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//===-- RegisterClassInfo.h - Dynamic Register Class Info -*- C++ -*-------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements the RegisterClassInfo class which provides dynamic
// information about target register classes. Callee saved and reserved
// registers depends on calling conventions and other dynamic information, so
// some things cannot be determined statically.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_CODEGEN_REGISTERCLASSINFO_H
#define LLVM_CODEGEN_REGISTERCLASSINFO_H
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/BitVector.h"
#include "llvm/Target/TargetRegisterInfo.h"
namespace llvm {
class RegisterClassInfo {
struct RCInfo {
unsigned Tag;
unsigned NumRegs;
bool ProperSubClass;
uint8_t MinCost;
uint16_t LastCostChange;
std::unique_ptr<MCPhysReg[]> Order;
RCInfo()
: Tag(0), NumRegs(0), ProperSubClass(false), MinCost(0),
LastCostChange(0) {}
operator ArrayRef<MCPhysReg>() const {
return makeArrayRef(Order.get(), NumRegs);
}
};
// Brief cached information for each register class.
std::unique_ptr<RCInfo[]> RegClass;
// Tag changes whenever cached information needs to be recomputed. An RCInfo
// entry is valid when its tag matches.
unsigned Tag;
const MachineFunction *MF;
const TargetRegisterInfo *TRI;
// Callee saved registers of last MF. Assumed to be valid until the next
// runOnFunction() call.
const MCPhysReg *CalleeSaved;
// Map register number to CalleeSaved index + 1;
SmallVector<uint8_t, 4> CSRNum;
// Reserved registers in the current MF.
BitVector Reserved;
std::unique_ptr<unsigned[]> PSetLimits;
// Compute all information about RC.
void compute(const TargetRegisterClass *RC) const;
// Return an up-to-date RCInfo for RC.
const RCInfo &get(const TargetRegisterClass *RC) const {
const RCInfo &RCI = RegClass[RC->getID()];
if (Tag != RCI.Tag)
compute(RC);
return RCI;
}
public:
RegisterClassInfo();
/// runOnFunction - Prepare to answer questions about MF. This must be called
/// before any other methods are used.
void runOnMachineFunction(const MachineFunction &MF);
/// getNumAllocatableRegs - Returns the number of actually allocatable
/// registers in RC in the current function.
unsigned getNumAllocatableRegs(const TargetRegisterClass *RC) const {
return get(RC).NumRegs;
}
/// getOrder - Returns the preferred allocation order for RC. The order
/// contains no reserved registers, and registers that alias callee saved
/// registers come last.
ArrayRef<MCPhysReg> getOrder(const TargetRegisterClass *RC) const {
return get(RC);
}
/// isProperSubClass - Returns true if RC has a legal super-class with more
/// allocatable registers.
///
/// Register classes like GR32_NOSP are not proper sub-classes because %esp
/// is not allocatable. Similarly, tGPR is not a proper sub-class in Thumb
/// mode because the GPR super-class is not legal.
bool isProperSubClass(const TargetRegisterClass *RC) const {
return get(RC).ProperSubClass;
}
/// getLastCalleeSavedAlias - Returns the last callee saved register that
/// overlaps PhysReg, or 0 if Reg doesn't overlap a CSR.
unsigned getLastCalleeSavedAlias(unsigned PhysReg) const {
assert(TargetRegisterInfo::isPhysicalRegister(PhysReg));
if (unsigned N = CSRNum[PhysReg])
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;
}
/// Get the register unit limit for the given pressure set index.
///
/// RegisterClassInfo adjusts this limit for reserved registers.
unsigned getRegPressureSetLimit(unsigned Idx) const {
if (!PSetLimits[Idx])
PSetLimits[Idx] = computePSetLimit(Idx);
return PSetLimits[Idx];
}
protected:
unsigned computePSetLimit(unsigned Idx) const;
};
} // end namespace llvm
#endif
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