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[NFC][Regalloc] Factor out eviction decision from eviction attempt 

This splits tryEvict into a const tryFindEvictionCandidate, which
attempts to find a candidate, and the actual eviction (should the former
be successful)

The newly introduced tryFindEvictionCandidate will move subsequently
into the RegAllocEvictionAdvisor.

RFC: https://lists.llvm.org/pipermail/llvm-dev/2021-November/153639.html

Differential Revision: https://reviews.llvm.org/D113941
This commit is contained in:
Mircea Trofin 2021-11-15 13:27:00 -08:00
parent 7bfa9bd155
commit c6b9b702a0
1 changed files with 20 additions and 11 deletions
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31
llvm/lib/CodeGen/RegAllocGreedy.cpp
View File

@ -428,6 +428,8 @@ private:
MCRegister tryAssign(LiveInterval&, AllocationOrder&,
SmallVectorImpl<Register>&,
const SmallVirtRegSet&);
MCRegister tryFindEvictionCandidate(LiveInterval &, const AllocationOrder &,
uint8_t, const SmallVirtRegSet &) const;
MCRegister tryEvict(LiveInterval &, AllocationOrder &,
SmallVectorImpl<Register> &, uint8_t,
const SmallVirtRegSet &);
@ -1099,17 +1101,9 @@ bool RAGreedy::isUnusedCalleeSavedReg(MCRegister PhysReg) const {
return !Matrix->isPhysRegUsed(PhysReg);
}
/// tryEvict - Try to evict all interferences for a physreg.
/// @param VirtReg Currently unassigned virtual register.
/// @param Order Physregs to try.
/// @return Physreg to assign VirtReg, or 0.
MCRegister RAGreedy::tryEvict(LiveInterval &VirtReg, AllocationOrder &Order,
SmallVectorImpl<Register> &NewVRegs,
uint8_t CostPerUseLimit,
const SmallVirtRegSet &FixedRegisters) {
NamedRegionTimer T("evict", "Evict", TimerGroupName, TimerGroupDescription,
TimePassesIsEnabled);
MCRegister RAGreedy::tryFindEvictionCandidate(
LiveInterval &VirtReg, const AllocationOrder &Order,
uint8_t CostPerUseLimit, const SmallVirtRegSet &FixedRegisters) const {
// Keep track of the cheapest interference seen so far.
EvictionCost BestCost;
BestCost.setMax();
@ -1167,7 +1161,22 @@ MCRegister RAGreedy::tryEvict(LiveInterval &VirtReg, AllocationOrder &Order,
if (I.isHint())
break;
}
return BestPhys;
}
/// tryEvict - Try to evict all interferences for a physreg.
/// @param VirtReg Currently unassigned virtual register.
/// @param Order Physregs to try.
/// @return Physreg to assign VirtReg, or 0.
MCRegister RAGreedy::tryEvict(LiveInterval &VirtReg, AllocationOrder &Order,
SmallVectorImpl<Register> &NewVRegs,
uint8_t CostPerUseLimit,
const SmallVirtRegSet &FixedRegisters) {
NamedRegionTimer T("evict", "Evict", TimerGroupName, TimerGroupDescription,
TimePassesIsEnabled);
MCRegister BestPhys =
tryFindEvictionCandidate(VirtReg, Order, CostPerUseLimit, FixedRegisters);
if (BestPhys.isValid())
evictInterference(VirtReg, BestPhys, NewVRegs);
return BestPhys;