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Change the way we choose a free register: instead of picking the first 

free allocatable register, we prefer the a free one with the most uses
of inactive intervals.

llvm-svn: 16148
This commit is contained in:
Alkis Evlogimenos 2004-09-02 21:24:33 +00:00
parent 095c3a80f3
commit 9f82237f4e
1 changed files with 15 additions and 4 deletions
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19
llvm/lib/CodeGen/RegAllocIterativeScan.cpp
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@ -463,17 +463,28 @@ void RA::assignRegOrSpillAtInterval(IntervalPtrs::value_type cur)
} }
unsigned RA::getFreePhysReg(IntervalPtrs::value_type cur) unsigned RA::getFreePhysReg(LiveInterval* cur)
{ {
std::vector<unsigned> inactiveCounts(mri_->getNumRegs(), 0);
for (IntervalPtrs::iterator i = inactive_.begin(), e = inactive_.end();
i != e; ++i) {
unsigned reg = (*i)->reg;
if (MRegisterInfo::isVirtualRegister(reg))
reg = vrm_->getPhys(reg);
++inactiveCounts[reg];
}
const TargetRegisterClass* rc = mf_->getSSARegMap()->getRegClass(cur->reg); const TargetRegisterClass* rc = mf_->getSSARegMap()->getRegClass(cur->reg);
unsigned freeReg = 0;
for (TargetRegisterClass::iterator i = rc->allocation_order_begin(*mf_); for (TargetRegisterClass::iterator i = rc->allocation_order_begin(*mf_);
i != rc->allocation_order_end(*mf_); ++i) { i != rc->allocation_order_end(*mf_); ++i) {
unsigned reg = *i; unsigned reg = *i;
if (prt_->isRegAvail(reg)) if (prt_->isRegAvail(reg) &&
return reg; (!freeReg || inactiveCounts[freeReg] < inactiveCounts[reg]))
freeReg = reg;
} }
return 0; return freeReg;
} }
FunctionPass* llvm::createIterativeScanRegisterAllocator() { FunctionPass* llvm::createIterativeScanRegisterAllocator() {