInterval *li) const {
- for (LiveInterval::Ranges::const_iterator
- i = li->ranges.begin(), e = li->ranges.end(); i != e; ++i)
- if (i->end.getPrevIndex() > i->start)
- return false;
- return true;
+// Return the preferred allocation register for reg, given a COPY instruction.
+static unsigned copyHint(const MachineInstr *mi, unsigned reg,
+ const TargetRegisterInfo &tri,
+ const MachineRegisterInfo &mri) {
+ unsigned sub, hreg, hsub;
+ if (mi->getOperand(0).getReg() == reg) {
+ sub = mi->getOperand(0).getSubReg();
+ hreg = mi->getOperand(1).getReg();
+ hsub = mi->getOperand(1).getSubReg();
+ } else {
+ sub = mi->getOperand(1).getSubReg();
+ hreg = mi->getOperand(0).getReg();
+ hsub = mi->getOperand(0).getSubReg();
+ }
+
+ if (!hreg)
+ return 0;
+
+ if (TargetRegisterInfo::isVirtualRegister(hreg))
+ return sub == hsub ? hreg : 0;
+
+ const TargetRegisterClass *rc = mri.getRegClass(reg);
+
+ // Only allow physreg hints in rc.
+ if (sub == 0)
+ return rc->contains(hreg) ? hreg : 0;
+
+ // reg:sub should match the physreg hreg.
+ return tri.getMatchingSuperReg(hreg, sub, rc);
}
+
+void VirtRegAuxInfo::CalculateWeightAndHint(LiveInterval &li) {
+ MachineRegisterInfo &mri = mf_.getRegInfo();
+ const TargetRegisterInfo &tri = *mf_.getTarget().getRegisterInfo();
+ MachineBasicBlock *mbb = 0;
+ MachineLoop *loop = 0;
+ unsigned loopDepth = 0;
+ bool isExiting = false;
+ float totalWeight = 0;
+ SmallPtrSet<MachineInstr*, 8> visited;
+
+ // Find the best physreg hist and the best virtreg hint.
+ float bestPhys = 0, bestVirt = 0;
+ unsigned hintPhys = 0, hintVirt = 0;
+
+ // Don't recompute a target specific hint.
+ bool noHint = mri.getRegAllocationHint(li.reg).first != 0;
+
+ for (MachineRegisterInfo::reg_iterator I = mri.reg_begin(li.reg);
+ MachineInstr *mi = I.skipInstruction();) {
+ if (mi->isIdentityCopy() || mi->isImplicitDef() || mi->isDebugValue())
+ continue;
+ if (!visited.insert(mi))
+ continue;
+
+ // Get loop info for mi.
+ if (mi->getParent() != mbb) {
+ mbb = mi->getParent();
+ loop = loops_.getLoopFor(mbb);
+ loopDepth = loop ? loop->getLoopDepth() : 0;
+ isExiting = loop ? loop->isLoopExiting(mbb) : false;
+ }
+
+ // Calculate instr weight.
+ bool reads, writes;
+ tie(reads, writes) = mi->readsWritesVirtualRegister(li.reg);
+ float weight = LiveIntervals::getSpillWeight(writes, reads, loopDepth);
+
+ // Give extra weight to what looks like a loop induction variable update.
+ if (writes && isExiting && lis_.isLiveOutOfMBB(li, mbb))
+ weight *= 3;
+
+ totalWeight += weight;
+
+ // Get allocation hints from copies.
+ if (noHint || !mi->isCopy())
+ continue;
+ unsigned hint = copyHint(mi, li.reg, tri, mri);
+ if (!hint)
+ continue;
+ float hweight = hint_[hint] += weight;
+ if (TargetRegisterInfo::isPhysicalRegister(hint)) {
+ if (hweight > bestPhys && lis_.isAllocatable(hint))
+ bestPhys = hweight, hintPhys = hint;
+ } else {
+ if (hweight > bestVirt)
+ bestVirt = hweight, hintVirt = hint;
+ }
+ }
+
+ hint_.clear();
+
+ // Always prefer the physreg hint.
+ if (unsigned hint = hintPhys ? hintPhys : hintVirt) {
+ mri.setRegAllocationHint(li.reg, 0, hint);
+ // Weakly boost the spill weifght of hinted registers.
+ totalWeight *= 1.01F;
+ }
+
+ // Mark li as unspillable if all live ranges are tiny.
+ if (li.isZeroLength()) {
+ li.markNotSpillable();
+ return;
+ }
+
+ // If all of the definitions of the interval are re-materializable,
+ // it is a preferred candidate for spilling. If none of the defs are
+ // loads, then it's potentially very cheap to re-materialize.
+ // FIXME: this gets much more complicated once we support non-trivial
+ // re-materialization.
+ bool isLoad = false;
+ SmallVector<LiveInterval*, 4> spillIs;
+ if (lis_.isReMaterializable(li, spillIs, isLoad)) {
+ if (isLoad)
+ totalWeight *= 0.9F;
+ else
+ totalWeight *= 0.5F;
+ }
+
+ li.weight = totalWeight;
+ lis_.normalizeSpillWeight(li);
+}
+
generated by cgit v1.2.3-18-g5258 (git 2.32.0) at 2025-05-02 02:52:32 +0000