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Provide a target override for the cost of using a callee-saved register

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for the first time.

Thanks Andy for the discussion.
rdar://16162005


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@204979 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Manman Ren 2014-03-27 23:10:04 +00:00
parent 2ea701e67a
commit d9524d66cd
2 changed files with 11 additions and 2 deletions
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5
include/llvm/Target/TargetRegisterInfo.h
View File

@ -689,6 +689,11 @@ public:
/// debugging downstream codegen failures exposed by regalloc.
virtual bool mayOverrideLocalAssignment() const { return true; }
/// Allow the target to override the cost of using a callee-saved register for
/// the first time. Default value of 0 means we will use a callee-saved
/// register if it is available.
virtual unsigned getCSRFirstUseCost() const { return 0; }
/// requiresRegisterScavenging - returns true if the target requires (and can
/// make use of) the register scavenger.
virtual bool requiresRegisterScavenging(const MachineFunction &MF) const {

8
lib/CodeGen/RegAllocGreedy.cpp
View File

@ -2123,7 +2123,10 @@ unsigned RAGreedy::tryAssignCSRFirstTime(LiveInterval &VirtReg,
unsigned PhysReg,
unsigned &CostPerUseLimit,
SmallVectorImpl<unsigned> &NewVRegs) {
BlockFrequency CSRCost(CSRFirstTimeCost);
// We use the larger one out of the command-line option and the value report
// by TRI.
BlockFrequency CSRCost(std::max((unsigned)CSRFirstTimeCost,
TRI->getCSRFirstUseCost()));
if (getStage(VirtReg) == RS_Spill && VirtReg.isSpillable()) {
// We choose spill over using the CSR for the first time if the spill cost
// is lower than CSRCost.
@ -2172,7 +2175,8 @@ unsigned RAGreedy::selectOrSplitImpl(LiveInterval &VirtReg,
// When NewVRegs is not empty, we may have made decisions such as evicting
// a virtual register, go with the earlier decisions and use the physical
// register.
if (CSRFirstTimeCost > 0 && CSRFirstUse && NewVRegs.empty()) {
if ((CSRFirstTimeCost || TRI->getCSRFirstUseCost()) &&
CSRFirstUse && NewVRegs.empty()) {
unsigned CSRReg = tryAssignCSRFirstTime(VirtReg, Order, PhysReg,
CostPerUseLimit, NewVRegs);
if (CSRReg || !NewVRegs.empty())