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Precompute some information about register costs.

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Remember the minimum cost of the registers in an allocation order and
the number of registers at the end of the allocation order that have the
same cost per use.

This information can be used to limit the search space for
RAGreedy::tryEvict() when looking for a cheaper register.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@172280 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Jakob Stoklund Olesen
2013-01-12 00:54:59 +00:00
parent b2f0b595a3
commit c7a275245f
2 changed files with 43 additions and 3 deletions
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22
include/llvm/CodeGen/RegisterClassInfo.h
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@@ -29,9 +29,14 @@ class RegisterClassInfo {
unsigned Tag;
unsigned NumRegs;
bool ProperSubClass;
uint8_t MinCost;
uint16_t LastCostChange;
OwningArrayPtr<MCPhysReg> Order;
RCInfo() : Tag(0), NumRegs(0), ProperSubClass(false) {}
RCInfo()
: Tag(0), NumRegs(0), ProperSubClass(false), MinCost(0),
LastCostChange(0) {}
operator ArrayRef<MCPhysReg>() const {
return makeArrayRef(Order.get(), NumRegs);
}
@@ -106,6 +111,21 @@ public:
return CalleeSaved[N-1];
return 0;
}
/// Get the minimum register cost in RC's allocation order.
/// This is the smallest value returned by TRI->getCostPerUse(Reg) for all
/// the registers in getOrder(RC).
unsigned getMinCost(const TargetRegisterClass *RC) {
return get(RC).MinCost;
}
/// Get the position of the last cost change in getOrder(RC).
///
/// All registers in getOrder(RC).slice(getLastCostChange(RC)) will have the
/// same cost according to TRI->getCostPerUse().
unsigned getLastCostChange(const TargetRegisterClass *RC) {
return get(RC).LastCostChange;
}
};
} // end namespace llvm